[ICOM] 756PRO3 - popping sound?

[Adam Farson]

Hi Bert,

One should not worry too much over all the "stuff" one reads. 

(I also owned an IC-765 from 1990 to 1992. An IC-751A and an IC-781 replaced
it.)

 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 Bert Almemo
Sent: 27-Feb-08 12:47
To: 'ICOM Reflector'
Subject: RE: [ICOM] 756PRO3 - popping sound?

Hi Adam et al,

Thanks for your comments and input. I have to admit I got a little concerned
when I read about the popping sound but have to agree that nothing is
perfect. I believe the PRO3 is one of the best radios for the money!! My
IC765 is still going strong. Great receiver!!

73 Bert, VE3OBU



-----Original Message-----
From: icom-bounces at mailman.qth.net [mailto:icom-bounces at mailman.qth.net] On
Behalf Of Adam Farson
Sent: Wednesday, February 27, 2008 1:20 PM
To: 'ICOM Reflector'
Subject: RE: [ICOM] 756PRO3 - popping sound?

Hi Bert,

There was a specific problem in the 756Pro which was caused by ripple from
the noise blanker getting onto the supply rail feeding the audio output
stages. There was a fix for it.

http://www.ab4oj.com/icom/756pro_nb/main.html

This issue was corrected in the 756Pro2.

I have never heard these popping sounds on my Pro3. The sounds described may
also be partially due to artefacts generated by the distant transmitter.

The choice of AGC attack time in a DSP-based radio is very tricky. In the
presence of a very strong signal, where the AGC has to slew very fast over
an extremely large range, some overshoot can occur under certain conditions.
This can be minimised by reducing front-end gain (preamp off, attenuation,
RF gain etc.) and by careful adjustment of the AGC menu. I would certainly
not regard this as a reason not to purchase the Pro3.

See also http://www.ab4oj.com/icom/ic7700/agc.html

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 Bert Almemo
Sent: 27-Feb-08 05:46
To: 'ICOM Reflector'
Subject: [ICOM] 756PRO3 - popping sound?

Hi guys,

The following message came in on another reflector. Anyone heard of this
problem on the PRO3?

73 Bert, VE3OBU

=

The original Icom 756 Pro receiver had an anoying popping sound that would
show up at the start of each morse element when listening to strong CW
signals.

The 'pop' was mentioned in the QST product review in 2000 as as
"characteristic of direct conversion receviers employing audio-based AGC
systesms" and "the pro has a habit of introducing pops on the make of each
CW element".

Before purchasing an Icom 756 Pro III, I was told (by Icom) that the
'popping' issue was addressed, but that's not the case. The problem still
exists and is especially obvious with fast AGC settings. It's not too bad
with the internal speaker, but it certainly shows up with headphones and
some external speakers.

Suggestions appreciated...

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Net: Sundays, 1700Z, 14.316 MHz Icom FAQ: http://www.qsl.net/icom/


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