I suggest that you check and be sure that you have resistor
spark plugs or resistor wires. The attached essay may be
HF MOBILE NOISE ELIMINATION
In my experience, there are three parts to the job of installing HF
mobile in a vehicle: Installing the radio, installing the antenna,
and suppressing noise. Of the three, suppressing noise is probably
The first question is what kind of noise you are experiencing. If it
sounds like a popping noise, and gets louder when you accelerate, it
is probably ignition noise. If it is a hash type noise, it is
probably an electric motor. The engine fans on my Tercel were very
bad, but only ran in traffic, so I just lived with it. I was told
that .001uf caps, short leads, from the motor to ground would help,
but never did it. Some electric fuel pumps can be very noisy.
One test to see if the noise is coming from the power cable or the
antenna is to disconnect the antenna. If you still have noise, work
on the power cable. If the noise goes away, the power is OK, focus on
suppressing noise at the source. If you connect the radio power cable
directly to the battery, you will probably not experience noise on the
power cable. (Don't forget to fuse both plus and minus at the battery
for safety). Heavy cable is advisable; I would not use anything
smaller than 12 ga, and some people use welding cable.
I assume here that you have broad-band noise across various bands. If
you have a single frequency birdie, you probably have noise from the
You might check to be sure that you have resistor plugs and wires
before starting more serious work. Also, be sure that your noise
blanker is on, although most radios do not have super-effective noise
On a 1979 Honda Civic with points, I used resistor plugs and wires,
which solved the problem, but meant that I had to change the points
every 5000 miles or so, as the ignition system was designed for
resistor wires only, and if the ignition system was not perfect, the
car ran poorly.
On a 1985 Toyota Tercel, I had tremendous luck suppressing ignition
noise by buying heavy copper tubular braid, and slipping it over
the spark plug wires. I built a copper box that covered most of the
distributor, bonded the braid to the box, and then bonded the box to
the block, keeping the wires short. This was a day and night
improvement, and I never felt the need to do any more ignition noise
On a 1996 Subaru Legacy, I again built a copper box, and bought more
tubular braid. However, I only got an improvement of about 2 S-units.
I needed more, especially on 40 meters, so I ran two ground wires
from the exhaust pipe to the chassis. This was probably worth more
than 2 S-units, and finished the job to my satisfaction.
If you are systematic, you should be able to identify the source of
any problems and correct them.
A couple of other notes on HF mobile installations. Don Johnson,
W6AAQ wrote the book, 40+5 YEARS OF HF MOBILEERING. Try to get
a copy. I use the Hustler antenna system, and find it adequate
except on 75 m. If you plan to operate 75m, consider a WB5TYD
Texas Bug Catcher or a Screwdriver antenna. Unless you have an
automatic or remote tuning system, the antenna bandwidth on 75m
will probably be only about 50kc or so. I have never invested the
time and effort required to achieve a satisfactory 75m installation.
Richard Ferguson, KA0DXM
November 19, 1996
> I need help to eliminate the radio static on my AM radio in my pickup truck.
> Checks which I have done include--Removing spark plug wires one at a time,
> disconnecting the alternator,changing radios,
> I have no static when the engine is not running and I have no static on FM.
> The static seems to be on all stations.
> Would it be a good idea to change the antennae?
> Any suggestions would be appreciated.
> Doug N.