[TowerTalk] coax stubs /bandpass filter

[Jim Brown]

On Tue, 30 Mar 2010 08:42:58 -0700 (PDT), Chris Wendling wrote:

>Does a higher "Q" coax yield more attenuation, all other things being
>equal? 

Yes. 

I know the notchwidth would be reduced, but was curious about notch depth.

The reduction in width is measured from the deepest part of the notch. In 
general, higher Q (lower loss coax) is better. I've made a lot of stub 
measurements and I'm still working on more to illustrate these issues. It's 
still a work in progress. 

>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?

Yes. It IS a good idea. There's great info in the W2VJN book about doing that, 
and how multiple stubs should be spaced with respect to each other. There's 
also some great info in the N0AX references from QST. 

>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. I'll work on that.

73,

Jim K9YC