[ICOM] Help needed with noise on HF in the mobile

[Des Pendergast]

Hello all,

My question is really aimed at those which may have particular
experience with this particular vehicle but other mobiles may have the
same problem.

Problem: engine noise.  The noise, which sounds like spark plug noise,
is so loud that a 9+ signal is required to get over the top of it.
Makes it really hard to work stations while mobile.  The vehicle
concerned is a V6 Mitsubishi Pajero - 3 litre model.

Noise seems to be coming in via the antenna, which is a screwdriver by
the way.  If I unplug the coax at the base of the antenna, the noise
disappears so this removes the possibility of it coming in via the power
lead.

The antenna is mounted on the 'bullbar' at the front of the vehicle.  I
guess one option would be to move it to the rear and hope this improves
things a bit - the thing which stops me from doing this at the moment is
the fact that a fair amount of work is required to set up an antenna
mount at the rear of the vehicle and the reception may be no better once
I do.

Anyone have any ideas of how I may be able to reduce the noise of my
installation?  Any reduction would be an improvement.

The radio is an IC-706 for what it's worth. The original model so no
DSP.

Look forward to some replies.

Best regards,

Des - VK3DMP.