There is a VHF frequency that is exactly a 10th harmonic of the civil GPS
one, and it is 122.760MHz. This is why some manufacturers, such as Garmin,
offer a plug-in notch filter. Although you may think that the power at the
10th harmonic is negligible, the GPS recieves signals from the satellites
that are below the noise floor (some clever signal processing and knowledge
of what the signal should look like allows it to be extracted from the
noise). If you are going to upset the GPS with a VHF airband transmitter,
this is the frequency that will do it.
Ian.
----- Original Message -----
From: <irampil@notes.cc.sunysb.edu>
Subject: Re: Europa-List: GPS Aerial
>
>
> Hi All,
>
> I just mounted my GPS antenna (a Trimble active version) inside my
> instrument
> module (is that a binnacle??). It works fine. It is less than six inches
> from my
> other avionics, but so far no trouble. GPS frequencies are quite distant
> from other
> avionics frequencies. I presume none of them are on a harmonic of 1090 MHz
> ;-)
>
> Ira
> N224XS
>
>
|