Phil wrote:
<< Anyone have any experience with the DX Engineering Hot Rodz top hat
extensions with the Hustler 6BTV vertical? The Hot Rods were originally
designed for use with mobile antennas, but are useable with base units
as well (according to the advertising).
Dave, WX7G, use to have similar items available from Nantenna, LLC
that you used with an RM-40(S) resonator on the Hustler 6BTV for
operation on 80 meters. Using the 40 meter resonator in conjunction with
the rods (instead of just the 80 meter resonator), improved the efficiency
and bandwidth on that band.
Anyone ventured there yet in attempting to improve the operation of the
Hustler on 80 meters? If so, I'm interested in the size rods used, any
problems encountered, etc. Thanks, 73 Phil / K4MPE >>
Hi Phil,
I have been using homebrew mobile HF antennas for just over 5 years. The
most efficient way to load a shortened antennas is top loading, typically
achieved with capacity hats in various configurations. It's interesting to
see that a commercial product has come out for just this purpose.
Top loading of fixed verticals can also be accomplished buy adding guys to
the top of the antenna. Starting at the top, the guys are wire, terminated
in insulators, then rope. You'll have to modify the resonator to remove coil
turns to re-resonate the antenna where tou want it.
If I remember correctly, the Hod Rodz are a set of spoke rods, with no
perimeter wire, with a little hub that clamps onto the whip.
For mobiles, this requires a much stronger whip, but the cap hats are
extremely effective in reducing the amount of coil (and losses) required to
load a short whip. The closer to the tip of the whip the loading, the higher
the efficiency. However, they can't handle trees too well!
I have made lightweight, spiderweb-looking, cap hats from stainless wire
that were effective but just not practical. I'm working up a new design that
is much more practical for mobile. I hope to have a new plan out on my
website soon to share the construction details.
The idea is to use a single, trailing whip at the top. Electrically, it's an
inverted 'L'. Since there is no ring/perimeter wire, and no other spokes, it
handles limbs nicely. The mechanical details are the rub.
The antennas I'm making now are homebrew inverted L bugcatchers. However,
the trailing top load would benefit a screwdriver antenna just as
effectively as a clip on accessory.
I'm using 6-7' long fishing rod cores, which are extremely light and stiff.
Since they point to the rear, they don't catch limbs.
Just be careful when backing up near any limbs! You guys out in open land
don't need to worry, but here in VA, there's lots of potential limbs to hit.
The vertical section of the antenna is about 10 feet, and the trailing 'L'
section is about 8 feet. With the coil bypassed completely, the antenna
resonates on 20m.
It is possible to also electrically disconnect the top load using a jumper,
without physically removing it from the antenna, allowing you to tune the
higher bands as normal.
Having the L section greatly reduced the amount of coil turns needed to
resonate the antenna, especially on 80m. This also tends to create more
vertical skywave radiation, and I have finally been able to consistently
work the VA Phone net on 3947 from the mobile.
To support such a top 'L' load, I use the combination of a stiff whip and a
guy line. The whip is a section of 1/2" solid fiberglass, with a spiral of
wide, tinned braid on it, and taped over. Imagine a Hamstick, but with 1/2"
wide braid on it. BTW, I'm using 1" copper water pipe for the base mast.
I'll save the mechanical details for the plan, but you get the idea. You can
make a clip that holds a commonly available Wilson 1000 CB whip at the top
for an 'L' trailing top load.
I have a pic of the mobile. If interested, send me an email and I'll send
you a copy. I'm still experimenting with the details and it will be a little
while before I post the plan on the web site.
I also have a jig now, which makes it much easier to wind air-core coil
stock.
Happy Building!
--...MARK_N1LO...--
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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