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Sinclair Duplexer and Combiner question.

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slowjoe6969

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I have a Sinclair Q3220E duplexer tuned to 463.075/468.075 and two Sinclair C3034 tuned to 463.8875 and 468.8875 respectively. On the spectrum analyzer each component is within spec and functions properly, link them together and insertion loss jumps through the rough. I suspect the reason this combination does not work together is simply the frequencies of the combiners and duplexer are to close together? Anyone familiar with tuning this product confirm my suspicions.

I tried reaching out to Sinclair through our sales rep and I received really nasty reply since there competitor won the replacement on this gear, but that is another story.

Thanks
 
prcguy

prcguy

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Here are some notes on the C3034: "By using three bandpass cavities and a reject cavity, the C-3034 permits multicoupling of Tx and Rx channels 2 MHz apart. Closer spacing of Tx only, or Rx only channels is possible in some systems."

They spec the combiner at 2MHz spacing and "some" systems might be able to go narrower. I see your frequencies are 880KHz apart at UHF which I think is far too close for a filter type combiner. Since the combiner has a notch it may also be the notch or the combiner is being used backwards where the skirts are not so favorable.

Another problem could be you need very critical cable lengths between the combiner and duplexers and that is usually found by testing with different length cables for the best return loss. Even two simple band pass cavities that are tuned to the same frequency need a critical tuned length of cable between them if your going to run them in series. Here is a video that explains testing to find the right lengths. The meat of the video starts about 10 minutes in.

 
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slowjoe6969

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I figured that I read that correctly in the tuning guides from Sinclair. Just building a lab setup for our junior techs, so retuned to a different pair over 10 mhz away from the first, and now all is good. I also learned that the tuning wasn't quite right in the combiners as originally thought. but even correcting that the large losses remained.

Thanks for the insight, the video was interesting as well.
 
prcguy

prcguy

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The tuning process can be tricky and cable lengths to the test equipment will be different than what's used in service, possibly causing tuning to be slightly off. I often cal the test cables with 6dB attenuators on each cable at the end that connects to the duplexer or filter. That way the filter sees a good, (12dB return loss) match and it takes away most of the cable interaction. Sometimes this helps get things tuned up the first time without interaction problems later.

slowjoe6969 said:
I figured that I read that correctly in the tuning guides from Sinclair. Just building a lab setup for our junior techs, so retuned to a different pair over 10 mhz away from the first, and now all is good. I also learned that the tuning wasn't quite right in the combiners as originally thought. but even correcting that the large losses remained.

Thanks for the insight, the video was interesting as well.
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