Greg, excellent that you're getting interested in contesting. Fun and
challenges since the 70s here!
Pete says pretty much exactly what I was going to say, with one exception: I
like 80 feet for my 40, but that's because I like domestic contesting. That
said, the 100 foot height is always helpful for more options on 80 and 160.
Greg, where Pete is dead on is to remind us all that, by definition, there
is not an optimum height for a tribander. In fact, if you optimize it for
one band, you are compromising on other bands, and it's possible you're
really hurting one of the other bands. You can learn this stuff by modeling
the antenna. Move the height around and look what happens to the pattern.
Pete has a great idea: use two smaller, lighter, cheaper tribanders. At
http://force12inc.com/ you can see that the C31XR lists for $2357. Two
C-3Es (like N4ZR) total $2286. The amount of flexibility you get when you
can rotate them independently (or even only rotate one) and also switch
between top/bottom/both is staggering, and also makes the contest a whole
lot more fun when it gets slow. You not only can select between different
directions if you want, you can beam two directions at the same time, or
pick the antenna with the better take-off angle (say for the Caribbean
compared to Europe or Japan). I absolutely encourage you to think like this
rather than putting up one very large tribander.
Good luck OM.
73 - Mark, N5OT
----- Original Message -----
From: "Pete Smith" <email@example.com>
Sent: Wednesday, June 17, 2009 6:37 AM
Subject: Re: [TowerTalk] Tower Height Question - Dual Yagi's
> FWIW, when I was building my first tower, 14 years ago, I was
> planning to go with 70 feet. W3LPL, who is (and has been) at the top
> of the class for antenna and propagation expertise, strongly urged me
> to go to ~100 feet for a single-tower station, and to put the 40M
> beam on top. I did it, and have been glad I did.
> I use this tower to support an 80-meter wire parasitic array (not
> quite a 4-square, but a lot simpler to build), and shunt feed it on
> 160 with good results.
> The tower currently has an EF-240S (F12) on top and two C-3Es (also
> F12). I deliberately chose these antennas because they are small and
> light enough (~30 pounds) that I could handle them on the tower,
> while the C-3E stack gives me gain approaching that of a single
> bigger tribander, and angle diversity that it can't match.
> 73, Pete N4ZR
> At 07:04 AM 6/17/2009, Greg Beam wrote:
>>Having been bitten by the DX and Contest bug, I was having a chat
>>with a friend Larry, K7MI, and he really has my mind moving
>>(spinning more like) about antenna / tower configurations which has
>>prompted me to query about a few things.
>>I'm in the design ( Thinking ) phase of building my first tower (
>>lots of things to consider for sure ) and I'm looking to find the
>>optimum height and / or configuration for a pair of Yagi's as well
>>as to maximize the overall use of the tower itself.
>>Hardware Under Consideration (but not limited too):
>>40M - Force-12 - 240N 2L (~10.7sqft wind load)
>>10-15-20 - Force-12 C-31XR (~10.7sqft wind load)
>>Tower Type: Rhon 45G
>>Rotator: PST2051 / PST61 or Equivalent Load Specs
>>Primary Interest: DX & Contesting
>>All the engineering precautions will be adhered to for guys and wind
>>load safety, which will include dual Phillystan 6700 guys (maybe
>>11200) at each level & guy point.
>>I'm considering a TH7 or TH11 (WARC band Bonus) instead of the
>>C-31XR (purely from a cost perspective), which has a similar wind
>>load figure but I'm not thrilled about the idea of having traps for
>>a long term installation.
>>I would like to have an 80/160 Vertical / Inv-L configuration using
>>the tower as the radiating element, but do not want to compromise
>>the optimum heights for the Tri-Bander & 40m 2L Yagi. Obviously this
>>would be either an end-fed 80m 1/2 wave situation or a full 1/4 wave
>>80m + 160M Inv-L switching configuration.
>> >From my understanding, ~70' is the first optimum point for a 40M
>> Yagi (please advise if this is not the case) so a tower height of
>> 60' + 10' above the Tri-Bander would would do nicely, but would
>> there be any advantage / disadvantage ( apart from cost ) in going
>> the additional 30/40ft to say 100' to 110' or there abouts, which
>> would get me close to what I need for a full size 1/4 wave 160
>> vertical and double as a 1/2 wave End-Fed for 80m? Alternatively,
>> could I possibly go lower on the initial tower height, using the
>> Yagi's as CAP hats to bring the overall electrical length up for
>> 80m/160m without compromise to the Yagi's performance?
>>Any Additional Options / Thoughts / Ideas would be greatly appreciated.
>>TowerTalk mailing list
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