Modifying RF channel of RS modulator

[old_tv_nut]

Well, to illustrate the perverse nature of inanimate objects:

I hooked up the modulator and a D/A converter through a reversed splitter to my CTC-5. Worked fine, except the channel 6 frequency was far enough off to require a good rotation of the fine tuning knob. In the process, the fine tuning broke (doesn't do anything on any channel), so now I'll have to fix that. (It had been binding to the channel selector, and still does, so the break is somewhere beyond the binding point. I'm hoping that there is minimal damage and I just lost some sort of coupling clip or the like.)

Also, the modulator board is fastened to the TOP of the enclosure, which means I can't re-tune the channel 6 frequency without taking it all apart again. When I do that, I'm going to drill an access hole in the top of the enclosure.

[zeno]

You probably cant get this to ch7. after ch6 you hit FM radio
then aircraft ( AM ) then public service hi band. If it can
be forced to work it will probably be crappy.....

73 Zeno
LFOD !

[old_tv_nut]

Originally Posted by zeno

You probably cant get this to ch7. after ch6 you hit FM radio
then aircraft ( AM ) then public service hi band. If it can
be forced to work it will probably be crappy.....

73 Zeno
LFOD !

Probably true. Apparently, from the fine tuning result, I didn't get all the way to channel 6.

There are multiple possible problems going higher, such as, the oscillator might not run at the higher frequency; the modulating element may be partially bypassed by stray capacitance, reducing the modulation depth; and so on.