W2PV's "Yagi Antenna Design" was published back in the early 1980 before
Yagi modeling programs were available to hams and it was considered the
bible of Yagi antennas by many.
The book does not really address the merits of either method of Yagi
construction. There is a brief paragraph regarding the driven element and
current on the boom basically due do to an unbalanced feed system as
compared to a balanced feed system. There is a section called
Boom and element clamping correction, but that information is not nearly as
accurate as can be obtained with today's software using NEC4. Yagi
Optimizer by Brian Beezley calculates for the equivalent cylinder and it is
used in the tapper schedule for the total element length based on the
element mounting system and element diameters.
I was wondering if it was possible to see a difference in performance
between two Yagi's one with insulated elements and one with grounded
elements. I also wonder if one type would have a lower noise floor when
compared to the other etc etc. My gut feeling is that the grounded elements
and a T-match driven element might be quieter but I have no real way of
telling for sure.
73 Pete N4KW
----- Original Message -----
From: "David J. Sourdis - HK1A" <hk1kxa@hotmail.com>
To: <towertalk@contesting.com>
Sent: Sunday, September 18, 2011 9:44 PM
Subject: Re: [TowerTalk] Yagi Antennas
>
> My knowledge on this relies on W2PV's "Yagi Antenna Design" book:The
> elements may, or not, be electrically connected to the boom by, i.e., U
> "muffler clamps". If the metallic clamp system separates the element from
> the plate, there is practically no correction for the element length. If
> there is direct contact with the plates, I think there was a rule of thumb
> correction, to avoid converting the plate dimensions to an equivalent
> round conductor section, lengthening the element tips by some amount
> related to a small percentage of the sum of the plate dimensions.
> This was before antenna simulation software was available for everyone and
> it might have changed. If so, let me (us) know.
>
> David
> HK1A
> EC5KXA
> AE5XQ
>
>
>> Date: Sun, 18 Sep 2011 13:11:04 -0700
>> From: jimlux@earthlink.net
>> To: towertalk@contesting.com
>> Subject: Re: [TowerTalk] Yagi Antennas
>>
>> On 9/18/11 12:41 PM, Pete Raymond wrote:
>> > I am wondering if anyone knows of any studies done with like Yagi
>> > antennas, one with elements insulated from the boom, and one with
>> > elements
>> > grounded to the boom, and how their respective performances compared.
>> >
>> > 73 Pete N4KW
>> >
>>
>> There's a huge amount of work on this in the VHF/UHF world
>>
>> From a theoretical standpoint (and borne out by practical experience),
>> there's no real difference, assuming the design accounted for whether
>> the boom was insulated or not. It's really all about the currents phase
>> and magnitude in the elements and their spacing, and for the most part,
>> you can get the same kind of things either insulated or not.
>>
>> That doesn't mean the design will be identical, or that there is some
>> simple automatic conversion (e.g. add 1" for insulated elements)
>> _______________________________________________
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