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[Towertalk] Shortening Inverted L Antennas

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Subject: [Towertalk] Shortening Inverted L Antennas
From: (
Date: Tue, 23 Jul 2002 11:00:24 -0600
Another way to fit an Inverted L into limited space is to fold the
end as needed, keeping the angle 90 degrees if possible.
You already have one bend at the apex.  Another near the
tail isn't going to hurt performance.

An Antenna Analyzer goes a long way toward simplifying 
tuning / matching.

Tom  N4KG

On Mon, 22 Jul 2002  "Nathan, Kevin" <KevNathan@DSB.WA.GOV> writes:
> Hi All,
> Thanks again to all who gave me information about shunt feeding my 
> tower for
> 160 and/or 80 meters.  I'm still thinking about this possibility but 
> want to
> look at another as well.  I am inspired in this second line of 
> thought by
> the antenna I just sent back.  It was, as I said in my post, an 
> inverted L
> for 80 and 160 with something called a resonactor in it.  It was 
> shortened
> to 105 feet by this resonactor and on air tests on 160 were pretty 
> good with
> it.  Just not good enough in light of it's problems on 80 to keep 
> it.
> However, the idea of an inverted L still sits there in my mind since 
> I have
> the radial system in place and a way to mount one.  So, here's my 
> question.
> This antenna can go up about 45 feet to the 2X4 crossbar on my tower 
> and
> then out for the remainder of its length.  The far end would end up 
> perhaps
> 20 feet off the ground if I'm lucky.  To keep it on my property, I 
> will need
> to physically shorten it and then load it to achieve resonance.  A 
> couple of
> questions arise from this.  First, is there a good rule of thumb to 
> use
> regarding how much coil to use to achieve a given amount of 
> shortening?
> I've read some articles where you wind the same length of wire onto 
> a coil
> form as you want to shorten the antenna i.e. if you want to make the 
> antenna
> 20 feet shorter, wind 20 feet of wire on the coil and so on?  Is 
> this a good
> place to start in practical terms?  Second, again is there a good 
> rule of
> thumb for where to place the coil?  I'm assuming in the horizontal 
> section
> but how far back from the end.
> I would sure appreciate any practical advice on this and thank you 
> in
> advance for your help.  73
> Kevin, K7RX
> Kevin Nathan, Independent Living Coordinator
> Dept. of Services for the Blind 
> 3411 S. Alaska
> Seattle, Wa 98118
> Voice:  (206) 721-6450
> Cell:  (206) 604-4767
> Toll Free:  (800) 552-7103
> Fax:  (206) 721-6403
> Email:
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