Thursday, June 29, 2017

A New Line of Transceivers ~ DifX


Transceiver Architecture 2.26

Yesterday we swapped out the 12.7 MHz filter pair for ones operating at 16 MHz as we suspected there was an issue with the 12.7 MHz USB filter (actually the LSB Filter --sideband inversion). I also opened up the tuning range so that the rig will tune from 300 kHz to 30. MHz which now lets me check out the performance across the HF ham bands. While tuning 15 Meters I ran across one of the Thirteen Colonies Special Event Stations. I made a short video of that station. The configuration is a the MMIC as the RF amp stage, no band pass filter and just the two Plessey amps. The Mixer and Product Detector are ADE-1's.


Houston we have ignition, the bird is flying!


Today I wired up the Si5351 board plus the display and that worked well. Here are some snaps of the assembly and while I was at it I used the FFT function on my Rigol DSO to look at the outputs from the two clock generators. I was pleased.
This is the BFO at 12.7 MHz (fixed).

This is the LO at 26.9 MHz

In both cases the output looks pretty clean. Try that with an AD9850 and you might be surprised what you see.
Below is a video I took of the rig operating on 20 and 40 Meters. To change sidebands all is required is a DPDT switch with one half powering on the proper steering diodes for the mode selected (USB/LSB) and the other half of the switch tells the display which sideband should be displayed.
Some further tests not shown in the video is where I tuned in WWV at 10 MHz and then switched the sidebands back and forth and there was clear copy of the voice announcements at either sideband setting. I did the same test with one of my SSB rigs (Ten Tec Omni 6+) where I set the frequency and then speaking into the microphone transmitted into a dummy load in USB and then LSB. I changed the filter on the test rig to match what was used on the Omni 6+ and perfect copy with either sideband. There was no changing of the Omni 6+ dial so the sidebands are in sync depending what filter is in line.
This was a great day. The next step is to complete the wiring of the 1st mixer and then do the up-conversion test at 45 MHz and then down to 12.7 MHz. Basically we know the back end is working and so now can concentrate on the front end.
Stay Tuned! De N6QW --Pete 73's.