The QRPer Board

How long can i go with RG316 before the losses are too much. i usually carry 35’ of RG58 just thinking something smaller and more manageable for a push up mast.

cheers,
KF7ZVL / Kelley

Kelley wrote: ↑Mon Nov 20, 2023 1:31 am How long can i go with RG316 before the losses are too much. i usually carry 35’ of RG58 just thinking something smaller and more manageable for a push up mast.

regarding the RG58, check the loss here

https://messi.it/en/comparison-chart-50-ohm-cables.htm

and then, regarding cable, check out the list here

https://messi.it/en/catalogue/50-ohm-rf ... t-coax.htm

notice that the "POTA" ones may be the cables you're seeking for

I use 25' of RG-316 in my POTA (QRP) setups and I can tell you that it works just fine. (Of course, as one of my professors once said, someone's personal experience is a statistical argument based on a sample size of one. )

So, if you need something more scientific, there are various online coax loss calculators. Here's one: https://kv5r.com/ham-radio/coax-loss-calculator/. I didn't see RG-316 on that page (it may be on others), but RB-174 is similar. Running 20m at 5 watts through 25 feet of RG-174 to a perfect antenna (SWR = 1.0) yields a loss of 0.746 db (16%, or an output of 4.211W). Running it to a mismatched antenna (SWR=2.0) increases the loss to 0.901 dB (19%, or an output of 4.063W).

Using your 35' yields a loss of 1.044dB and 3.93W out (at SWR=1.0) and 1.2dB and 3.752W out (at SWR=2.0).

Hope that helps,
73 Skip K4EAK