In a conversation with N2CQR the other day, I commented that one of the most popular posts on this blog during 2024, so far, is the 30M CW Transceiver. Bill mentioned that he thought that perhaps a step up would be a DSB Transceiver. I suspect he was drawing upon his experience with the high school students and the DCR project. The students were not really interested in CW but the thought of voice contacts peaked their interest.
That came across to me as a DSB Transmitter and a Direct Conversion Receiver linked with a Digital VFO.
Before jumping off into one of my standard components, the MC1496, it would be well to address what is Double Side Band (DSB) and who is the Oracle at Delphi on the subject.
My simple take is a DSB transmitter is the workaround for the lack of a SSB Filter. In effect you
transmit on both sidebands (like AM) but no carrier is present. The circuitry is simpler and no BFO or CIO (Carrier Insertion Oscillator) is needed as the LO (or in the case of the Analog aficionados LC VFO) is the only RF source needed for either the Receiver or Transmitter.
The Key circuit modules for the Direct Conversion Receiver (DCR) and Double Side Band Transmitter are the Balanced Modulator and the Product Detector. These can take various forms such as the passive Double Balanced Mixer with the diodes and toroids or active devices like the MC1496.
The Gurus for DSB Transmitter are many but one is notable and that is VK3YE, Peter Parker. Peter has a ton of You Tube Videos and a large segment covers DSB rigs. Of consequence is that Peter's designs typically are spare in the design and complexity with the added bonus of the use of very common parts. Read low cost, easy to build and practical!
Also notable is N2CQR with his videos on DSB transceivers. I think one video highlights his winning the ARRL Northern Virginia DSB section in one of their contests. Like VK3YE, spare, common parts and practical.
My offering in the DCR/DSB project arena is the MC1496, Double Balanced Modulator, Demodulator and Mixer Integrated Circuit.
For perhaps 50 years I have used the MC1496 and they still are available. This device was also popular with the commercial manufacturers and can be seen in Ten Tec and Yaesu Radios.
For me, one part of that equation for such a transceiver project exists with my MC1496 Direct Conversion Receiver that was published in SPRAT. There is no one more surprised than me that a DCR can sound so good. That article was well received by the SPRAT community and many were replicated using the MC1496 and the Si5351 for the LO.
Returning to the MC1496 data sheets, application circuits were published that focus on the Balanced Modulator and the Product Detector. Figure 25 is the basic DSB transmitter kernel and Figure 28 is the receiver kernel.
For my DCR receiver we added the Band Pass Filter, the RF Amp and an Audio Amp stage. the details to build the MC1496 DCR are here.
For the DSB transmitter we need a Microphone Amp stage (yesterday's posting) a Pre-driver (BFR106), a Driver stage (2sc5706 or 2N2219A) and the final an IRF510. Don't forget the W3NQN Low Pass Filter. Remember our posting on standard components? They sure are present in this suggested effort. In fact if you visit :
Here you can find the designs for these other pieces that can be strung together to form the DSB transmitter. All of the building blocks exist and are documented so it is a matter of tying the blocks together.
A couple of years ago I did diddle a bit with trying to kluge together a DSB transceiver and I think there may be one or two You Tube Videos on that effort.
Of note is that the Digital LO used TWO clocks of the Si5351. Using the clock enable clock disable functionality in the code I turned off/on CLK0 and CLK2 depending whether you were receiving or transmitting. Thus a separate feed to the DCR and the DSB. The PTT sent a signal to the Arduino to do this
The cost would vary depending on how deep your junk box is and your level of creativity. Certainly those with a bent toward fundamentalism would bypass the MC1496 and take the homebrew DBM (Diodes/Toroids) route and an Analog LC VFO.
As my ancestors would say: All Roads lead to Rome. With certainty such a simpler approach would get you there and so I won't discount that as a potential build. For me, however, I would use the MC1496 and the Si5351.
The biggest challenge in building such a radio is to have a cogent answer when the guy at the other end with his IC7300 says he can copy your opposite sideband. It is perfectly legal to use DSB, although you will get the proverbial load of crap about using more spectrum. There is an answer for that, but it can't be mentioned on my G Rated Blog.
Regrettably, likely no builds will result from this posting but it is another opportunity to start a homebrew journey. I also like that this can take a building block approach. Build the DCR and use an analog LC VFO. You have avoided at this stage using the Arduino/Si5351. Once that is working and you see the benefit of the DCR then add the Arduino/Si5351. Next move on to the DSB transmitter building on the DCR base background. Chunking the project makes it less onerous than just dumping a box of parts on a card table and wondering what goes where.
A really clever homebrewer would figure out how to use all of the boards from Todd at
to build the DCR like the ADE-1 for the Balanced Modulator/Product Detector and the BFR106 for the RF Amp stage, He plans on selling the modules from the P3ST so the Driver and Final would be nailed. Lots of possibilities including the BF998 board as the Product Detector. You get the drift -- much of the work has been done for you -- so get off the couch and heat up the iron.
73's
Pete N6QW