Radio-headset problem

The ATR Dittel radio in the glider works fine when output is to a speaker. With a regular headset the voice volume is very low even when maxed out when using a Lightspeed or DC headset. If an old Telex is used the volume seems more appropriate. The socket seems to have a resistor soldered across it. Can anyone tell me what I must do to be able to use a modern headset?

Buy a Trig?

On my Dittel we had to add a resistor to the mic circuit which was used to add " phantom voltage" to excite mic to
Modulate, all it would do before was send the carrier. No modulation. The only reason to have a resistor in the earphone jack would seam to be for impedance matching,
But my was fine without that. Possibly some of electrical experts on here can help?

Charlie Longley said:

Buy a Trig?

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Lol! There is that.

The radio audio is most likely set up for low impedance. Measure the resistance of the audio side of your Telex headset. Low impedance will measure around 8Ω. High impedance will measure 150Ω or higher. Also, be aware that plugging in a stereo headset that is not configured to mono (no such thing as a stereo com) will cause weird stuff to happen.

Web

Jim if you want to PM me I think we might be able to help
Your call
E

Any word on this? Still an issue or all sorted out?

Web

wireweinie said:

Any word on this? Still an issue or all sorted out?

Web

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It has been suggested to remove the resistor or jumper across it to see if that helps. It’s been too hot to work outside but I will try that next.

jimboflying said:

It has been suggested to remove the resistor or jumper across it to see if that helps. It’s been too hot to work outside but I will try that next.

Click to expand...

Do that and the Telex or the speaker will not work correctly. Go find yourself an old school David Clark, mono (high impedance) headset and plug it in. if it works, the problem is with the other headsets. If it doesn't work your radio may be set up to work with a low impedance headset. (what specific model radio do you have?)

And for all you guys that won't ask me how to tell the difference between a mono and a stereo headset, look at the pic. The plug on the left is a mono audio plug. The plug on the right is a stereo audio plug. And audio is ALWAYS a bigger diameter than the mic plug.

Web

Original post mentioned an "ATR Dittel" radio. Specific model not stated. Here's the English language manual for the common ATR-720:

https://pngc.co.uk/documents/instrument-manuals/ATR720A-Manual.pdf

WARNING! I am NOT any kind of expert on electronics. But I read and comprehend fairly well. As is typical of the German glider radios, the output is selectable/adjustable for different speaker, headset, and microphone configurations. For example, a common setup would be a dynamic "swans neck" mike at 200 ohms, vs. a carbon hand mike at 50 ohms; and either a 4 ohm speaker, or 200 ohm headset. I'd speculate that someone has kluged the circuit to use what was on hand. See the circuit pinouts Figure 2-6. More modern radios do the same thing with software, or in some cases an externally accessible switch. I fly with one of these 40 year old relics, occasionally, and it works pretty well for what it is, but they're not high value avionics: Seem to be trading on ebay in the ~$100-150USD range at this time. Maybe Web can help further with interpreting the manual and pinout diagram.

In its favor, I see by the image that it's installed in a PIK-20 (very under-appreciated type, in my opinion), so it's what the antique and classic aircraft people would call "period correct." I wouldn't use a headset myself, unless it's a PIK-20E motorglider, but that's just my preference. [Of course, by the period-correct standard, I should be using a VHT-3 or maybe a Mk. II....].

Now I've told you more than I know.

Thanks. cubscout

It is in fact an ATR 720 Comm avionics Dittel radio and it is in a PIK 20E so the noise level is quite high with the engine running. ATC is very busy here and it is important to hear them clearly so hence the headset.

jimboflying said:

It is in fact an ATR 720 Comm avionics Dittel radio and it is in a PIK 20E so the noise level is quite high with the engine running. ATC is very busy here and it is important to hear them clearly so hence the headset.

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I wear a headset in my ASW-20. Seems I just can’t quite hear as well as I used to…
It used to have a Dittel but I switched it to a Trig a few years ago and have been very happy with it.

Jim,
This definitely sounds like an impedance mismatch. Most aviation headsets are high impedance, while most non aviation stuff is low impedance. Plug a high impedance headset into a low impedance circuit and you’ll get precisely what you described.

The military years ago specified high impedance, and most aviation headsets were set up for high.

MTV