[TenTec] Re: Heil ProSet on Orion - reprise

[Bruce Small]

Duane, et al:

I know just what you are talking about, having walked down this path two 
months ago when my Orion arrived.

Paul knows what he is talking about; trust him. This is not an RF 
problem - when I used a configuration with the PTT ground tied to pin 2 
of the TT connector (as the stock Heil adapter cables do), closing the 
PTT switch would produce spurious audio tones in the background, even 
with the microphone disconnected - thus RF output was next to nothing.

With the Pro Set Plus connected, Mic Gain had to be up to near 100 in 
order to provide sufficient audio drive, and the audio sounded 
distorted. Turning on speech processing, even at a setting of 1, 
rendered the signal just about unreadable due to distortion.

This is also not a ground loop problem. Removing every other piece of 
gear from the operating table, leaving just the Orion and power supply 
made no difference. Using a different power supply also made no difference.

My woes ended when I made up a cable with a 1/8" jack (Mic In) connected 
to pins 1 and 2 of the TT 4-pin connector, and a 1/4" jack (PTT) 
connected to pin 3 and to the cable shield. Using this to connect the 
ProSet Plus to the Orion, I now use a Mic Gain setting of about 35, 
speech processing works the way it is supposed to, and on-the-air audio 
sounds fine. Keep pin 2 isolated from the cable shield/connector shell, 
and you will be happy.

Good luck,

Bruce, KM2L

Duane A Calvin wrote:

>Paul's words were that pin 2 should never be tied to chassis ground. 
>That is essentially what Heil's page recommends - a general
>recommendation, not Orion-specific.  (Pin 2 connects to the shield of the
>ProSet microphone cable.)  Also, Heil uses this pin as the return for the
>PTT switch, while Paul said this should go to chassis ground (i.e.,
>connector shell.)  
>
>My original postings last month go into the detail of the problem - I
>won't repeat it here.  I do not think I have an RF problem, and still
>need to rule out ground loops.  [...]
>  
>
>I'll let the list know what I find that fixes it on the off chance that
>someone else has the same problem later on.
>
>        73,  Duane
>
>  
>
>Duane Calvin, AC5AA
>Austin, Texas
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>