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I have a few CB ssb sets in my junk box.
It is time to use them for ham operation.
Those CB radios can be converted to 10 meter. However 10 meter propagation is poor.So I will make a transvererter to 40 meters.It should not take too much time to build. I have a few other projects that need to be finished.

Building a transverter from cb to one of the lower ham bands has been done before. I found a few examples on the Internet. I expected to find more though, After all a lot of these sets are available at low prices.maybe the quality of the cb sets is not good enough.

The CB radio that I will use is an Uniden 5500. This is supposed to be one of the better CB sets.A transverter needs just a few milli watts so I have disconnected the final and the driver stage. The radio now produces 1,5 milli watts. This signal sounds good on a hf receiver so the basics are ok. I think I will add 12 volts DC to the output signal while transmitting. That DC signal can be used to switch the transverter between TX and RX. AM transmission does not work anymore. That is fine, I don't need AM. Transmitting in AM mode produces a carrier. That is great for tuning the antenna.

A CB radio has a 10 KHz channel raster. However sometimes the space between two adjacent channels is 20 KHz. This raster is unusable so some kind of finetuning is required. The set has a clarifier we hams call it RIT. Maybe it can be modified to work during transmit. However it won't span 10 KHz let alone 20 KHz. So finetuning will be build in the transverter.

Design ideas:

I will build a (super) VXO at 20 MHz. This signal goes to one of the RF pins of a diode mixer. The transceiver is connected to the other RF port of the mixer.
The IF port of the mixer is connected to a band pass filter for 7 MHz. That is basically It. This transverter is bidirectional, no TX/RX switch is needed.
Of course the output is low, I expect 0.5 milli watts. The received 7 MHz signal will be attenuated as well but I guess that won't be a problem.
During TX the signal is amplified to 5 watts. Relais are used to switch between RX and TX. The 3db attenuators are used provide proper match for the mixer.