NAVAIR 16-30ARC38-502, Handbook Service Instructions Radio Set AN/ARC-38 and AN/ARC-38A from 30 June 1958, changed 15 October 1971
Section 5, Paragraph 5-29A SMO Performance Test. Pages 84 to 85 gives a good explanation and also care and feeding instructions for the SMO assembly.
5-29C tells about the problems that may occur if the switches fail or get dirty and the procedures for cleaning them.
Section 6, table 23 is the SMO fault isolation chart and 6-53, page 123 to 132 cover alignment.
I have only ever found this available from W7FG Vintage Manuals and do not know if this is available anywhere on line.
I did my ARC-38 years ago and at that time it was common to have to pay sometimes more money for the manuals then the radio.
Ray F/KA3EKH
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: [email protected] [mailto:[email protected]]
On Behalf Of Ray Fantini
Sent: Sunday, December 31, 2023 12:40 PM
To: [email protected]
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