[TenTec] Orion Transmitted Audio Question

[Joe Giacobello]

I had previously reported that I had been discussing my problem with Bob 
Heil.  After discussion with him and some testing this week, I think 
(hope) the problem is solved.  The bottom line here is that the special 
ground connections to the mike connector's shell do not seem to be 
necessary...at least with the HM-10.  However, I'm still experimenting.  
I have pasted excerpts from my latest message to Bob below.  I'd be 
interested in hearing others' comments.

73, Joe

Bob, you may be interested in what appears to be the solution to my 
problem.  First of all, I checked the wiring on the standard four pin 
mike plug.

   1. Pin 1 is connected to mike audio.
   2. Pin 2 has all the grounds (mike, PTT and shield) connected.
   3. Pin 3 has the other side of PTT.
   4. Pin 4 has no connection.

These all conform to pinouts on the Orion mike plug.  However, there is 
no connection to the mike plug's shell.

I cannot get the XLR connector apart without using brute force, and I 
don't want to damage it because I don't have a replacement available.  
Nevertheless, I checked the connections between it and the mike plug 
with a DVM, and they conform to the pinout given on  your website:

   1. Pin 1 is ground and is connected to mike plug pin 2.
   2. Pin 2 is audio and is connected to mike plug pin 1.
   3. Pin 3 is PTT and is connected to mike plug pin 3.
   4. Pin 4 is the other side (ground) of PTT and is connected to mike
      plug Pin 2.

There is no connection to the shell.  The bottom line is that the 
microphone works with the Orion despite the absence of the recommended 
ground connections to the shell. The scope pattern is clean with typical 
horizontal "Xmas trees."

I believe the problem that I originally reported with "noise" arose from 
having the mike gain wide open.  Although there were no signs of flat 
topping, the high gain seems to amplify the background noise excessively 
when one pauses between words, etc.  Apparently, the HM-10 is more 
sensitive in this regard than the Studio One. 

I have observed, and others have also  reported, that there is a wide 
dead spot in the Orion's mike gain adjustment.  After one gets past a 
threshold at a relatively low setting (15-30), further increases in the 
mike gain have very little effect, if any, on the amplitude or 
appearance of the modulated signal.  However, I suspect that  the 
Orion's audio circuitry may have some AGC feature associated with it.  
There is no doubt that when I stop speaking into the mike, with either 
the HM-10 or the Studio One, that the background noise increases 
substantially.  (I am listening with headphones on a second receiver.)  
I wouldn't be surprised that when one turns the mike gain past the point 
at which the amplitude of the modulated signal has maxed out, one is 
increasing the AGC effect as opposed to the audio gain itself.

I turned the audio gain for the Orion down to about 60 with the HM-10 
this morning and had several stations give me  critical audio checks.  
They said the audio sounded fine and that there were no signs of noise 
of any type on the signal with either cartridge.  I am continuing to do 
some more experimenting, etc.

I will pass along these observations to Paul at TenTec service and the 
folks on the reflector.  Perhaps they will have some further inputs.