Return of the Simpleceiver Plus!
8/23/2017 ~ Audio Amplifier Time.
I am starting the project with the audio amplifier as it is "my process". You can start wherever you want; but by starting from the back end and working forward, each piece that is added becomes a part of the test system.
Long standing I have a thing for not building the discrete part audio amp as it uses too many parts, usually results in wiring errors and gives only marginal performance. You are welcome to use anything that you prefer but you are on your own if it is something other than the two suggested circuits.
The first circuit shown below is one of the pre-amp stages and this has been simulated in LT Spice. Convince yourself by actually using the software and look at the results. I strongly recommend that builders do this simulation to learn the power of LT Spice.
The Upper Plot Shows the Gain is Flat over the Audio Range.
Those wanting more juice (and what is in my Simpleceiver) is the circuit below which uses a low noise version of the NE5534 followed by the LM380. This hummer is good for in excess of 1 watt output. This circuit was originally developed for use in my KWM-4 and simply reproduced for use in the Simpleceiver -- no wimpy audio here.
Either circuit will work well with the project although the first probably has less current drain which may be a consideration for those who simply have to drag a rig out to the middle of nowhere and try to make 10000 QSOs on a Saturday afternoon. Most of my stuff is intended to stay on the desk but for portability the 2N3904/LM386 is a less of a current drain.
I got overcome by other commitments on 8/22 and today does not look any better. But I still plan to build a version of the 1st amp on a small chunk of perfboard. Stay Tuned.
8/22/2017 ~ This project is one fast moving Freight Train and I just hope I don't get run over in the process as I have to really move fast to keep up. Let me explain.
Previously I had mentioned about building techniques such as my approach using the CNC machine or the W1REX MePads or plain old Manhattan style. Several blog readers taking this one step further have designed boards using technologies such as ExpressPCB, Toner Transfer and KiCAD. Shortly I will be showing their work BUT these kind souls have also provided links where you can download the board information/files so that you can have your own PC Boards fabricated.
Since the same basic template will be used for many parts of the project having access to multiple universal boards will facilitate the building of the entire project and also hopefully minimize wiring errors. While not a sure cure for mistakes (or is it misteaks) it does remove some of the obstacles.
The first input I got on a board design was from Bob N7SUR who came up with a Manhattan Pad layout using ExpressPCB and the board is small like 1.5 X 1.7 inches. Since there will be many such boards in the project a compact layout keeps the overall project to a reasonable size. I should note that Bob made this layout before I revised the layout to include T1 which is the matching transformer but the board will work as is -- just install the transformer in place of C3 and add the 22K in lieu of C2 and the Coupling cap to Gate 2. Thanks Bob.
Next we have some help from VK land with Greg who has designed a Board using KiCAD which seems to be a favorite among many homebrewer's. Below is the output from the KiCAD files and here is a link where you can download the KiCAD files. Thanks Greg.
This is a Zip file which Greg has temporarily placed in this location. We are evaluating a better method for some sort of repository to hold the info so it can be downloaded. That may involve the use of the github of which I am in the dark ages of how to execute so that will require some study on my part.
Finally we have DuWayne KV4QB. If do a search on this blog from the earlier project documentation you will see that DuWayne provided a complete Schematic of the Simpleceiver. Now this time he has provided a layout using the Toner Transfer method and there are also link to a dropbox where you can download the artwork.
And for those of you with better eyesight than N6QW here is a SMD version from DuWayne.
Here is the dropbox link from DuWayne:
Thank you Bob, Greg and DuWayne! Given this range of options for the build -- there is no reason for you to remain seated on the Couch. Start collecting those parts! This is exciting to see so much interest in the rebirth of this project.
Later today, I hope to add an audio amplifier to this posting so you can start collecting the amplifier parts and building the 1st stage of the project. Just to mix things up I plan on building the audio stage on a piece of perfboard currently available from All Electronics --- the board size is about 1.5" X 1/5".
BTW any suggestions about the best way to archive the files for downloading would be most appreciated.
8/21/2017 ~ Some updates and new information. First let me say that I have received over a dozen replies (world wide) from fellow homebrewer's who want to join in on the fun.
I have updated the schematic / pictorial layout shown yesterday to include a matching transformer into Gate #1 and to add the pieces not originally shown for Gate #2. The Gate #1 matching transformer is a 3 turn Primary to a 20 Turn Secondary wound on a FT37-43 core. I tried to keep all interfaces at 50 Ohms and this transformer T1 matches 50 Ohms to the forced input of 2.2K Ohms. The match is 1:44 and with the 3/20 Turns Ratio you get 1:44.4 (close enough for Government work. I also included the schematic from the LT Spice Simulation. If I can figure out how to link to the .asc file I will do that otherwise you will have to replicate the drawing in your LT Spice.
I did receive a technical question about the 2.2K resistor on Gate #1 and was referred to Solid State Design for the Radio Amateur Chapter 6, Page 124 Figure 19 where we have a Naked Gate #1. (No 2.2K). Well I responded that I got that from Hayward and never questioned its use. Actually in going back over my hen scratch notes I found that it was DeMaw in his W1FB Design Notebook Page 139, Figure 5-22 where he uses 5.1K on Gate #1 for several of the 40673's. I think I might have used the 2.2K to facilitate a 1:44 match.
In my response back to that input I suggested that different values of the Gate #1 resistor be tried (including no resistor) and use LT Spice to simulate the response. That should extend the comfort zone as to whatever to use, if any resistor, and what value. Let's use the tools we have.
The J310's can be replaced with 2N3819 with a change in the Source resistor to 120 Ohms. So Ok here comes the question why did you do that -- well I used LT Spice and found that 120 Ohms worked best with the 2N3819 and 680 Ohms worked the best with J310 -- use the tools we have.
I am presenting this circuit now so that prospective builders can start collecting parts. Noteworthy here is that the simulation used the LO (BFO) frequency of 7.030 MHz. This means you could build a simple 7.030 MHz Oscillator (Crystals can be purchased through ESE, QRP SPRAT or Halted Specialties [HSC] out here on the left coast.) Then with a simple oscillator connected like a VXO you could tune around the 40 Meter QRP CW watering hole. Or build the amazing PS Kang 160 KHz VXO with a single 7 MHz ceramic resonator and tune the whole band.
The next piece that I will highlight is the audio amplifier and then the Band Pass Filter and finally the J310 DGM RF amplifier. So while you are collecting parts for the PD get two sets as you will need those for the RF amplifier stage. BTW the RF amp stage will have a gain control. The last piece will be the LO and we are looking at a conventional Analog VFO (shudder), a crystal mixed heterodyne VXO and finally the Si5351. The Si5351 is the most desirable in a configuration where this is turned into a SSB transceiver as it can supply the LO and BFO all from the same board.
There was a 22 part series on the Simpleceiver that was done in late 2015 and early 2016. Using the search block on this blog you can be connected to that earlier work.
Stay Tuned & 73's
8/20/2017 ~ I have already received some feedback from several readers about their desire to participate in this project. So here is a little more information about how the project will progress.
There are many ways to initiate a radio project with some advocating building the toughest nut to crack as a first item such as the Analog VFO or a Digital VFO and then follow on with the easy stuff. While my preference is to always start at the back end and work your way forward so that what is built and tested then becomes part of the test system for the next stage to be added. That is how this Simpleceiver Plus project will progress and the first element will be the audio amplifier stage.
My plan is to try to use / reuse a common circuit in as many places as possible since that affords an opportunity to minimize the numbers of different parts used and a common building block enables/facilitates trouble shooting. That common building block is two J310s configured (mostly) as a Dual Gate MOSFET (DGM). I now have this common J310 DGM circuit element configured as a Microphone Amplifier, RF Amplifier, IF Amplifier, Oscillator, Mixer and Product Detector -- we are just getting started here. Along with this is the extensive use of LT Spice Simulation software (a free download from Linear Technology). Thus you have a solid technical basis for the design that has been simulated with known results and thus enables experimentation to evaluate circuit changes and improvements.
Because the DGM has four connections much like a Tetrode vacuum tube, Gate 2 affords us the opportunity to use this port as a secondary signal input port for applications such as in a Mixer or Product Detector. If however a variable voltage is applied to Gate #2 it then becomes a variable gain amplifier stage which is desirable for application involving the addition of Manual Gain Control or AGC. Hopefully you are now seeing the rationale behind my choice of design approach. Stay Tuned!
There may be a good chance of a group project being undertaken called the Simpleceiver Plus, much like the LBS project. Only this time it will be done incrementally with hopefully the blog readers following right along as we build first a Direct Conversion Receiver and then either a DSB Transceiver or an uptown SSB Transceiver.
In line with keeping it simple get a stock of J310 FET's as these will form the basic building blocks for the project. Most of the circuits will use homebrewed Dual Gate MOSFET's made from two J310's. In many cases LT Spice Simulations will be provided so that the builder can "tinker" with the circuit elements.
Below are two videos where you can see & hear the Simpleceiver in action. Yes, initially it has the dreaded Analog VFO and a homebrew Crystal Filter built NOT Using the Dishal Method. Listen closely to how the filter sounds. The IF is at 12 MHz so a 5 MHz LO gives you the 40 Meter Band.
Let me know if you would be interested in building along with me on this project.