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AM radio tower accessory question

J

JasonW

Guest
Hello All,Two AM radio towers near me, for KCBF 820 and KFBX 970, recently had their old-style apex red blinking beacon lights replaced with red LED beacons (plus a daytime apex strobe on the KCBF 820 tower).Next to the new beacon unit atop each tower is a short VHF-size whip antenna. Does the whip transmit the beacon status and/or accept remote commands for the beacon? If it does transmit the beacon status, what frequencies are typically used? Just out of curiousity I'd like to try picking up these signals, if any.Many thanks in advance to anyone who can help. -- Jason
 
I converted an AM tower to LED several years ago and still love it. Far brighter than incandescent and cuts the power bill radically. Plus it doesn't have to be re-lamped every year and saves big bucks on tower-climbing.I believe you'll find that small whip is nothing more than lightning protection for the beacon. No status transmitted. Status is accomplished by monitoring the current flow to the beacon (and separately, to the obstruction lamps). This involves modifying the lighting controller or outright replacing it. In the case I worked with it meant adding multiple turns to the toroid current-sensor for each. Damned tight fit to get all the necessary wire through the small center hold.
 
I see--thank you for that information. The solid-state LED beacon circuitry probably is more vulnerable to induced voltages from a nearby lightning strike than the old brush dimmer and motor.Some of the old beacons were (and may still be) monitored over dedicated telephone lines. Signals from the moving brush contacts indicated whether or not the intermittent on/off cycle was working.In around 1960, a late friend of mine once got roped into driving 15 miles into downtown Miami to check one of these telephone-monitored beacons on his day off from work. His supervisor at Bell Telephone called him at home and asked him if he would check the beacon on the microwave tower atop a downtown office building, to make sure the bulb was working (the monitor only indicated the dimmer motor status). He said "Sure," and then walked out into the yard at his South Miami home and looked toward downtown, where he could easily see the beacon. "Yes," he assured his boss, "I can see it working." His boss then informed him that company rules required him to physically go to the tower site to confirm that it was *that* particular tower whose beacon he was seeing. Needless to say, he never volunteered to do such a thing again... :) -- Jason
 
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