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A question about extending repeater coverage

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#21 Radioguy7268


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Posted 24 October 2019 - 08:56 PM

The repeater is reachable in all most all locations, but not on handhelds, and if it is it’s vary unreliable. The desence is higher then I’d like when the repeater is in TX but it’s not really that bad at all compared to simplex. I’ve got a Sinclair q3220e and another can in the RX I can’t remember. But it’s not really about extending range just solidifying the coverage I have.


Any desense is too much. I've run plenty of 4 cavity duplexers in the scenario you describe (adding a bandpass cavity to the receive side) with absolutely no measured desense at 50 watts.


If you can hear desense, you're probably seeing at least 2dB of loss in the receive path. 2 dB doesn't sound like much, until you realize that 3dB better of receive sensitivity would double the coverage area of your system's portable talk in.


I guess it's human nature, but people will always pick the 4 watt portable over the 2 watt, yet how many of them will spend the time & money to improve the receive side of their repeater to gain 3dB? The net effect is the same. Getting 3dB of receive improvement will make your 4 watt portable seem like it's suddenly putting out 8 watts.

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#22 WRAF213


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Posted 14 November 2019 - 11:04 PM

You can't use analog RF linking on GMRS. There's nowhere to put the links anyways. Use point-to-point Wi-Fi for building networks. If the repeater's receive side is solid in all desired locations, try improving the repeater's sensitivity with more robust filtering and a LNA before trying to figure out where you're going to put a bunch of voting receivers. Simulcasting would be overkill.


RTCMs don't take a 10 MHz clock directly, they require some PLL device to shift the frequency down to 9.6 MHz. There's plans to build such a device that are readily available, but there isn't an off-the-shelf solution. A 9.6 MHz OCXO would work for voting purposes as well. All of this is far more complicated than improving the repeater's receiver, since it turns a standard duplex repeater into a computer-controlled radio network.

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#23 kb2ztx


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Posted 17 November 2019 - 07:05 AM

AS a few have said I'd look to increasing the performance of the current repeater. A good pre-amp and filters will go a long way. I am fortunate that I run a split antenna on my repeaters thru a combiner and multi-coupler. That allowed me a DB408 on RX and a DB404 on TX. The 408 gives me a bit better RX then adding in the pre-amp and filtering I have portables that can get in but can't hear the system. Its all about balance. I'm glad to see you have your power at a low level. Many think more power the better but thats not always the case. 

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