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  #21 (permalink)  
Old 05-23-2017, 4:13 PM
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Quick report - so far the results are NOT encouraging. Kayn's prediction appear to be correct and the separation is not sufficient. In fact, so poor that I need a spacing of 11MHz before I get a system that would be usable. I had hoped that 8MHz would be acceptable but the repeater even on low power desenses the receiver far too much. I'm now on plan B. Kenwood repeater in a 4U rack, with a small fixed station duplexer, wrapped in foam in the 2U empty space, and a single antenna. Takes up far too much space, but appears to be a working solution.
If you have the ability/separation, I'd obtain a mobile duplexer. Epcom (El Paso Communications) has the best pricing I've seen so far on mobile duplexers...$215 before shipping. Getting it across the pond may be an issue though.
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Old 05-23-2017, 4:16 PM
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Originally Posted by paulears View Post
Quick report - so far the results are NOT encouraging. Kayn's prediction appear to be correct and the separation is not sufficient. In fact, so poor that I need a spacing of 11MHz before I get a system that would be usable. I had hoped that 8MHz would be acceptable but the repeater even on low power desenses the receiver far too much. I'm now on plan B. Kenwood repeater in a 4U rack, with a small fixed station duplexer, wrapped in foam in the 2U empty space, and a single antenna. Takes up far too much space, but appears to be a working solution.
I will suggest it again.

The Hytera portable repeater(you already own), with a mobile duplexer. If you need one, buy one of the Chinese ones, while they are a PITA to tune due to the screw and nut tuning 'rod', they will meet or beat the specs. of the Sinclair mobile duplexer they are a rip-off of.
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Old 05-24-2017, 1:42 AM
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The experiment with a duplexer does clearly show that I have to do it properly to get more than 400m or so range. My hope the split would add enough isolation was clearly wrong.

Is there a design difference that makes the mobile duplexers more expensive - externally, they appear the same, and I have a couple here, one UK built and one Chinese sourced that appear extremely similar. As the function of these and construction seems the same - has anyone cut one of the Chinese ones open to look at the engineering?
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Old 05-24-2017, 8:51 AM
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The experiment with a duplexer does clearly show that I have to do it properly to get more than 400m or so range. My hope the split would add enough isolation was clearly wrong.

Is there a design difference that makes the mobile duplexers more expensive - externally, they appear the same, and I have a couple here, one UK built and one Chinese sourced that appear extremely similar. As the function of these and construction seems the same - has anyone cut one of the Chinese ones open to look at the engineering?
I do not think so. The probable reason the Chinese ones are so cheap is the cost to make them. Like I said before, the Chinese ones tune up as good as the Sinclair ones they are a copy of. I have had them side by side on a bench with test hear. The big difference is the way the tuning rods are built. The Sinclair ones use a compression nut, where as the Chinese ones have a threaded nut on a screw.

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Old 05-24-2017, 2:12 PM
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I do not think so. The probable reason the Chinese ones are so cheap is the cost to make them. Like I said before, the Chinese ones tune up as good as the Sinclair ones they are a copy of. I have had them side by side on a bench with test hear. The big difference is the way the tuning rods are built. The Sinclair ones use a compression nut, where as the Chinese ones have a threaded nut on a screw.

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The Chinese ones generally don't use silver plated connectors. Then again, some of the offerings from RFS (Celwave) don't either.


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