Thursday, January 18, 2018

2018 ~ The Year of SSB Transceivers

The IC Transceiver Design (Based on K1BQT)

2/15/2018 ~ Thinking out of the Circuit.

One thing I now look at when I am designing a circuit is how can the design be used to better advantage. At times I have been criticized that something I designed was no good for those who like to strap on a back pack, climb up some hill in a god forsaken place and run a QRP marathon. That is never one of my design goals. But of late my goals have taken a twist --how to build things so that circuits could do double duty.
This is not out of laziness but time constraints. I have so many projects lined up that unless I look to building less in a project it will be impossible to build more projects. So going back to our 40 (or 20) Meter Driver stage my thoughts drifted toward how this could be used on both transmit as well as receive. Let us start with the basic circuit shown below.

This board is way too large for a compact type back pack rig but was purpose built as I knew I would be adjusting, tinkering and changing things. I often build two versions as the first serves as a prototype and the second becomes the production unit. Often these prototypes have found their way into yet other rigs. In 2016/2017 I built several "Junk Box" rigs out of such leftovers. So initially the thought was this board would be put in the junk box.
I jokingly say that I do my best thinking while I am asleep and often my brain awakens me with some sort of an amazing idea --unfortunately it often is at 3:00 AM with my never returning back to sleep.
Well it happened again several nights ago specifically with this board. So here is how my brain sent me a message. Suppose we were to introduce some relays on the board so that the signal path could be changed in that the J310's instead of being used as the pre-driver to the 2N2219 was instead "steered" so that is now was the Receiver RF Amp stage, and the Band Pass Filter that followed the J310s' was now steered ahead of the J3110s and what was the output of the BPF that normally fed the 2N2219 was now connected to the antenna circuit. On Transmit the signal path would be restored by the relays to the original design.
What we have below is a block diagram of how that would happen. The R & T designations show how the relays would be connected so that the circuit elements could function on either transmit or receive. Now all that extra board space can be fitted with SPDT relays -- four of them. Assuming that an additional RF linear amp stage is added to the 2N2219 (say an IRF510) then you would need to have the 8 element W3NQN filter following the IRF510. So the receive side would have the benefit of both the LPF and the BPF. If one chooses to use just the 2N2219 (at 300 MW) then replace the 5 element LPF with the 8 element and then the LPF could be switched between the BPF and the output of the 2N2219.
My next task would be to add the relays --All Electronics sells these neat SPDT relays for 60 cents a piece. As it turns out the dual filter test board could now be mated with this prototype board and we now will have another transceiver on line. I already know the 2N2219 stage will drive my outboard amp to 30 Watts so I may just skip the IRF510 stage. For those with the backpack stations --lets see you make some contacts at 300 MW.

BTW this also will prove the suitability of buying those filter boards from Israel for $34 delivered to your door. In one of the videos I had of the test setup with the boards spread out on the bench, I received a "negative" comment that it was such a junky mess. Well that may be true but it does work!

Pete N6QW

2/08/2018 ~ Time to Drool! The ASUS Tinker Board is Alive and working with Quisk and a Softrock.

For those radio illuminati who lurk the reflectors such as EMRFD and uBitx --let's see yours! The ASUS Tinker Board works with Quisk and is a better alternative to the RPi3.

Pete N6QW

2/5/2018 ~ Some important Updates: Stay Tuned!

Here are the final schematic for the 40 Meter Driver Stage and the plot of the output. Note the 5 element Low Pass Filter in the final schematic. If you were to use this as a standalone output stage I would suggest using the 8 element W3NQN filters to give you confidence that nothing is slipping through. In my designs following the IRF510 stage I have the 8 element filter as the final filter

News Flash ...

Over the weekend my newly purchased Asus TinkerBoard arrived. This board sports a 1.8 GHz Quad Core Processor and  2 GB of onboard RAM. It is better than the RPi3! --  You tube videos and Netflix are amazing. Here is something more ...

Above is the latest Quisk SDR Software which has a built in test signal --look close and you can see the test blip on the screen. This is the year of transceivers at N6QW -- so one more in development.
You have to stay tuned for this --it may be a bust; but so far this may be one of the first SDR transceiver implementations using the TinkerBoard. BTW -- I was able to take most of the files that I used when I installed Quisk on a PI2/3 and simply loaded them onto the TinkerBoard. Some of the files required that you use a later version as explained in the latest Quisk documents -- but that went on without a hitch. I guess Linux is Linux.
Check my website and there is a link to the documents used with the Pi2/3. Once again -- N6QWmay be ahead of the curve. See if you can find any info using the TinkerBoard on any of the radio illuminati reflectors? I hope to update the documentation for the TinkerBoard as there are some unique changes that are required. But for now just drool!
BTW -- the TinkerBoard is very easy to interface. I plugged in my 5 inch  HDMI Touch Screen and boom it worked. With the Pi3 --there is a lot of hand-hockeying to get it to work. Music playback is very crisp.
Pete N6QW

2/2/2018 ~ 40 Meter Driver Board is Finalized!

This morning I soldered up all of the components that would go on the 40 Meter Driver Board including the Low Pass Filter. Success! We are getting close to 10.5 Volts Peak To Peak through the Low Pass Filter measured across a 50 Ohm resistive load. With the driver stage potted I will now start on the main transceiver board. With a bit of effort two Driver stages can be built on a single 4X6 board which likely will be a PC board versus the single sided copper vector board.

More info ... This afternoon I connected the output of this driver stage to my commercial amp which is a Communication Concepts Inc. AN762 --good for almost 150 watts output. With just the drive coming out of the 2N2219 --I was hitting over 30 Watts PEP. So this combo is now on par with the amp that was originally designed for the K1BQT project. I could even envision this small driver stage with one of the $15 amp kits being sold on eBay that are good for about 45 watts.

A new day has dawned and for very little $$$$ invested you can have a rig that is good for making lots of contacts.
Pete N6QW

1/30/2018 ~ 20 Meter Driver Final Stage Data.

Yesterday I posted the 40 Meter results and this morning using LT Spice I simulated what would be needed for the 20 Meter version. There are three circuit changes including the transformer on the output. Since we are bit higher in frequency the FT-37-43 had a few hiccups and burps to get it to peak on 20 Meters. That is when I went to the FT-50-61 core and with 16 Bifilar Turns put it smack on 20 Meters. I also changed the in/out coupling caps to 10 NF (0.01 uf). Having the Band Pass Filter ahead of this will insure just the 20 Meter energy is getting to the stage. This would then be followed by the 20 Meter Low Pass Filter. This could be a breakthrough module used in many driver applications.

Pete N6QW

1/29/2018 ~ A Breakthrough -Driver Finalized!

I attempted to use the BS170 as the final stage -- and while it looked good on paper it flunked the smell test. So I shifted gears and went to a conventional BJT to do the heavy lifting and we were successful! Boom this stage is potted.

While the sketch shows 12 Turns on the BFT --use 13 turns as that value produced the following plot from the LT Spice simulation

Notes on the schematic the center wiper on the 200 Ohm trim pot is connected to the 100 NF cap and the settings are proximate. Look at the output on a scope and find the setting for the best linearity. The Resistor R7 is a 200 Ohm trim pot connected as a variable resistor is in parallel with a 100 ohm resistor. These two trim pots give a coarse and fine setting of the output. Tune for max smoke and best linearity.

Finally we have a video. Even I am impressed at what we now have for the IC Transceiver. With the 20 Meter Driver we will need to put less turns on the FT-3743 Core. I will determine that value and post it on the blog.

I plan on building the LPF and will rerun the tests --but for now we have moved the needle.

Pete N6QW

1/28/2018 ~ Adding the Band Pass Filter.

I built the filter and it wouldn't tune up and the pattern looked like crap. I thought maybe a bad capacitor --but that wasn't the case. The problem was on boot up the Arduino was set for 20 Meters and the screen was not facing me. Then I had an Ahh Ha moment --the filter is on 40 Meters. A quick change of frequency in shirt order showed it was a solid design -- And I get out about 3 Volts Peak to Peak. That should be a good place to start when I finish off the BS170 stage.
Pete N6QW


1/27/2018 ~ Pete's Build of the Driver Stage.

Today I started work building the 40M version of the driver stage. This is a prototype build and thus quite large real estate wise. Ultimately this circuit will be built on the single sided copper vector board. I often build two or three prototypes before we "freeze" the design. Of these prototypes end up in new transceivers.

I just finished the first part of the build which is the substitute circuit for the 40673. I am very encouraged! The power out just from this stage was 10 Milliwatts. Follow on work will involve the Band Pass Filter. the BS170 RF Amp stage and then the 40M Low Pass Filter. Watch the video.
This is starting to get exciting.
Pete, N6QW

1/26/2018 ~ IC Transceiver Builders Report.

Nick, G8INE has done several things to take on this project. First he purchased a table top CNC Engraving/Milling Machine. Unlike me it did not cost him $250K. He is using one of the machines that can be had in the $200 to $300 range. Next he taught himself CAD and designed a SMD board for the IC Transceiver Driver stage. Finally he cut a board and wired it up (should say no wiring involved). The board will shortly undergo testing to verify the performance as indicated in the LT Spice Simulations. Here is Nick's handiwork.
Kudos to Nick and his board. We will report on his test results. Nick did comment to me that once he had a board that it was a lot easier to build the module. Now the icing on the cake --when he goes to build a second board he simply chucks up a piece of PCB stock, calls up the program and punches the start button. That easy!
I was a bit waylaid on building my board as my time was spent on the SBE-33 whose transmit signal sounded like crap. This prompted replacing all of the electrolytic caps in the HV power supply and the microphone amplifier stages. I suspected the rather unusual voltage regulation circuit may need a rebuild too. I did make one on the air contact and there was a report of FM'ing on voice peaks. That is a well known problem traced to impacts of voltage regulation on VFO circuits. Now if there was a Si5351 in there we would not be talking about that subject.
Thanks again Nick for sharing your efforts.
Pete N6QW

1/24/2018 ~ More Trips back in Time. The SBE-33.

Final fixes included opening the TR relay case and added a drop of De-Oxit to each of the contacts. Tribal Knowledge use the end of a wooden toothpick to apply a small drop to each contact. I also (using the low setting) applied a bit of De-Oxit spray into the Volume Control and Microphone Control. SBE recommends a dynamic microphone or a powered crystal microphone but avoid a pure crystal microphone. Note an Electret Microphone will not work with this directly --no bias at the microphone jack. I hope the OBTE have taken notes with their latest Iphone.
I hope to check into the Vintage Sideband Net tomorrow evening.
Pete N6QW

1/23/2018 ~ Inconclusive Results. Trial By Test.

I tried several simulations and the results were not what I reasonably thought they should be. First I changed the resistor from Gate #1 to Ground to 10K Ohms just as in the original design without changing the turns ratio on the Input matching transformer. Boom the output jumped another 5dB to something in excess of 30 dB for the 40 Meter version. Most of the heavy lifting is in the final stage with something close to 25 dB just in that stage. Without changing the turns ratio that 10K would look like 225 Ohms at the primary. So that certainly left a big question mark.
Several other configurations were evaluated that step down the 10K impedance using various simulations. A simple 10 Bifilar turn FT-37-43 was connected "step down" was tried. Using the bifilar approach results in a 4:1 --so I could make 10K look like 2.5K which then would mean changing the Gate resistor to a 2.5K Ohms and this would replace the matching transformer. That configuration resulted in less gain. So we are back now to testing configurations with real hardware and evaluate which one works best.
One option would be for the final configuration would be to "build per print" with the 10K resistor on Gate #1 as T1 does give a 4:1 so that the third winding results in a 10K value.
However to evaluate the amplifier block with actual hardware and a BS170, I will use the 2.2K Ohm with the matching transformer first specified as I will be driving this stage during the test and evaluation from an ADE-1 which has a Zout of 50 Ohms. I have the board cut so now I need to start adding parts. The evaluation essentially has two components --1) does the circuit work as an amplifier and the gain developed and 2) what works the best when connected to U7.
Pete N6QW

1/22/2018 ~ Not so Fast Batman --The Batmobile may have a problem!

For many years now it has been obvious that while asleep my brain keeps churning away thinking about problems/issues/concerns with designs I am working on at that time. It is both a blessing and a curse. A blessing because I may find a problem before it raises its head as a problem. The curse part is that it is usually around 3:00 AM and I am awakened --never to get back to sleep. It happened last night.
Sometimes when we chunk a project into modules --we miss something at the interface. This might be the case with the K1BQT original design. Below are two parts of the original schematics. Take a minute to look these over. Read on.

T4 on the output side of U7 is a trifilar wound transformer consisting of 9 Turns X 3. Thus two of the windings are connected bifilar fashion which essentially puts two of the windings in SERIES for a total of 18 Turns. The third winding, the output is stand alone with one end grounded and the other end that ends up on Gate #1 of the 40673 which has a 10K resistor to ground.
So we have an impedance transformation from the output of the MC1496 to the input of the 40673. So lets look at that transformation in light of turns ratio squared. Thus 18^2 = 324 and 9^2 = 81. We have a classic 4:1 transformation (For the OBTE 324/81 = 4). So the output impedance looks like 1/4 the value in terms of the input to the 40673.
You might want to Google Maximum Power Transfer Theory in relation to impedance matching. You get max juice when the impedances are matched. So now the Question would be what is the Output Impedance of the output of the MC1496 and what does the input impedance look like for the 40673. Not withstanding the actual values --there is a 4:1 transformation taking place. So we need to go down that bunny slope to assure there was matching taking place as that impacts what we do in the redesign.
In the Simplecever Plus Project I addressed this issue by forcing the input of the J310s' DGM to be 2.2 K Ohms and then did a match from 50 Ohms to 2.2K Ohms with a 3 Turn to 20 Turn Broad Band Transformer. Thus 3^2 = 9 and 20^2 = 400 resulting in 400/9 = 44.4. Now if you take 2200/50 = 44 --close enough. Thus 50 Ohms at any output will look like 2200 Ohms at the Input of the DGM.
Below is an example of how this matching was done on the Simpleceiver IF stage. The 1st match was 3 to 20 turns and the 2nd out of the crystal filter was 170 Ohms to 2200 Ohms thus a slightly different turns ratio but always presenting 2200 Ohms to the input
I have now modified the two driver amps to include input matching from 50 Ohms to 2200 Ohms
Some tribal knowledge here -- if you simulate these in LT Spice and add the inductor mutual inductance notes (K9 L8 L9 1) be certain that when you make that note to check the dot that says invoke Spice Command --otherwise you will get no output.
These changes added about 10 DB to the output. Now lets see if we can track down the output Z of the MC1496. Maybe K1BQT accounted for this in the Out/In impedances but given I am changing his design I want to make sure I have accounted for the matching.
You can scroll down this posting and look at the original plots. Matching is important!
When I get the output impedance of the MC1496 we can modify Transformer T4 on the schematic (if necessary) so that its output winding is 50 Ohms. Now we could be really clever and once we know the output impedance we could use a single transformer so that the primary Zout matches the Secondary Zin to 2200 Ohms. I prefer two transformers but it could be done with one.

So let us now check the MC1496 Data Sheet that can be found here. The Output Resistance for the Parallel Outputs is 40K Ohms. So if we look at K1BQT's transform it is 4:1 and thus 40K looks like 10K into the base of the 40673. Thus the design as presented is absolutely correct. K1BQT was spot on!

Now how do we match that into my 2.2K Ohms?

Well lets us start by looking at T4 so we would have a 40K to 50 Ohm match which is 800:1 and with only 18 turns on T4's Primary -- you would end up with less than a half turn on the secondary --that won't work. So now lets look at the transformer on the input of the J310s and what can be done with the primary side. A 10K to 2.2K transformation is a 4.55:1. So now if we modify my input transformer to have a 15 turn Primary and 7 turn secondary we have the following: 15^2 = 225 and 7^2 =49. 225/49 = 4.59:1 is close enough. So I will run some plots with this transformer.

Now alternatively we could change the input to 10K and see how those plots look with a source of 10K pumping RF into Gate #1 with a 10K resistor to ground.

This exercise has served the purpose of looking at impedance matching and how to adjust input / output impedance matching.

Stay tuned tomorrow for the plot data with the new input transformers.

Pete N6QW

1/20/2018 ~ Prototype board layout for the Driver.

I will start the build of the first prototype Driver stage. My process begins with using G Simple to lay out island squares and the cut it on my CNC. The layout facilitates parts changing, circuit changes and lots of measurements. Once I get a working circuit I will convert this to the single sided copper board which will be another prototype. Finally I will build two "production units" for 20 and 40 Meters. I have left space on the board to add shields should that be necessary. If one desires this could be done over a sheet of copper PCB using Rex's W1REX MePads.  For reference purposes the CNC will cut this board using a single piece of 4X6 board and pretty much fills the board.

That is the beauty of having a CNC Mill. Five minutes after I finished the design I had a board in my hand.

CNC Engraving/Router Mills can be had for about $200 to $300 on eBay. So within reach of many homebrewer enthusiasts. This  board is way larger than needed but since it is a prototype we will be doing lots of "peaking" "tweaking" and adjusting and thus the extra room

Stay Tuned.

Pete N6QW

1/19/2018 ~ Cleaned up Schematics for the 20 & 40 Meter Driver Assemblies.

I took some time to clean things up on the schematics so that the components were more readable and to include any coil winding data. The plots previously presented are essentially the same.

The 40 Meter version has slightly more gain but the minimum gain is 5 DB in both cases. Note that "R" on the schematic is a combination of a 10K trim Pot (Drive Control) where the top end is connected to the bottom end of the 22K resistor, the Center Wiper connected to gate #2 and the other end is connected to a 2.2K resistor which has its other end grounded.
K1BQT has a ferrite bead connected to the lead on Gate #2. Since my trim pots are board mounted I have not found this necessary. That said should you panel mount a pot then more care in lead routing and a ferrite bead may be required.
Caveat Emptor -- These circuits were simulated in LT Spice and not actually built which will be the next step. However, The J310's stage and the Band Pass Filters have been built and used in other rigs so these parts are known quantities. The substitution of the BS170 for the 2N7002 and the simple Low Pass Filters are new and thus will be evaluated. Should these two circuits work well then they will become a standard module that could be used in any rig design. I am hopeful this is the case.
I would encourage those with more sophisticated test gear than I have to build one of the circuits and run a Spectrum Analysis and share with us what you find.
One more thing: I used T-68-2 Red Cores for the 14 MHz networks. I invite your attention to the information in the chart below provided courtesy of Amidon.  Red Cores are OK at 14 MHz.  The Q's are good enough with the T-68-2 cores (Al = 57) . But if your shorts are all wadded up, then with the inductance values provided you can calculate the turns required for the type 6 (yellow) cores for the 14MHz networks. Al value for yellow T-68-6 cores = 47. 
Stay tuned -- this is the year of SSB Transceivers!!!
Pete, N6QW


We have earlier presented the reference document for this project and in looking over what will be kept pretty much intact versus design anew, the first piece to be designed is the driver stage following the IC lower level stages.
The basic LM1496/MC1350 pieces will literally go untouched. That said the driver, final RF amp and Audio Amp stages will likely get a going over. My initial thoughts were for a two band rig that will be switched by a simple DPDT toggle switch. This starting point affected what I did with the driver stage.
From K1BQT's design the driver stage looked like this:

In 1985 this was state of the art and we will build on the idea of a Dual Gate MOSFET driving a N Channel Enhancement Mode FET. Since 40673's are not like a stock item I will build one using two J310's. This is a proven approach and works perfectly! The IRFD1Z3 is like un-obtanium and so we'll substitute a BS170.  Touring Rick's design the 40673 can have an adjustable "Drive" level. We will do likewise with the J310s. The 40673 was followed by a Band Pass Filter and then to the IRFD1Z3 with a Low Pass Filter on the output. K1BQT was very careful to state that if you use bands other than 75 Meters you will need additional filtering.
So if we use just the J310's and the BS170 as a single amp we would have to be able to switch the Band Pass and Low Pass Filters which adds a lot of diode and/or relay switching.
So what if we built two complete separate driver assemblies and then it would only involve a SPDT relay at each end of an  Assembly to switch between the Assemblies and then a third SDPT relay to provide power to the Assembly being used. This approach does several things for us including making the switching a bit less complicated but more importantly each driver assembly can be optimized for the band being used. The added cost would be for a couple of devices (2X J310 and 1 X BS170) and a few resistors, caps and ferrite cores.

Today I took a crack at designing or should say simulating two separate Driver Assemblies. Should mention that the Dual Gate MOSFET Stage is a stock design that I have used in several rigs as is the Band Pass Filters. What has not been previously tested is the BS170. So after presenting this design I will build a prototype and run some tests. the simulated plot as a starting point shows great promise. 

Take a hard look at the schematic and note that the Band Pass Filter is terminated at each end with 50 Ohms. If you want a rude awakening remove the input side 50 Ohm resistor and run the plot. Do not remove this resistor.

Again these are the first pass and I will build a prototype to insure they works as deigned.

Stay tuned and start ordering the parts.

Pete N6QW


Sunday, December 31, 2017

2018 ~ The Year of SSB Transceivers

Clean Off the Work Bench ~ New 2018 Transceiver Projects!

1/18/2018 ~ Now you found it -- How to Fix It?

I was so excited yesterday that I found the source of the problem --it was not the rig per se or a test of my schematic reading or soldering skills --it was RF in my back yard!

One comment on the you tube video --how do you fix it as this will also have implications on the IC Transceiver build. My XYL suggested moving to an upscale neighborhood that has antenna restrictions. Should note for over 50 years she has absolutely hated the hobby so her response is quite clear -- make me QRT.
In the Page 104, SSDRA design had as a front end a simple coil and a cap for  20 Meters. Whereas the 80 Meter filter uses a Cohn type tuned network. So one possible fix for me since I don't operate CW or Digital modes is to come up with a Band Pass Filter in place of the simple tuned circuit that would be centered on the phone band and with care could offer a 15 to 20 dB reduction to signals below 14.150 MHz. That is possible.
Another would be to design a trap "notch filter" centered on 14.075 MHz which of course if I did operate digital would kind of makes things hard for any digital operations; but not incompatible with my operating mode desires.
This is a first for me but it does appear to be limited to 20 Meters.
Pete N6QW

1/17/2018 ~ Trouble Shooting Mystery Solved

So Ok, yesterday I determined that some evil external force was de-sensing the front end of my new (rebuilt) transceiver. But the wild goose chase was invaluable as I had a real chance to dig into what I had done some 35 years ago where the documentation of what had been done got lost in one of the 10 moves I made in that 35 years. I even rebuilt the active mixer --so all is not lost. My detailed recent journey did affirm I knew what end of the soldering iron was hot --even 35 years ago. BTW I did have to go before the FCC Examiner to get my Extra --no box tops here!
This morning I had an inspiration and that was to connect my Rigol scope to the rig's antenna with the rig turned off and just see what I could see. Initially there was a bit of background noise and then the screen filled with signal. I had the counter function engaged and quickly noted that the frequency of the strong signal was 14.07475 MHz and it was really strong. I observed several cycles to affirm and verify what I first initially thought this morning. Boom someone close by is operating in the digital mode --and I mean close by like maybe 800 feet. It was a ham on the next block and just recently I noted he sprouted a new antenna on his roof.
Next I turned on the rig and tuned down to 14.07475 and still with the scope connected across the antenna spotted the screen filling up and at the same time the rig's S Meter showed about a 30 DB /S9 signal. I watched that for several cycles and indeed that was the culprit. Keep in mind that was 30 DB/S9 in a de-sense mode. My ham friend must have gotten a new radio toy for Christmas as I have never had this problem before.
For your amusement and amazement I made a video of this morning's solving of the mystery. See below. There was a method to my sharing this adventure. In troubleshooting a rig, often you have the data right in front of you -- the problem is one of how to connect the dots. It took me two days but was an invaluable learning experience for me -- there was nothing wrong with the rig! The problem was the rig was being subjected to very strong signals in close proximity -- connected to a beam only made the signal stronger!

 There we have it -- another ham is the problem. Feel a lot better now.

Pete N6QW

1/16/2018  Tribal Knowledge Trouble Shooting (1/17 Update)

As we prepare to build the IC Transceiver I wanted to spend some time on a real world rig
problem that directly applies to the IC Transceiver project. What to do when something is not right? In the most recent transceiver project (in 2018) I rebuilt something that I had originally built in about 1985.
The 2018 Reborn 1980's rig. The LED next to the Meter Glows Green on Transmit. How Cool?

There is a story behind this rig and it all started with the Solid State Design for the Radio Amateur (SSDRA). You have often heard me say that I prefer this publication over EMRFD. Rebuilding this project affirmed that position. If you go to Chapter 5 page 104, you will see a two band Superhet (20/80 Meters) which uses a 9 MHz IF. When I looked at that schematic, back some 35 years ago my first thoughts were why can't this be made into a transceiver --which it was.

(For those who do own a SSDRA there is a close parallel to the page 104 design and the K1BQT 75M Transceiver in that both use an active mixer, both use the MC1350 and both use the same AGC circuit. Don't overlook the diode steering in K1BQT's rig to steer the signals into/out of the filter. Undoubtedly there has to be parallel influences at work here! So spending some time with SSDRA is most useful before building the IC Transceiver. Like I said my copy of EMRFD is a great bookend!)
The Front End active Mixer is a 40673. Having some 3N211's I used that for the active mixer. The plan was to use diode steering so that the Rx signal would be diode steered into the IF stage. The other half of the steering would be the output of a diode ring balanced modulator with a 741 Op Amp microphone amplifier.

Thus signals passing through the IF would either be the Received signals or the low level Transmit signals. Based on a concern I had at that time with using the KVG 5 Pole filter I added a simple 2N3904 buffer stage ahead and following the filter. The idea was both in SSDRA and the seminal ON5FE 1970's IF Module. From there just as on page 104 the signals were routed to the MC1350 IF amp and thence on to the singly balanced diode ring. Noteworthy I kept the AGC circuit with thoughts of using it with ALC like in the IC Transceiver. [That may not actually be a good idea --will explain in a later post --but the ALC control level is affected by the level set for the AGC.]
So now looking at the singly balanced mixer (the OBTE are left to figure that out) I added more diode steering to the what is normally the LO Port. Thus I had diode steering of the BFO on receive and more diode steering of the output of the single balanced mixer to the audio amp.
But on transmit the LO port was now fed the LO signal from the VFO and the output now steered to a band pass filter and then on to a 2N5179 RF stage. [Hayward loved 2N5179's]. From the 2N5179 the RF signal was passed to a driver stage and then on to an IRF510.
So the changes I made in the upgrade are I ditched the diode balanced modulator and removed the carrier oscillator circuitry. In its place I installed an ADE-1 and the BFO signal is now supplied by a CLK2 from the Si5351. The LO signal (above the incoming at 23 MHz) is supplied by CLK0 of the Si5351. I was unhappy with having a single balanced mixer on today's bands so I removed all of that circuitry and installed a TUF-1. [As an experiment with some surplus DBM's there is now a TFM-2P installed there which is a TUF-1 on Steroids.] The RF Driver is a 2N2222 driving a BD139 and the final a IRF510. Needless to say NO Analog VFO's or Crystal BFO as these technologies are out of step with the rigs of today!
Active Mixer now a 3N209

TFM-2P DBM, MC1350 to the right of the DBM

BPF and 2N5179

2N2222 and BD139 Driver Stage

IRF510 Final Amp bolted to the back wall of the case. Having a CNC sure is nice!


So all was going nicely with the new rig when suddenly I would encounter an intermittent condition on receive where the signal level (more like volume) would be reduced. The Transmit signal appeared to be not affected. So it was a receive problem.
My first "noodling effort" was to focus on the active mixer stage. Why? --well everything after the mixer is more or less common to transmit and receive. The only item not so other than the receive mixer would be the audio amplifier chain.  But I concluded, that the only  possibility since it worked well on transmit, was the active mixer.
The trimmer caps originally installed were orange in color and had a range of 15 to 60PF which I found in other installations had a finite life of so many rotations. I thought perhaps they were failing and would change value thus "untuning" the tuned circuits. So I decided to replace all of the components in this stage. I replaced the 3N211's with a 3N209 which was actually sent to me by the man himself, W7ZOI. With everything replaced I fired up the rig and all worked. The only thing this proved is that 1) I did not make any wiring errors and that 2) I do know how to read a schematic.
My euphoria was short lived for the problem returned. Again transmit was not affected only receive. I guess I should have read the tea leaves more closely as when the condition occurs the signal drops but does not go away.  It just loses signal strength. I prodded and poked components all along the receive path yet the condition did not abate.
A little more about what I am seeing (hearing). It is a cyclic thing where the signal weakens for a short duration and then gain comes back full on. Hmmm could there be a bad component in the AGC circuit that was cycling the MC1350 so that gain was being reduced intermittently. I was mystified. Again transmit was not affected. Disconnecting the AGC had no affect on resolving the cyclic de-sense.
So some other things I tried -- looking at the whole system. What about an antenna issue where maybe there was an issue with coax/beam (20 Meters)? So then I switched antennas to the dipole which is actually 3/2 wavelengths on 20 Meters. Boom same problem so that led me (falsely) back to the rig. Should have thought a bit more about that conclusion --if it loaded OK on transmit with no issues then it was not the antenna. I was bummed out as I just could not see what was the problem.
Well I decided the best course was to lay aside the rig for a bit and give this more thought. I heard a few stations on and so I put a different 20 Meter rig on the air -- Boom and double Boom --Same problem! Wait a minute. Tried a third 20 Meter radio -- same problem and so it was with a 4th 20 Meter Rig. Additionally one rig is a 20/40 Meter version -- there did not seem to be a problem on 40M. Thus the de-sense signal is not totally broad band. Thoughts floated back to when as a kid I built a TV killer which blanked out one of the TV channels so I didn't have to watch the Ed Sullivan show but avoided impacting the other channel which was the Colgate Comedy hour. Hmm was some one in the neighborhood trying to stop me from operating on 20 Meters????
So now the pieces were beginning to fall into place. There is something new in the neighborhood that is cycling on off and is a very strong signal that is causing my rigs to "de-sense".
So while replacing the active mixer may have not been necessary it does make me think it was not all bad. Tomorrow I will do more snooping around the neighborhood, On my morning walk I will bring along the rig with a battery pack and a short antenna to see if I can pinpoint the culprit.
All of our utilities are underground and it was not my neighbor welding in his garage as I know when he is doing that. Several years ago we had the "pot lady" growing weed in her garage and it was the cycling of the grow lights that made RF noise. We didn't get any new appliances so it is not in my QTH. It has to be a pretty strong field to cause a de-sense of the front end. I am having a hard time internalizing that the signal would be so strong as to essentially overload the rigs. Hearing RF interference (pot grow lights) is an order of magnitude different from overload.
I want to also re-verify that all the rigs are affected and that I have not missed anything. Oh I have three power supplies -- the same problem with any of the supplies. So I eliminated the power supplies as the root cause. Time now to rest and reflect.
This is a classic "Easter Egg Hunt" looking where all the eggs are hidden. I have never seen anything like this before.
Will keep you posted. But this could be a problem that might have been encountered with the IC Transceiver and I would have been chasing a bad circuit/component/wiring error when it was something entirely different. Sometimes the obvious is not so obvious --why did I immediately think there was a problem with the rig? Good question to always ask first!!
Pete N6QW

1/13/2018 ~ More Considerations: To QRP or Not QRP That is the Question?

For those who may not know this I am a member of the QRPARCI Hall of Fame. I believe my selection was quite accidental and most likely those who are board members and regular members probably are wondering why as well. I am not a closet QRO guy hiding out as a dye in the wool QRPO guy; but freely admit my penchant for something more than 5 Watts!
There are many choices in our hobby so don't get snooty about having a DXCC certificate having done so running no more than 5 watts. All I can say is congratulations; but also be a ham and recognize others may not share your interest.
My interest in QRP is not driven by a desire to put a rig in a back pack, don foul weather gear and climb to a local mountain so I can operate in a driving snow storm and claim that I worked a station 200 miles away on 200 milli-watts SSB all the while braving off the elements.
Let me tell you why so many of my rigs end up being QRP. Early on I tried to build rigs that put out 50 watts from just the rig itself. For the most part I was terribly unsuccessful! Some how everything worked FB, until I got to the final amp stages where regularly there seemed to be problems with RF Feedback, bias issues and the heat problem creeping over to other parts of the rig. Was I being punished for running more than 5 watts?
What I did find is that almost 100% of the time everything worked great up to the 2 to 5 watt level coming out of the driver stages. Thus a solution -- build rigs that reliably put out 2 to 5 watts with no hiccups or burps and then add an outboard amp. So QRP level rigs for me was not to be a QRP enthusiast; but rather as a solution to some technical problems. I frequently run 600 watts with my homebrew rigs with no problems. On rare occasions I run my rigs straight through to an antenna running just 5 watts just to say I can run QRP but that is not my usual approach.
Now to the IC-Transceiver. While I intend to follow my usual practice of having an output in the 2 to 5 Watt range just to say it works flawlessly, there are some amps that look like they can be built in the rig itself without problems. One of those is a 20 Watt amplifier from K5BCQ which can be found at this link (scroll down as there are a lot of other projects on the page). Keyes and John know their potatoes so it is an amp that is "bullet proof".
So this is another piece to IC Transceiver. At the 20 Watt level you will get an order of magnitude (that is 10X for the OBTE) of greater contacts versus 5 Watts and thus a worth while approach. The 20 watts will also drive many of the MOSFET Solid State Amps to the Kilowatt level. But that is a project for another time.

Stay Tuned.

Pete N6QW

1/12/2018 ~ Design Considerations & Decisions

For the most part we will be building the basic K1BQT transceiver or I should say a major part of the design --very likely 51% but not all of it. Today's post will cover the original design and what we will be changing and how we will change it. Firstly the original article was for a single band (75M) and employed a rather exotic way of getting 30 watts (a 28 VDC RF MOSFET) to the antenna. Some 33 years later we have at out disposal many tools and techniques that weren't even on the drawing boards in 1985. We hope to do this in an ordered fashion:
  1. The original design used an analog VFO and crystal BFO. The obvious 2018 change would be a Si5351 which will handle both functions and costs $8 as a complete board. The control of the Si5351 will be an Arduino Nano and the display a color TFT. With a bit of shopping this can be had for a $20 bill. The Arduino using built in capability enables ready band changing and control of other functions --so a bonus. More on this to come.
  2. The transmit mixer stage which is a MC1496 has a broad band output which is fed into a gain controlled 40673 Dual Gate MOSFET (DGM) . If you look at the schematic you will see a trim pot connected to Gate #2 which is labeled "Drive". That is a nice feature --we will keep it, But we will first start by ditching the 40673 (unless you have one in a bin) and replace it with two J310's connected as a DGM which are much more readily available and can be had for 20 cents a piece. The output side of the 40673 in K1BQT's design is connected to a band pass filter (yes OBTE that is a BPF) and in turn that drives the IRFD1Z3 which has a low pass filter on its output -- the classic 3 pole. Today you would probably want something a lot stiffer than 3 poles! The IRFD1Z3 is literally "unobtanium" but it looks like the BS170 would work and I will runs some tests to affirm that choice.
  3. So N6QW's Plan would be to follow the DGM stage with a switchable Band Pass Filter and using the W3NQN's stock filter design follow the BS170 stage with these filters, again switchable.  Rick, K1BQT, was careful to note that if you placed his design on other bands --you needed more filtering. To recap we will be changing the driver stage to include J310's with a BS170 amp stage and more/better and switchable filters. There is some solid sense to have a LPF follow the BZ170. In the original design the IRFD1Z3 could produce 300 MW of output thus you could make this a Qrppp rig and bypass the final stage or pick off the output and run that into a transverter for use on VHF or UHF SSB. Lots of possibilities but definitely more filtering needed.
  4. While we are on filters, when I built the LM373 transceiver which can be seen at  I was faced with a situation, because of this being a single IC transceiver of how to add Band Pass Filtering without using a lot of exotic switching. The answer was two Band Pass Filters with one in the receive side and the other on the transmit side. So while it adds a bit to the project in terms of cost and hardware, I am proposing two sets of band pass filters. The original design did this! You will note the BPF ahead of the MC1496 receive mixer and we just discussed the one following the 40673. The only difference we will be having switchable filters depending on the band.
  5. The original design used a 28 VDC RF device the MRF138. That is one expensive device and was a bit of a problem in that portable operation would be difficult but not impossible. One approach would be like the Sideband Engineers SBE-33 vintage 1963 --it was an AC only unit and to use it mobile they had a DC to AC inverter. Small 150 Watt DC to AC Inverters can actually be had for a $20 bill -- but that is not so easily done if you want to take it trail camping. Technology offers us netter solutions today. One solution is to use an IRF510 and limit yourself to 5 Watts. Lots of QSO's can be had with 5 watts. Other RF MOSFET's from Mitsubishi (RD series) can put out a lot more juice at 13 volts DC -- like 20 watts. There are kits being sold that offer all that you need [Check the K5BCQ website for available kits.] Communications Concepts Inc. sells a Bipolar kit that will produce 20 Watts with 100 MW of drive --another option for you.
  6. Now comes the "how to switch the filters" part. We have previously identified three locations where switching is needed actually there are 5 places. 1) the LO, 2) Rx BPF's, 3) Tx BPF, 4) Driver Tx LPF and 5) Final Amp LPF. So how do you do this? We have many options and I will take a few minutes to look at a subset of the switching. Boiled down we have basically two options for the switching and those include diode steering and relays. Diode steering relies on the principle that under certain conditions a diode when biased properly can act as a switch for AC signals. Typically these are low level signals although a company located right here where my laboratory is located (Newbury Park, CA) makes high power RF capable diode switches -- these are like watts not microwatts. But for higher power levels (and most ham budgets) a relay does the job. I purchased a stock of surplus micro-sized relays and so that will be my option.
  7. We are now circling back to our Arduino and its control capability. In several transceivers I have used switches for input and for controlling the switching of the BPF's and LPF's. In the FPM-5 I used a two pole 6 position band switch. One pole provide input to the Arduino to change bands and the second pole powered on the appropriate relays commensurate with the band chosen. In the Big Kahuna rig a simple DPDT switch did the same job. In my KWM-4 I took advantage of the K5BCQ controller that produced a 3 digit BCD code as you changed memory channels. Not knowing any better , I took the 3 digit decode and decoded it using a 74 series chip that took in BCD and the output was a digital pin that went high with an open collector. The output from the IC fed a PFET that powered on the relays in the KWM-4. Later I found it could have been done with a single IC --a CD4028 -- same principle as what I designed. So we could generate a 2 or 3 digit code -- 2  = 2^2 = 4 possibilities and 3 = 2^3 = 8 possibilities and decode those for the band switching. Now we could just take an output from an Arduino pin  and "hot up" a 2N3904 and switch the relays. The uBitx from VU2ESE takes this one step further --it reads the frequency internally generated and automatically switches in the proper relays. In the final analysis I will use either the DPDT or a real band switch. Your choice. Lots of possibilities. [For those who lurk the EMRFD and uBitx forums --the decode switching was done 5 years ago by Pete the Genius.]


Today's journey was to explore some of changes we will be making to the original design and what we have dubbed the IC Transceiver. Essentially the IC mainboard will remain intact.

  1. The receiver front end will have switchable Band Pass Filters.
  2. The Driver stage will use the J310's configured as a DGM and the driver will be a BS170. This stage  will have switchable Band Pass and Low Pass filters.
  3. Micro-sized relays will provide the signal switching/steering except for the diode steering on the mainboard.
  4. The Final will be an IRF510 and have switchable Low Pass Filters.
  5. The Arduino Nano & Si5351 will provide the LO and BFO Signals.
  6. Band  switching will be either a DPDT Toggle Switch or Rotary Switch.
Stay Tuned there are exciting things happening.

Pete N6QW

1/11/2018 ~ More on Copper Coated Vector Board .

Firstly here is where you can purchase the Copper board. Yes it is expensive --about $28 for a piece. But if you follow the process -- you could likely get three mainboards out of a single piece. [DigiKey is the supplier.]
Now I have also done work with this type of board using Surface Mount Devices and the following two photos should expand your mind to see the possibilities. Once again Pete, The Genius is ahead of the curve. The process starts with a Fine Point Sharpie Pen and connecting the dots of the areas where you want to create an island. Next using a pencil draw a couple of guidelines around the area identified, which is then followed using a steel square and exacto knife remove the area between the guidelines. Leave at least one open hole in the island so you can connect wiring. [Yes Virginia this was done seven years ago and not invented last week by an OBTE on the EMRFD or uBitx Reflectors.]

In case you haven't guessed the hole spacing is 0.100 inch which makes it ideal for SMD application using the larger size 1208 parts.

This approach affords you the opportunity to rapidly prototype a circuit using short direct connections and a solid ground plane provide excellent RF properties. The other distinct advantage is that should you need to shield circuits a piece of scrap PC Board can be soldered directly to the mainboard. I have found it necessary at times to provide additional shielding and it was a simple matter to simply solder the shields in place. 
Stay tuned as we quickly move along with these projects -- you need to start drinking energy drinks and lots of coffee to keep up.
Pete N6QW

1/10/2018 ~ More Examples of Single Sided Copper Vector Board used in my Rigs.

Keep in mind short direct connections and a common ground plane are always the "best" approach when building RF circuits. Tell me when it is not? There are probably one or two OBTE who will tell you they heard something third hand on the EMRFD reflector that it was not --my response consider the source.
In 2007 (that was 11 years ago) I started building transceivers using a common IF frequency ~ 4.9152 MHz and at the same time was actively pursuing an elusive goal of a shirt pocket sized SSB transceiver. I have come close to getting to the shirt pocket SSB goal; but not the final goal --one built entirely in an Altoids tin --maybe in 2018?
One of the 1st attempts was a 17 Meter SSB transceiver and like many of my projects I built two versions --the first typically looks like crap and is a true prototype. The second builds usually incorporate the "ahh" moments where you realize the better way. The K1BQT 2nd build will take advantage of what I learned from the 1st build.
The 17M  transceiver used a couple of innovative approaches. First using the 4.9152 MHz IF places the LO above the incoming at around 23 MHz. For the OBTE -- 23.04 - 4.9152 = 18.1248 MHz which is of course right in the middle of the phone band on 17 Meters. So how does one get to 23.04 MHz. The main frequency control is a VXO (variable Crystal Oscillator). Using several crystals in parallel configured as a Super VXO it is possible to move the frequency 10 to 30 KHz and thus you have a VFO like action using crystals.
The icing on the cake is the number of cheap computer crystal available to us. In this case, one of the stock frequencies is 11.520 MHz. The OBTE will quickly say --hey that is not 23 MHz. But if you use a diode frequency doubler (Thanks to W7ZOI) you can turn that 11.520 into 23.04 MHz. Now the real beauty is that what is ever changed in frequency at 11.52 MHz is doubled. So a 10 KHz swing at 11.52 MHz is now a 20 KHz swing at the output of the doubler circuit.
But I soon found that I did not have full coverage of 17 Meters. Thus a second set of crystals was custom ordered (ouch $50) and using a small relay I could switch the bank of crystals used in the VXO. Now with four crystals I can cover almost all of 17 Meters. I am missing a 6 KHz of coverage from about 18.141 to 18.147 MHz. Keep in mind this pre-dates the Si5351 and now $20 would give you full coverage with a Color Display -- but again this was 11 years ago. I may yet retrofit this rig --maybe with a 1/2 size OLED.

The above photos show how the single sided board was used for the 17 Meter  transceiver. Two things came from this 17 Meter project which were used about 4 years later in the shirt pocket transceiver on 20 Meters. The two items are the single sided copper vector board and the crystal switched VXO. Actually I should also include --the same IF frequency 4.9152 MHz was used in both rigs! The 20 Meter Shirt Pocket Rig photos (V1 and V2) are shown below.

Again the real advantages with the single sided board are short direct connections and the common ground plane. Today we have seen two examples of transceivers that were built using the single sided copper vector board. Also don't discount the crystal switched VXO as a LO source and the choice of 4.9152 MHz for a homebrew Crystal Filter. [If this choice of IF was good enough for Elecraft in the K2 why not in your rig.]
I sense the excitement building --hang in there as what I am covering now will be very useful if you decide to build the IC Transceiver. Some other parts you need to start finding --aluminum spacers with 4-40 threads. Look for 1/4 inch and 1/2 inch high spacers. The initial size goal for the mainboard is 4.5 X 6 inches. I will know more once I go through the iterative process of parts layout.

BTW in case you would like to see the documentation for the 17 Meter Transceiver see the link below:
Yes Virginia, in addition to there being a Santa Claus there are hams scratch building real homebrew transceivers and the 17 Meter/ 20 Meter projects are original designs. So what are you waiting for --get off that couch and start building!
Pete N6QW


1/09/2018 ~ Alternate Part Sources for the IC Transceiver. Also Tribal Knowledge on the Construction Practices to Build the Rig.

I love it when someone can find better parts bargains for projects and so it is with my friend Bob, N7SUR. He advised me that the MC1350 @ $2.50 and the MC1496 @ $1.35 can be purchased from Dan's Small Parts in Missoula, Montana. Dan can be found via Google and indeed has a lot of hard to find parts and some amazing prices.
Several years ago I purchased some vertical Style S Meters from Dan and these can be seen on my Belthorn III and Big Kahuna SSB Transceivers. The cost was very reasonable. May need to look to see if he still has those meters.

About 10 years ago I did build the K1BQT transceiver for 20 Meters and was delighted with its performance. That rig was given to another ham and now my desire to build a second unit. But this one will be a departure from my extensive use of the CNC Mill as it will use a technique that is quite excellent and not Manhattan nor Isolated Pads. The construction by the way is probably as fast or faster than having a specially fabricated circuit board.
Vector (as in Vector Board) makes a single sided copper Vector board and comes in sheets like 4.5 inches by 17 inches long. It is not cheap but one piece is enough for several projects. The beauty of this board is that the top side is a common ground plane. So any connections to ground are simply soldered to the top of the board. Below is the W7ZOI HYCAS IF amplifier strip/Product Detector  as built for my JABOM Transceiver project. Once it was built and tested I soldered a copper strips around the sides to form a copper box enclosure. There was a trick here. The finished board was mounted on aluminum spacers during the soldering of the copper sides. Now when you are done the whole assembly can be screwed down to the chassis base plate. The second photo shows how the point to point wiring was done on the under side (insulated) of the single side board. Those who like to pick things apart (as they do on the EMRFD and uBitx Reflectors) there is only one connection that crosses over the wiring. [Further note -- this project was built 7 years ago and described in a QRP Quarterly Article. Pete the Genius was once again breaking new ground!]

Now I am going to share some Tribal Knowledge about how to make the part layout and minimize cross overs and have the parts laid out to minimize connections. In the case of the HYCAS it was an iterative (meaning doing several times) process that first starts with a piece of PLAIN (no copper) vector board and the schematic that you will use. Liberal use of small wood blocks and masking tape facilitates the process. Another tool is a metal cookie baking pan that is about 12 X 18 inches. Typically these pans only have about a 1/2 inch high side.
Start first by taping the wood blocks to the cookie pan base spaced slightly shorter than your plain vector board. Next tape the board to the wood blocks  and assuming the builder knows where is pin 1 start by inserting one of the IC sockets (yes 14 pin DIP Machined Pin Sockets, MPS) into the board. Using the schematic insert parts into the board so that you get a compact layout and visually see how to minimize connections and cross overs. Take small sections at a time to do this. When you are satisfied that you have all of the parts on the board for that section and that the connections are minimized and the shortest possible connections are used. Take a photo with you phone camera. You will use this photo to do the final layout on the copper board.
  1. Now as to the why use the plain board for the initial layout --it is the oil and acid on your hands. The trick is to minimize the physical handling of the final board to minimize any discoloration and difficulty soldering based on corrosion build up. You might consider wearing rubber surgical gloves during the final soldering process. I do.
  2. The plain board with the cookie pan enables you to stop work without having to clear off everything and just moving the pan out of the way keeps everything neat and tidy. It also helps prevent the loss of parts as the pan acts as a captive mechanism.
  3. The process really helps you understand the circuit elements as it goes beyond just stuffing a board with parts like the OBTE frequently experience without the knowing the why.
  4. The wood block are about 1 inch high which lets you push through the leaded components so that they are flush with the plain vector board. The blocks are a must!!!!
An important tool must be built prior to working on the final single sided copper board and this is shown below and is comprised of two parts. A 1/8 inch knob and a 1/8 inch drill bit. Resist simply taking a 1/4 inch knob and a 1/4 inch drill bit like the OBTE would do. This tool is used to remove a small amount of the copper material around a part that will be placed on the board and not grounded, meaning it will be connected to other components on the underside of the board. Before you insert any non-grounded component, twist the drill bit a couple of times to remove the copper around the penetration hole and then inspect the whole to assure no burrs remain.

The reason the 1/4 inch should not be used is that too much copper would be removed. You want to remove just enough so the parts are not shorted to ground but not too much to reduce the ground plane effect. In the case of the IC sockets I remove copper for every pin (14 or 8) and you will also find since I use machined pin sockets (a must) that each hole for the DIP sockets must be slightly enlarged to accept the machined pin sockets. If you don't know what a machined pin socket is --turn off your soldering iron and take up another hobby. The why of the MPS is to assure the socket doesn't float around and that you have a solid pin to affix components to and finally a solid soldering base.
This is a good place to stop --today we gave you an alternate source for the IC's, introduced you to the single side copper PC Board method of construction and shown a special tool you will need to build the project.
Pete, N6QW


1/08/2018 ~ Getting a "Head Start" on the K1BQT Rig

So OK you got some Amazon Gift Cards for Christmas and are wondering where to spend the loot. The very 1st thing you do is go to Bill's, N2CQR, SolderSmoke blog and click on the Amazon Link and begin your shopping for some of the parts to build this rig.
I just know there are many homebrewer's who simply can't wait to build this amazing rig --even before me. So if you have that kind of itch to scratch, then visit my website 
On that site you will find an amazing array of projects from the N6QW Laboratories and only one or two even hint of being Bitx related.
The project you want to view in detail is "The Big Kahuna" which is extensively documented. There are three pieces from that project that will be used with the IC Transceiver (That is now what I am calling K1BQT;'s transceiver.)
The three pieces are:
  1. The Arduino Sketch for the Big Kahuna uses the 9.0 MHz IF and thus already puts you in the ball park. This sketch has you use a DPDT toggle Switch for band change with 1/2 the switch providing the input to the Arduino to change bands and the other half provides voltage to the relay banks to select the proper set of matching Band Pass and Low Pass Filters in sync with band showing up on the display. The display is the very large 320 X 240 and offers some possibilities for displaying other data.
  2. Now Genius Guy that I am --the sketch includes the code for 5 Bands which are linked to five pins on the Arduino -- thus by selecting the proper pins you can steer your build to what ever two bands you chose. Like 80/20 or 80/40 or 20/15. Guys with a 9 MHz IF I have chosen to stay away with anything saying 17 Meters. Now if you change the Filter Frequency say to 8 MHz then you can use 17M; BUT you will have to change the numerical data in the code to account for the IF offset and the new BFO frequencies. You can do that --don't ask me to do it. The wiring of the display and the level shifter (CD4050) is embedded in the sketch.
  3. The Band Pass Filter Data for the 20/40 selection is in the Big Kahuna complete with LT Spice Simulation, plots of the curves and the component values. If you chose other bands you will need to develop the schematics -- the LT Spice schematics should be a clue for you. Don't ask me to do it
  4. The Low Pass Filter Data is a lift from W3NQN so you have the numerical data for the various ham bands. The calculation of the turns for other bands is your exercise not mine. This is a good time to venture out on your own.
So having these three pieces already available eliminates about 35% of the project that will need development. We will endeavor to use other N6QW building blocks such as the driver stage [EMRFD lift] and the IRF510. Thus even more hardware can be built ahead of the main IC board.
Pete N6QW

1/07/2018 ~ A Link to the 1985 HR Issue

Thanks to another Pete in very cold Illinois he found a link to the issue where the original article appeared.

Thanks Pete!

Pete N6QW

1/06/2018 ~ Coming Up in the Queue - Start Planning Your Moves and Locating Parts! (See Block Diagram Add)

K1BQT's XCVR from November 1985 ~ With 2018 Updates!
Visit Jameco Electronics and you can find the following critical parts
  • MC1350 IF Chip P/N 24942 Price $3.95
  • MC1496 (four required) Double Balanced Mixer P/N 23211 Price $1.95
  • IRFD1Z3 (not available anywhere) But I believe a BS170 will work
For the IF Filter (9.0 MHz) I will be using the Crystal Filter from the GQRP club. I believe they still have a very small quantity left in the bins. You will also need to find some 40673 Dual Gate MOSFETs or you can use two J310's configured like a DGM. The Final Amp can be a IRF510 (also at Jameco). This will be a two band radio --a simple toggle switch for your two bands of choice like 80/20 Meters or 40/20 Meters. Guys forget 17 Meters with a 9 MHz IF. My design will have separate band pass filters for the two bands.
K1BQT's design has a key feature (maybe that is where I got the idea for my last 2018 project) and that is the MC1350 IF amp chip is used on both transmit and receive. Also his rig not only had AGC but ALC -- just a few more parts. Like in my last rig --it will have a cool analog S Meter OR the S meter included on the Color TFT.
The updating will include the Arduino Nano, Si5351 and the 160X128 Color TFT display.
This is not the very next rig on the bench; but the info is being provided early so you can start to get organized. The first trick is finding the article. The Ham Radio Magazines were free on line. But someone evidently filed a law suit and they were removed.


I will create schematics of what I build since it is different than the original article. This should not violate any copyright issues. BTW the original article used the TO-5 Version of the MC1496 and the ones being sold are the 14 Pin DIP --not to worry I will provide the magic decoder ring.

Below is a block diagram of how this new transceiver (new for 2018) might be fashioned. The building blocks are pretty standard.

A Post Script --the Ham Radio Magazine cost but $2.50 and unlike the ham radio magazines of today did not focus on contests and operating news -- this was a publication for homebrewer's. (For the box top extra's this means something other than appliance operating your latest ICOM or Yaesu)

Post Post Script: On eBay currently is a IF board out of a commercial radio (being sold from Israel) that has three 9 MHz Filters on the board. I had an earlier posting about a rig now in work that uses two of the filters (USB/LSB). That rig is still in the queue for 2018. The board from one of the sellers costs $34 including the shipping . But also on the board are the critical MC1350 and several MC1496's. So this board already contains many of the parts. NOW a huge caution if you are unskilled with a soldering iron and the removal of parts from a manufactured board --this is not a good option for you for the parts other than the filters.
Pete N6QW

1/05/2018 ~ Listening to the new Rig!

The 1st SSB Transceiver of 2018 from N6QW ~ 35 years in the Making!
It only took 35 years but we now have achieved our goal. High marks for an Old/New Technology Rig. Get off that couch and start building --we soon will moving forward on another new rig --or I should say and old rig that has been reformed! You got to keep up.
Pete N6QW

1/03/2018 ~ It is alive!

I am happy to report the 1st QSO with the reformed rig and it was with a station in Hawaii, Thanks Norm for the 1/2 hour QSO. (An oddity in our 5X9 running a FLEX 6700 rapid fire QSO Mode.)

The D-104 microphone gives you an idea of the size. I was also constrained by what holes in the front and back panels existed as a result of the original build and several reincarnations. The upgraded changes include USB/LSB select, 128X128 Color TFT, a new driver stage (2N3904/BD139) and the IRF510 as a final amp. the IF is at 9.0 MHz.
Some changes to the main board include removing the homebrew diode ring single balanced mixer that was used as the Product Detector on receive and as the transmit mixer stage on transmit. A TUF-1 replaced all of that hardware. I also removed the homebrew diode ring balanced modulator and replaced that with an ADE-1. Man the new devices sure replaces a lot of old hardware.
I mentioned in an earlier post one of the problems I found with the original build -- a bad diode in the single balanced mixer used as the PD / Transmit mixer --this is what prompted the shift to the TUF-1 and while I was at it I changed out the original balanced modulator to the ADE-1. The TUF-1 is just below the GQRP Crystal Filter and the ADE-1 is mounted on a vertical board just behind the panel meter. You will see some open space behind the vertical board --all of the was formerly jam packed with Balanced Modulator components. The microphone amp was a 741 ( a staple for 1980's transceivers). Just behind the vertical balanced modulator is a brass shielded enclosure that originally housed the BFO. In that now resides a relay that switches power to the receive and transmit circuits that do not run continuously. BTW I bought these relays which have 12 VDC coils and are SPDT capable of handing 8 amps --from Jameco Eeletronics on closeout -- 10 for $6
Mind you again this was originally built in the 1980's and the architecture relied heavily on diode switching. On the receive side the 1st stage is a Dual Gate MOSFET mixer which was diode steered through the IF chain. The other half of the diode steering was the Balanced Modulator.
The IF chain used a pair of 2N3904's on either side of the 9.0 MHz Filter similar to what ON5FE used in his 1970's Transceiver IF Module. That stage is followed by a Motorola MC1350. This device was chosen so I could add AGC on receive and an S Meter. On transmit this stage has fixed gain applied. Following the MC1350 is the TUF-1 where on receive the BFO is diode steered and we have product detection where from there it goes on to the audio amp stage (2N3904 / LM386-3). On Transmit the LO is diode steered to the TUF-1 and this now is the transmit mixer.
Following the TUF-1 (on transmit) is a 20M Band Pass Filter and then on to a 2N5179 RF amp. The 2N5179 was the Hayward device of choice in many of his SSDRA circuits. From the mainboard we have the driver stage and the final amplifier.
One challenge I had was space -- the box was already pre-determined! Where was I to mount the TR relay and the Low Pass Filter. My mechanical engineer son (the one with the super knack) has decoded what I want for Birthdays and Christmas presents. Yes, Hardware! Thanks to son Nick I am well stocked on nuts, bolts, spacers and connectors! Here is how I resolved the TR relay and external amplifier switching. I used four 1 inch standoffs to mount the small circuit board to the same mounting holes as the copax connector. Right near that is the small circuit board built on the CNC that is the LPF. The connections are short and the assemblies fit in the cramped quarters
Below are a couple of shots of the Final Amp board (IRF510). I have designed a standard RF amp Circuit board that can accommodate most any RF device that comes in the TO-220 package style. Thus some of the island squares are not used for the IRF510. When I need a new board --chuck up a piece of stock in the CNC and press "Start".

I will continue to fine tune this rig as there are some functions the need to be completed. I have a small push button on the front panel that will initiate the Tune Tone. That wiring needs to be installed as well as build the three stage RC filter to take the square wave 988 Hz tone generated by the Arduino and convert that to something close to a sine wave which is then routed to the balanced modulator for Tune Up.
Pete N6QW

Well these are only new if you consider that they will be/are newly reformed old projects.

I often mention that I have two boxes of projects ~ one very large box with ones that sorta worked, worked once and died, never worked and finally never would work as configured. The other much smaller box are ones that work --and nicely I might add. So I have dug really deep into the very large box and pulled out three that in their present state are not air worthy; but the goal is to make them so. Along the way we will add goodies like digital VFO's, Color TFT display and only commercial filters. Frankly I have better things to do than screw around with Dishal software.
The first which I have already started is about 75% there and shown below. This was a solid state rig built in the early 80's and while it did work --was never quite what I thought is should be. Recently I found out why. I will cover that in a future posting.
By the way most of the stuff that is in the large box was built using the SSDRA [Solid State Design for the Radio Amateur]. Do what you can but get yourself a copy even if that means selling your EMRFD. I just think for someone who would like to start building radio projects EMRFD is not the 1st choice and SSDRA will get you farther and faster along the learning curve. Just my opinion but there is a sound basis for that opinion. I have found a good use for my EMRFD --it is a great bookend!
The above rig started life as a 20 Meter QRP rig with an analog VFO, Crystal BFO, 9 MHz KVG Filter and an IRF510 Final. This was not someone else's design but something I conjured up using building blocks taken from various publications and reference books. This rig was built Pre-Internet. Many of the circuit blocks are from Hayward and DeMaw and some pulled out of thin air.
I will document what I did and how the radio was constructed --for now just drool over the photo.
BTW I am now in therapy after participating briefly in the forum. I have since sworn off reading any more posts from that group. The uBitx is a superb rig and I will stop there!
Happy New Year!
Pete N6QW