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" <[email protected]> To: [email protected], [email protected] 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:[email protected]] On Behalf Of [email protected] Sent: Friday, February 14, 2014 12:18 AM To: [email protected] 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 _________________ Topband Reflector Archives - http://www.contesting.com/_topband _________________ Topband Reflector Archives - http://www.contesting.com/_topband
