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Re: [TowerTalk] 80/40 coax trap dipole design

To: <>
Subject: Re: [TowerTalk] 80/40 coax trap dipole design
From: "DJ7WW" <>
Date: Thu, 16 Dec 2010 16:01:42 +0100
List-post: <">>
Hi Gerald,


Sure, a parallel LC circuit (trap) will do it but not a coil alone.

Traps should not resonate on a frequency one wants to use anyway.






From: [] 
Sent: Donnerstag, 16. Dezember 2010 15:36
Subject: Re: [TowerTalk] 80/40 coax trap dipole design


Peter, you might want to look at the pdf copy of the original article. There
is no "trap" per se in the design.


Instead, there is a clever arrangement using a parallel LC circuit that
provides inductive loading on the lower frequency and capacitive loading on
the higher frequency. It just so happens that this LC circuit does resonate
at a frequency that is about halfway between the low and high bands of the


The cool thing about this design is that the entire length of the antenna is
used on both bands; providing a bit of gain on the higher band in a manner
similar to a collinear dipole or distributed C design.



Gerald K5GW





In a message dated 12/16/2010 8:08:25 A.M. Central Standard Time, writes:

It will not work on two bands without a trap


-----Original Message-----
[] On Behalf Of Jim Thomson

Barry's designs use a loading coil in each leg rather than a trap, and 
the coils are roughly at the point where the insulator would be for a 
half wave on the higher band. Then the coils, and a bit more wire.  The 
160/80 version is roughly 160 ft long, the 80/40 version is a bit under 
100 ft. 


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