[Icom] Precise meaning of DSP re: IC-756 etc.

[Frank N. Haas]

Dear ICOMers:

I own an ICOM IC-756 PRO II. Have had it only a few weeks but feel very 
comfortable with it and am generally pleased with the investment. I also 
own a JPS NIR-12 Noise and Interference Reducer. For those of you who are 
not familiar with the NIR-12, it is a highly configurable digital signal 
processor that is placed in series with the audio output of a receiver and 
drives a speaker or headphones.

I have used the NIR-12 with my ICOM 751A and ICOM 761 and it was the single 
best accessory I have ever added to my station when these rigs were the 
primary HF radio.

I agree that some comments about DSP can be less than fully comprehensible. 
Being more precise would be a good thing.

There is, of course, no question that the IF DSP of the PRO II is about as 
configurable as one could hope for when it comes to removing adjacent 
frequency interference. The PRO II does not offer any meaningful AUDIO DSP, 
which for $3000 seems like an oversight. I still use the NIR-12 with the 
PRO II. Having the NIR-12 online gives me the flexibility to find the 
absolute best combination of RF and AF interference removal.

The NIR-12 offers Noise Interference Reduction that is adjustable from 
almost nothing to fully automatic, Dynamic Peaking that pulls voice audio 
out of the noise and makes voice audio much easier to hear, audio bandwidth 
that can be varied from wide open to as narrow as 50 Hertz with the audio 
peak frequency adjustable from 200 Hertz to 3400 Hertz. The NIR-12 includes 
an automatic notch that can eliminate as many as 5 heterodynes 
simultaneously from the audio output. This feature is similar to the PRO 
II's automatic notch. In short, the NIR-12 is an absolutely amazing and 
effective enhancement to any HF receiver. With the IC-751A and IC-761, I 
found that I ran the RF filtering fairly wide and let the fully adjustable 
capability of the NIR-12 do most of the selectivity work for me. [ NIR-12 
originally retailed for about $300. ]

[ Unfortunately, JPS has discontinued serving the Amateur market. Their 
products are no longer available. :-(  ]

The PRO II is capable of amazing feats of RF selectivity. However, if you 
monitor a voice net or engage in a lengthy voice or CW ragchew, the random 
noise and static can be draining. No amount of IF DSP will remove the hiss, 
static and random noise found in the demodulated output of the receiver's 
RF section. The NIR-12 processes the audio output of the PRO II and 
essentially eliminates noise, hiss, most static and accentuates voices (or 
the desired CW pitch) so well that listening for a long while is a 
pleasure. You have to hear it to believe it.

If the PRO II included AUDIO DSP in addition to its IF DSP, then it truly 
would be the most complete and perfect amateur HF radio available anywhere. 
With the addition of the NIR-12, my PRO II is indeed the perfect HF radio 
for me. Perhaps someday there will be a 756 PRO XXXVII which includes all 
of the AUDIO DSP functionality I have described herein.

So [ if you've made it this far ] perhaps it would be best if messages 
posted included a more detailed description of the type of DSP being 
discussed since there is such a clear and distinguishable difference 
between the RF and AF DSP capabilities one can enjoy in these fine HF radios.

Hope this helps.

73,
Frank N. Haas KB4T
Florida