http://elecraft.85.s1.nabble.com/Transmission-line-loss-tp366525p366528.html
capacity. Also, there are some low-loss RG-8X cables out there that cut
the loss difference by half again. I bought a 500' spool at a hamfest
some years ago. It's double shielded. I've used short runs to UHF
antennas for satellite work with good results. But, no doubt that the
> First of all, I have to congratulate the posters in the earlier thread on line
> loss, etc., for prompting me to actually get my calculator & ARRL Handbook out
> and read up on transmission line loss, dB calculations, etc.
>
> My interest has come up as I'm planning on installing a flag pole vertical in my
> yard, due to CCRs, and the coax run will be around 100 feet outside the house,
> plus 28 feet inside.
>
> Here's my take on line loss, and please correct me if I'm wrong. For today's
> discussion, let's assume the power is 100 watts, total run is 100 feet, that I
> can tune this vertical up to 50 MHz, and the SWR at the antenna hits 5:1 (it
> won't, as I'll have a remote tuner there, but just for discussion...).
>
> Davis RF-brand "RF-9914F Bury-Flex" has a published matched line loss of 1.1
> dB/100 ft at 50 MHz. Per the Handbook, a 5:1 SWR at the load will add around
> 1.2 dB of loss, for a total of 2.3 dB over the run, for about 60% efficiency.
> (I'm still fuzzy on the percentage calculations.)
>
> A variety of brands of RG-8X have a matched line loss of 2.0 dB at 50 MHz per
> 100 ft. A 5:1 SWR adds 1.7 dB, for a total of 3.7 dB loss, for a little over
> 42% efficiency.
>
> Am I reading something wrong here, or is the 1.4 dB difference between the two
> cables correct? Can you extrapolate that to an S-meter at 6 dB/S-unit? If so,
> I'd say the 1.4 dB would be barely noticeable on the receiving end at best, and
> the extra cost of lower loss coax isn't worth the money. Operation at HF would
> be even less of an difference than at 50 MHz.
>
> I realize there may be other considerations as to the type of coax used that
> could sway one's decision. In my case, I want direct buriable, and I haven't
> come across any 8X that allows this. Longer runs and higher SWR would obviously
> sway the argument as well.
>
> RG-6 seems to be in between the RG-8X and Bury-Flex as far as loss, but the cost
> may be much better (from what I've read here).
>
> In my searching, I came across a pretty handy document from Cisco relating to dB
> loss and gain:
>
http://www.cisco.com/en/US/tech/tk722/tk809/technologies_tech_note09186a00800e90fe.shtml> Thanks for your input.
>
> 73,
>
> Mike
> KW1ND
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