Some were HC-18 wire and some were surface mount. This will give a spread all the way up past 28.7 MHz. I further purchased standard computer crystals at 9.49, 9.545, 9.625, 9.8306. I found two CB crystals in HC-25/U holders at 9.510 and 9.555 MHz. I found that if the bank of six were moved up to 9.5 MHz that would move the frequency up to 28.3 MHz and beyond. Originally the bank of six crystals were in the 8.1 to 8.4 MHz range. In the case of the Midland the bank of four frequencies are 11.0035, 11.0135, 11.0235 and 11.0425 MHz. These two models include the Midland Model 13-883 and the Pace Model Sidetalk 1000M. Two radios have been converted and initially the results look very promising. A majority of the synthesizer circuitry is dedicated to summing and mixing the various frequencies to generate the injection frequencies above and below the IF (which is set by the 7.8 MHz crystal filter).įor the conversion process to work with some semblance of logic in keeping the channel sequence, the bank of six crystals is the one that will be changed while the bank of four is kept in tact.

In the later case since the LO frequency is higher this results in a sideband inversion previously mentioned. When supplying a Local Oscillator signal above the operating frequency the mixing process (subtractive) results in a sideband inversion. Typically in the CB mode for USB a mixing frequency at 34 MHz was used and for LSB and AM 19 MHz was used as the Local Oscillator. Thus the mixing process in receive and transmit was shifted to LSB or USB depending on whether the Local Oscillator was above or below the Intermediate Frequency (IF). To switch between USB and LSB, in lieu of using two crystals, injection Frequencies 7.8025 MHz above and below the desired operating frequency are generated. One popular SSB generation scheme used by many manufacturers was to employ a 7.8 MHz Crystal Filter and the carrier frequency was generated at 7.8025 MHz which typically gives an Lower Sideband output when used in an additive mixer stage. Typical frequencies for the banks of crystals were in the 11 MHz range for the bank of six and in the 7 to 8 MHz range for the bank of four.

Interestingly the first three crystals in the bank of four are separated by 10 kHz but the last channel is 20 kHz. Then the second crystal in the bank of six is mixed in succession with the four crystals to give channels 5 to 8. The bandswitch is arranged so that the first crystal in the bank of six is mixed with the four crystals in succession so that at initiation that would give channels 1 to 4. The typical crystal synthesizers uses two banks of crystals arranged in a bank of four and bank of six arrays. With crystals that raised the possibly to utilize commonly available inexpensive Computer Crystals to move the frequency to 10 Meters. After digesting those inputs I chose to look at the 23 Channel units since many of these radios use Crystal Synthesizers.

I received many helpful inputs and suggestions. Untitled Document Conversion of SSB CB Radios to 10 Meter QRP OperationĮarly in 2009 I posted an inquiry on the QRP-L Reflector about any and all that may have converted SSB CB Radios to 10 Meters.

Pace sidetalk 1000m schematics