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Notch duplexer question re power loss

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respondernz
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Notch duplexer question re power loss

Postby respondernz » Tue Aug 27, 2013 10:25 pm

I'm putting in around 40watts into the notch duplexer and getting a miserable 20watts out of it. I have very little knowledge of notch duplexers. It does seem to be tuned when I test it using sig gen and H/H signal meter. I'm not sure why, probably something simple?? What is an acceptable loss?? Freq Repeater Tx 151.3250 Rx 155.50625. Any ideas greatly received.

Thanks

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Bill_G
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Re: Notch duplexer question re power loss

Postby Bill_G » Wed Aug 28, 2013 4:17 am

2db (drop approx one third) is not unusual. 3db (drop one half) seems a bit tall. Research the model of duplexer you have. A 4Mhz split may be acceptable, or maybe not.

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d119
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Re: Notch duplexer question re power loss

Postby d119 » Sat Aug 31, 2013 8:48 am

respondernz wrote:I'm putting in around 40watts into the notch duplexer and getting a miserable 20watts out of it. I have very little knowledge of notch duplexers. It does seem to be tuned when I test it using sig gen and H/H signal meter. I'm not sure why, probably something simple?? What is an acceptable loss?? Freq Repeater Tx 151.3250 Rx 155.50625. Any ideas greatly received.

Thanks


Agreeing with Bill as always, but the equipment you are using to look at the tuning is also unacceptable. To get a real picture of what's going on, you need to look at it on a tracking generator.

p1350m
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Re: Notch duplexer question re power loss

Postby p1350m » Mon Sep 02, 2013 7:13 pm

What is the brand of the duplexer? Some of the cheap notch duplexers out there aren't the best performers. Do you have a picture of it?

com501
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Re: Notch duplexer question re power loss

Postby com501 » Mon Sep 09, 2013 12:37 pm

If it is a compact VHF notch duplexer it is below the minimum split.

AEC
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Re: Notch duplexer question re power loss

Postby AEC » Thu Sep 12, 2013 12:53 pm

since you admit to operating the duplexer at below the minimum split, you are losing any separation of TX and RX, allowing one to cause desense to the other, I.E..TX into RX side.
I doubt you can clean this up unless you place a band pass cavity on the RX side to assist in notching out the transmitter.

When using 'mobile' duplexers, every dB of isolation is necessary, as you have almost no leeway. Even minor sideband noise can degrade those duplexers, including noisy transmitters with improper tuning/alignment.


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