[TowerTalk] Electrically "changing" Boom length

[NPAlex at aol.com]

Dink,
You might try your idea of hanging some wire to "lengthening" the boom, but 
 the approach I would consider is the technique of removing guy wire 
resonance by  breaking them up with insulators.  Break the boom up using 
Fiberglass  tubing or solid material. Remember you can sleeve tubing together to 
effectively  increase the wall thickness.  I will add a little weight to the 
boom, but  it will be very strong.  You may have to have some pieces machined 
to  achieve a tight fit.  There are readily available sizes up to 2 in OD,  
larger sizes may be a little more difficult, but either PVC or Aluminum may 
be  used as a filler to accommodate the boom diameter.
Regards,
Norm W4QN
 
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Message: 4
Date: Mon, 30 Nov 2009 14:45:24  -0800
From: mwdink <mwdink at clearwire.net>
Subject: [TowerTalk]  Electrically lengthening a boom

I have a 40M beam underneath a tribander  with about 8 feet of
separation. The tribander is on the mast and
the 40M  beam is on a Tic Ring so both can be rotated independently. All
is well as  long as both booms are aligned.
Once the the two start getting a few degrees  (~30) out of alignment,
the SWR on 20M starts rising until I get to
90  degrees (3.3:1) then starts going down again until I reach 180
degrees. Yes,  the boom of the 40M beam is
darn close to resonant  on 20M as it's about  32 feet long. (15M and 10M
are unaffected)  I've put up with this
for  a couple years because I really don't want to bring that 40M monster
(to me)  down.

So, I was investigating detuning the boom (all the elements are  isolated
from it) when I came up with another
possible idea for  electrically lengthening it. Why can't I...

1) drill a small hole in the  boom
2) insert some stiff wire (or even tubing) inside the boom and push  it
through until it comes out one end
3) electrically connect the wire to  the boom where it goes through the 
hole.

Wouldn't that make my boom  longer as far as the 20M elements of the
tribander are concerned?  I  wouldn't think I would have to go too far out 
the end
of the boom.
Even if  the wire hangs down a bit off the end that shouldn't be an  issue.

Suggestions?

cheers
dink,  n7wa


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Message: 6
Date: Mon,  30 Nov 2009 13:06:39 -0800
From: Michael Dinkelman  <mwdink at clearwire.net>
Subject: [TowerTalk] Electrically lengthening a  boom
To: Towertalk <towertalk at contesting.com>
Message-ID:  <4B1433DF.7040202 at arrl.net>
Content-Type: text/plain;  charset=ISO-8859-1; format=flowed

I have a 40M beam underneath a  tribander with about 8 feet of 
separation. The tribander is on the mast  and
the 40M beam is on a Tic Ring so both can be rotated independently. All  
is well as long as both booms are aligned.
Once the the two start getting  a few degrees (~30) out of alignment,  
the SWR on 20M starts rising  until I get to
90 degrees (3.3:1) then starts going down again until I reach  180 
degrees. Yes, the boom of the 40M beam is
darn close to  resonant  on 20M as it's about 32 feet long. (15M and 10M 
are  unaffected)  I've put up with this
for a couple years because I really  don't want to bring that 40M monster 
(to me) down.

So, I was  investigating detuning the boom (all the elements are isolated 
from it) when  I came up with another possible idea for electrically 
lengthening it. Why can't  I...

1) drill a small hole in the boom
2) insert some stiff wire (or  even tubing) inside the boom and push it 
through until it comes out one  end
3) electrically connect the wire to the boom where it goes through the  
hole.

Wouldn't that make my boom longer as far as the 20M elements of the  
tribander are concerned?  I wouldn't think I would have to go too far  out 
the end 
of the boom. Even if the wire hangs down a bit off the end that  shouldn't 
be an issue.

Suggestions?

cheers
dink,  n7wa




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