[K3CAL] Cara mount hope repeater

[James Tetlow]

Dave,
Very nice of you to share the test with us! If it is tough to have someone come in to tune the cans, my thoughts are wait until the new system is in place in new shelter, then see if cans can be tuned. I am only saying this since the Moto is only a temp radio till Yaesu is ready, cans may require retune with Yaesu in place, and could be changed when cans are physically moved to new shelter (where or when ever that may take place). 
Your plan is good, the test shows retuning is necessary, it would be nice to see if retuning changes sensitivity, or we need to replace cans. I am only thinking that having to request someone come in two or three times may be a bother to them.
Only a suggestion to think on.
I for one am very pleased with the work you have been doing, and even if the Moto doesn't hear as well as it could.......it sounds outstanding! The quality of the audio out on that old radio is 200% nicer sounding to my old ears than the Yaesu. But that is just my old ears, and very few to talk to on two meters in Calvert. Of course my old ears think Yaesu Fusion Digital is the best sounding digital mode.......but only a few of us can realize that!
Thanks Dave, nice job.    

Sent from my iPad,
Best Regards,
Jim Tetlow
jimtetlow1007 at comcast.net



> On Jun 1, 2018, at 10:53 AM, 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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