Topband: IC-756PRO

[Bill Hohnstein]

The following is a comparison of my new IC-756PRO vs my TS-870.
I'll try and deal with the things that concern topband use only
due to the name of this reflector.  The two were each using a
different parallel, short spaced Beverage that have shown to
receive almost identically (the Beverages have since come down for 
the season to prepare for planting).
To have a fair comparison I set the 756 bandwidth to the same that I
almost always use with the 870:  400 Hz.  I tried to duplicate
everything possible between the two.  For weak to moderate signal
DXing on 160 I almost always am using the Noise Reduction feature of 
the 870.  I left that on and turned on the similar feature on the 756.
I was immediately struck by the difference in the tone of the
background noise (which is similar without N.R. turned on).  The 756
had a lower pitch noise than the 870.  Changing the PassBand Tuning
and CW Pitch controls on the 756 really didn't change this much.  I'm
not sure which I prefer yet--the 756 sounds like it might wear on my 
ears less than 870.  The 756's lower pitch appeared to be related to
its fault with strong static bursts and close to strong signals.
Those conditions would cause a lower frequency pop in the audio.  It
sounded somewhat like the 870 would when its AGC was set way too fast.
However, adjusting the 756's AGC speed had no effect on this popping.
Similarly, I couldn't signficantly effect this popping by changing the
756's preamp, adding input attenuation, or changing filter bandwidths.
Direct comparison 500 Hz off of a strong cw station 756 vs 870 wasn't
as bad as I was expecting, but the 870 was still the clear winner as
far as being able to hear a weak station there.
The 756 did have less filter ringing with bandwidths less than 400 Hz
compared to the 870.
Listening to a weak European on 160M on a low static day, away from
interference, it was a very close call on which receiver would copy
better.  The 870 seemed perhaps a slight bit better.  Switching the
Noise Reduction feature OFF and ON with a weak signal made a
significant improvement in readability on both.  It was hard to tell
which improved reception more.  The difference in the tone of the noise
colored the perception.
Looking for a way to minimize the bad effects of the popping on a
later high static day I decided to try using the manual notch while
on cw (something that the 870 doesn't have).  Adjusting it to
minimize the lower frequency popping I found a significant reduction
in the bad effects of the noise.  It was late and EA3VY was the only
European heard then.  He was CQing without much response.  I compared
the two radios on receiving him.  The 756 seemed to be the winner on a
high static day!  It was so unexpected that I switched the parallel
Beverages around for receive.  The 756 was still better.  The
comparison was influenced though by the fact that the bandwidth of the
756 was then less than that on the 870 due to the effects of the manual
notch.  Not an ideal solution to the 756's "popping problem," but
perhaps a way to somewhat go around it.  Comparing reception on other
non-EU signals that night again showed the 756 to be the slight winner.
The spectrum scope was handy in spotting new 160M activity.
My other reactions deal more with general and non-topband important
features...
Maybe it would have been better to wait until after the rumored
other brand high-end radios show up at Dayton(?).  When will that
Perfect Radio of my dreams show up?

73,  Bill     K0HA



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