Ed:
I am using a HyGain HyTower which I modified to work "better" on 160 meters
and 80 meters. To avoid the problem of blowing the insulator which separates
the stinger from the tower I simply connected the top of the tower to the
stinger with a strap. One can use one the holes already in the top plate of
the tower and a U-bolt with a keeper at the point where the stinger passes
through the top of the tower. This change will make the HyTower no longer a
multiband antenna without some sort of feed point matching network at the
base, but it does prevent one from having voltage flashover at the midpoint
of the antenna.
I connected a single wire, 45 feet long, at the top of the stinger and ran
it out as close to horizontal as I could without too much bending of the
stinger at the top. If one wished they could use more wires to add to the
top hat, but it may not make much difference. I use a 'classic' on the
ground (or just below the grass) set of radials - about 28 of them about 60
feet long. The length and number is governed by the land ownership I have.
My particular configuration gives me an input impedance of 13-j200 ohms at
1.83 MHz. An inductor of 17 uH in series with the feed removes the
capacitive reactance and a 1:4 Unun provides a step up to a nominal 52 ohms.
The bandwidth is from 1.800 MHz to 1.890 MHz with a VSWR of 2:1 or less.
To operate on both 160 and 80 meters I switch out the matching network for
160 and switch in matching networks for either 80 meters or 75 meters.
Because the feed point becomes inductive on 80/75 and has a higher
resistance value (on the order of 38+j40), those networks use an L matching
network with shunt L and series C. The values are not extreme -- perhaps 3
uH of shunt inductance and 400 pF of series capacitance. I forget the exact
values. The VSWR 2:1 bandwidth on 80 meters is on the order of 100 kHz and
about the same on 75 meters which provides the coverage I am seeking. I
switch bands using remotely controlled relays. These changes have been in
place since Autumn 2003 and I am generally satisfied with the performance of
the antenna for transmitting.
Originally I used the base coil loading described in the HyGain information.
It is not designed to handle 1.5 kW input. I tried the alternate
arrangement for 160 which uses about 120 feet of wire running horizontally
from the top of the tower (about 24 feet up). The HyGain version has a 40m
trap at that point. I did not use the trap since I did not use the HyTower
on 40 meters. While things did work, I was not really satisfied that it was
performing as well as it should and so I went to the modified version I
described. I am of the opinion that if you want to get the efficiency of the
HyTower to be a little better than 'out of the box' on 160, you will need to
do some sort of modification and top loading to get the feed point
resistance higher relative to the ground loss resistance.
73, Tod, KOTO
> -----Original Message-----
> From: towertalk-bounces@contesting.com
> [mailto:towertalk-bounces@contesting.com]On Behalf Of Ed
> Sent: Monday, February 02, 2004 7:11 AM
> To: towertalk@contesting.com
> Subject: [TowerTalk] Hy-gain Hy tower
>
>
> I have several questions for anyone using the Hy Tower.
>
> I'm am renovating an older Hy Tower. It's in the air but not yet
> completed.
> I do have the 40 meter trap (MK-160 kit) which will allow 160m use.
>
> Is anyone using this antenna with elevated radials?
> Has anyone used an added inductor to the wire radiator to lower the 80m
> resonance point to the CW portion of the band?
> Successfully used the antenna on WARC bands?
> Comments on 160m operation?
>
> Thanks, Ed W4EP
>
> _______________________________________________
>
> 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.
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
_______________________________________________
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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