[Mobile-Portable] Radio Shutdown problem

[Rick Markey, KN3C]

I had a similar problem with my most recent mobile setup.  I was getting a 
great deal of RF back the control line from the screwdriver antenna.  I put 
in-line RF chokes in the DC feed to the motor switch, and wrapped the motor 
lead around a ferrite core.  Alternatively I could have slipped a few 
ferrite beads over the control lead where it enters the antenna.  If the 
ferrite beads get hot, add a few more beads.  They're definitely soaking up 
some RF!

Remember that the antenna is a vertical and it's always looking for it's 
"other half" so to speak.  It will use the outside of the coax, the control 
wire, or anything else it can find for an RF path.

I had RF in the dashboard, the car stereo, you name it before I choked the 
RF out of the control lead.

You can get the ferrite beads and in-line DC chokes from Mouser.

de Rick, KN3C

----------
From: 	Scott Neader KA9FOX[SMTP:ka9fox@qth.com]
Sent: 	Sunday, August 18, 2002 17:30
To: 	mobile-portable@mailman.qth.net
Subject: 	[Mobile-Portable] Radio Shutdown problem


Hello all.  I'm in a bit of a panic, and hoping you can
assist.  I'm going on a trip and wanted to have this working before
I left, but it is not looking good.  Actually, it was working fine,
but something has changed... I'm not sure what.


My set up is:  IC-706MKIIG with Hi-Q Antennas 3/80 screwdriver-type
antenna and AmCom ASAC Automatic Screwdriver Antenna Controller.



My problem:  Every time I try to apply power on 20 meters (even the
Lowest power setting on the 706) the radio immediately shuts down.



Solution?  If I unhook the 12 volt line to the Antenna motor, the
problem goes away.


The Antenna Mfg suggests putting Toroid Cores around the 12v leads, as
close to the base of the antenna as possible.  The manual
says:


{quot}If you ordered the red toroid cores to use as RF chokes on the
motor DC lines,

install them as close to the motor as possible. Simply loop the motor
leads

through the cores, one at a time."


I do have the red toroid cores, but I guess I didn't install them
correctly... I separated the + and - leads, and put one toroid around
each lead, looping each lead through a toroid two times.  So, I have
a toroid on the + lead, with two loops around the toroid, and I have a
toroid on the - lead, with two loops around the toroid.   I
guess it's worth ripping it apart and trying to keep the leads together
and loop them BOTH through both toroids.


However, later in the manual it states:


{quot}It is also a good idea to use the clip-on, data type line chokes
on the wires coming out of the antenna motor leads. Wrap the wires around
the core at least once. Do the same

thing for the coax cable. Toroids may also be used. This will eliminate
the RF "pick-up" that may alter VSWR readings or affect the vehicle's
electronics. To prevent RF feed back on the motor lines you can add a
pair of 100 ?H, 2 amp chokes at the base of the antenna."


FYI, the installation manual for the antenna is located at:



http://www.hiqantennas.com/Stealth-Mounting-Tips.pdf

Is a {quot}100uh 2 amp choke{quot} something I'm going to find at
















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