Topband: Receivers

[Robert McGwier]

There is little doubt that from the time of the introduction of the
IC-746 through the IC-756 Pro II there was ONE acceptable receiver
introduced by ICOM.  It was the IC-746.  I have no idea how Icom
could show their faces in amateur radio circles where each succeeding
generation 756, 756 Pro,  746 Pro, 756 Pro II got WORSE in one way
or another in the receiver department  (Read the ARRL lab tests).  I
have a favorite contester that I operate with. I have no idea what he
sees in the IC756ProII.  It is such a dog in the presence of strong
signals (especially on the low bands) that it is a testimonial to
his abilities as an operator that he gets the scores he puts up
every year.  I get fatigued after listening to the 756ProII after
two hours and my brain shuts off (what little is left of it).

The IC-765 is a very good receiver as is in the IC-781.  I have growing
experience with both of these receivers at N2NT and K3LR.  They are
terrific in the presence of strong signals on 40, 80, 160 meters.  I am
not certain that Icom has beaten the 781 with the 7800 given the ARRL
lab results.  I make no other comments on the 756ProIII or the 7800
since I have no experience.

I owned the 756ProII for one year and got rid of it and got my
FT-1000 and heavily modified it.  I also hope to prove (in the heat
of battle) that the SDR-1000 is close to the ultimate low band receiver.  I
measured it with Leif Asbrink SM5BSZ (author Linrad and receiver expert) and
the BDR was outstanding and the dynamic range was good and the
receiver was as good at 1 Khz separation as it was at 20 Khz with IP3
of 29.5 dBm.  It is not ready for prime time for contest operation because
of the packaging and the computer interface for anything other than use as
an outboard receiver.  That will change I think with time.  It would be good
for individual operation.  I will report later on my results.

Bob
N4HY


-----Original Message-----
From: topband-bounces at contesting.com
[mailto:topband-bounces at contesting.com]On Behalf Of Ford Peterson
Sent: Saturday, November 13, 2004 6:03 AM
To: topband at contesting.com
Subject: Re: Topband: Receivers


I recently acquired a new MKV.  My 'other' radio is an IC746 (not pro).
Given the budget constraints of <$1K, the 746 is not a bad radio at all.  In
fact, next to the stock MKV, I'd take the 746 on Topband.  Admittedly, I
need to get the new Roofing filter mod done (won't be here until mid
December) on the MKV, and without the IF mod, the MKV collapses.  I'll
reserve final judgement until I get all the mods done on the MKV.  So far,
the MKV is a big yawn by comparison.  The QSK on the 746 runs circles around
the MKV.

The 746 has an exceptional MDS.  I can hear the flames already.  Why the
heck do you need MDS on topband?  The 746 falls apart when you turn on
either of the two preamps (MDS -143dBm).  Turn off the preamps and put in
the attenuator (~10dB-15dB), and it's a pretty rugged front end during
contests.  Add filters to both IFs, and clamp it down to 80Hz 'peaking' DSP
on the real weak ones or deep pile-ups, and you can hear stuff down in the
noise that is quite unbelievable.  On the beverage, the 746's MDS becomes
pretty important for weak signal work.  And the 746 uses the IC781's VFO
topology.  The VFO is excellent--very versatile for a single receiver radio.
There are many parts of the 746 that I miss when running the MKV.  And you
don't have to do 14 modifications to make it work right.  What is missing in
the 746 is the extra receive antenna port, the second receiver, and two
mods...

746 lowband mod (simple and reversible)
Plug-in filters in both IFs (standard ICOM IF)

For the money, the original 746 is an excellent 160M-2M radio (If you can
pry one out of somebody's hands).

Ford-N0FP
ford at cmgate.com


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