[K3CAL] Cara mount hope repeater

[David Weaver]

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 1st.

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/pdf/emr-corp-antenna-duplexers.pdf 

 
<http://www.repeater-builder.com/antenna/intro-to-duplexers/intro-to-duplexe
rs.html>
http://www.repeater-builder.com/antenna/intro-to-duplexers/intro-to-duplexer
s.html 

 

 

 

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