[TenTec] More from Rob Sherwood, NCØB Re: Is the Orion Noisy?]

[Curt Gamble]

Curt, WØALC

Here are my comments to one of the posts asking valid questions, which 
you may post for me.

I have had an Orion II on loan from Ten-Tec for over 9 months so I can 
continue to give input to Jack Burchfield on firmware issues.
I had a 7800 for five months, though I recently sold it to a friend in 
California.

Here are my comments on the major issue of how the Orion II sounds with 
S2 or S3 signals.
The issue of the noisiness of the Orion II has to do with the operation 
of the AGC code, not general sensitivity.  Once a signal starts to move 
the S meter, a radio should start quieting down, and one should be able 
to run the AGC slowly enough smooth out the signal.  When signals are S2 
or S3, even an Icom R-71A receiver sounds quieter than the Orion II.  
The Orion AGC is not delayed, and starts acting at very low signal 
levels, and for some reason the time constant is effectively very short 
at at these low signal levels.  Thus the AGC fills in any spaces between 
"words" on SSB or "dits" on CW with band noise.  During a "word" or a 
"dit", the Orion II is likely no different than any other radio, the 
problem is in-between words or dits.  Sensitivity has not been an issue 
since the 75A-4.  I can copy a very weak SSB signal on 15 meters as well 
on a 75S-3B as on any modern rig.  Here are a few of Jack Burchfield's 
comments to me after my listen tests last Labor Day.

We believe that the difference at low signal levels is due to numerical precision in the DSP.   
There are only a few bits left at that [low] level and may well cause the inaccuracy.  

A more general problem is how modern IF DSP rigs deal with noise, and 
some feel that an analog rig sounds better in noise than a DSP rig.  
Noise is very complex, and there are at least two ranges of issues.   
How does DSP and AGC handle weak signals in noise, and how does it 
handle a signal in during impulse noise or QRN.  All the recent DSP rigs 
(IC-7000, IC-7800, Orion, FTDX-9000 & FT-2000) exaggerate noise 
transients, drastically reacting to 1 millisecond clicks, ticks and pops 
that are for all practical purposes ignored by older designs, like the 
IC-756 Pro line or the TS-2000.  Older analog rigs like the IC-781 or 
classic tube radios also do not have the exaggerated transient noise 
problem. 

While switching a 20 meter yagi back and forth between an Icom R-71A and 
the Orion II on weak S3 signals, I noticed the analog Icom was receiving 
properly within an estimated 50 msec.  The Orion took about 1 second for 
the DSP to settle down and stabilize.  It appears that it takes DSP a 
significant time to process signals in noise and adjust its parameters.  
Thus it is not a moot point as to how DSP handles transient noises and 
QRN crashes.

Finally, yes I may be inadvertently comparing a $4500 rig to a $10,600 
rig, but I am comparing rig A to rig B.  In this case both the Orion II 
and the IC-7800 have strong points and weak points, regardless of their 
cost.  They each do some things better than the other. 

73, Rob Sherwood, NC0B


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