[TenTec] Heil Orion mod

[N0KHQ@aol.com]

On the back of the circuit board that has the 4  pin foster plug make sure 
that you cut the trace that is carrying the 9+ volts  to pin #4. And then solder 
a wire (I would use 14ga wire-lamp cord) to pin #4  long enough to get to a 
good close chassis point ground.
In addition to this  I would solder a 0.01pf cap from pin# 1 (audio send +) 
to pin#4 (chassis ground)  this cap will allow for audio frequency's to pass 
but will not allow for radio  frequency's to pass, they will taken straight to 
ground and not allowed to enter  the audio chain.

If you have a later Orion, manufactured after May or  June of 2004 the above 
mod is not required. If your not sure that your Orion  already has a balanced 
mic input, take an ohm meter and measure the resistance  from the Orion mic 
shell to the ground wing nut on the back of the Orion. If  your rig has the 
factory ground mod, then your meter will read a direct short,  if not the meter 
will read an open and the above mod is required.

Now to  the mic. If you are using a mic wiring setup (XLR) that has 3 wires: 
Audio Send  + (pin #2), Audio Return - (pin#3) and Ground (pin# 1) you will 
want to make  sure, on the solder side of the XLR that pin# 3 is NOT jumped to 
pin# 1. If it  is cut the jumper.

>From my testing here, using the PR-40, Goldline Pro  and Heritage mics very 
good audio can be achieved by 1st using the Orion TX-EQ  to balance out the 
audio and then setting the Orion SP to about 2. This is  easily seen using a PC 
based Spectral Analyzer like SpectraPlus or Hamalyzer.  Set the Orion low roll 
off to 50hz and the TX bandwidth at 3K to 3.15K. Just  remember that low audio 
frequency's (50hz - 100hz) carry the Power of speech and  the higher 
frequency's (2K to 3K) carry the intelligence of speech. Its  important the these 
frequency's be balanced. Too much low and people will have a  hard time 
understanding what you are saying, too much high and it will sound  like you have your 
shorts pulled up to high. Balance, balance, balance. You will  want to strive 
for the low frequency's and high frequency's to gradually roll  off nicely, not 
sharply.

On my Orion, the ground wing nut has a 12ga wire  running from it to an 8' 
ground rod outdoors and is in no way tied to anything  carrying RF frequency's 
or AC grounding. Its what I call my DC  Ground.

Have fun and take your time. 

73

John / N0KHQ / St.  Louis
http://www.hamuniverse.com/antennas.html
http://www.cebik.com/moxon/n0khq.html