[TenTec] Decision Made/PRO III

[JS]

>Don't do anything hasty about the ICOM PRO III until you hear from 
>my experience, which isn't quiet complete.
>I bought one from AES and ran some Spectrogram patterns on the 
>receiver. Mine has serious problems at narrow BW settings, namely 
>huge noise spikes, far out of the passband.
>I sent it back to AES along with a print of the problem. They will 
>either send me a replacement or a refund. I have a feeling it's a 
>design flaw but I must give them a chance to check it out. 
>Meanwhile, see this link where I compared the PRO III with an Omni 
>VI+. The picture was taken during last week during heavy QRN on 80m. 
>Both rigs set for 250hz with their noise reduction turned on. The 
>Omni was very quiet while the PRO III was making horrible clicking 
>sounds as if it were converting the static to wide band transients.
>http://www.webham.com/Noise%20Pulses.jpg
>Steve N4LQ

Hi Steve:

That is an interesting screen shot. I am curious which model scope 
you use and how
you set it up.

My first impression was that the Pro III was noisy and passing 
signals probably way out
of its passband. Perhaps this is a DSP distortion due to radio 
settings such as too much RF gain,
AGC, NR.  It would be neat to see simultaneous scope screens with 
each radio receiving
(or attempting) the same signal in the presence of the same noise.

I own a 756 Pro 2 and have weekend access to a LeCroy scope. I tuned 
to 3512 kHz last night
and did Power Spectrum FFTs (F1 top trace) and then did an additional 
math traces (F2 bottom) of
the roof data (peak and hold) of the FFTs so I could see envelope of 
maximum FFT values.

 
http://www.qsl.net/wd1v/LeCroy.jpg

The Pro 2 is showing > 30 dB - typically 45 dB of attenuation outside 
of its 250 Hz wide passband. The full dynamic range is limited by the 
LeCroy's 8 bit front end. But since we are just looking at the 
maximum values, its illustrative for noise contours. I think the Pro 
2 is somewhat noisy until
I tweak settings and then it looks and sounds textbook perfect.  F2 
was 40 acquisitions.  Cursors
were just to show the BW scale was the same for both traces.

Maybe some of the PSK-31 waterfall display software developers will supply
the ham community with tracks of signal energy vs. noise energy so we 
see the effect of
the many adjustments we make. Most are subtle but collectively, the 
trend data could be
very useful.  The LeCroy scope can do this and its very revealing. As 
you know, the scope in the
Icom is a fixed gain stage and you can't see your own specific 
passband. Nirvana might be automating settings to maximize S/N.

73 es Happy New Year

John / WD1V
Manchester, NH
(Considering Orion and Pro 3, own Pro 2 and K2)

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