Good recommendations. I did a couple of things differently for my 160 T
hung to 3 trees,
I use Lewmar or Ronstan or Harken small swivel blocks, cheaper, more
durable in tough environments and the swivel helps keep lines from
tangling or twist from messing things up. Don't use 3 strand rope.
Whichever I can find cheapest in 30mm or so.
http://www.mauriprosailing.com/us/product/LEW29925001BK.html?gclid=CLC7qJefr8sCFYRrfgodbeYH_Q
http://www.fisheriessupply.com/lewmar-30mm-synchro-control-blocks
For any serious load the ball bearing blocks are terrific. I loop my
hoist line thru the block to the tie off (or weight or bungee), so if
the antenna wire breaks, I still have a line through the pulley. I use
a separate line over the tree branch for the pulley and after a while
the tree grows around it and it won't come down. The wind oscillation
should be in the antenna hoist line, not the pulley line to minimize
chafe. Let the block sheave do the moving. With a loop the hoist line
can be replaced with a new one with a careful splice/tape to go thru the
block. 1/4" braid dacron from Synthetic is awesome and plenty strong
enough, and ok on the hands with gloves to what I can pull (100# +).
For the top T wire, I use Davis RF 13ga copperweld stranded with the
poly cover, no stretch, less weight, high strength, and less corrosion
http://www.davisrf.com/antenna-wire/polystealth.php
I always use a bowline knot and Scotch 33 tape the bitter end after
another half hitch. It's a great knot but I've seen them shake out
under cyclic loads.
I use a 50::25 ohm TLT which is a very good match for my antenna, easy,
broad band and zilch loss. My T is tuned low in the band and then use
series caps to cover the band to 1980 or so.
Grant KZ1W
On 3/7/2016 9:48 AM, Jim Brown wrote:
Hi Gary,
The antenna you describe should work quite well on both bands, but
I'll suggest a couple of tweaks to make the matching easier. First,
make it a Tee -- if you have a catenary, you can support a Tee as
easily as an L. Second, make the top section a fan (like a fan
dipole) with short elements to resonate it on 80 and longer ones for
160. Third, don't worry about remoting the tuner unless you feedline
is very long. Unless the match is really bad, feedline loss on 80 and
160 is pretty low, especially if you use RG8. Also, you can make the
tuning more broadband (and electrically lengthen the vertical section
by 1-2 percent) by using two parallel runs spaced 12-18 inches, tied
together top and bottom. Do a simple NEC model to get dimensions.
Finally, use as many radials as you can, don't worry a lot about
length, just think more is better. :) BTW -- 50 ft on the ground will
be close to a quarter wave on 80, 100 ft on 160.
As to physical details -- get a good pulley at each end, tie one end
down, put a weight on the other end, and use some sort of "mechanical
fuse" at the feedpoint so that wind doesn't break it. I use a mating
pair of Pomona connectors -- when the wind blows, they simply
un-mate. For the fan spreaders, cut short lengths (12-18 inches is
great) of 1/2-in PVC conduit, drill holes about 3/4-in from each end
to pass the wires through. Make this antenna as physically robust as
possible to withstand the wind. At a minimum, #10 THHN for the long
top sections that carry the stress. #12 or #14 is fine for the shorter
top sections. Don't make any soldered connections -- they don't
weather well, and wire tends to break at a soldered joint. Instead,
use split-bolt copper clamp connectors sized to fit the wire you're
using. For support rope, use 5/16-in rope from
http://www.synthetictextilesinc.com/supportham.html It's resold by
lots of ham vendors, but Synthetic Textiles is a bit cheaper. Smaller
rope is sufficient for strength, but you'll appreciate the larger size
when you're trying to pull on it to maximize tension, which pulls it
higher. :) Don't use hardware store pulleys -- instead, use marine
pulleys (good) or this excellent "rescue" pulley, which is also easy
to rig.
http://www.ropescoursewarehouse.com/catalog1/advancedwebpage.aspx?cg=1851&cd=4&SKUTYPE=202&SKUFLD=SKU&DM=1250&WEBID=914&gclid=CKfCobGOr8sCFQWUfgod5DUOHQ
Out here in CA, the West Marine is the place to buy marine pulleys.
73, Jim K9YC
On Mon,3/7/2016 5:50 AM, NC3Z Gary wrote:
Now I want to be able to use this antenna for 80M as well as the non-DX
portion of 160M. I can house a autotuner at the base (or make my own
network but that would require control lines). My thinking is to make
the 160M a 5/16 WL vs 1/4 to be more beneficial to 80M tuning without
loosing anything on 160M.
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