[TowerTalk] Fwd: Insulated elements, Yes - No?

[Hans Hammarquist via TowerTalk]

 Thank you, Ian.

Hans - N2JFS

 

 

-----Original Message-----
From: Ian White <gm3sek at ifwtech.co.uk>
To: 'Hans Hammarquist' <hanslg at aol.com>; towertalk <towertalk at contesting.com>
Sent: Thu, Aug 7, 2014 2:55 am
Subject: RE: [TowerTalk] Insulated elements, Yes - No?


>
>I still don't know if attaching the elements with conducting plates to
the
>boom require an increase or decrease of the element length.
>
>Hans - N2JFS
>

My first reaction was "Go Google for it!" because there is lots of
information about element length corrections on the web. However, there
is surprisingly little on the web about corrections for HF Yagis that
use large mounting plates or custom clamps. 

The quick answer to your question is that a metal boom, mounting plate
or clamp will always require an INCREASE in the element length to bring
the element back to its electrical length. 

The main source of information for HF antennas is Leeson's book on
'Physical Design of Yagi Antennas' which seems to be out of print. As a
primer, you could try this ancient discussion from the
rec.radio.amateur.antenna newsgroup:

<https://groups.google.com/d/topic/rec.radio.amateur.antenna/YXm1eclV5F0
/discussion>

Then continue searching for the keywords 'Leeson' and 'Yagi'.


73 from Ian GM3SEK