dme freq.
 

Hello,

I have a question. Given shall be a STAND ALONE DME like Friedrichshafen. FREQ. shall be 112,500 MHz.

Regarding DMEs I have found in a JAR questionary database the following task:

The DME (Distance
Measuring Equipment)
operates within the
following frequencies:

329 to 335 MHz
962 to 1213 kHz.
962 to 1213 MHz
108 to 118 MHz

correct is charlie. My question: How is any of the frequencies btw. 962 + 1213 MHZ (other sources state 960 - 1210 MHz as the ICAO conformal solution...) allocated to the airborne cockpit setting of 112,500 MHz? Why do I not set a stand alone frequency directly?

Why are the frequencies different from those set in the cockpit at all?

yours lusthansa + thx for answers

As most DMEs are associated with co-located VORs or ILS's, a decision was taken a long time ago to use "frequency pairing".
The principle being that it is less prone to error and that NAV and DME boxes can be linked to do it automatically.

The actual frequency pairing is published and easily available if you want to know the actual frequencies used.

@ mark
 

hi mark, thx 4 reply, where can I get access to the freq. pairing allocation scheme´?

thx lusthansa

I'm ready to stand corrected but I think the answer is:

In most cases a VOR and a DME are co-located.
For each VOR frequency there is a pre-defined DME frequency.
So when you tune the VOR/NAV receiver to a VOR frequency (VHF band), the DME transponder in the a/c is automatically tuned to the corresponding frequency in the 962 to 1213 MHz band.

So what happens in the case of your standalone DME on "112.500 MHz" is that the DME transponder is tuned to the correct DME frequency, even if the VOR receiver will not have a signal.

You might also come across a stand-alone TACAN :\, mostly at MIL airfields.

To get the correct freq. to tune for DME read-out, you need to consult the Jepp NAVAIDS section, where the channel-to-freq paring is listed.

Have a look at this: http://isddc.dot.gov/OLPFiles/FAA/010459.pdf

Appendix 3 about 60 pages in.