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

[Hans Hammarquist via TowerTalk]

Well, the driven element will not need any correction as that stays insulated, unless you want to change from direct connect to gamma match). I just wondered if anyone had the experience with what correction was needed. Do you have to increase or decrease the length of the passive elements if you have to change the mount from insulated to electrically attached?


Hans - N2JFS

PS. I want to remember that several AM stations in the early age had to add length to their towers if the towers were tapered (as most self supporting are). That might be something similar.



-----Original Message-----
From: K7LXC--- via TowerTalk <towertalk at contesting.com>
To: pulsarxp <pulsarxp at embarqmail.com>; towertalk <towertalk at contesting.com>
Sent: Wed, Aug 6, 2014 11:07 am
Subject: Re: [TowerTalk] Fwd:  Insulated elements, Yes - No?


>  This brings up a big question in my small mind.   Assuming you need to 
correct element length,  I can see you can use SWR to  adjust the driven 
element.  But how do you correctly know how to correct or  adjust the reflector, 

or for that matter any parasitic element?  During the  Dark Ages when I 
first got licensed, you just made the reflector around 10%  longer then the 
driven element.  How do you do it in 2014?  (I really  don't want to think of 
remote field strength measurements while adjusting the  parasitic element.)  
If you correct the driven element by 1 inch to lower  the SWR, do you then 
just adjust the reflector by the same 
 
    What you do is to feed the element just like dipole  and adjust it for 
the frequency of interest. This is easy to do with split  elements like the 
F12. Just leave the other elements open and tune each one. 
 
    I think F12 used something like 2.5-3% or so  instead of the 10% you 
mentioned. If the manufacturer doesn't give you the  element resonance, you 
could model it for your requirements. 
 
    With non-split elements, I'm not sure how you'd do  them.
 
Cheers,
Steve     K7LXC
TOWER TECH
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