Gerry Low end is 108 Mhz TVOR's and ILS Al ----- Original Message ----- From: "Gerard M Foley" <gfoley@xxxxxxxxxxxxxxx> To: <AIRLINE@xxxxxxxxxxxxxxxxx> Sent: Saturday, January 15, 2005 10:03 AM Subject: Re: [Sky-1] Shreveport radio shut down due to RF interference > From: "Travel Pages" <travelpages@xxxxxxxxx> > > Sent: Friday, January 14, 2005 6:59 PM > > >> That business of FM ending at the bottom of FAA radiowaves is exactly the >> issue still around today concerning the use of cellphones. >> >> Someone will know better than I, but in the 1960's I believe a TWA DC3 >> hit >> an AA DC4 in fog over the East River in New York --- authorities >> allegedly >> found in a child's carryon a radio in the ON position at the top of the >> dial.... and that, I belive, was the beginning of the story about radios >> mucking with nav equipment.... >> > Almost all radio receivers are superheterodynes, invented by Edward > Armstrong. who also invented FM radio as it is used today. > > In a superheterodyne receiver the incoming desired signal is mixed with > the > output of a local oscillator, which is in effect a little radio > transmitter. > In many FM receivers, the local oscillator is on a frequency 10.7 MHz > above > that of the desired station. Thus when tuning in an FM station on a > frequency of 101.3 MHz, the a frequency licensed for broadcasting in North > America, the local oscillator frequency of such a set is 101.3+10.7=112 > MHz, > the low end of the aircraft band which covers 112-136MHz. Such a radio > tuned to a station at 107.9 will have its oscillator running at > 107.9+10.7=118.6, a frequency which might be used for a navaid. > > Thus the problem at Barksdale is probably not from the radio station per > se, > but from poorly shielded receivers close to the air base tuned to that > station. > > Good receivers are shielded to prevent the local oscillator radiation from > getting out, but many are not. > >> W Wilson <wlw-jr@xxxxxxx> wrote: >> The radio station probably 'just' needs a tuning and a subsequent visit >> from a "Flight check" aircraft to fly a series of approaches. >> > There is probably nothing wrong with the station. I don't know why the > investigators are mystified, if my guess is correct. > > Gerry K8EF (Senior Member, IEEE) > http://www.pbase.com/gfoley9999/ > http://foley.ultinet.net/~gerry/aerial/aerial.html > http://home.columbus.rr.com/gfoley > http://www.fortunecity.com/victorian/pollock/263/egypt/egypt.html >