[ARC5] [Milsurplus] ARC-2 use ?

[David Stinson]

I have a nice ARC-2 which Mike Hanz helped me get running.
On the original dynamotor with mount and control box.


I tried the "change the IF interstage coupling caps"
but there is a snag with that:
The connections between modules and IF cans are made
with tiny coaxial cables, and the center conductor has a very
low melt-point; trying to disconnect these cables to facilitate
changes, even with a lower-temp setting on the soldering iron,
damages the center conductor's insulation.  It's very
easy to melt it into a short.  One cannot just replace these with
regular wiring;  the ARC-2 design uses these shielded cables and
the metal-envelope tubes to prevent feedback between stages.

IMHO, the limited amount of improvement gained by trying to
change those caps is not worth the real risk of damage.
If you want to use the ARC-2 on CW, use an external audio
filter.  Don't set the filter too narrow.  So many people, rather
than train the "filter" between the headphones as we did
as Novices, make the mistake of setting the digital filter in the
"computer-with-an-antenna" they call a "radio" to 50 Hz or
narrower.  They call CQ and someone answers them 100Hz off.
He never hears the reply.  I believe a lot of the decline
of CW QSOs can be laid at the feet of misused "features."

If one replaces a metal tube, you must use a metal replacement.
Everything is so crammed into the limited space in the ARC-2,
if you replace a metal tube with a glass, removing the metal shield,
feedback may occur.

One change I very much recommend if you're going to do CW
with it:  increase the BFO injection capacitor from 5 or 10 pFd
to 50 pFd.  The stock BFO injection is weak.  This simple and
reversible change will make a great improvement.
I prefer to use the ARC-2 on AM despite the broad IF.
If you were a Novice in the early 70s, your brain
will remember how to "pick them out of the pile."

I like the ARC-2 a lot and it has a place in my retirement shack,
assuming the Bony Old Man with the hour glass leaves me
be for a few more years ;-).
I once accidentality left the ARC-2 on for 18-straight hours
with the dynamotor chugging away.  No problems.

GL OM DE Dave AB5S
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