Topband: Palomar R-X Noise Bridge

[donovanf at starpower.net]

Null depth is a function of cable loss. 

Heliax produces the deepest null, small diameter coax (RG-59, RG-58) is quite poor 

75 vs. 50 ohm should make no difference. 

73 
Frank 
W3LPL 

----- Original Message -----

From: "Charlie Cunningham" <charlie-cunningham at nc.rr.com> 
To: mapa50 at windstream.net, topband at contesting.com 
Sent: Friday, February 14, 2014 4:16:30 PM 
Subject: Re: Topband: Palomar R-X Noise Bridge 

I would expect it to work OK with 75 ohm cable. An open-circuited 1/4 wave 
line looks like a short at its sending end and you would be looking for a 
null as the line reaches a 1/4 wavelength, so I would expect the method to 
work fine with 75 ohm line. In fact, the 50 or 75 ohm line, if we consider 
it to be lossless would be operating at infinite VSWR so I wouldn't think 
the modest difference in characteristic impedance would make any real 
difference. 

73, 
Charlie, K4OTV 

-----Original Message----- 
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of 
mapa50 at windstream.net 
Sent: Friday, February 14, 2014 12:18 AM 
To: topband at contesting.com 
Subject: Topband: Palomar R-X Noise Bridge 

I have a question about using the noise bridge. I have used it cut stubs to 
1/4 wavelength using 52 ohm cable with no problems. I now need some stubs 
using 75 ohm cable which I have on hand. 

Will the same procedure work for 75 ohm that works for 52 ohm cable, or 
will the different impedance need to be accounted for. I started to cut 
cable and this question came to me. My first thought is that it will work 
fine, but I am not sure. I did some searches on the web but found nothing 
about it. Any help would be appreciated. 

Thanks, Pat Armstrong 
KF5YZ _________________ Topband Reflector Archives - 
http://www.contesting.com/_topband 

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