Tom,

Line loss is more of an issue as frequency increases, and is of 
greatest concern on VHF/UHF (2 meters and above).  We could quibble 
about theoretical differences, but for an HF installation, I don't 
think you have to worry as long as the cable is good, and your 
connections have been made carefully.  Besides, it's only a 20 foot run.

Steve

On Monday 5/22/06 08:19 T Behler wrote:
>Hi, all.
>
>I am finally making progress in terms of getting my new HF Predator
>screw-driver-type antenna installed onto my RV travel trailer.  Hope to have
>it done by this week-end. ... My question is this:
>
>The person helping to install the antenna has already put Belden RG8X coax
>on the antenna.  The coax run will be about 20 feet, going from the back of
>the trailer to the inside where I'll have my Icom 718 HF rig.  We will have
>the coax running in a PVC conduit which will run along the frame of the
>trailer, and the coax will come up through a hole at an appropriate spot
>inside the trailer.
>
>Someone has suggested to me that I really ought to be using thicker coax for
>this purpose, in order to minimize loss.  I do have a 100 foot chunk of RG8U
>coax with a foam dialectric that I could get the needed coax from, but don't
>want to go to all the trouble of re-doing the already-existing connections
>on the antenna if it really won't make much difference.
>
>The guy who installed the original coax on the antenna looked Belden RG8X up
>in the ARRL antenna book, and found that it has .7 DB loss per 100 foot on
>10 mhz, so any loss for a 20-foot run would seem negligible to me.
>
>Am I ok here, or should I really consider the thicker RG8U stuff?
>
>I know there are likely to be a variety of opinions on this one, and I
>suppose I could always change coax runs later, but I want to try doing
>things right the first time if possible.
>
>Thanks as always for your very helpful advice.
>
>73 from Tom Behler: KB8TYJ