[Milsurplus] SCR-274N VHF: More on Using Programmable Oscillators.

[David Stinson]

On subbing programmable oscillators for crystals:

While a real crystal from a reputable supplier like Bry,
AF4K, is always preferable, freqs are not always available
and multiple custom crystals are for people with more 
money than I have. This may give you an option.

Most of you know I had success replacing unavailable 
crystals in the 4-channel "ARC-5" VHF
receiver using programmable oscillators. 
Was listening to aircraft on 122.8 UNICOM 
carrying jumpers just this lovely morning.
The only problem with this 72-year-old receiver
is keeping the relays working.

Respectfully- I've heard all the arguments about noise 
and jitter, etc. These oscillators are much better than 
the ones made just a few years ago. I've used them 
on-the-air at fundimental and to feed multipliers. 
I have had no serious issues. Works with just about 
any Pentode-based crystal osc. 
Not enough drive for Triodes like the Pierce.

http://home.netcom.com/~arc5/ARC5/ProgOsc/ProgOsc.jpg

I finally got to work on the BC-950 transmitter.
$4 Epson CMOS oscillators at the crystal frequencies
(F/18) for 122.8 and 146.52 MC. Powered at 6.25V 
via one of those inexpensive (2-3 bucks) little "buck" 
DC-DC converters feed by the 24V A+ buss. 

http://home.netcom.com/~arc5/ARC5/ProgOsc/progosc1.jpg
http://home.netcom.com/~arc5/ARC5/ProgOsc/progosc3.jpg

Mounted that with some hefty double-sided tape.
The set works spendidly. 
Service monitor says the carriers are on 122,7997 
and 146.5200 and are clean.

http://home.netcom.com/~arc5/ARC5/ProgOsc/progosc2.jpg

I even made a nice contact- Don't ask.
I'm tickled to pieces.

GL OM ES 73 DE Dave AB5S