[Fourlanders] DCI Bandpass Filter - High Reflected Power

[Tom McElroy]

Brian,
I just built a 5 section pi filter and had to troubleshoot it. I set it up
on the tracking generator and spectrum analyzer to see the insertion loss.
It was real easy to find the cold solder joint by poking at the inductors
with an orange-stick while watching the reponse curve displayed as I went.

So you're welcome to bring your filter over and we can narrow down the
problem.  BTW - the cold solder joint was due to some funk on the coil
wire.  It looked perfectly good under magnification and at DC.

Tom
KI4WOU

On Sep 7, 2010 9:27 AM, "Brian McCarthy" <brian at rfacres.com> wrote:

I know that we have had occasional problems with filters used for the
contests. My DCI-223.5-3H has developed a problem. With 30 watts in at
222 MHz I get 10 watts returned. I have opened up the unit. I found no
obvious problems. I closed it back up, but made sure to carefully
clean the center contacts on the SO-239's (MEK and cotton swabs). No
change. I guess I will open it up again and check for hairline
fractures, or bring it to work where I can reheat the joints with one
of the monster soldering irons.

One added data point of information, I NEVER feed the output of the
amp through the filter. I always use it between the transverter and
the Lunar Link.

Does anyone have any other suggestions?

When we had trouble before with DCI filters, what were the failure modes?

Does anyone have a similar filter appropriate for 222 MHz that I could
conveniently borrow?

Thank you!
Brian
NX9O
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