[ICOM] Running mobile with some CW problems

[Jerry Kessler]

John,

The cigarette lighter connection is likely a main part of your 
problem.  You can determine for certain if under key-down conditions 
the supply voltage between the plug and the radio drops, or after 
extended use, the body of the cigarette plug becomes warm to the 
touch (indicating voltage drop).  Cigarette lighter connections are 
not commensurate with high power radios like the 706, even at 40 
watts.  You should seek a more direct path to the vehicle battery 
with proper precautions and fusing observed.  The fact that you have 
10 or 12 gauge wiring to the cigarette lighter connection is of 
little consequence if there is significant voltage drop across the 
cigarette lighter connection.

The reasons a DC low voltage problem may not have manifested itself 
with your previous radio units is because the earlier units may have 
been more tolerant of low voltage, the radios were more efficient at 
their operating powers requiring less current draw, and/or the 
cigarette lighter connection is not as good today because of 
deterioration or poorer connection with the current cigarette lighter 
plug.  GET RID OF THE CIGARETTE LIGHTER CONNECTION!

Alternatively, you point to hot chassis conditions and chirp.  Are 
your antenna connections or the position of the radio relative to the 
antenna any different today than when the earlier radios were in 
use?  You may have an RF feedback or excessive VSWR condition that is 
affecting frequency control.  Even if VSWR is within reason, be sure 
the radio is grounded well to the vehicle chassis.  Do not rely on 
the antenna coax shield as ground.  You want to establish a good RF 
ground, or as good as possible in a vehicular installation.

The adapter plug at the CW key connection should not be an issue 
unless it is picking up stray RF but not a lot of aperture there.

Do you have any reports of FMing on SSB?  If so, likely due to swings 
in supply voltages.  If RF distortion is present in the audio, look 
further at the antenna situation and ground the radio.

Hope this helps.

Jerry Kessler
N4JL


At 05:36 PM 8/6/2013, John Geiger 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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