I've made a number of modifications to my FRG-7 over the years.
One of the easiest changes is to replace some of the knobs with
more convenient styles. The toggle switch between volume and mode
switch selects a 3 kHz Collins
Mechanical filter.   The AM/ANL position of the mode
switch has been rewired to switch on a crystal oscillator at
exactly 455.00 kHz. When the received station is zero-beat with
this, the Digital Display reads the exact carrier freq.
Visible in the bottom view are several of the mods. On the lower right is the added mechanical filter. On the upper left is the added buffer PCB board for the digital display. The added PCB board on the upper right side is the 455.00 crystal controlled BFO.
This closeup of the added Digital Display buffer board also shows
the switch which selects the mechanical filter, and also on the lower
right, a pair of 455 kHz ceramic resonators. Replacing the IF amplifier
emitter bypass capacitors with ceramic resonators sharpens the response
of the IF amplifier.
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Copyright © 2004 John Kolb Last revised Jan. 3, 2004