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Old March 19th 15, 01:19 PM posted to rec.radio.amateur.antenna
Tom W3TDH Tom W3TDH is offline
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First recorded activity by RadioBanter: Nov 2012
Posts: 26
Default Connecting multiple filters to multiband antenna

On Wednesday, March 18, 2015 at 1:32:51 PM UTC-4, Jeff wrote:
On 18/03/2015 13:54, Tom W3TDH wrote:
On Wednesday, March 18, 2015 at 8:13:58 AM UTC-4, Jeff wrote:
On 18/03/2015 10:49, Brian Morrison wrote:
On Wed, 18 Mar 2015 06:44:55 -0400
Jerry Stuckle wrote:

I would not expect matching a 50 ohm antenna to a good quality filter
(which these are) would affect their response significantly enough to
cause a problem. After all, this is the exact type of operation they
are designed for.

The stop band performance is dependent on the antenna and filter
impedances out of band, at certain phases this can lead to a
re-entering stop band. I've been dealing with the consequences of this
in my day job very recently, it is a real and significant effect in
some circumstances. It's also not trivial to fix.



Indeed Brian, also if you look at the DCI filters there are quite
large returns in the stop bands.

Jeff


What are the effects of this on my proposed operation?


The effects are that it is not a good idea to parallel filters using
coax and tee pieces.

Jeff


Jeff

Are you deliberately trying to be obscure? "It's a bad idea" is not an effect but rather a rather vaguely stated opinion. Would you please advise what the deleterious effects of connecting the filters in that way would be.

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Tom Horne W3TDH