- All electrical connections need to be first
class, and insulated from weather with
self-sealing tape or heat-shrink tubing.
Satellite Television and Radio Antennas
We looked at some of the issues concerning
GPS and DGPS antennas in Chapter 14, but
we haven’t yet addressed the seemingly inert tele-
vision disc antennas used on many boats.
These, like most of the antennas we’ve dis-
cussed, use coaxial cable to connect to the back
of the television, so all the RFI and coiling rec-
ommendations apply here as well. These anten-
nas typically come with 30 feet of coaxial cable
attached that can be extended if necessary, as
long as the loss factors are kept to a minimum.
Many disc-type television antennas also
have amplification circuitry built into them to
enhance reception. This circuitry requires sep-
arate DC (positive and negative) wiring and,
as with all DC wiring, voltage drop should be
kept to a minimum. But since this is not a
critical device, a 10% voltage drop would be
acceptable under ABYC standards.
You might assume that these are receive-
only devices that may pick up interference
from radios transmitting at frequencies close
to the VHF, UHF, or FM bands. However, a
few years ago the U.S. Coast Guard deter-
mined that some TV antennas can interfere
with GPS antenna reception, causing inaccu-
racies in GPS positioning or even blinking
out. Reports to the Coast Guard indicate that
GPS on vessels as far as 2,000 feet from an
active TV antenna have been affected. On the
other hand, I’ve heard of cases in which inter-
ference problems were solved by increasing
separation by a mere 12 to 18 inches.
The FCC identified three specific antenna
models in a safety bulletin issued December
30, 2002 (TDP Electronics [i.e., Tandy Cor-
poration] models 5MS740, 5MS750, and
5MS921), but stated that the problem may
not be exclusive to these three. Similar prob-
lems were found in RadioShack model 15- 1624
and Shakespeare SeaWatch model 2040 with
code dates of 02A00 and 03A00.
The best way to check for a problem between
the TV and GPS on your boat is to first turn on
both the TV and the GPS, then shut down the
TV while watching the GPS to see if any changes
occur with the GPS reading or display.
Little information is available from vendors
regarding mounting location, although one
vendor suggests that the TV antenna be mounted
as high as possible, and above all other onboard
antennas. This makes sense, but it may not be
feasible in many cases—for example, on a sport-
fishing boat with a 30-foot SSB whip antenna.
You may have to resort to the trial-and-error
approach, experimenting with different loca-
tions for the TV and GPS antennas before
making the installation permanent.
As of this writing, satellite radio represents
one of the hottest accessories on the market.
Most satellite radio antenna vendors provide a
12-foot length of coaxial cable, although this
length is not crucial. And these antennas do not
appear to be too sensitive as to where you locate
them. As long as they have about a 90-degree
clear view of the sky as measured from the cen-
ter of the antenna dome (i.e., a 45-degree arc
from the vertical centerline), all will be well.Cell Phone Antennas
Most people jump on their boat and cast off
without giving their cell phone’s ability to make
or receive calls a second thought. This generally
works out because, in most cases, the body of
water these people are on is actually never too
far from a cell tower. But suppose you are
20 miles offshore doing a coastal delivery or
anchored out at an offshore fishing ground, and
you want to use your cell phone. Odds are it
won’t work when you’re standing on a deck 1 orcoaxial cable and antennas 183