On Jun 18, 2009, at 8:09 AM, [email protected] wrote: > The buzz you are hearing on 440 is from airborn radar. I know on the > B52s that they turn on ECM (Electronic Counter Measures) when > leaving the coast and when returning.
ECM doesn't transmit unless it's attempting to jam incoming "bad things". Otherwise, ECM is a passive system, listening. If you'd said they turn on active RADAR, the comment would have made sense, and I'd agree with that. Probably a defensive flying endeavour to help them "see and avoid" the insane amounts of traffic at the coast. Always a nice option for the PLT if you have active radar and can see other people trying to run into you, but they're talking to ATC also... just a secondary information source. More "electronic eyeballs" outside the cockpit... Ironically, this indirectly means that UHF Amateur receivers apparently are an excellent way to know when certain military RADAR systems go active, and that in and of itself is a bit of an intelligence coup, if you think about it. Buy an HT if you're wondering if the big iron is up and active... :-) Amateurs on the coasts near Naval bases regularly receive unintentional interference from Navy RADAR, inland it's usually aircraft (think about the ERP/power requirements to hear OFF-FREQUENCY UHF noise on your Amateur Repeater... whew... those boys have some power on board!) or fixed installations, and can be DF'ed (if a ground source) right to the antenna. Of course, not all of it is off- frequency... depending on the RADAR or Comm system. A number of Colorado Amateurs DF'ed the EPLRS noise at Buckley AFB right up to the antenna (with appropriate permission to be on-base at the time) and later some careful "negotiation" with the system manager included pointing out that if he didn't notch out the Amateur repeater inputs (which the system CAN do, since it's so frequency agile), he was basically "giving away" the dates/times of active training missions to anyone with an Amateur UHF HT talking on a repeater in the area, along with just general begging... I hear that this is very location dependent, and probably also had to do quite a bit with the fact that one of the Amateurs talking to them was a RADAR/SIGINT expert from a past life... I think. He won't say. Hah... those of you who've done those jobs "get it" when I joke about that. Anyway, haven't had any EPLRS noise now for many years here in the Denver area... I'm sure one can spin the dial and still hear it in other sections of the band during missions, but not on the repeater inputs... system manager here was SMART and "got it". Active transmitters means others know something useful about what you're up to... -- Nate Duehr, WY0X [email protected] http://facebook.com/denverpilot http://twitter.com/denverpilot
