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Re: Reality check on capabilities of GRMS repeater

 

Very true.. I once had a repeater site that was free and had a PBX phone line available but the noise was horrible. The receiver on the bench was hearing 0.2 microvolts. At the site hooked to the Hustler G7 antenna, the effective sensitivity was over five microvolts! Needless to say the range kind of sucked.. ironically the noise was gone at 220 and the control receiver which was on a quarter wave ground plane had better coverage than the 2 m input.. Spectrum analyzer test confirmed it

Plans were made to move the repeater to an FM tower about 3 mi north.. It involved myself and K5PFE climbing the tower on a hot Sunday at August afternoon and replacing the DB224C elements with 150 MHz A elements. This was to allow the FM station RPU receivers at 161 megahertz and the 2 m repeater to share the same antenna.. which it did beautifully. The coverage got to the point to where handhelds could get in where 25 watt mobiles were noisy before.?

All that was lost in a fire at the transmitter site in January of 1989... Luckily the RC850 was not at the site, the backup repeater was in use at the time. Unfortunately the duplexers had been borrowed from a friend of mine, and I had to give him my WP-641s as a replacement.?

Ironically 30 years later I bought the duplexers back from him and they have been back on the air on my 146.94 repeater at a LPTV tower site at 475ft with a DB228 since 2014

Chris WB5ITT?


On Wed, Mar 12, 2025, 10:03 PM Mike via <prcradio=[email protected]> wrote:
Putting a bow on the final installation by performing a sensitivity test with antenna vs a load and measuring any desense is very important. It doesn’t matter how well the repeater system works on a bench, you need the equipment and knowledge on how to perform final testing as duplexers can detune during shipment. Otherwise the installed repeater can be operating at many dB below what you think or saw on a test bench. If you don’t have access to a service monitor it can get very expensive hiring someone to perform testing and touch up tuning on site.
“All the rest of the tasks of building a repeater out of mobiles still exist: Duplexer tuning, Radio programming, Radio interconnect cabling, etc. and those are the more complicated tasks.”
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