On Tue, 03 Mar 2009 21:47:22 -0800, VOR-DME wrote:

Who knows something about 50KHz spacing for glideslope receptors?
Traditionally we have 40 GS frequencies, with 150KHz spacing from
329.15MHz to 335 MHz. But I see European ILS's requiring "50KHz
Glideslope spacing". Anyone know what receptors do this? Or why we would
want to do this? 8.33 spacing for VHF coms is easy to understand, but
are 40 ILS frequencies in a given reception area really insufficient?

Hmmm.

How are these new frequencies being implemented? Do you have some
documentation?

Currently, each ILS frequency is channeled to a particular GS frequency.

Given 50kHz spacing, and given that the ILS frequencies are 108.10 to
111.95 (and given that if the Freq*10 is even, it is a VOR frequency),
there are only 40 available ILS channels in that frequency range:

e.g. 108.10
108.15
108.30
108.35
...

The 150kHz spacing from 329.15-335 also results in 40 GS frequencies.

So unless there is some change in the ILS specs, it seems odd that there
should be a change in the GS specs.

Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)