[Milsurplus] [ARC5] Interesting ARC-3

[COURYHOUSE at aol.com]

Oddly enough  we had  ARC-3 units as  backup   VHF  tower com. and Guard 
Channel   units to back up BC-640 tx and  BC-639 rx AT Luke AFB in Arizona  
BETWEEN  1970 AND  1974. I do not  remember any problems  with them, however,  
we  did not pull PM on them... they were the responsibility of the Avionics 
Squadron  I was  told. They were stashed at a remote  Receiver Site   so  
people  could  go in and out  and  since I spent  most  time at  TX  site I 
could have missed any activity that  happened to them.
 
Ed Sharpe Archivist  for SMECC _www.smecc.org_ (http://www.smecc.org)  
And... former  30454 Luke AFB  ( and  for a while  when  recovering  from 
an auto accident  worked at and eventually ran the  MARS station for a little 
 while!)
 
 
 
In a message dated 11/26/2017 9:12:47 A.M. US Mountain Standard Time,  
kk5f at earthlink.net writes:

There  was the 8-channel R-77()/ARC-3, the 16-channel R-428()/ARC-36, and 
the  48-channel R-608()/ARC-49.  Now this.

This appears to be a  commercial or other-country aftermarket modification 
of an original  R-77//ARC-3 (without the never-issued guard receiver IF 
input connector of  R-77A and later).  It obviously has three banks of eight 
crystals  arranged under the metal blank cover, and the photo of the receiver 
with the  top removed shows the added shelf with the three crystal bank 
select  relays.  The crystals are much smaller than the original CR-1A/A, likely  
similar to the CR-18/U used in the 48-channel R-608/ARC-49.  Three  
crystals would be associated with each LO harmonic select dial, just as there  were 
two crystals in the R-428 and six crystals in the R-608.

The  crystal select control box looks more commercial-service than 
military, yet  the entire modification is way beyond ham hack quality.

It's too bad  that there are no photos of a nomenclature plate that might 
indicate the  source of the modification.

Interesting variation, Dave.  Thanks  for posting, and including the link 
and enough info to make going there  worthwhile.

If the AN/ARC-3 had a guard channel, and been built in one  box, it would 
have been the perfect WWII command set.  It's a very  innovative true 
auto-tune system.

Mike / KK5F

-----Original  Message-----
>From: David Stinson  <arc5 at ix.netcom.com>
>Sent: Nov 26, 2017 8:36  AM
>
>This is an interesting ARC-3 variant. 
>24 channels,  but where do the crystals go?
>The original 8-channel sockets are  blocked
>with a plate.  Are the crystals in the  control
>box?
>
>https://www.ebay.com/itm/292343727195
>
>73  OM DE Dave  AB5S
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