[K3CAL] Cara mount hope repeater

Dave davehardy0101 at aol.com
Fri Jun 1 12:48:14 EDT 2018


My personal opinion is to go ahead and tune them now if convenient.  We don't know when the move will happen.

Thanks for the update and work on this.

In Oakland CA for a few days for a graduation then north to Vancouver. 

David Hardy    davehardy0101 at aol.com KB3RAN  

On Friday, June 1, 2018 David Weaver <W3PQS at comcast.net> 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 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/intro-to-duplexers/intro-to-duplexers.html 

 

 

 

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