[R-390] R-390A Coax question

[roy.morgan at nist.gov]

Quoting DW Holtman <future212 at comcast.net>: 
> Is the coax cable used throughout the receiver 50 ohm impedance?

DW,

I think so, but it probably does not make much difference what you use.

> If it is 50 ohm, would RG-74 make a good replacment,

I don't remember offhand the nature of RG-74, but if it is about the same
diameter as the original stuff, then it will work in the MB connectors.

 should I try to find
> some better coax, with lower loss?

Loss at HF for those distances is irrelevant.


The runs are only about 1 foot long, I
> think the loss at HF would be insignificant, but maybe someone has some
> better ideas.
> 
> How hard is it to re-work the Mini BNC connectors? 

It's not all that difficult if you know a couple of tricks:

 1) Heat the solder of the covers on the connector and tap it just right against
the edge of the bench and the little cover will fly out.

 2) A very sharp knife will allow you to strip insulation correctly if you are
gentle so as to  not cut through the shield wires.

  I have looked high and low
> on the web and don't think they are available.

Contact RF Connections - they may well have them.
http://users.erols.com/rfc/index1.htm

Ask also if they have the correct coax for use in the radio.. they may well have
it.  Buying just a few feet will not break you. 


Roy Morgan
7130 Panorama Dr.
Derwood MD 20855