Yesterday I was trying to tune up the duplexers one can at a time as listed in this Sinclair Youtube Video.

After tuning them my receive is awful and my transmit is somewhat not what it used to be. What could be the reasons?

Here is my last photo on the meter before hooking it up:

Final tune..

Any advice on how to tune these things?

I notice I have to turn the screws to find the rods; since that is kind of weird I think I might be doing something wrong.

Typically hooking the input into the antenna portion of the duplexer and then the output on either side with a dummy load on the other end.

I have a Sinclair Duplexer Model Q2330E.


1 Answer 1


There is a trick to balance the notch tuning johannsen cap adjustment with the coupling ring loops to meet the required rejection per side with minimum insertion loss. I believe I tuned mine to reject 40-45dB rejection per cavity at max. First, I would get the pass rod approximately at the pass frequency, then tune notch under cap. If too deep or shallow a notch, less than -40 or more than -50dBm, rotate coupling loop slightly and retune pass and adjust notch cap until you find notch maximized at about 45dB on rejection frequency. Just make sure you aren't fully open or tightened on the notch cap or else you cannot fine tune the notch later. Once you get one cavity right you can approx the others by copying position, but they will still need to be adjusted finely with service monitor the same way because cans are not exact. Then do same for cans on other side. After done connect harness and fine tune pass rods. Then adjust notch caps. You should see around <= -1.5dB Insertion loss with over 100dB rejection... You must balance the rejection with rotating the coupling loops which is what most people don't expect they need to do.

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    $\begingroup$ Hello and welcome to ham.stackexchange.com! That looks like a great first answer! Would you consider expanding your answer a bit? Pictures would be ideal, but step-by-step instructions would at least be easier to follow. $\endgroup$
    – rclocher3
    Commented Jun 4, 2020 at 15:15
  • $\begingroup$ Hey thanks for the reply on this!! I just got this by the way! We ended up sending these cans off at one point getting them fixed then shipped back to us. Then we got hit by the Lightning took out some radios and power supplies heck even the feedline wasn't right ended up having to replace a lot of that anyway thanks so much for the explanation I will know for next time! $\endgroup$ Commented Oct 24, 2022 at 6:11

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