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Ancient avionics

Peter wrote:

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.

The DME is pretty advanced system. The basic principle is simple enough, but when you start looking into details like the search and track modes, how aircraft can distinguish their own replies given that pulses carry no identification of their origin and how the DME station adjusts its receiver sensitivity you’re become more and more amazed that it works at all.

Last Edited by Airborne_Again at 11 Jan 15:23
ESKC (Uppsala/Sundbro), Sweden

I had one of these windshield wiper type Narco UDI-4 DME’s in the 70’s. When searching for a distance fix, it would look like a windshield wiper with the needle going to 0 and the sweeping to the right until it would finally lock on and stay at a distance indication.

I also still have a vintage omnigator.

KUZA, United States

It would seem that there is a special trick in making an analog DME very simply, because 7-segment displays have been around since at least the early 60s. I suppose driving them, from say a decade counter, wasn’t so easy in the early 60s (no 7490 etc chips).

Administrator
Shoreham EGKA, United Kingdom

I think these systems used vacuum tubes. I know my early Narco and King Nav Com units did.

KUZA, United States

Peter wrote:

Analog distance readout. Never knew this even existed!

Hmmm, ancient…. I have flown both of the King units pictured, and was happy to have them at the time! One in a club 172, and the other in a very well equipped IFR Aztec I used to fly.

In the mean time, King is on my s$#t list right now, as the KLX135 Comm/GPS, which I bought brand new in 1989, and used constantly since, has had a GPS clock failure, and will not navigate. I called the avionics shop, and they tell me that King does not support that unit any more, and it’s not repairable (yes, I’ve changed the circuit board battery). So, I guess it’s ancient too, as it doesn’t matter how old something is, if it doesn’t work, and cannot be repaired!

Home runway, in central Ontario, Canada, Canada

Another offering on the “ancient junk” site

Amazingly people are selling this as working stuff, just removed in working condition from a plane. Is that real? Can it actually be used in the current geological epoch?

Administrator
Shoreham EGKA, United Kingdom

I can’t imagine they are legal even in non 8.33 countries – is there anywhere where a 360 channel radio is still legal?

Andreas IOM

I think that in the US, these Comms aren’t at all “illegal” to use in an aircraft. Of course, they are mostly useless, because you can only tune sone frequencies and other not.

I rember having a 2nd Comm like this in the 172 which I did my IR in in Texas in 2001…

I guess there are still quite a few aircradt with 360 channels Comms installed in aircraft in the US.

Last Edited by boscomantico at 04 Mar 13:55
Mainz (EDFZ) & Egelsbach (EDFE), Germany

I have a whole cabinet full of this stuff. Gave a lot away to an interested collector. I am always referring it to my avionics museum (but then again any aircraft with a “Full IFR” silver crown stack installed get’s called by that name). We also have several old GPS units among them. Garmin 55, Garmin 100, Trimble Approach 2000 (i think).

I think the analogue stuff looks cool, but has little real value, other than serving as on-side-nice-looking paperweights or building bricks for the aero-clubs bar.

mh
Aufwind GmbH
EKPB, Germany

i found some AOPA US news about these old radios from 1996…

https://www.aopa.org/news-and-media/all-news/1996/october/pilot/tuning-a-new-com

So, most of them, including these old Narcos, have not been legal for use for many years it seems.

Last Edited by boscomantico at 04 Mar 13:59
Mainz (EDFZ) & Egelsbach (EDFE), Germany
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