[ARC5] T-11 Crystals

[David Stinson]

----- Original Message ----- 
From: "Robert Eleazer" <releazer at earthlink.net>

>I have a few ARC T-11 transmitters and in a moment of unusually intense 
>insanity last night decided I should try to put one on the local Unicom 
>frequency, 122.975 MHZ,
...
> It says that the crystals operate in a Pierce circuit at either 1/12 or 
> 1/18 of the operating frequency....

First:
Likely more than one person is going to jump on you about
how using this gear to talk on modern aircraft freqs is "illegal"
because it's not "type-accepted."
FWIW, I don't think there's an FCC agent with his DF-geared
SUV in your parking lot, and a few test transmissions at
2-watts out to a receiver across the hanger aren't going to be heard
by the nearest monitoring station.
But there are people who worship rules, even when they
make no sense at all in this situation.  I wouldn't hesitate to
do such "test" transmission, but I wouldn't be doing
a bunch of QSOs with passing flyboys, either.
Well.... maybe one or two.... or three.....  YMMV.

Crystal freqs you need are either  10248 or 6832.
I will dig in my stock, but an old original is unlikely
for that freq, since it's a "new" 5 KC channel.

If you do manage to find "vintage" crystals for these,
they will oscillate off that freq to one degree or another.
Most of the old CR-1 crystals oscillate high.
This wasn't a big problem in 1946, since the receivers were
broad by design.  If you're going to talk to modern equipment
with their 5 and 10 KC internal filters, you need to be on frequency.
I did this in my "type-17" A.R.C. set by using a 5-30 pFd variable
across the crystal to "rubber" it onto frequency.

This brings me to a project which is still in the "noodling" stage.
"New" crystals can be ordered, but the price is prohibitive-
$40 to $50 for one!
But there is an alternative- custom frequency clock oscillators.
You can order these programmed for any frequency you like
for just a few dollars each.
Voltage derived from the filaments will power them.
May or may not need a little "buffer" stage after the
output.  This would be easy to build and install
right at the crystal socket.
This on my "hot project" list, which means I just
might get it done this year ;-).

Now don't write me saying it won't work-
yes; it will.  Just got to "get it right."
When I do, I'll write it up.

GL ES 73 DE Dave AB5S