[CQ-Contest] Icom 756PRO as a CW contest rig

Rick Lindquist, WW3DE ww3de at comcast.net
Sun Jan 2 15:49:06 PST 2011

Yes, he did. I made the mistake of assuming off the top that he was talking
about the last model. My bad.


The IC-756PRO represents the IF DSP technology in place at the time of its
design in the 1990s, which likely explains why serious contesters still
favored crystal filtering back then. It is what it is, and I would think
seriously about buying one for use as a primary contest radio; it might be
okay for a second rig in an SO2R setup, but that's just a guess. 


As I wrote, in part, in the QST "Product Review" (available to ARRL members
on the League's Web site):


Several operators have noticed what

we'll call "idiosyncrasies" while using the

IC-756PRO. For example, at some wider filter

settings and with a band filled with signals,

the radio generates a low-level rumble.

This was confirmed by looking at the band

scope. When no signals were present, the

rumble was gone. The more signals in the

bandpass, the more rumble. This is especially

noticeable when using headphones

that have above-average low-frequency response.


With headphones or a speaker that

rolls off the lower frequencies, you probably

won't notice it. One new owner told us he'd

sent his radio back to ICOM for repair or

adjustment because of this phenomenon.

"ICOM indicated that what I'm hearing is

an 'artifact' of the quiet receiver design,"

he reported, adding that reducing the RF

gain does eliminate the "minor problem."

Other users said they just got used to the

rumble and ignored it after a while.


Some operators complained that the PRO

degraded the tone of strong CW signals,

making them sound "flutey" or even a bit

on the rough side. As one user described it,

the receiver seemed to be on the verge of

overloading, even to the point of occasionally

clipping signals, resulting in distortion.

We noticed it too, especially on stronger

signals, compared to the same signal monitored

on the TS-850 we had on hand. This

tends to be just slightly less noticeable with

the noise reduction off. Besides the roughness

or flutiness, the PRO has a habit of introducing

pops on the "make" of each CW

element. One user compared it to the sort of

effect characteristic of direct conversion receivers

employing audio-based AGC systems.

Once again, less gain yielded a better sounding

received signal. Adjusting the AGC

parameters can help.


The PRO also reacts differently to atmospheric

noise. One user speculated that the

"crinkling cellophane" noise he was hearing

at wider bandwidths was related to "real noise

signals" coming into the receiver. The

noise was "an artifact of the way the DSP

presents clipped noise peaks in the audio,"

he theorized.


ICOM attributes this effect to the sharp

skirts created by the digital filters. Their response

to this statement is: "Poor shape factor

results in lots of high frequency hiss.

Sharp skirts kill the hiss-all that you hear

is the low frequency noise."


73, Rick / WW3DE


From: David Gilbert [mailto:xdavid at cis-broadband.com] 
Sent: Sunday, January 02, 2011 12:53 PM
To: Rick Lindquist, WW3DE
Cc: 'John Geiger'; cq-contest at contesting.com; 'ICOM Reflector';
okdxa at mailman.qth.net
Subject: Re: [CQ-Contest] Icom 756PRO as a CW contest rig


Well, he asked about the 756Pro.  The ProIII is a considerably better rig,
and even the ProII is a step up from the original Pro.

I'll say it again ... the 756ProI is a very poor contest rig.

Dave   AB7E

On 1/1/2011 9:04 PM, Rick Lindquist, WW3DE wrote: 

I reviewed the IC-756PROIII for QST more than five years ago, and I own one.
It's not the greatest radio for really busy bands (I operate primarily CW),
but it has some features I would hate to part with. Mine has the Inrad
narrow roofing filter mod installed, and that does offer some improvement,
but I would not call it dramatic.
Just for the sake of comparison, the PROIII's two-tone, third-order IMD
dynamic range on 14 MHz at 5 kHz spacing (the narrowest HQ was testing at
that time) was 77 dB - Not so hot anymore. The third-order intercept was
calculated at a rather lame  -17 dBm. 
Far better performers, such as the Elecraft K3, have come down the pike in
the intervening time. The K3's DR on 14 MHz at 5 KHz spacing was 105 dB (103
dB at 2 kHz spacing), with a TOI calculated at +28 dBm. That's quite an
The PROIII has been replaced by the IC-7600 in ICOM's lineup, as you
probably already knew. I reviewed that model in 2009, and it is a quantum
leap from the PROIII. The IC-7600's DR at 14 MHz, 5 kHz spacing came in at
94 dB, and the TOI was calculated at +10. A substantial improvement over the
PROIII but not quite a K3. As with the K3, the DR actually dropped slightly
at the 2 kHz measurement. 
Of course, if you have the bucks, it's hard to beat the FTdx5000 in terms of
receiver performance.
The above measurements were done in the ARRL Lab. I've cited the "preamp
off" measurement. See the respective reviews for more specifics.
73, Rick / WW3DE (ex-N1RL) 
-----Original Message-----
From: cq-contest-bounces at contesting.com
[mailto:cq-contest-bounces at contesting.com] On Behalf Of John Geiger
Sent: Saturday, January 01, 2011 8:47 PM
To: cq-contest at contesting.com; ICOM Reflector; okdxa at mailman.qth.net
Subject: [CQ-Contest] Icom 756PRO as a CW contest rig
How does the Icom 756PRO do under heavy CW QRM?  Some of the eham.net
reviews weren't very flattering in terms of CW performance.
73s John AA5JG
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