[TenTec] Orion AM ALC

Rsoifer at aol.com Rsoifer at aol.com
Sat Jun 12 15:47:10 PDT 2010

Mine doesn't seem to work that way.  With PWR set to 100, output is 96  W.  
So far, so good.  Then, when I hit the PTT, output is 12 W. .I  then talk, 
whistle, etc.  When I'm done, but with PTT still on, output  reverts to 12 
W.  That is with 2.044A.  Doug must have been writing  about a different 
version of firmware.
In a message dated 6/12/2010 8:17:05 P.M. GMT Standard Time,  
merlebone at charter.net writes:

This is  the write-up that Doug Smith did on the Orion AM ALC. It 
is taken from a  paper he did on the Orion.
Sorry I can't include the diagram but I think  you will get the  

A  Unique AM ALC

Here is a novel AM ALC system that sports zero carrier  shift and 
100% maximum modulation, regardless of transmitter gain and  
baseband wave shapes. Refer to Fig 6.

A DSP obtains information  about peak transmitter output power 
from a bridge, as above. Since it  already has information about 
its peak drive level, it can compute the  transmitter's gain. It 
is then relatively easy to find the drive level  that produces a 
carrier of exactly 25% of the set power level.

An  audio compressor is employed that sets the maximum baseband 
peak level  identical to that of the carrier. When modulation is 
performed, the result  is a 100%-modulated AM wave. The audio 
compressor uses a full-wave  rectifier. If the baseband voltage 
had a higher negative peak than  positive, 100% downward 
modulation would be reached in compression before  100% upward 
modulation could occur.

Carrier amplitude does not  change because the transmitter gain 
calculation is performed on the  peak-detected combination of 
Vc+Mt, where Vc is the peak carrier level and  Mt is the peak 
modulation level. DSP computes the peak drive level based  on 
carrier plus modulation; it computes the carrier level based on  
transmitter gain. Carrier shift, therefore, is avoided entirely--   
Doug Smith,  KF6DX.

When  you go to a new band on AM, and say the first word or two, 
the Orion DSP  does the gain calculation talked about above and 
sets the carrier to 25%  of the power setting on the power knob 
(Using the gain calculation of the  radio on that band/frequency). 
The actual carrier power will then change  as the power knob is 
changed. I am using the LP-100 Wattmeter to measure  the power out 
on my Orion running V2.063X. It is easiest to measure the  carrier 
on the average power setting on the LP-100 and measure the peak  
transmit power on the peak settings (Mic gain to zero to measure  
carrier). Once the carrier is set for a particular power setting, 
it  is stable with just slight (Less then 1 watt change) variation 
from the  main ALC. On 75M AM the output power drives to 103 W 
with the carrier at  25.X watts (The power numbers are accurate to 
about 3% and were calibrated  with NIST traceable calibrated 
equipment). I am sure the accuracy of the  carrier level varies 
some due to the frequency associated measurement  error of the 
Pretty much as the write-up predicts.
73, Merle  - W0EWM 

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