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Re: [TowerTalk] Best coaxial to make Chokes

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Best coaxial to make Chokes
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Tue, 12 Nov 2013 21:07:03 -0800
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
On 11/12/2013 8:20 PM, Roger (K8RI) on TT wrote:
may be wrong, but I've always looked at the solenoid coil as if it forms two resonances. The choke itself forms a parallel resonant frequency with a rather high Q So it may work on one or two bands and it also forms a second resonant frequency with the overall coax length which can be worse than no choke at all.

That's a good way of looking at it, but also an optimistic one. The resonance of the solenoid coil (no ferrite core) has a rather high Q (so it's a narrow resonance) and is usually much higher than the band where it needs to work, in which case the resonance is of no value. It's also optimistic that only one resonance will form with the coax. :)

73, Jim K9YC
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