As you mentioned Peter it is the First Edition. Other papers he gave and
updates in Scuttlebut included the boom discussion and his reason for
selecting those particular lengths. In addition I used the all metal T match
which was grounded to the boom. I used that to overcome the low feed
impedence which I felt could not be adequately handled by a gamma match.
Besides, the all metal construction was immune to rain and most snow static,
that really offered an edge in some contests and DX pileups.
In one installation I had all 3 bands stacked with a total separation of
about 12-13 feet. I could detect no performance change from initial tests or
from his curves. When I moved and had a different tower for each band and 4
high stacks the performance was again excellent.
During one misguided moment I had two 20M Cushcraft 4 el on ~ 33' booms.
Stacking interaction at 40' separation was very apparent until I rebuilt
them as PV's That final array was at 40/80/120/160', independently rotatable
and with 4 switching options.
Carl
KM1H
Carl
KM1H
----- Original Message -----
From: "Peter Voelpel" <df3kv@t-online.de>
To: <TOWERTALK@contesting.com>
Sent: Thursday, July 19, 2007 6:37 PM
Subject: Re: [TowerTalk] Yagi designs?
Hi Carl,
I wonder why he is not mentioning that in his book to take precaution and
avoid certain boom length?
In opposite he writes:
"The simplified Yagi model also neglects the conducting boom; this is
justified only if the real yagi is completley symmetric around the boom.
Symmetry guarantees zero electrical potential at the center of each
parasitic element and no mutual coupling to the boom.
Hence no current will be induced in the boom by the parasitic elements.
If the driven element is open at its center and driven from a balanced
source, then it will induce no urrent along the boom.
Thus, for the symmetric Yagi with balanced feed there are no currents in the
boom, and therefore no effect of the boom on antenna performance"
Source: Yagi Antenna Design, First Edition
So if that is true, any antenna nearby inducing current into the boom by
mutual coupling is not doing any harm and will not disturb as the boom is
not ccoupling to the symmetric elements of that antenna.
And vice versa, if the other antenna is symmetric, it will not induce boom
current and the boom will not radiate to it´s neighbor antenna
73
Peter
-----Original Message-----
From: jeremy-ca [mailto:km1h@jeremy.mv.com]
Sent: Donnerstag, 19. Juli 2007 23:55
To: Peter Voelpel; TOWERTALK@contesting.com
Subject: Re: [TowerTalk] Yagi designs?
Only when the antenna elements share a resonance 20/10; 40/15. Booms were
mostly overlooked until computers came along in everyones home and office.
Many manufacturers continued schleping the same tired design until new
upstart companies with computers showed them up. W2PV used an IBM mainframe
and was the first of the new breed.
Carl
KM1H
----- Original Message -----
From: "Peter Voelpel" <df3kv@t-online.de>
To: <TOWERTALK@contesting.com>
Sent: Thursday, July 19, 2007 5:47 PM
Subject: Re: [TowerTalk] Yagi designs?
>I always thought the problem with close spacing and stacking interference
> were not the booms, as the are not parallel to the elements, but the
> elements themselves?
>
> 73
> Peter
>
> -----Original Message-----
> From: towertalk-bounces@contesting.com
> [mailto:towertalk-bounces@contesting.com] On Behalf Of jeremy-ca
>
> Nothing beats the W2PV designs for gain or F/B especially over just the CW
> band. With 4 elements on 40/27/20 foot booms for 20/15/10M the wind load
> is
> less than designs with more elements. The booms are non resonant on any of
> those bands so stacking interference is minimized allowing closer spacing.
>
> Ive used them singly or in stacks since 1983.
>
> Carl
> KM1H
>
>
>
> ----- Original Message -----
> From: "Reicher, James" <JReicher@hrblock.com>
> To: <towertalk@contesting.com>
> Sent: Thursday, July 19, 2007 4:23 PM
> Subject: [TowerTalk] Yagi designs?
>
>
>> Does anyone have a good design for a home-brewed four element monoband
>> yagi for 20 meters, and maybe a 5 element yagi for 15 meters? I prefer
>> the CW end of the bands.
>>
>> 73 de N8AU, Jim in Raymore, MO
>>
>> Light travels faster than sound... This is why some people appear
>> bright until you hear them speak.
>>
>> _______________________________________________
>>
>>
>>
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>>
>
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>
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