Hi David, I know of no specific problems with a correctly functioning GPS compared to any other PED (Portable (or Personal) Electronic Device) as the aviation industry likes to call them. Thes is as others pointed out problems with clock leakage. There is also the issue that a lot of PED's can't be fully turned off, just put to sleep. The only "special" risk with GPS's would be a fault condition with an active antenna or LNA oscillating and radiating on L1. There have been problems with active TV antennas doing this and they don't have a nice resonant antenna or filter to keep them on frequency. Robert G8RPi.
--- On Sun, 4/10/09, David I. Emery <[email protected]> wrote: From: David I. Emery <[email protected]> Subject: Re: [time-nuts] GPS from a window seat To: "Discussion of precise time and frequency measurement" <[email protected]> Date: Sunday, 4 October, 2009, 7:08 PM On Sun, Oct 04, 2009 at 09:14:29AM +0000, Robert Atkinson wrote: > Hi, > This is correct. There was also an issue with harmonics from the local > oscillator in the aircraft's own VHF nav/comm receivers blocking the > GPS. The answer is a 1575MHz notch filter, e.g. > http://www.edmo.com/index.php?module=products&func=display&prod_id=18006 I have not (not being involved in avionics professionally) heard of any problems with GPS receivers causing interference to other GPS receivers or other avionics ... I would be interested in your comments on whether you know of any such issues and what the mechanisms are. Obviously I - and I think most anyone on this list - would never consider doing anything or using any equipment that might endanger an aircraft (especially one I am flying on, needless to say) - so I have tried to keep aware of any issues that might remotely exist with handheld GPSes on planes. > Another problem was bias oscillators in tape players, these could > interfere with Omega/VLF receivers. Not a problem now of course. While > on the subject of Omega/VLF If you come across a Global GNS-500A OEU > box, it has a Efratom FRK Rb in it. There is one on ebay at the moment, > item 150257671674, but the price is way to high. I had heard of that, I know many cheap tape recorders radiate enough to be detected at some distance - this has been used in the past by TSCM specialists to find covert planted recorders. > It's very had to predict interference on aircraft. While the > probability is low the consequences during take-off and landing are > severe. Hence the total ban on electronics during these flight phases. > The "illegality" is endangering an aircraft, however you do it. Avionics > design is my day job. I have read that there have been studies with a spectrum analyzer system on planes that have shown that compliance with the no radiating device rules and electronics off during takeoff and landing is far less than 100% though I certainly would not personally deliberately violate the law whether or not the probability of it causing a problem is significant. Apparently one or two cellphones can be seen registering with cell systems during takeoff and landing on many flights - probably most of them unintentionally left on. Publicly discussed and documented cases of interference causing serious problems are fairly rare... it is unclear how many actual cases there have ever been. -- Dave Emery N1PRE/AE, [email protected] DIE Consulting, Weston, Mass 02493 "An empty zombie mind with a forlorn barely readable weatherbeaten 'For Rent' sign still vainly flapping outside on the weed encrusted pole - in celebration of what could have been, but wasn't and is not to be now either." _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
