Re(2): [Antennas] quagi vs yagi at vhf

[Saandy Eban]

What Deon point out makes sense!
The Quagy elements are basically shorted turns. As such, they have a finite
impedance all along their circumference.  Interconnecting them with a
metallic boom will create a coupling path between the various elements, with
inevitable subsequent field distortion. This is why KD5SFA recommended
weatherproofing the boom: to avoid unnecessary coupling if the wood becomes
too conductive.

Alex Eban	5Z5KS
alexeban at gmail.com
      050-7774300
      03-9067913

-----Original Message-----
From: antennas-bounces at mailman.qth.net
[mailto:antennas-bounces at mailman.qth.net] On Behalf Of KD5SFA
Sent: Friday, December 01, 2006 9:15 PM
To: antennas at mailman.qth.net
Subject: Re: Re(2): [Antennas] quagi vs yagi at vhf

Use fiberglass...or seal the wood real well.

-----Original Message-----
>From: DavidE Benedict <iam at pmug.org>
>Sent: Dec 1, 2006 12:48 PM
>To: zs1zl at telkomsa.net
>Cc: antennas at mailman.qth.net
>Subject: Re(2): [Antennas] quagi vs yagi at vhf
>
>
>But with a wood boom don't the antenna characteristics change when it
>rains & soaks the wood?
>
>David
>W7DBH
>Mobile in Oregon
>
>
>>
>>However, it is important to note that the original quagi design by Wayne
>>Overbeck is for a wooden boom with the elements passing through the boom.
>>Tests have shown that the performance and charactersitics of the quagi is
>>affected a lot when the boom material is changed to metal.  The element
>>lengths and spacing have to be recalculated to achive the same results as
>>the wooden boom quagi and I have not seen a metal boom quagi which rivals
>>the original wooden boom.
>>
>>Deon ZS1ZL
>>
>>----- Original Message ----- 
>>From: "Bob Stein" <hamstuff at sbcglobal.net>
>>To: "G B" <microsys at alltel.net>
>>Cc: "Antennas" <antennas at mailman.qth.net>
>>Sent: Thursday, November 30, 2006 12:42 AM
>>Subject: Re: [Antennas] quagi vs yagi at vhf
>>
>>
>>For a given boom length, there should be no appreciable difference in gain
>>between a Yagi and quagi.  Gain is a function of boom length, and has
>>nothing
>>to do with the driven element if both designs are optimized.  There may be
>>slight differences in the side lobes, but I can't really say.
>>
>>Bob, w6nbi
>>
>>
>>G B wrote:
>>> Hello,
>>>
>>> I have been searching the internet for a study on long boom vhf quagis
>>> when
>>> compared
>>> to long boom yagis.  I could not find anything.
>>>
>>> One of the EU guys who is famous for vhf yagis told me he did not think
>>> loops worked
>>> very well.  That is contrary to my experience, but, mainly, I find
>>quagis
>>> easy to
>>> construct and they are inexpensive.  I have compared the 8 element quagi
>>> here to two
>>> different colinear verticals which claim to have 6dbd and 8dbd
>>> respectively,
>>> which are
>>> located well above the quagi.  The quagi is at least one, and many times
>>> two
>>> S units
>>> better.
>>>
>>> Anyway, I am considering building a twenty foot boom yagi using a T
>>match
>>> and insulated
>>> elements for sideband.
>>>
>>> I would sure like to see hard evidence on a test range.
>>>
>>> As a side query, I know I can find those stainless keepers for the 3/16"
>>> elements on a couple
>>> websites, but:  Where do they get them from?
>>>
>>> As an example, the 'insulators' they sell for the elements go for $0.20
>>to
>>> $0.35 each.  They are
>>> just shoulder washers, and I found some for $0.01 each.  So, I figured
>>> these
>>> keepers have an
>>> official industry name, but cannot find one.  I am expecting that
>>several
>>> of
>>> our local club
>>> members are going to build some of these antennas, and we will need some
>>> quantity.
>>>
>>> Thanks for listening...
>>> 73
>>>
>>> Glen K4KV
>>>
>>>
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>>
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>
>
>
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