On Wed, 27 Jan 2010 22:37:55 +0000 (UTC), ke2d@comcast.net wrote:
>I am in the midst of installing a new tower and need to start
>ordering materials.- I need 2000ft of LMR400 style cable, 200ft
>of LMR600,
Before buying coax, I suggest that you study data sheets and
select cable that best meets your needs. I would NOT pay a premium
price for LMR cable -- I recently measured the HF loss of LMR240
and found the published attenuation specs to be "optimistic." When
I have the opportunity, I'll do the same for their larger cables.
No debate that it's good cable, but my measurements show that it's
loss is only VERY slightly less than Belden's published data for
their RG8X, 9258, and The Wireman's RG8X, CQ118.
Authorities note that at HF, loss in coax is almost entirely due
to copper loss -- that is, plain ordinary Ohm's law, as modified
by skin effect. Dielectric loss kicks in at high VHF. If you're
buying coax for use on HF, simply study the Belden catalog and
that of other mfrs and buy the coax that has the lowest DC
resistance of the center conductor and shield combined from a
manufacturer that you trust. Commscope 3227 is great if you can
find it, probably better than LMR400.
>probably 1000ft or so of dipole wire
I have a lot of wire antennas in tall trees. I buy #10 or #12 THHN
(house wire) from Lowe's or Home Depot. If you're hanging in trees
or on a mountaintop, use #8 or #10.
>insulators
I like egg insulators from RF Connection.
>center feed baluns or insulators
Do NOT buy a commercial "balun" -- roll your own FAR better than
you can buy following my Cookbook.
http://audiosystemsgroup.com/RFI-Ham.pdf
For center insulators, I like the one with a coax connector
attached that The Wireman sells for about $10. The Alpha Delta is
a lot more expensive, but seems solid. Some like the Budwig, but I
find the attachments not sufficiently robust for high dipoles in
trees.
>Also 200ft or so of HD rotor cable.
This may sound crazy, but for the 250 ft run to my tower, I used
two parallel runs of 14-3 house wire from Lowe's (each is four
conductors, counting the "ground"). As it turns out, you can buy
this stuff cheaper than you can buy 6-conductors of #18 in a
jacket. To go up the tower (120 ft), I found a shorter length of
multi-conductor in a jacket and spliced it at the base.
>Has anyone used the newer Belden RF400 series cable?- Or the
>knockoff brands of LMR400 equivalent?
It all comes down to who you trust. I trust Belden, Commscope, and
Times to make very good cable (although I don't trust Times'
published specs for attenuation).
>There are two vendors on eBay selling 1000ft rolls of LMR400
>equivalent cable for $325/1000ft roll, which so far seems hard to
>beat.
Everything depends on quality. There are LOTS of WHORES (brokers)
in the cable biz, most of whom don't have a clue about
engineering.
73,
Jim K9YC
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