[Icom] Re: Icom digest, IC-746PRO issues

[George, W5YR]

Keith, many times I have tuned in an AM station on SSB and tuned the
carrier beatnote right down to as low as frequency as I could detect -
about 20 Hz for these old ears. The monitor scope still showed a signal.
Going still lower the signal finally flattens out into a straight line. I
can't measure the low end but  it is close enough to zero for government
work.

I have run extensive spectral plots on the Kachina, the IC-765, the PRO and
the K2 and the PRO is the only one with such a remarkable audio response on
the low end. Adam Farson has posted the 765 and PRO plots on his website if
you would like to compare them with some of yours. The PRO is down 6 db at
at about 55 Hz on the low end with the 3600 Hz filter engaged as seen on
the SpectroGram plot using band noise input.

Remember that I am taking the receive audio directly from the D/A converter
before it goes through any of the bandlimiting elements in the analog audio
system within the radio. I  feed that signal via a Behringer 802A mixer/EQ
into the amp and speaker system that I described and/or use my Heil ProSet
on the Phones output the 802A to monitor the audio output and transmit
input of all three radios in the shack.

Give this a try - it really works.

73/72/oo, George W5YR - the Yellow Rose of Texas         
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe   
Amateur Radio W5YR, in the 56th year and it just keeps getting better!
QRP-L 1373 NETXQRP 6 SOC 262 COG 8 FPQRP 404 TEN-X 11771 I-LINK 11735
Icom IC-756PRO #02121  Kachina 505 DSP  #91900556  Icom IC-765 #02437


"j. keith carter" wrote:
> 
> Hi George; I'm surprised at your comment re the response down to DC. For a number
> of years now I have used the ARRL Lab procedure of injecting white noise in the
> Ant connector and looking at the complete passband response with the software
> program "Spectogram". Generally the filters start to roll off at about 300 Hz and
> depending on the filter shape you don't hear the garbage at line frequency or
> harmonics. This procedure can generally, with AGC off, allows you to look to
> about -60 db or a little better. You can generally see line (60/120 Hz) but it is
> down at least 40 db. Regards, Keith, VE3JKC. ps: I haven't looked at the PRO.