[ICOM] Amazing Comparison

Adam Farson farson at shaw.ca
Thu Aug 18 13:20:27 EDT 2005


Hi Bob,

You have touched upon a very interesting bit of 756Pro-series history.

Originally, the -60 dB bandwidth for the 2.4 kHz SSB filter was shown as 2.8
kHz. For the 500 Hz CW filter, the corresponding figure was 700 Hz.

When I purchased my IC-756Pro in July 2000, I recall that there was an
erratum sheet in the user manual. This sheet restated the -60 dB bandwidth
for the 2.4 kHz SSB setting as 3.6 kHz. The -60 dB figure for 500 Hz CW was
unchanged. Unfortunately, I did not keep the sheet - it went to the new
owner of the radio. It is puzzling that Icom never updated the IC-756Pro
brochure, service or user manual to reflect this change. 

The figure of 3.6 kHz at -60 dB applies to the 756Pro, the 756Pro2, the
746Pro (7400) and the 7800. This equates to a -60/-6 dB shape factor of 1.5.

The selectivity specs appear to be worst-case values. In recent tests, the
following approximate -60/-6 dB shape factor values were obtained for the
2.4 kHz SSB filter:

756Pro:   1.18

756Pro2: 1.27 (SSB SHARP setting)

756Pro3: 1.24 (SSB SHARP setting)

Cheers for now, 73,
Adam VA7OJ/AB4OJ

-----Original Message-----
From: icom-bounces at mailman.qth.net [mailto:icom-bounces at mailman.qth.net] On
Behalf Of KE5CTY Bob
Sent: 17 August 2005 20:23
To: Icom Reflector
Subject: [ICOM] Amazing Comparison

I did a little research today and downloaded the manuals for the whole 756
line including the Pros.

After looking at the specs closely the Interesting thing was the selectivity
is less on the new ones II and III than on the IcomPro by almost a full
kilohertz.

Any other differences that offset that change?

73 fer nw,
Bob
KE5CTY 


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