/***************************** Convert your 23 Channel Tram Titan IV to 40 Channels  *****************
                                                  01-2026


Basic Instructions: (not in order) 

o - Obtain a Si5351 Arduino or equivalent DDS-VFO  (I found mine on Ebay)

o - Remove 20 Mhz Crystal band and Channel Selector 
    o - Mode selection:  S6 Sect 4 remove the wires from the 20 Mhz Osc
        See pic for Tram Wiring :
        DDS pin D9 thru a 10K resistor to the USB tab on the selector switch (Sect4)
        DDS pin D9 thru a 10K resistor to the LSB tab on the selector switch (Sect4) (not a repeat)
        DDS pin D8 thru a 10K resistor to the LSB tab on the selector switch (Sect4)
        Note: the AM position is left open. 

o - Build a 9 volt power supply for the DDS-VFO (see pics)
 
o - Build a transmit keying circuit. T/R switch for the DDS-VFO (see pics)
    o - tap R235 (100 Ohm) for a 8Volt transmit source.

o - Pull (or remove) up one end of R610 to disable the original 20 Mhz OSC.

o - Pull (or remove) one end of R118 to disable the original 4 Mhz OSC.

o - Remove C114 and C118 
    o - Connect a 18pf cap between Q102 Drain and Q103 Gate (this bypasses the 4Mhz OSC.)

o - RIT: connect a 20uh inductor to Q104 Gate , the other end to the front panel RIT control.
o - XIT: connect a 5pf capacitor to Q601 Gate , the other end to the front panel XMIT control.

o - Connect the DDS-VFO  
    o - Solder the output of the DDS-VFO to C607 the L600 side (leave C607 in place)
    o - Remove C119,(next to Q103)  Remove C606 (cap to the Xmit pot) 
    o - connect an 20pf capacitor between C607 (L600 side) (output of DDS) to Q103 Gate (input to 4 Mhz 2nd mixer.)

 

o - Tuning: 
    o - Xmit LSB:  adjust C610 for center slot of any transmit channel
    o - Xmit USB:  adjust C609 for center slot of any transmit channel
 
    o - RIT: LSB The front panel Xmit control is a tad off to the left for center slot.
    o - RIT: USB The front panel Xmit control is a tad off to the right for center slot.
    o - XMIT/RIT  AM is center slot. 

Notes:
    o -  Schematic Sams Photofact CB radio Series CB-49
    o -  One unexpected issue with this Mod.
         The SSB offset for CH 38 USB and Ch 39 LSB 4.565 Mhz. Has a Birdie.
         Cause Harmonic related to the BFO oscillator. 
         Birdie present only in SSB mode on the above channels.