----- Original Message -----
From: DAVID CUTHBERT<mailto:DAVIDNNAN@MSN.COM>
To: towertalk@contesting.com<mailto:towertalk@contesting.com> ;
topband@contesting.com<mailto:topband@contesting.com> ;
WarrenWolff@aol.com<mailto:WarrenWolff@aol.com> ; DAVID
CUTHBERT<mailto:DAVIDNNAN@MSN.COM>
Sent: Sunday, December 26, 2004 7:43 PM
Subject: Even more: Topband: New Antenna
ï
----- Original Message -----
From: DAVID CUTHBERT<mailto:DAVIDNNAN@MSN.COM>
To: towertalk@contesting.com<mailto:towertalk@contesting.com> ;
topband@contesting.com<mailto:topband@contesting.com> ;
WarrenWolff@aol.com<mailto:WarrenWolff@aol.com>
Sent: Sunday, December 26, 2004 7:38 PM
Subject: More: Topband: New Antenna
ï
Warren,
I thought I had better really simulate the flagpole rather than just
dismiss it out of hand. Here are some possibilities:
1) wire from the top of 35' flag pole to the tower, at the 35' level. Rr =
7 ohms
2) wire from the top of the 35' pole towards the top of the tower. Rr = 16
ohms
3A) wire from the top of the 70' tower (not attached to the tower) towards
the top of the 35' pole. Rr = 16 ohms. Fed at the base.
3B) wire from the top of the 70' tower (not attached to the tower) towards
the top of the 35' pole. Rr = 16 ohms. Feed at the 70' level. About 40 ohms.
4) wire connected to the top of the 70' tower towards the top of the 35'
pole. Rr = 17 ohms. Shunt feed.
5) tower feed. Rr = 16 ohms. Shunt feed with a wire to the top as you
proposed.
6) top load the 70' tower with a coil and a top hat or spike. Rr = 25 ohms.
Feed with coax at the base of the spike/top hat. It can be thought of as a
vertical with elevated feed or an Isotron.
Number 1 looks bad. Scratch that one. Numbers 2-6 all look good from a
performance standpoint. Numbers 2, 3A, 3B, 5, and 6 are interesting. Number 6
can be matched with a 90 degree, 75 ohm coax, as the input R is around 140
ohms. Number 6 has the highest performance and might be the way to go if your
ground system is not very good. You get 9 ohms more Rr at the expense of a
couple ohms of top loading coil loss. For ease of getting it to work I would
chose 2, 3A, or 3B.
These sims are subject to having better inputs (dimensions, ground,
radials, etc.) but I believe them to be good for comparison of the different
designs. All of the rest are adjusted to resonance by the length of the
horizontal wire.
BTW, I use a 38' top loaded vertical. It is all I can fit in my antenna
unfriendly neighborhood and small back yard.
Dave WX7G
----- Original Message -----
From: WarrenWolff@aol.com<mailto:WarrenWolff@aol.com>
To: towertalk@contesting.com<mailto:towertalk@contesting.com> ;
topband@contesting.com<mailto:topband@contesting.com>
Sent: Sunday, December 26, 2004 12:29 PM
Subject: Topband: New Antenna
Greetings,
I have a question about choices on 160 meters.
I expect to have a new home at Lake Havasu City next summer.
I will have a 60/70 foot fixed tower topped by a couple of OptiBeams
(16-4 and a 4-40).
About 100 feet away, I expect to have a 30/35 foot flag pole.
What is my best way to get on 160 with this arrangement? A couple
of ideas come to mind.
1) Shunt feed the tower
2) Use a wire between the top of the tower and the top of the
flagpole to use as top loading for vertical wire in the center
of it.
3) Extend an arm out from the top of the tower, say around 6-8
feet and drop some kind of vertical element to be base-fed.
Advice is needed; please donât say I am nuts.
Warren; W5KKW
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Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
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