[amsat-bb] A question about 75 Ohm connectors

[Estes Wayne-W10191 <W10191@xxxxxxxxxxxx>]

Phil wrote:

I have built two crossed aerials (one for 146 MHz and the other for 435 MHz) that use a 75 Ohm phasing harness. I used a PL259 Tee and connectors on the VHF aerial but I now discover that I can't buy any 75 Ohm N connectors or a Tee for the UHF aerial.
I should be able to use 50 Ohm N connectors with a quarter wave length of RG59, shouldn't I (assuming that I can find an N connector that will take RG59 cable)? Or is there some other alternative?

Wayne replies:

You could use BNC connectors.  The matching harness on my 7x7 435 MHz portable antenna uses a 50 Ohm BNC tee and 75 Ohm BNC connectors.  On the input to the tee is a N-female to BNC-male adapter.

It seems to work okay, except the shield on my cheap RG-59 cable is not very robust.  On two occasions a BNC connector has come apart when moving the portable antenna, dragging a long piece of coax.  The shield strands all broke under tension.  Now I have a strain relief on the cable.  Also, I didn't screw the BNC connector as tightly on the replacement cable.  I think I weakened the shield strands on the first cable by clamping them too tightly in the BNC connector.  

Wayne Estes W9AE
Mundelein, IL, USA
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