[majortom]

Which coincidentally are the same I was using to make the 1/4 wave stub filters from.
Handy doo dads to have around...

 

[majortom]

Can you define ‘extremely long runs’ in feet or meters? My 20-year-old coax is beginning to disintegrate, and it’s time to replace...

For your own application, you can tell us...
From your specific coax specifications, you'd take the Worst Case DC Ohms/ft times the length of the run in ft to get the total Ohms. Once you have the total ohms DCR, you simply use Ohms Law to determine the voltage drop using the worst case DC Current draw. Once you have the DC voltage drop to expect, you compare that to the product spec of the device your trying to run. I would probably try to shoot for less than 10% DC Voltage drop. Less than 5% even better, and less than 1% better than that...

 

[Hitechluddite]

I've measured RF loss in Coax quite a bit over the years,but never DC loss. It will be interesting to measure some new cable vs old. I would think RF would degrade first...

 

[ExDilbert]

AC and RF will degrade more. DC is a pure resistance loss. AC and RF add losses from inductance and capacitance to the mix. The higher the frequency, the greater the loss.

 

[RevBob22]

I have been comparing specs on all the different flavors of RF-6 that Newark lists and I'm at a loss as to why the big price difference given that the published loss factors are nearly identical. I know some is direct burial and some is quad sheild etc. But why would some cost almost $1000 for a thousand feet ans some $180 with identical loss figures, velocity factor etc? What am I missing here? They are all belden brand cable....

https://www.newark.com/w/c/cable-wire-cable-assemblies/coaxial-cable/prl/results?st=rg6%20patch%20cable

The expensive cable is plenum cable, which is usually more expensive than non plenum. The story is the PVC Gods declared that plenum cable costs more to make, thus we pay more for it.
Has to do with additives that theoretically keep the jacket from burning and generating intense smoke that will then be carried throughout the building via plenum.

 

[Hitechluddite]

The expensive cable is plenum cable, which is usually more expensive than non plenum. The story is the PVC Gods declared that plenum cable costs more to make, thus we pay more for it.
Has to do with additives that theoretically keep the jacket from burning and generating intense smoke that will then be carried throughout the building via plenum.

Welcome to the forum! Lots of good info here, happy reading