Hi Dan,
Yes, it´s all dependend on the skip angle and the nulls.
The addition of the highest antenna resembles an amp at the very low angles
only.
I use 13m spacing and EZNEC predicts the following over flat ground:
lower two alone 16.8dbi @ 11°
all three 18,1dbi @ 8°
upper alone 15.4dbi @ 7°
Looking it up in HFTA with my sloping foreground to the U.S. the added dbs
by the top antenna are at
5° 6.5
4° 5.5
3° 3.5
2° 5.0
1° 7.0
0.8° 10
73
Peter
-----Original Message-----
From: Stan Stockton [mailto:k5go@cox.net]
Sent: Donnerstag, 26. August 2010 16:08
To: DF3KV; towertalk@contesting.com
Subject: Re: [TowerTalk] XM240 to Moxon
Peter,
I would expect that if you have three 20M Yagis stacked for 20M that
they are spaced something like a wavelength apart and the difference is
in the angle that is covered by that high one which is probably up
something like 50m. EZNEC is not going to show you the angle at which
the signals are traveling between you and the West Coast of the US so
that might explain why when you throw in that high one you see that
much
difference. You probably don't see a HUGE difference in those cases
between all three and just the high one alone like you see when you
compare the lower two to all three. In the case of comparing two
different stacks at the same heights, the results should be more like
what the software would predict.
Stan, K5GO
> ----- Original Message -----
> From: "DF3KV" <df3kv@t-online.de>
> To: <towertalk@contesting.com>
> Sent: Thursday, August 26, 2010 7:03 AM
> Subject: Re: [TowerTalk] XM240 to Moxon
>
>
>> Yes, I have a three stack of 5L KLM yagis.
>> The lower two are hard wired phased and fixed direction U.S.
>> If I add the highest yagi to the stack I almost always get 10db
>> higher
>> differences reported from west coast stations.
>> The EZNEC simulation shows just +2,31db
>>
>> 73
>> Peter
>>
>> -----Original Message-----
>> From: towertalk-bounces@contesting.com
>> [mailto:towertalk-bounces@contesting.com] On Behalf Of Jim Thomson
>>
>> ## Does anybody else see similar effects... whereby gain differences
>> are
>> way nore than what
>> software predicts? The diff between a rotary dipole on 80m.. and a
>> 2-el is
>> another one that baffles
>> me [same deal on 40m]. It's like throwing a light switch.
>>
>> later... Jim VE7RF
>>
>>
>> _______________________________________________
>>
>>
>>
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>
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