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1. 08:10 AM - Re: Re: PTT Y adapter for RST intercom (Robert L. Nuckolls, III)
2. 11:15 AM - Re: PTT Y adapter for RST intercom (messydeer)
Message 1
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| Subject: | Re: PTT Y adapter for RST intercom |
At 11:35 PM 11/23/2011, you wrote:
>
>Hmm...I didn't think if they were or weren't single or double
>throws. Here's Dynon's quote:
>
>"I took a look at your schematic and I don't think this
>configuration will work with the DX15..."
>
>He's referring to the earlier 'RST intercom mic out ptt wiring.jpg' diagram.
Unless he sits down to study the RST intercom internal
wiring, he's shooting in the dark.
Do you want both pilot and copilot headsets to access
the DX15 transmit function?
Bob . . .
Message 2
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| Subject: | Re: PTT Y adapter for RST intercom |
Dynon said "the DX15 only sends power to the mic when it is transmitting". I assume
this means it's somehow disabled when receiving. Or is there a concern that
the radio can't get power to the headsets? I thought they got power from the
intercom.
Weir said "some radios ground (disable) the microphone audio in receive mode, this
type of PTT switch is unsuitable for use with an intercom system." I assumed
then that the DX15 would have the mic grounded when receiving as the mechanism
to cutoff power to it.
I've never read how exactly the RST or any other intercom treats the mic out signal.
I thought the VOX switch in the intercom transmitted the mic signal from
the pilot's and copilot's mics to both the headsets whenever a certain threshold
was reached. From what Weir has written, it sounds like there is no switch
or gatekeeper between the intercom and mic out to the radio. Whenever one of
the mics overcomes the VOX threshold, the signal goes through the mic out line
to the radio.
I also thought the intercom would function fine without being connected to the
radio at all. There's power supplied to the intercom and the headphones and mics
from the headsets are plugged into it. But Dynon said their radio might not
have enough power to supply two headsets in parallel, sounding like the intercom
does not supply enough power to the headsets.
I don't know what needs to happen for a radio to transmit the mic signal. I thought
engaging the PTT, shorted the tip to the shell, which caused the radio to
transmit. Both the PTT button on the side of the handheld and the one in the
stick acted the same way. I thought that once this was done, the radio would transmit
whatever signal was coming in from the mic.
If the intercom's VOX threshold has been exceeded while the PTT is pushed, the
mic signal is sent to the radio and gets transmitted. I don't understand what
Dynon means when he says the DX15 sends power to the mic. I know he says it does
it only when transmitting, but I don't know what it means. It sounds like power
from the radio to the radio's mic jack is needed as well as the signal from
the mic out line from the intercom to the radios's mic jack.
I'm sure the workings of a radio mic, its power, grounding and transmitting functions
are fairly simple to understand, but I don't have that knowledge. I'd be
terribly grateful if you could explain this to me, or where I could get this
information.
The thing that bothers me about wiring the PTT with a SPST switch, leaving the
mic out line connected to the radio, is that both the designer of the intercom
and that of the radio say this is not a good idea and suggested the DPDT solution.
How could I test my radio, headsets, and intercom with my current SPST PTT
switches? Would I just hook everything up, set the radio to some locally unused
frequency and try it out?
> Do you want both pilot and copilot headsets to access
> the DX15 transmit function?
>
While I'm taking flight lessons, I can imagine it would be nice to have that capability
for both me and the CFI. Afterwards, it seems unlikely I'd ever need
it, except when there'd be another occasion for someone to be taught communication
skills.
--------
Dan
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http://forums.matronics.com/viewtopic.php?p=359121#359121
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