[TowerTalk] Tribander Spacing

[Joe Subich, W4TV]

Do a sanity check by modeling in EZNEC, 4NEC, etc. over flat earth.
HFTA uses point (isotropic) sources and ignores coupling.  HFTA will
show more ground reflection than is actually present with real yagis
(due to the side nulls in real yagis) and misses the reduction in
stacking gain when the antennas are too close.

73,

    ... Joe, W4TV


On 2015-02-20 11:26 PM, Keith Dutson wrote:
> Thanks Pete.  Your spacing is only 28 feet, less than a half wavelength on
> 20.  I also had a recommendation of 5/8 wavelength on 20.  That calculates
> to 41 feet.  I was thinking 35 feet.  Guess I need to put it in HFTA to see.
>
> 73, Keith NM5G
>
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Pete
> Smith N4ZR
> Sent: Friday, February 20, 2015 2:57 PM
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] Tribander Spacing
>
> Assuming you meant a second C-3, I did extensive modeling of pairs of C-3s
> back in the late 90's when I put my stack up.  There was an NCJ article, but
> if you like I can try to dig up the manuscript here.
>
> I wound up with C-3Es at 97 and 69 feet. It's too wide for the best 10m
> pattern and not wide enough for optimum on 20, but it worked out to be the
> best overall compromise.  I would have put up a third antenna at around 35
> feet, but the tower would have been marginal.
>
> Your case will depend on local terrain, and on take-off angle data for your
> part of the country. HFTA modeling will give you figures of merit for
> various paths that you can use to reach the best compromise, given your
> location and, perhaps, the prospects for 10M in the next cycle.
>
> 73, Pete N4ZR
> Check out the Reverse Beacon Network at
> http://reversebeacon.net,
> blog at reversebeacon.blogspot.com.
> For spots, please go to your favorite
> ARC V6 or VE7CC DX cluster node.
>
> On 2/20/2015 3:36 PM, Keith Dutson wrote:
>> I have a F-12 C3 up at 120 feet.  I want to add a second C-2.  What
>> would you recommend for spacing?  QTH is Houston, TX area.  Thanks.
>>
>>
>>
>> 73, Keith NM5G
>>
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