[ICOM] Running mobile with some CW problems

[Stephen Budensiek]

Hello,
   Worked 150 countries plus mobile with a 706Mk2, lot of them CW (yes, I
was driving, running 30 wpm).   Some thoughts, the owners manual with the
IC706 list the running voltage at 12 volts.  That means 12.0000 volts or
more, not 11.9, 11.8, or lower.  Running a 706 on a battery (even a large
car battery) without charging will give problems with a little transmit
time, the battery drop below 12.00 volts on key down, the 706 gets very
unpredictable after that!   That's why some innovative people market and
sell the little step up switcher units, that will keep the voltage above
12.0 volts to the radio, even if the battery sags to 11 volts or lower.
   Some have stated above, cigarette lighters are not designed for high
current.  They are usually wired with #16 wire or lighter by car makers.
Put a DVM at the radio, and watch the voltage sag with key down.  Even with
engine running, 11.0 volts at the radio is not unusual with a IC706 at 100w
output.   Google a cigarette lighter plug data sheet, they're just not
rated for that kind of current!
   Having a good #10 or #12 wire to the battery can even cause problems, if
you use cheap fuse holders.   A good high current one can need cleaned
after a years use, especially in high humidity or coastal area's with salt
in the air.   Here on the coast of Florida, I have fits keeping the IC-706
head working, plugged on to the radio body.  Have to clean the contacts
every few months to keep it reliable.
   The IC-706 manual states explicitly to connect directly to the battery.
It warns against a cigarette lighter.   It's almost guaranteed problems
(I've had to clean up several installations like this for people).   I've
even had problems with using the pickup chassis for the ground, I've seen
the ground loose 4 volts between the battery ground terminal, and the frame
by the radio, I've resorted to running a #12 ground wire from the radio to
the battery Negative terminal on any installation I do.

73's de Stephen, K0SD


On Tue, Aug 6, 2013 at 5:36 PM, John Geiger <af5cc at fidmail.com> wrote:

> I was running my Icom 706MKII mobile over the past few days and made quite
> a few QSOs on the County Hunters Net.  However, 2 interesting things showed
> up, that I am looking for solutions for.  I had my 706 plugged into the
> cigarette lighter on a 2007 Chrysler Town and Country Minivan. The cables
> were 10 or 12 guage so there shouldn't have been much voltage drop. The
> antenna was a MFJ mini hamstick (3 feet tall on a 5 inch mag mount) for 20
> meters.  I had the rig set to 40 watts due to the current limitations of
> the cigarette lighter.
>
> The first thing I noticed was that I was getting RF bites off of the set
> up MFJ mini travel paddles I was using.  Also off of the rig case at times.
>  This is intersting because it didn't happen last month when I was using a
> Yaesu FT857 with the same setup.  The only difference was that the paddles
> have a 1/8" plug on the end, so they plugged directly into the FT857's key
> jack, whereas I had to use a 1/8' to 1/4" adaptor for the key jack on the
> Icom 706MKII.  Don't know if the adaptor could cause something like that.
>
> Secondly, a couple of stations told me I had a chirp on my signal, like
> the battery was low.  I didn't get this report when the FT857 either,
> running at around the same power, nor with an Icom 706 original I used to
> have. Could the 706mKII be more sensitive to lower voltages?
>
> I wonder if others have experienced these problems with their 7-6s or have
> an idea as to what could be going on with my setup.
>
> 73 John AF5CC
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