Uploaded November 2024 | Updated September 2026, 3 weeks ago
Some 60 Years ago the R L Drake company introduced the TR-3 as a response to the Collins KWM-2 Transceiver. (Close but no cigar). It has a few shortcomings like only a 4 pole filter, two of them, for SSB and that has some issues. The idea is that the BFO is fixed at 9 MHz and the two filters one above and one below the BFO are switched in line depending on whether USB or LSB,. In time one of the filters goes wonky and then you can only do one side band per band. It gets more complex than that as what will work on 40 and 20M gives you USB on 75M and LSB on 15M.
These soup can filters as they are known as both 4 pole filters are soldered inside of a "soup can".
K9SUL has a fix where as long as you have one good filter, he disabled the 9 MHz BFO and installed an Teensy Micro-controller and a Si5351. The front panel switch essentially selected one of two filters. Now it selects one of two BFO frequencies. Another possible fix is to install a commercial 9 MHz, 8 Pole filter and then use the K9SUL approach of selecting either the USB or LSB frequency in the Si5351.
This will move the TR-3 up a notch. The TR-4 is a better transceiver.
Some 60 Years ago the R L Drake company introduced the TR-3 as a response to the Collins KWM-2 Transceiver. (Close but no cigar). It has a few shortcomings like only a 4 pole filter, two of them, for SSB and that has some issues. The idea is that the BFO is fixed at 9 MHz and the two filters one above and one below the BFO are switched in line depending on whether USB or LSB,. In time one of the filters goes wonky and then you can only do one side band per band. It gets more complex than that as what will work on 40 and 20M gives you USB on 75M and LSB on 15M.
These soup can filters as they are known as both 4 pole filters are soldered inside of a "soup can".
K9SUL has a fix where as long as you have one good filter, he disabled the 9 MHz BFO and installed an Teensy Micro-controller and a Si5351. The front panel switch essentially selected one of two filters. Now it selects one of two BFO frequencies. Another possible fix is to install a commercial 9 MHz, 8 Pole filter and then use the K9SUL approach of selecting either the USB or LSB frequency in the Si5351.
This will move the TR-3 up a notch. The TR-4 is a better transceiver.
