Feedline install at apartment

[N3HGN]

Hello,

I have settled on 9913 coax since a generous local ham here provided me with some for free.  Just one problem, I need to get it through a small hole in the patio.

I have some RG8x that fits through.  I would like to splice the cable for just a few inches and using the 8X as the bridge.  I plan to seal the cable using black electricians tape and a sealant recommended by the local radio shop here.  I am worried if the 8x will leak or cause issues thus defeating the 9913.

I have to run the 9913 indoors along my living room for approximately 20 feet and out the door.  I was told the 9913 is excellent in that it has low loss.  Any thoughts?

Keith, N3HGN

[WB2WIK]

9913 has low loss, but unless you're using it at 144 MHz or higher frequency, and using at least 50 feet of it between your station and antenna(s), you won't be able to take advantage of that "lower loss," because the loss in RG8X, for 50', below 144 MHz, is so low that if it were completely eliminated you probably wouldn't note the difference.

9913 loss per 100' at 30 MHz: ~0.9 dB
RG8X loss per 100' at 30 MHz: ~1.0 dB

Not much difference.  The difference starts to become obvious when longer lengths are used, or at higher frequencies.  There's a large difference in loss at 1.2 GHz, for example.

The obvious disadvantages of using 9913 will become very apparent to you as you start to use it.  It's stiff (inflexible), yet quite fragile due to its internal construction.  It cannot be walked on, stepped on, kinked, or even tightly bent (in a small radius) without significant damage.  9913 was developed originally for cellular telephone sites, where it would be used only in straight lines going up the sides of poles, at frequencies near 900 MHz.  For that application, it is ideal.  For many amateur applications, especially temporary ones, or installations where the antenna must be moved or rotated, or the cable must be walked on because it's exposed to that, 9913 is not a wise choice.

73 de Steve, WB2WIK/6

[WF3M]

Get yourself some good quality RG8-X(Believe it or not, Radio Shack's RG8-X is pretty good stuff.)and forget the 9913.

It's much easier to work with and you'll never know the difference. Spend your efforts on building the best antenna you can. That will make the most difference.

Bill Bosler
WF3M