On 3/18/2015 6:49 AM, 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.


True. However - this was specifically made for 144/440 mhz with 50 ohm
impedance. As long as these are the bands he's using and he stays
within a reasonable range of 50 ohms, I don't see what the problem would be.

Again - these units are DESIGNED for this operation. What good would it
be to design and sell such an item if it doesn't work?

DCI has good engineers who know their stuff. Their equipment is top
quality. And while I've never tried this particular unit, I know they
would not let something with your perceived problems out the door.

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On 3/18/2015 1:52 PM, Brian Morrison wrote:
On Wed, 18 Mar 2015 10:55:18 -0400
Jerry Stuckle wrote:

Again - these units are DESIGNED for this operation. What good would
it be to design and sell such an item if it doesn't work?

Well, not much, sometimes you can get caught out by something
unexpected when a change is made to fix a problem and does so but then
you discover some unintended consequences.

That's exactly what I have been dealing with in a system where it's not
easy to measure the frequency response of a combined antenna and filter
in a radiated test. But we managed to do it, just took a while to
create an appropriate test system.


It may not be easy to measure when that isn't your main business. But
for a company which is, I'm sure they have the appropriate equipment and
procedures.

--
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Remove the "x" from my email address
Jerry, AI0K

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