COAX Choice for Base Station

[doctordave]

Am I likely to notice any improvement of signal at 39 MHZ by switching my 50 ft base-application coax run from 75 ohm to 50 ohm cable (loss figures for both brands of cable are comparable)? I've heard that there can be a bit of mismatch when using 75 ohm cable on low band freqs.

Thanks.

Dave

 

[K5MAR]

Dave, this is a topic that usually stirs up a bit of debate. But at 39 MHz, there probably isn't any significant difference. If you are only monitoring lowband and not transmitting, use whatever you have. The improvement from using the 75 ohm coax (a quality coax such as RG-6QS, not RG-59) comes at the higher than VHF frequencies where most 50 ohm coax (especially RG-58) becomes extremely lossy.

If I was only monitoring VHF-low, I'd use a tuned lowband antenna and RG-8 coax. When you start adding other bands, particularly UHF and above, then you need a quality coax such as LMR-400 (50 ohm) or RG-6QS (75 ohm). Again, this assumes you are only going to receive, not transmit. If you are going to transmit, then you need to stick to 50 ohm coax.

Always use quality coax!

Mark S.

 

[K2KOH]

Rule of thumb...use the best coax you can without burning out your wallet. As Mark said, you can use 75 ohm RG6 QS...works well, and I can attest to this since this what connects my discone to my Icom 7100.