Re: [DSTAR_DIGITAL] Re: IC-91AD vs 92AD

Nate Duehr Tue, 21 Jul 2009 13:40:35 -0700

Sounds like 146.200 is a multiple of an oscillator frequency in
the display driver chipset or similar... the "modification"
probably reworks the display to move the oscillator frequency of
the CPU out of the ham (and maybe nearby commercial) bands?
Just a guess... but sounds plausible to me, having seen a few
similar types of problems in RF transmitter devices and
interference with "themselves" in the past.

The public safety radio probably was on a frequency that also hit
the multiple or there's a missing bypass capacitor on a data line
that needs one, or similar.
--
Nate Duehr
n...@natetech.com

On Tue, 21 Jul 2009 12:05 -0500, "John Gianotti"
<w...@sbcglobal.net> wrote:

As f*&(ing bizarre as this sounds, THIS IS NOT A JOKE. This is
the in
response to my previos post about the 92AD going blank next to a
public
service vehicle.
I first noticed a problem with my 92-AD while working an event on
July 4
(notice the date is NOT in early April). I was standing next to a
police
officer and had the HT in my hand and just then the officer
transmitted on
his commercial radio. THE DISPLAY BLANKED!!! I was most
concerned. I had
seen the YouTube videos where someone passes an HT over the Icom
and the
display blanks, but we were not that close.
I called Icom a few days after to see what was going on. They had
heard of
the problem but could not reproduce it. I was concerned as my
radio was
brand new.
I called ICOM again July 20 to see if there was any update (this
is where it
gets weird!) and in talking with the tech he asked me to perform
a simple
test. Here is what I had to do:
1. Tune HT to 146.200 MHz FM (I did this on the A side, don't
know if
this makes a difference).
2. Hold HT to the side of my head with the antenna horizontal to
the
ground and antenna sticking to the rear (similar to how one might
hold the
HT while using it but perhaps more horizontal). At this point I
am looking
around for the candid camera guy to jump out of my closet but I
did it
anyway.
3. Transmit
I did so, and then looking at the display on my HT and I saw . .
. NOTHING!
It was blank!!! The tech said "send it in for a modification"
. So, I am.
According to him this is the only way they can reproduce the
problem. Their
theory is that in this position enough RF reflects off of one's
skull and
gets back into the radio to cause a problem. Standing next to a
commercial
radio with higher power must have had a similar effect. The radio
still
works when the display is blank but it is rather hard to make
changes to
frequency, etc. Powering off, then on restores the display.
He also said they did not have the parts at the moment but I am
sending mine
in anyway just so I can get in the queue. Apparently the mod is
not
something one can do at home. Evidently they add some shielding
to the CPU
and also the cable that goes to the display. He asked me to send
it with
the antenna so I wonder if there is a problem there also (usually
I don't
send in the antenna with HTs I send for repair). So anyway . . .
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References

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Re: [DSTAR_DIGITAL] Re: IC-91AD vs 92AD

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