[Milsurplus] AN/ARC-38 question

[kd3ht]

The cheaper phenolic switch sections on the PTO can cause alignment issues
when cycling.   Relays can be replaced but are also a failure mode.  I
started to rewire mine since I picked up a power supply rack but haven't
finished.    

Jack wa7dia has had his on in the past couple of weeks but again ran into an
issue he is trying to debug.    Wonder if the vibration in the planes they
were used in actually helped to wiggle things back into alignment!! 

I don't know the last time Pete, Wb2jwu fired his up.  He kept it tethered
to 3885 to eliminate the switch issue above.

 

 

Steve, kd3ht

 

From: milsurplus-bounces at mailman.qth.net
[mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of Ray Fantini
Sent: Sunday, December 31, 2023 12:40 PM
To: milsurplus at mailman.qth.net
Subject: [Milsurplus] AN/ARC-38 question

 

when referring to an ARC-38 or an ARC-38A they have two components that make
up the frequency selection, the simple part is the Collins PTO assembly that
feeds the radio. from what I recall it operates from 2 to 4 MHz and the
radio uses doublers beyond that for the other bands. Thats simple being it's
a fairly standard PTO, but that's driven by a mechanical assembly that
interprets the commands from control head and uses maybe one of the most
complex and unexplainable processes for setting the PTO to the correct
frequency. It has cryptic numbers on wheels, eccentric cams and planetary
gears. I have no idea how it works; I have a running ARC-38 that I use on AM
and am happy that the mechanical computer still clicks along but if it
failed beyond cleaning and lubricating, I would be screwed. Just looking at
the servos of the PA and variable IF you have to think that those engineers
back in the middle of the last century must have been giants compared to
what we are doing today. I have always regarded my fully working ARC-38 and
180 antenna tuner a marvel of analog technology.

Have to wonder in today's world of doing everything digitally if anyone
would still be able to develop such a mechanically complex system ?

 

Ray F/KA3EKH

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/milsurplus/attachments/20240101/86d1be9a/attachment.html>