APN1 Altimeter - UK Vintage Radio Repair and Restoration Discussion Forum

Cheapskatepilot · 23rd Mar 2018, 1:41 am

I bought an Old Navy APN1 altimeter a few years ago with the hopes that I could over time, obtain the remaining parts to get it working.

Until that happens, I was wondering if anybody on here knew of a way to manually get the thing working.....as in apply the correct voltage or frequencies to the terminals on the back of the instrument to get a certain reading.

If anybody has any information on how I could accomplish that....Or any of the necessary parts for sale, I would greatly appreciate it.

M0FYA Andy · 23rd Mar 2018, 9:48 am

A pal of mine can demonstrate one working. He uses a drum of coaxial cable as a delay line between the transmitter output and receiver input, this causes the system to 'think' its at an altitude of, I think, about 500 feet. This could obviously be made more sophisticated by switching between different lengths of coax to simulate different heights. I'll ask him for more details if it would be of interest.
I'm not sure without studying the system how many of the peripheral parts you need, but I would imagine the display instrument is certainly needed.
I do have all the peripheral parts, including a test set, but I've never attempted to connect it all together.

Andy

Cheapskatepilot · 23rd Mar 2018, 4:36 pm

A few photos are attached.

It is a General Electric unit marked U.S. Navy on the case and stamped with BU. Aero US Navy on the face of the instrument behind the glass.

There are 5 terminals on the back, marked A through E with the numbers 18-20-11

jamesinnewcastl · 24th Mar 2018, 1:27 am

Hi

I too have all the parts of the system - well I don't, the connectors are rare.

I do have a few documents but really these are from the internet - hmm I think anyway, In any event I will send them to you if you IM me your email address. Attached are some sample pages - I think that the full documents will get you started - but let us know how you get on. These are probably American with British covers on.

My documents are AP2533 A C and D - now I think about it I think these were from the RAFM. I think they probably contain Andys test set too (nice find incidentally!).

I suspect from the cleanliness of my unit that it will probably go from the off! You won't need to connect to an auto-pilot the lights and dial should be enough to demonstrate the system.

I heard a tale of a man who assembled his in a wheel barrow and effectively gained 'hieght' by simply orienting the antennas along the ground at buildings which could therefore be a good distance away and a bit of running around would simulate a varied 'flight'.

Cheers
James

jamesinnewcastl · 24th Mar 2018, 1:39 am

And we musn't forget the British documents....

Thinking some more I know that these were fitted to Stirlings late on - very useful for 'Gardening' and for landing in the dark as they gave a nice presettable 'traffic light' - you are going to hit the ground on RED.... I read the story from a crew member who assumed that the equipment was a Blind Landing system.

James

M0FYA Andy · 24th Mar 2018, 8:30 am

I realise I misunderstood the original question, I thought you had the 'main unit', i.e. the Tx/Rx, so suggested you need to find the Indicator, whereas it is the Indicator you have.............
I guess this is because here in the UK the main units turn up frequently, whereas the other parts take a bit more finding.
I'm sure simulating an input to the Indicator can't be too hard, offhand I don't know what sort of signal it requires. Do you know, James?
I now recommend you try to find the main unit, it's a beautiful example of electronic build quality.
Andy

Hans PE1KWH · 24th Mar 2018, 10:11 am

Not quite helpful to your question but it is definitively an WW2 unit.
Navy Contract NXsa 43386 was issued between 11-43 and 12-43
CG stands for General Eletric but that you already knew.

For others identifying old us equipment, look at http://www.usmilitariaforum.com/foru...avy-contracts/
for Navy contract dates.

jamesinnewcastl · 24th Mar 2018, 5:41 pm

Hi

Yes, enthusiasts getting carried away!!

OK you just want to use the indicator - oddly enough there is text in the document to help you. See attached at 110 (iv) Check the calibration of the Meter...... You need a 2V supply, a 250 ohm resistor, a 2k pot and a 10 mA ammeter. Connect the negative to pin D of the Altitude meter and the other items in series to pin E. You don't actually need the ammeter but your enemy will be a bad connection to the meter which may encourage you to wind up the current too much just before you make a good connection...... I'd leave the Altitude meter out of the circuit initially and just set a current of 0.5mA and then apply it to the Altitude meter, check the meter twitches and then get the connections nice and tight before winding up the current!

The altitude meter is a moving coil device and so if you get the current too high a tiny light will blink briefly and that will be the end of your meter!

The text states that the meter has a tendency to stick - hmmm not reassuring!

You should find the connector lettering on the connector but just in case here is a clip of the circuit which should help as the pattern of pins on the connector should match the circuit diagram! If not let us know.

Good luck!
James

23rd Mar 2018, 1:41 am	#1
Cheapskatepilot Retired Dormant Member Join Date: Mar 2018 Location: Philadelphia, PA, USA Posts: 2	APN1 Altimeter I bought an Old Navy APN1 altimeter a few years ago with the hopes that I could over time, obtain the remaining parts to get it working. Until that happens, I was wondering if anybody on here knew of a way to manually get the thing working.....as in apply the correct voltage or frequencies to the terminals on the back of the instrument to get a certain reading. If anybody has any information on how I could accomplish that....Or any of the necessary parts for sale, I would greatly appreciate it.

23rd Mar 2018, 9:48 am	#2
M0FYA Andy Nonode Join Date: May 2007 Location: Preston, Lancashire, UK. Posts: 2,511	Re: APN1 Altimeter A pal of mine can demonstrate one working. He uses a drum of coaxial cable as a delay line between the transmitter output and receiver input, this causes the system to 'think' its at an altitude of, I think, about 500 feet. This could obviously be made more sophisticated by switching between different lengths of coax to simulate different heights. I'll ask him for more details if it would be of interest. I'm not sure without studying the system how many of the peripheral parts you need, but I would imagine the display instrument is certainly needed. I do have all the peripheral parts, including a test set, but I've never attempted to connect it all together. Andy

23rd Mar 2018, 4:36 pm	#3
Cheapskatepilot Retired Dormant Member Join Date: Mar 2018 Location: Philadelphia, PA, USA Posts: 2	Re: APN1 Altimeter A few photos are attached. It is a General Electric unit marked U.S. Navy on the case and stamped with BU. Aero US Navy on the face of the instrument behind the glass. There are 5 terminals on the back, marked A through E with the numbers 18-20-11 Attached Thumbnails

24th Mar 2018, 1:27 am	#4
jamesinnewcastl Heptode Join Date: Jul 2009 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 722	Re: APN1 Altimeter Hi I too have all the parts of the system - well I don't, the connectors are rare. I do have a few documents but really these are from the internet - hmm I think anyway, In any event I will send them to you if you IM me your email address. Attached are some sample pages - I think that the full documents will get you started - but let us know how you get on. These are probably American with British covers on. My documents are AP2533 A C and D - now I think about it I think these were from the RAFM. I think they probably contain Andys test set too (nice find incidentally!). I suspect from the cleanliness of my unit that it will probably go from the off! You won't need to connect to an auto-pilot the lights and dial should be enough to demonstrate the system. I heard a tale of a man who assembled his in a wheel barrow and effectively gained 'hieght' by simply orienting the antennas along the ground at buildings which could therefore be a good distance away and a bit of running around would simulate a varied 'flight'. Cheers James Attached Thumbnails Last edited by jamesinnewcastl; 24th Mar 2018 at 1:51 am.

24th Mar 2018, 1:39 am	#5
jamesinnewcastl Heptode Join Date: Jul 2009 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 722	Re: APN1 Altimeter And we musn't forget the British documents.... Thinking some more I know that these were fitted to Stirlings late on - very useful for 'Gardening' and for landing in the dark as they gave a nice presettable 'traffic light' - you are going to hit the ground on RED.... I read the story from a crew member who assumed that the equipment was a Blind Landing system. James Attached Thumbnails Last edited by jamesinnewcastl; 24th Mar 2018 at 1:46 am.

24th Mar 2018, 8:30 am	#6
M0FYA Andy Nonode Join Date: May 2007 Location: Preston, Lancashire, UK. Posts: 2,511	Re: APN1 Altimeter I realise I misunderstood the original question, I thought you had the 'main unit', i.e. the Tx/Rx, so suggested you need to find the Indicator, whereas it is the Indicator you have............. I guess this is because here in the UK the main units turn up frequently, whereas the other parts take a bit more finding. I'm sure simulating an input to the Indicator can't be too hard, offhand I don't know what sort of signal it requires. Do you know, James? I now recommend you try to find the main unit, it's a beautiful example of electronic build quality. Andy

24th Mar 2018, 10:11 am	#7
Hans PE1KWH Triode Join Date: Jul 2016 Location: Hilversum, Netherlands Posts: 33	Re: APN1 Altimeter Not quite helpful to your question but it is definitively an WW2 unit. Navy Contract NXsa 43386 was issued between 11-43 and 12-43 CG stands for General Eletric but that you already knew. For others identifying old us equipment, look at http://www.usmilitariaforum.com/foru...avy-contracts/ for Navy contract dates.

24th Mar 2018, 5:41 pm	#8
jamesinnewcastl Heptode Join Date: Jul 2009 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 722	Re: APN1 Altimeter Hi Yes, enthusiasts getting carried away!! OK you just want to use the indicator - oddly enough there is text in the document to help you. See attached at 110 (iv) Check the calibration of the Meter...... You need a 2V supply, a 250 ohm resistor, a 2k pot and a 10 mA ammeter. Connect the negative to pin D of the Altitude meter and the other items in series to pin E. You don't actually need the ammeter but your enemy will be a bad connection to the meter which may encourage you to wind up the current too much just before you make a good connection...... I'd leave the Altitude meter out of the circuit initially and just set a current of 0.5mA and then apply it to the Altitude meter, check the meter twitches and then get the connections nice and tight before winding up the current! The altitude meter is a moving coil device and so if you get the current too high a tiny light will blink briefly and that will be the end of your meter! The text states that the meter has a tendency to stick - hmmm not reassuring! You should find the connector lettering on the connector but just in case here is a clip of the circuit which should help as the pattern of pins on the connector should match the circuit diagram! If not let us know. Good luck! James Attached Thumbnails Last edited by jamesinnewcastl; 24th Mar 2018 at 5:52 pm.