How to convert GE MASTR series radios from 450 to 425 MHz

  Three items need to be addressed:  1.    Helical front end [L301, L302, L303, L304, L305] needs more inductance. Open the bottom of the front - end and take out the American Beauty [150W] and unsolder the 5 coils.  Using  #10 solid copper, make a one third turn coil to match the coils that were taken out. Take off the enamel on the end of the original coil and solder the 2 coils together. After soldering the coils into the chassis, be sure to align the coils (by bending). 2.    Next is the oscillator / multiplier which needs a lot of work!  Pull the oscillator board out since it will be easier to work on. Solder a wire from H7 / F1 / brown wire to ground. Pull the brown wire off the board. This is the F1 crystal ground.  Unsolder the white wire at H3 and fold it back with a tie. Make a jumper and short the 10v  trace (red)  to where the white wire (receiver oscillator control) was attached.  Add a 2-4 pico farad capacitor across C407. Run a 7” wire from H6 / blue wire / compensation line to P903, pin 5. A FB slipped over pin 5 is great. On this wire install a ferrite bead - (low frequency type).  Install two chip capacitors (.001 - .01 uF) near  channel element on the 10 volt line and the compensation line to ground. Disc caps – OK. Install another chip (.001) at R419 to ground. Install a .01 chip capacitor on the channel element – pin 4 to ground. The compensation line really radiates RF. 3.    Next is the preamp.  Install a 10uF Tant. Cap across C2308. Install a .001uF chip capacitor across C2307.  Unsolder the metal shield on L2301. Solder a small solid wire (resistor wire) at the top where it is folded over and will form an X - capacity hat.   For Reliability:  Resolder: crystal –ch. ele., 6 pins on ch. Ele., 6 pins ch. Ele. on osc board, 7 pins, J602 and 7 pins P903/IF DET Board Stabilant: 6 pins/ch. ele.,  7pins/J602, 7 pins/P903, 5 screws on preselector (L301 – L305),  3 screws (L306 – L308) osc/mult.  Info: Osc/mult board @ 425 mhz, Hi side inj. Xtal = op. freq.+ 11.2/27                              L401 - 3X     48.46 mhz                              L402 - 3X    145.4 mhz                              L407 - 3X    436.2 mhz Compensation range: -10 to 50 degrees C, 3.7v to 4.3v   ****** For best  (lowest) distortion*******   Always pick the IF det. Board that has the adjustable IF cans and not the fixed inductor boards. These boards let almost 4 ¼ Khz dev. pass vs about 3 Khz for the fixed inductor.