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Our club repeater also ended up interfering with the local tower.
It seems that the transmitter PLL was unstable, and "hopping" between that frequency, and ours. We were clearly audible in their recordings. Ouch. That'd be categorized as a "double-plus ungood" for certain! Lest any "experts" step in and claim that you can't receive FM on an AM receiver, I'd ask them to consider what effect the passband filter of the AM receiver's IF might have on the FM signal as it deviates from side to side.... I believe the magic words are "slope detection". The resulting audio on the AM receiver isn't great (it's often distorted) but it's certainly there. I hit the magic codes and took the repeater down, once we determined that this was indeed the source. A re-tweak of the transmit PLL, and a stub filter cut to pass 146.730 and reject the tower frequency, cured the problem, and insured that if it ever happens again, they probably won't hear us. The tower now has our phone numbers in their books, in case there is ever another problem. The tower complimented our rapid and assertive handling of the problem in their closing letter to the FCC. Well done! -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
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