[TowerTalk] coax stubs /bandpass filter

[Chris Wendling]

Jim,



Great info on stubs, and very timely given that Field Day is only 2 1/2 months away.

A couple of quick questions:

Does a higher "Q" coax yield more attenuation, all other things being
equal? I know the notchwidth would be reduced, but was curious about
notch depth.

Also, we've used stubs in the past at Field Day, but still get some de-sensing and "cliks".

Do you have any ideas on multiple stubs to attenuate the same
frequency, and what levels of attenuation might be achieved with more
than one stub?

Finally, in your excellent first draft of  "Some Q&A about coax and stubs for your HF station"
in the section on "Q: What's the best way to measure a stub" you only
give the physical test layout. A couple of pointers on the test
procedure itself could be helpful.



Thanks for the great work!

73,

Chris AI4MI

--- On Tue, 3/30/10, jimlux <jimlux at earthlink.net> wrote:

From: jimlux <jimlux at earthlink.net>
Subject: Re: [TowerTalk] coax stubs /bandpass filter
To: "Tower and HF antenna construction topics." <towertalk at contesting.com>
Date: Tuesday, March 30, 2010, 9:01 AM

Along a similar note..

The stub is just a moderate Q resonator that's easy to fabricate.  Why 
not put a lumped LC shunt trap across the feedline?

Too hard to get the Q low enough?
Doesn't have the nice harmonics property? (a coax stub for 40 is also a 
stub for 15)

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