PAW, Dittel KRT2 and audio warnings

[Smaragd]

No doubt a radio problem, but perhaps someone else has come across the same PAW interaction. I have a Dittel KRT2 radio with integral intercom, which has a VOX feature which mutes the mike when one is not talking (a “v” is displayed when mike is live). When I feed the Dittel audio input from my Walkman the music is audible at all times (whether or not “v” is displayed), even when I reduce the volume on the Walkman until it is very quiet. However when I replace the Walkman with the PAW audio output I can only hear warnings when the mike is already live (“v” displayed). Stop talking and the PAW warnings stop. Any thoughts?

[brinzlee]

It sounds like some sort of Squelching parameter on the Audio input or maybe even some kind of standby connection....Have you tried testing the audio source from PAW within the 192.168.1.1 CONFIGURE and try pressing the Audio Test several times and see if that says "Pilot Aware". I've seen some powered speakers that go into a kind of standby when no input is present and then when there is a signal the first part of the audio message is clipped.

[Smaragd]

I thought at first it might be a squelch on the audio, but, as I mentioned, music from my Walkman gets through even when much quieter than the messages from the PAW, and gets through when there's no "v" visible on the display. On the other hand, the PAW audio only gets through when the mike is active. Ditto if I trigger PAW warnings  - only audible if the mike is live.

[Admin]

Could this be related to stereo/mono signals ?

[brinzlee]

Is the PAW running by battery or USB converter from the aircraft power supply ?

[Moffrestorer]

I think Lee has a point regarding the audio. It sounds like a wiring issue to me. The Dittel is probably mono input and when fed with stereo from the Walkman might be feeding audio to a second input that functions with the mic inactive (as well as the vox input).

[exfirepro]

Just to add to the mix....

Not strictly a PAW issue in his case, but IIRC Alan Gee had a similar problem when trying to feed audio from his (Samsung) tablet into his (Flycom) intercom via a bluetooth link with VOX voice operation. Each time the tablet sent a message, the delay in the VOX turning the link 'on' resulted in him only getting the latter part of the messages. As I say, not a PAW issue, but a similar problem.

In your case, I have a feeling it may be due to the method of switching your VOX which may not simply be driven by the audio level. It might be worth re-reading the manual for your Radio or speaking to Dittel or your supplier.

Sorry can't be more helpful as I have no experience of Dittel equipment.

Regards

Peter

[Smaragd]

Thank you for your inputs. In reply:
The PAW is running on a battery, not the aircraft supply.
The Dittel audio input is mono - and therefore whatever the PAW and Walkman are supplying is going through the single mono input (signal and earth). There is no second audio path from the audio socket.
I understand the point about Vox delay clipping the message - but with the Walkman there is no Vox activation - the "v" symbol which indicates mike live remains off, but the Walkman signal is played by the radio. So why is there a Vox effect on the PAW signal going through the same mono plug?
I had started to discuss this with the UK supplier, and assumed perhaps that the PAW signal was not strong enough to trigger Vox, but that was before I had tried the Walkman and found that that signal got through without Vox being triggered.
I'll keep investigating.

[Paul_Sengupta]

What happens if you pause the Walkman for a while then restart the music, is there a delay then?

[Smaragd]

Not that I noticed - but the Walkman is not being muted/unmuted by Vox, it's there even when Vox is muting the mike.

[tnowak]

Possibly an impedance mismatch or because your Walkman's audio output is higher than the PAW output?
Although I don't know anything specific about the Dittel it is most likely its ext audio input is looking for a compatible audio signal with a 600 ohm impedance. For example, the audio from a VOR receiver.
You are probably just "lucky" that you can get the audio from your Walkman to be heard.
The VOX circuit on the microphone input, when triggered by speaking, most likely just allows you to hear anything on the audio "receive" part of your Dittel radio, including anything connected to the ext. audio input.
Tony

[Smaragd]

That's possible, Tony. In terms of volume, the Walkman still gets through (without Vox) when much quieter than the PAW with Vox. But perhaps it's a matching problem. Will look at the numbers.

[Moffrestorer]

Hi Smaragd,

I understand you still haven't sorted the audio problem as yet.

There appear to be 2 versions of the Dittel KRT2, non-colour screen (V1), and colour screen (V2).
The sales info for V2 shows there is a display field for audio status; a=Aux on, v=vox on, e= external intercom. Can you confirm that you have status a=Aux on enabled while feeding PAW or Walkman audio to the radio? 

I have only found a Operation Manual for V1, online. Section 4.4.7 describes setting the External Input Volume, which must be between 01 and 10 for the input to function and for the flag "a" to be displayed.

Very interesting presentation yesterday evening at the Bristol Strut get-together. Thanks for advertising on the Flyer Forum.

Regards,

Chris

[Smaragd]

Thanks Chris, glad you enjoyed it. My Dittel is the earlier version, and "a" is showing; "v" shows when the mike is live. Walkman music gets through whether "v" is there or not, PAW messages only when "v" is showing. I have tried various volume settings. Haven't had time to investigate further over the  last 3 weeks; hope to do so shortly.

[Moffrestorer]

Smaragd,

As "a" is displayed, I'd expect the Walkman audio to get through, so the question is, why isn't PAW? Doesn't appear to be wiring, because it's OK when "v" is displayed. Is the PAW audio at a similar volume to the Walkman, I.e. Could it be lack of drive level? Presume you have adjusted the input sensitivity of the aux input to max because PAW (Rpi) audio output is pretty low.

Hmm, just noticed your earlier post when you said problem persists when Walkman level is lower than PAW. Tis a strange one! I think I'd still try setting the aux input level to max sensitivity to see what happens, if you haven't done so already.

I believe it is possible to turn off the VOX so mic is on all the time. Does this have any effect? 

The Rpi audio output is 4 pole, I.e. Tip (LH audio), Ring 1 (RH audio), Ring 2 (Ground), Sleeve (Video output). If you plug in a 3 pole plug (same length as 4 pole, I believe) then all you are doing is grounding the video output, all other connections should remain the same.

Regards,

Chris