You must have a good install to eliminate the most common problems.
You will get rid of most of your poor reception, RFI, and low power
problems with proper installation.
Mount your radio in a good stable position where you can access the
rear of the radio, coax, power lines and etc without having to un-install
After mounting the radio, run a good ground to the radio (I know the
radio already has a ground going to it, and that the coax also is a
ground, just do it anyway.)
Make sure that there are fuses in both the hot and ground power leads.
Then twist them as tightly as you can, twist, twist, twist. I know that
getting your radio mounted as close as you can to the power source is
only possible if you have a remote mountable control head, do what you
can to keep your power leads short. Please hook up only to the battery,
and only the battery. Resist the urge to go under the dash and hook up
to power supplying your fuse/breaker box. Going to the battery box will
help you eliminate noise, if you go to the breaker/fuse box you will be
getting noise from other things that are running thru that main power
line. In other words, your battery will act somewhat as a noise filter.
Don't have any weak or loose connections, everything has to be tight or
you will get noise.
Start your vehicle, turn on your radio, before attaching a coax, turn
on your pre-amp and listen for noise and RFI on all the bands. Now shut
down your truck and see if there is a difference. If there is then your
noise is coming thru your power lines. You can solve those problems by
installing inline filters that are available at Radio Shack, or you can
wrap your power lines with ferrite. The more turns, the better.
Everything else that you hook up to your radio will need ferrite. I put
ferrite at both ends of every lead. Example: Extension speakers, I put
ferrite right next to the speaker, and also right next to where it
plugs into the radio. This may seem a bit like overkill, but doing all this
during installation will certainly eliminate the headaches, and weeks
of searching for for RFI later on. You will certainly be taking steps
that are not necessary, and may not be appropriate for your installation,
but by doing everything in excess, you will be able to operate well,
and actually hear the far off and weak stations without having to shut
down your truck to hear people.
OK, now for the coax. Use the best coax that you can find. I use RG213
it is double shielded, and completely insulated. I can run all the
power that I want without the center conductor melting into the braid,
and it is fairly flexible, so bends in the install are possible. Make sure
to have good connectors on both ends, and for the end that goes outside
paint it up with waterproof goop, or liquid electric tape. If you
aren't using a connector, but you are using a split, make sure that you have
good soldered connectors, and again paint your outside connections to
insulate from the elements. Now, start your truck again, turn on your
radio, and listen for noise. (you will get some atmospheric noise now,
maybe even hear people talking on your favorite frequency, but RFI should
be hopefully non-existent) If you are getting RFI, perhaps you have run
your coax alongside other wires that run fans, motors, etc., but that
shouldn't be an issue if you used good coax, and quality connectors. I
still put ferrite on both ends of the coax, near the radio, and near the
antenna. The ferrite will not take away any signal, but will steal RFI
from the coax braid.
Mount your antenna as far from noise makers on your truck as you can.
My ECM is (everybody's)on the left side, so I get less noise from
the screwdriver on the right side of the truck and I do from the
screwdriver on the left side. Also, if you have loud tires, a fender mount may
not be your best move. Mounting your antenna behind the cab is NOT an
option, your trailer will block and absorb your signal. Having your
antenna on the side of your truck is an option if you can get it away from
the cab some. I have one fender mounted on the right, and mirror
mounted on the left. I run a Kenwood TS 480, and a Henry SS-750 amp. The
radio has it's own antenna switch, but I use a manual switch so that I can
use the power thru the amp on either antenna.
Grounding the antenna, This is where the fun begins. The more grounds
that you have, the bigger your signal will be. You will know when you
have enough grounds (the point of no gains) by tuning your radio to a low
band frequency on 75 or 160 meters while Bobtail. Then hook up to a
trailer. If you don't have to retune your antenna, you probably have
enough ground. Your ground (just like a dipole) is 1/2 of your signal. If
you run a braid to the bottom of your antenna, the braid needs a short
run to the frame. I also walked around my truck with a multi-tester, and
checked everything under the hood, and under the sleeper of the truck.
Anything that didn't have continuity to the frame got a braided ground
strap. This quieted the truck as well as increased the size of my
Build a Sniffer:
We are all truckers, and we all have old CB radio coax. Just cut one of
the connectors off, expose the center conductor by peeling back the
braid an inch or more. Then dip the conductor in liquid electric tape
(the last thing you want to do is allow your conductor to touch something
while you are sniffing, you could zap your radio, so insulating it will
After building your sniffer, get some 20ft or longer headphone cords to
plug into your radio, start your truck, wear your headphones, walk
around your truck probing with your sniffer. You will be able to hear
everything that makes noise thru your headphones. Your sniffer is now
your antenna, it is small, and won't hear much unless it is close to the
noise maker. Once you have found the source of the noise, you can work
on eliminating it.
Most noises can be eliminate by grounding, shielding, the use of
ferrites, and capacitors. If you do a proper installation, have good grounds,
good coax, get your antenna away from noise, you have a head start.
Good Luck, Jim K6TEX
Any questions email Jim:
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