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Best Mobile Duplexer

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BlueDevil

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I am looking for a mobile duplexer to be used in a low powered (5w-25w) portable repeater with about 8MHz frequency separation.

Does anyone have any suggestions on mobile duplexers to stay away from or have any recommendations on what mobile duplexers seem to be superior or preferred as to others?
 
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Celwave (which got bought out if I remember correctly) or Sinclair (I seem to remember them making some). Telewave might as well.
 

12dbsinad

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I'll second Celwave.

Stay away from the cheap china Ebay special. I've seen nothing but issues with those.
 

12dbsinad

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What kinds of issues?
Stability issues. After tuning one try checking it again after a few light taps with your hand. You may be surprised how unstable they become. At least that is my opinion on them. A Celwave, You can beat it to death and I've never had a issue.
 

baltimorecs

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I have mostly Celwave and other US duplexers in our GR1225s but I have one Chinese "ebay special" and it has not had any issues. Still going strong after two years of use.
 

N4GIX

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I have mostly Celwave and other US duplexers in our GR1225s but I have one Chinese "ebay special" and it has not had any issues. Still going strong after two years of use.
If you don't ever move the cheap Chinese duplexers after tuning, they might be okay. However, I've got one here that was supposedly tuned for my frequencies before shipment.

The duplexer I ordered was supposed to be tuned for
TX: 462.7250
RX: 467.7250

It is not tuned properly. It seems to be tuned to:
TX: 462.2500
RX: 467.2500
Using my new Rigol DSA815 TG spectrum analyzer, I've not been able to (re)tune it adequately. Even when the reject is perfect, there's still nearly 5db loss on the transmit side, which means zero watts passing through to the antenna port.
 
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kayn1n32008

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I have seen Chinese ones tune up and stay stable... Met and beat a Sinclair equivalent. Being Canadian, I would recommend Sinclair over cell wave... Both are excellent... I prefer to buy Canadian.


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Thunderknight

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Even when the reject is perfect, there's still nearly 5db loss on the transmit side, which means zero watts passing through to the antenna port.
what do you mean? How does 5dB of loss equate to 0 watts? If you were transmitting (from the transmitter) with 10 watts, wouldn't that still be 3 watts out the antenna port?
 

kayn1n32008

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If you don't ever move the cheap Chinese duplexers after tuning, they might be okay. However, I've got one here that was supposedly tuned for my frequencies before shipment.





Using my new Rigol DSA815 TG spectrum analyzer, I've not been able to (re)tune it adequately. Even when the reject is perfect, there's still nearly 5db loss on the transmit side, which means zero watts passing through to the antenna port.


That is actually pretty decent plot for a mobile duplexer...

FYI: Your markers are in the wrong spot to measure loss from the transmit port to the antenna port. Also you have not calibrated the tracking generator to the spectrum analyzer... (Uncal)

You are wrong... 5dB of loss does not mean zero watts out of the antenna port.


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N4GIX

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That is actually pretty decent plot for a mobile duplexer...

FYI: Your markers are in the wrong spot to measure loss from the transmit port to the antenna port. Also you have not calibrated the tracking generator to the spectrum analyzer... (Uncal)

You are wrong... 5dB of loss does not mean zero watts out of the antenna port.
The traces were done before the Rigol lost it's calibration. Also, note the lack of symmetry in the traces. The valley should have symmetrical slopes on both sides. So, it is far from what I'd consider "decent..." ;)

I had already moved marker 1 to the transmit frequency to determine the loss. I seem to remember it was about -5dB down, but my memory isn't what it used to be. Evidently it was much higher, probably -15dB

30 solid watts in, ZERO watts at the antenna port. If I slightly detune the receiver side's reject I can get about 6 watts out, but by then I've de-sensed the receiver considerably.

Using my Service Monitor receiver sensitivity at the antenna port is 0.28µv sinad, when connected to the duplexer's antenna port sensitivity is 1.86µv sinad.

For comparison, the Cellwave duplexer in my Bridgecom BCR-40U repeater allows 50 watts in, 40 watts out. The receiver's sensitivity is 0.28µv sinad.

I'm fixing to give this problem child one more pass at getting tuned, before I demote it to a door stop... :roll:
 

jim202

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I am looking for a mobile duplexer to be used in a low powered (5w-25w) portable repeater with about 8MHz frequency separation.

Does anyone have any suggestions on mobile duplexers to stay away from or have any recommendations on what mobile duplexers seem to be superior or preferred as to others?
I don't want to be taken the wrong way, but don't you think it would help if you at least provided what frequency band you intend to use this on?
 

kayn1n32008

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The traces were done before the Rigol lost it's calibration. Also, note the lack of symmetry in the traces. The valley should have symmetrical slopes on both sides. So, it is far from what I'd consider "decent..." ;)

I had already moved marker 1 to the transmit frequency to determine the loss. I seem to remember it was about -5dB down, but my memory isn't what it used to be. Evidently it was much higher, probably -15dB

30 solid watts in, ZERO watts at the antenna port. If I slightly detune the receiver side's reject I can get about 6 watts out, but by then I've de-sensed the receiver considerably.

Using my Service Monitor receiver sensitivity at the antenna port is 0.28µv sinad, when connected to the duplexer's antenna port sensitivity is 1.86µv sinad.

For comparison, the Cellwave duplexer in my Bridgecom BCR-40U repeater allows 50 watts in, 40 watts out. The receiver's sensitivity is 0.28µv sinad.

I'm fixing to give this problem child one more pass at getting tuned, before I demote it to a door stop... :roll:

There is something else going on... 30watts in and zero out is a heck of a lot more than 5 or 15dB of loss. This is not to sound condescending, but try switching the feed lines around...


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freddaniel

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I hate to say this, but is sounds like it was connected backwards to get 0 watts out.
If not, make sure you are not retuning the low side to the high side of the duplexer, and the high to low. This will work but the pass loss will be higher.
Last, only use double shielded cable like RG-400 or 223 with silver plated crimp connector on both cables to the radio.
 

kayn1n32008

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I hate to say this, but is sounds like it was connected backwards to get 0 watts out.
If not, make sure you are not retuning the low side to the high side of the duplexer, and the high to low. This will work but the pass loss will be higher.
Last, only use double shielded cable like RG-400 or 223 with silver plated crimp connector on both cables to the radio.

30 in and 0 out is closer to 30-40dB loss... Like you said... Connected backwards.
 

N4GIX

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If not, make sure you are not retuning the low side to the high side of the duplexer, and the high to low. This will work but the pass loss will be higher.
HI Pass side notched for 462.675 - TX port
LO Pass side notched for 467.675 - RX port

I also noticed that tapping any of the cans lightly will cause the notch to shift randomly up or down. I believe that it is defective.
 

RFI-EMI-GUY

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N4GIG those notch freqs seem reversed for a repeater. Also I recommend using 3DB pads on each if the test cables and a 50 ohm load on the unused port. You can calibrate out the loss of the pads when setting a baseline. The oads and dummy load are to make sure the duplexer is being tuned into a 50 ohm load.
 

RFI-EMI-GUY

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Maybe i misinterpreted your notation about the notches. Still use pads and a dummy load. Also make sure the cablesvare double shielded and have no adaptors.
 

N4GIX

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Maybe i misinterpreted your notation about the notches. Still use pads and a dummy load. Also make sure the cablesvare double shielded and have no adaptors.
I spent a few hours (re)tuning this duplexer the other day and finally got it working acceptably. BTW, I do use pads and a 50ohm dummy load on the port not being tuned.

What I found however is that the first can on the receive side has to be de-tuned 3MHz down from the notch frequency. It is not a 5MHz split can!

When that can's notch is set correctly, there is a -5.38dB loss at the transmitter port! As I shifted the first can's notch down frequency, I noted a significant change in the loss at the transmitter port. I therefore tuned the first can's notch to produce the lowest loss, which ended up being 0.58dB...

Placed back in the repeater using double-shielded cables, the repeater now works as well as can be expected. Receiver sensitivity through the Rx port on the duplexer is 0.32µv (sinad). Transmitter is set to insert 30 watts into the Tx port, a solid 28 watts is measured at the antenna port.
 
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