[ARC5] Collins stuff and RCA jacks

[Glen Zook]

I have told this before about RCA connectors.

Back in the 1970s, there was an amateur radio operator here in Richardson, Texas, that was employed as an engineer in the Texas Instruments r.f. laboratory who was constantly berating the use of the RCA connector by Collins Radio.  Since Richardson was the "new" corporate headquarters of Collins Radio, quite a few operators were employed by Collins Radio Company.  After a while, some of the Collins Radio employees challenged the operator to actually verify the performance of the RCA connector in the Texas Instruments laboratory.  The TI engineer accepted the challenge.

He tested a total of 4-different connector types:  BNC, Type "N", UHF (PL-259 / SO-239), and the RCA connectors.  Laboratory measurements were made on all amateur bands between 1800 kHz and 1296 MHz (he did not try any higher frequencies).  Several examples of each type of connector were tried numerous times within the frequency range chosen.

After the experiments were completed, the TI engineer came back, "hat in hand", and disclosed his findings.  The UHF series was, by far, the worst of the 4-types tried.  Up to around 30 MHz they were "OK".  But, as the frequency increased above 30 MHz, things like impedance "bumps", losses, and so forth, increased to the point that the connector was very problematic at 144 MHz and was really unsuited at 432 MHz.  However, the other 3-connectors, BNC, Type "N", and RCA, were running so close together that, within the measurement errors of the equipment used, he determined that they were pretty much equal in performance.  The only thing was that the BNC and RCA could not "handle" as much power as the Type "N"!
 
Glen, K9STH


Website:  http://k9sth.com


________________________________
 From: Kenneth G. Gordon <kgordon2006 at frontier.com>


It has been proven repeatedly that the RCA jack has a lower (like none) 
impedance "lump" than an SO-239, is easier to use (no cross-threading 
problem, doesn't vibrate loose), and is fully as capable at the 100 watt level. 
Furthermore, those insulated with ceramic are even better.

Using those was another example of Collins' wisdom, not "cheapness".

Heathkit also used those, although they eventually switched to 
plastic-insulated ones. And other companies did the same.

The main reason so many hams changed the RCA jacks to SO-239s is that 
every other piece of equipment they owned already had those, and swapping 
back and forth between the two types became a problem for them, or they 
were using RG-8 and needed the larger connector. I haven't found any of 
that to be a problem since I have adapters if I need them.

There is absolutely nothing wrong with the RCA jack in RF service at the 100 
watt level with small coax, especially when good quality ones are used.