[Milsurplus] RCA phono connector impedance

Wed Nov 29 14:08:29 EST 2023

I don't know if other RF connector types will allow the use of the PM-2 power supply.  The photos in the PM-2 manual of the cutouts for the KWM-2 rear apron look kinda tight to me.  
When I was in the Air Force some 50 years ago, all MARS stations seemed to have at least one PM-2 power supply.Jim
Logic: Method used to arrive at the wrong conclusion, with confidence.  Murphy 

    On Wednesday, November 29, 2023 at 12:47:20 PM CST, W2HX <w2hx at w2hx.com> wrote:  

Agreed. However the RCA connector is suboptimal from a mechanical perspective. Screw or bayonet connectors are mechanically more robust and probably more stable for that reason. But otherwise, the RCA isn’t bad at all.

73 Eugene W2HX
Subscribe to my Youtube Channel: https://www.youtube.com/@w2hx/videos

From: milsurplus-bounces at mailman.qth.net <milsurplus-bounces at mailman.qth.net>On Behalf Of Jim Whartenby via Milsurplus
Sent: Wednesday, November 29, 2023 1:30 PM
To: milsurplus at mailman.qth.net
Subject: [Milsurplus] RCA phono connector impedance

The RCA phono connector doesn't seem to be a bad choice.  In fact, it is looks pretty darn good considering the cramped space of the rear apron of the KWM-2.  See:

https://wv0h.blogspot.com/2014/11/rca-phono-connector-characteristic.html

It might be worth noting that only one of the Collins supplied RCA phono cables for the KWM-2 was meant to be used as RF coax.  The rest are just for interconnecting the KWM-2 to other equipment with no regard to impedance.

Regards,

Jim

Logic: Method used to arrive at the wrong conclusion, with confidence.  Murphy

On Wednesday, November 29, 2023 at 10:47:17 AM CST,mstangelo at comcast.net <mstangelo at comcast.net> wrote:

The RCA was a bad choice but as Ken mentions Collins had a cult following. I would replace the RCA connectors with BNC connectors.

Mike N2MS

> On 11/29/2023 11:28 AM EST Ken <kgordon2006 at frontier.com> wrote:
> 
> 
> Yes.
> 
> The ceramic-insulated RCA connector is far more likely to not introduce an impedance "bump" at the connection, unlike the SO-239 which does: but since the PL-259 is almost ubiquitous at the ends of RF cables, I suspect THAT is the main reason so many of us change our Heathkits to the SO-239.
> 
> In the case of Collins owners, the initial cost of their rigs coupled with their overweening "respect" for Art's designs preclude them from "desecratimg" those rigs in the interests of convenience.
> 
> In addition, of course, the PL-259-to-RCA converter is so un-reliable that it must be treated carefully to ensure constant contact, especially when the use of RG-8 sized cable is involved.
> 
> Ken W7EKB
> 
> 
> Sent via the Samsung Galaxy S21 5G, an AT&T 5G smartphone
> 
> 
> -------- Original message --------
> From: Mike Morrow <kk5f at earthlink.net>
> Date: 11/29/23 06:11 (GMT-08:00)
> To: milsurplus at mailman.qth.net
> Subject: Re: [Milsurplus] Nomenclature Tags
> 
> The US military purchased the KWM-2A as the RT-718/FRC-93.
> 
> The KWM-2A was introduced in 1961. Just by itself...no power supply, microphone, speaker, or any other accessories...it sold for $1,250. That is equivalent to $13,000 today.
> 
> The Collins S-Line used RCA phono connectors everywhere except the RF output of the 30L-1 and 30S-1 amplifiers. For almost 60 years it has amused me to see ham "engineneers" very frequently replace the same quality ceramic insert phono sockets on Heathkits with SO-239 sockets in false belief that the SO-239 is a superior RF connector. Yet, one almost never heard of a Collins S-Line owner doing likewise. :-)
> 
> Mike / KK5F
> 
> -----Original Message-----
> From: Bruce MacMillan <wirelessset at hotmail.com>
> Sent: Nov 29, 2023 12:05 AM
> 
> A former co-worker used to work for Collins in Australia. He said on more than one occasion a KWM2 would have S/N's removed before it was "gifted" to a friendly party.
> 
> Bruce
> M0SOE
> 
> 
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