[K3CAL] Cara mount hope repeater

[Monica]

Thank you, Dave!  Great explanation.  This is what people like me need 
to better understand ham radio.

Monica

KC3DAS


On 06/01/2018 10:53 AM, David Weaver wrote:
>
> As you know, I am working on the new repeater system. There are some 
> issues with the equipment that is still in operation
>
> this is to keep everyone informed of what's happening with the system. 
> I have contacted a local, ham , to check the duplexer's
>
> this may take some time as we all know it's a volunteer and people 
> have jobs to come 1^st .
>
> Thank you for your patience. If you have any questions, please email me
>
> David W3PQS
>
> Here's a summary of tests at Mt Hope conducted on May 30, 2018
>
> Receiver sensitivity test on the Motorola repeater.
>
> Equipment: Fluke 6071A synthesized RF signal generator
>
> A dummy load was placed on the output of the repeater.  The Fluke was 
> connected to the repeater's receive port using a short length of 
> RG-58.   The Fluke's modulation function was used to FM modulate its 
> output with a 157 Hz tone (close enough to 156.7 to trip the repeater PL).
>
> Since a (S+N)/N meter was not available, *the tests were 
> qualitative*.  The magnitude of RF input needed to just bring the 
> repeater up was measured.  Then the RF input was slowly raised until 
> the repeater output, as monitored on a nearby HT, reached 
> (subjectively) full quieting.  There was enough output "leakage" from 
> the repeater's transmitter and the dummy load to make this possible.
>
> A second test was done with the duplexer connected to the repeater and 
> the Fluke's output applied to the antenna connector on the duplexer 
> cans.   The transmitter input to the duplexer was terminated with a 50 
> Ohm termination (recall the TX output of the repeater was attached to 
> a dummy load)
>
> Results:
>
> Fluke connected to the Motorola RX input
>
> Signal amplitude needed to bring the repeater up    0.1 microvolts
>
> Signal amplitude need to subjectively reach full quieting   1.0 microvolts
>
> Fluke connected to antenna input on the duplexer cans
>
> Signal amplitude needed to bring the repeater up    0.5 microvolts
>
> Signal amplitude need to subjectively reach full quieting   2.0 microvolts
>
> Estimated duplexer Antenna-to-RX-port Loss
>
> To bring the repeater up....   loss = 20*log(0.1/0.5) = 14 db
>
> To reach full quieting ....       loss = 20*log(1/2) = 6 db
>
> Normal expected duplexer loss from antenna port to RX output port    1 
> to 3 db
>
> *Conclusion: Duplexer needs re-tuned*.
>
> References: 
> http://www.repeater-builder.com/antenna/pdf/emr-corp-antenna-duplexers.pdf 
>
>
> http://www.repeater-builder.com/antenna/intro-to-duplexers/intro-to-duplexers.html 
>
>
>
>
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