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Ancient avionics

I’ve just seen this for sale in a US FB site where people are trying to get rid of all kinds of old junk. This item has apparently just come out of a plane

Analog distance readout. Never knew this even existed!

Shoreham EGKA, United Kingdom

Peter wrote:

Analog distance readout. Never knew this even existed!

In one of his books (“Stranger to the ground”, IIRC), Richard Bach refers to the “TACAN distance drum” of his fighter jet. The distance part of the TACAN system is, of course, identical to the civil DME.

ESKC (Uppsala/Sundbro), Sweden

Have a look at the Caravelle simulator project. They made the old analogue drum-style DME work with the simulator software (X-Plane). IIRC it’s an odometer type rather than what you have above. (the web page is here: – it’s a bit out of date, there’s a load of YouTube videos on this with bits of progress from getting hold of the cockpit to the finished product, including a half hour documentary)

I’d love to see the RF section of that King DME and compare it to what’s in newer ones.

Last Edited by alioth at 11 Jan 10:13
Andreas IOM

One would think that by the time you have done all the digital processing to send and receive the packets, the analog readout saves you nothing. I was using 7 segment LEDs in 1973… not sure when they came out. But nixie tubes, and 7-seg filament lamps, existed way before that. Calculators used them in the late 60s and these were mass produced retail products.

Shoreham EGKA, United Kingdom

That King DME is probably entirely analogue though.

Andreas IOM

For anyone with a DME the military tacan is very useful still. Their use was taught in my PPL training days and I still use them occasionaly

UK, United Kingdom

Mechanical drum DMEs were very common in GA not that long ago. This is from a KN65:

Avionics geek.
Fairoaks. EGTF

I looked this up and while it is surprisingly hard to find the detailed info, it looks like DME could be done with a fairly simple microwave pulse generator.

Shoreham EGKA, United Kingdom

I got an analogue ARC ADF in my basement if anyone is interested… complete with controller, some cables and Indicator.

LSZH, Switzerland

alioth wrote:

Have a look at the Caravelle simulator project.

You or they should find Nils Alegren if you haven’t already, as I suspect he’d have some useful input on control responses etc. He is the guy that built a real live Caravelle simulator using the cockpit of a real aircraft. I think he’s currently in Sweden, having moved there a few months ago from Germany (where the simulator is located).

PS I just looked at the website link and wonder how that might be related to Nil’s effort.

The analog DME is awesome.

Last Edited by Silvaire at 11 Jan 15:28
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