Dme. Vhf/uhf
 

Why is the DME referred to as a VHF aid when in fact it operates in the UHF band?

Yes, you're quite correct about it being a UHF facility, but it's not normally selectable by itself. Almost always paired with a VOR. If there's no VOR (i.e the aerodrome only has NDB and DME), you select the DME frequency that applies to the VOR - whether there's a VOR or not. Thus the frequency for the DME is always published as for a VOR.

Uhf/vhf.
 

If there's no VOR (i.e the aerodrome only has NDB and DME), you select the DME frequency that applies to the VOR - whether there's a VOR or not. Thus the frequency for the DME is always published as for a VOR.


How do you select a DME frequency when there is no VOR could you please explain further please. Is a UHF frequency assigned for each VHF frequency? Could you give me an example. Please.

The DME operates on a UHF channel as you are aware, as far as your airborne eqpt goes, mostly you are not able to independently select that channel so a frequency is published which is paired with the correct UHF frequency. Think of it more of a name or a number rather than a frequency. The important thing is that when using a vor/dme you should ident both elements separately.

Short answer...
 

For DME installations, yes.

An example...

Never been down there!
 

Sorry to say, I've never visited Australia or New Zealand so I don't know what you've got for navaids.

But in the US we've got:

TACAN (TACtical Air Navigation)...military
VOR (Very high freq Omnirange Radio)
VORTAC (VOR with TACAN)
VOR/DME (VOR with DME)

I'm keeping it real basic for the neophytes.

TACAN provides range (DME) and azimuth (course) on UHF.

VOR provides azimuth only. (VHF)

But a VORTAC (a VOR station co-located with a TACAN station) serves two masters: civilian and military.

Civilian guys get their azimuth from the VOR portion.
Military guys get their azimuth from the TACAN portion.

But *both* get their DME from the TACAN on UHF.

Since civilian guys don't have UHF equipment the UHF DME freq must be "paired" with a usable VHF freq....and it's real convenient that they use the same freq as the VOR.

And of course a VOR/DME is just a VOR station co-located with a DME station so effectively it operates the same as a VORTAC for a civilian operator but there's no TACAN available for military.

It's a little bit of mix and match but it works well. I hope that helps answer your question.

To further clarify for Novicef,
you tune a VHF frequency on your VHF nav receiver, and the dme then works, but the off flags remain on your CDI/OBS etc.

AFAIK, the ILS glideslope is also outside the VHF frequency range. We refer to the systems as "VHF" because it is convenient...

AFAIK DMEs are paired with a VOR or ILS frequency. Hence if a VOR is dialed up, a DME is "armed" whether or not the hardware is there. The charts often refer to "channel nn" in the VOR or ILS box and this channel is the DME.

G'day mustafa maaate!

In the "old" days in Oz, the "nn" referred to the Domestic DME channel number that could be independently selected on the old 200 Mhz DME box. These days, about the only reference I can think of for that is the TACAN channel number. AFAIK this can only be independently selected by the military.

It also depends on part the of the World you fly in. If you fly where aviation was invented (ie. Oz), they used to have (may be still have) an international standard of Domestic DME which, I believe was in the VHF band (it was so long ago that I flew there that I have forgotten the useful bits). Weird bit of kit, but it worked!

Intruder makes a good point...
 

Yes, Intruder makes an excellent point! The same thing happens when you tune in an ILS on your NAV receiver. The localizer is VHF (and that's the frequency you're tuning "on your radio dial"), but the glide slope is UHF, and the 'frequency pair' is a standard match...so, your glide slope receiver is automatically tuned.

In other words, anytime you tune in (let's say, for example) 109.5 on your NAV receiver, you're automatically tuning XXXX (whatever the corresponding UHF frequency is) in your glide slope receiver. The pairing list is published somewhere. I'd have to look to find it. But, it's a standard pairing.

Same for the VOR situation...


PantLoad

Vhf/uhf
 

So would it be fair to say that although the DME operates in the UHF band it is called a VHF aid because to get the equipment to operate a VH frequency has to be selected. Then through frequency pairing the DME operates.

YES
 

YES, it would be fair to say that....

But only in a practical sense, so probably not a good idea to rely on that for an exam type question...