[ARC5] tuning knobs (and local controls)

[Mike Morrow]

Rob wrote:

>Sounds like the demand for knobs is still there after all these years.
>Has anyone found a print of the part, or does one exist, and see if some machine 
>shop could make a quantity to satisfy demand. during these slow times, I bet there 
>is a shop that would make a quantity for a resonable price.

The standard part number for the local tuning knob is A.R.C. 6743.  Have you
examined one?  If an exact (or even just a very close) reproduction were to be
custom made in small quantity, I believe each would cost well above $100.

Original A.R.C. 6743 units show up on ebay fairly often, and even if the bidding
goes high, it is very likely that the price will still be far below even a
low-ball cost of a faithful reproduction.

There's the other standard tuning knob, the A.R.C. 9554.  This is actually
a local tuning key that is screwed on a storage base on the tube cover of the
AN/ARC-5 receivers only.  It was officially supplied only with the stabilized
communications receivers (R-25, 26, 27), which were designed to be lock tuned.
The receiver could be adjusted to frequency by the ground radio tech using the
9554 key, then the key could be turned backward and screwed down over the tuning
spline port.  The 9554 would be much simpler (but still not simple) to reproduce,
but it would be very marginal for routine use because of loose engagement of
the tuning spline and small knob diameter.  The navigation receivers (R-23, 24),
never lock tuned, were not officially supplied with the 9554 key, but I've seen
a couple that had one.  (The A.R.C. 9554 key is almost always missing from the tube
cover, and its a bit of a rarity too.)
  
An appropriate-sized piece of copper tubing can be driven over the spline teeth,
and a tuning knob then attached to that tube.  That's what I used 40 years ago when
I wasn't concerned about duplicating original configuration.

This talk about local tuning knobs leads to discussion of the next addition to
be made:  The receiver local control box.  The FT-260-A (SCR-274-N) and C-24/ARC-5
local control adapters are much rarer than the tuning knobs.  In addition,
these adapters do NOT have audio jacks.  Those jacks are on the receiver mounting
rack.  Thus, if one really wants a faithful, as designed, locally controlled
receiver, then a tuning knob, local control adapter, and receiver mounting rack
will be required.  To make it look good, the shock mount for the mounting rack
is also needed.  Authenticity is seldom easy or cheap!

Mike / KK5F