After my recent Jensen JHD-910 radio article was posted on
webBikeWorld, an astute reader commented about the importance of the
He and radio pioneer Marconi were
absolutely correct, in that any radio depends on how well the
Because this article could be used for
more than the Jensen radio recently featured, it will be treated as
a separate review.
To try to help readers choose an antenna,
we decided to try several and to compare them with the AM/FM radios in
a car and a minivan. But first, we had to come up with an
objective means of comparison.
We initially thought that we might contract
nearby state-of-the-art electronics testing lab that has an
anechoic room with all sorts of cones attached to the walls and
They do a lot of testing for military products,
certifications for cell phones, and other high tech gadgets.
But this idea died a horrible death as soon as we realized how much
it would cost to rent the laboratory. Time for plan B.
Plan B was simple. Rather than get
all techie and use specialized radio equipment, we wanted this in
terms that anybody could understand. Our area is rich in radio
stations, so we just used what we had by comparing how many stations
each antenna could pull in. After all -- relative performance
is what counts in day-to-day use.
The criterion was to simply count
legibly received AM and FM radio stations, even if some had
miserable quality, then to add notes about signal strength. We
manually stepped through the range of frequencies on each test.
The test was performed on two separate days and the results were
repeatable. There was a lot of button pushing...
First we started with a Ford Escape and
a Chrysler minivan, because the car companies employ people to
optimize the performance of the installed sound systems. We
wanted a baseline and the two vehicles were so similar that we used
the Escape for convenience. It was able to receive a total of
114 stations. Using the SEEK button, the Ford radio found 73%
of the same FM stations and 43% of the AM stations.
The Jensen radio on the Yamaha FJR1300
was then tested with three automotive antennas. All had been
made by Metra and purchased from a local auto parts chain store.
The first antenna was a typical
inexpensive 31-inch whip antenna that was the most plain-Jane basic
$9.99 universal antenna on the rack (photo above). The antenna
was a clone of the antenna that Ford had installed on the Escape and
the Jensen gave the performance closest to that of the Ford Escape
with this antenna.
The whip was able to pull in almost 92%
of the FM stations that the Ford found and 81% of the AM stations --
not bad for an aftermarket installation, but about 10% of the AM
stations had less strength.
Further, the whip picked up four Weather
band broadcasts with solid reception. The whip did have one
odd characteristic, though; when using the SEEK button, it found one
more station than was on the Ford's radio. However, the
whip also stopped seeking at 11 frequencies that did not have a
station and at times it was a small nuisance.
The second antenna was a Universal
Rubber Antenna with a 14-inch (37 cm) rubber mast that was also
purchased for $9.99 (Model AT-UT03R).
Affectionately known as a “rubber ducky”
antenna, this one had the same auto-fender base that was on the whip
antenna. It pulled in 90% of the FM stations that the Ford
found and the same 81% of AM stations that the whip received.
While the rubber ducky found almost as
many FM stations as the whip in SEEK mode, it only found 60% of what
the Ford found in AM stations. The reduction in AM strength
was similar to that exhibited by the whip antenna. The rubber
ducky pulled in three of the weather bands with solid reception and
a fourth faded in and out.
The reason that AM/FM antennas are all about 31 inches is because it
is a proportion of the average radio frequencies that the radios are
intended to receive.
A common trick in making rubber antennas
perform is to use the optimal length of wire and coil it within the
rubber. While the station counts were comparable, notes about
FM station reception strength were downgraded for 11% of what the
rubber antenna found, as compared with the whip.
It would be easier to make the rubber
antenna mounting less conspicuous and it would work well for
commuters. We tried taping it inside of the Givi top-case and
the performance changed very little (loss of several AM stations
that had been very weak), which could provide a way to conceal the
antenna. But the rubber antenna would not be able to perform
as well as the whip when on the open highway.
1. "Rubber Ducky" antenna. 2. Metra Deluxe antenna.
The third antenna was what we informally
called the concealed antenna. It was labeled as the Metra
Deluxe Universal Amplified Antenna (Model CK-UA200) and it was
purchased for $19.99.
The packaging for this dipole-looking
antenna (wires attach to the middle) said that it had been designed
to hide at the top of a car window, just below the headliner and our
hope was that if it performed well enough, we could hide the antenna
inside of the FJR's fairing.
This antenna had double-stick adhesive
for mounting and came with an alcohol wipe. However, the
concealed antenna was not only the most expensive; it was the worst
performer, despite its built-in amplifier.
Because the concealed antenna was
amplified, it needed a source of power and a ground connection.
A small red LED would signal when power was available and we tried
it both with and without the LED illuminated. The power did
make a significant improvement.
To have the best shot at functioning
well and to remove any influence that the engine or frame might
create, the concealed antenna was simply taped to the top of the
bike’s windshield. The antenna was also rotated and tried
vertically to change orientation. Orientation did affect the
results, but not by as much as we anticipated.
However, the bottom line was that the
best we could do with the amplified concealed antenna was still
significantly worse than the original 31-inch whip.
How much? The boosted hidden
antenna got 73% of the FM stations found by the Ford Escape and 60%
of the AM stations. It barely got only one of the weather band
channels. Further, our list of signal strengths for the
stations showed that many of the stations that it did receive were
substantially inferior to the performance of the whip and the rubber
Here's a table that illustrates the
comparative results in
31” Whip Antenna
Percentage of FM stations that the Ford radio found:
Percentage of AM stations that the Ford radio found:
Percentage of FM stations found by the SEEK button, as
compared to the Ford radio:
102 % (plus numerous empty frequencies)
Percentage of AM stations found by the SEEK button, as
compared to the Ford radio:
*Numbers do not convey reduction in
The automakers know what they are doing
and there is a reason for the 31-inch whip antenna to be a de facto
standard for car antennas. It works and would be our choice for a
mixture of commuting and use when not near a city.
commuters who stay near their favorite radio stations, the rubber
ducky gave good performance and might not be as conspicuous. The Metra Deluxe Universal Amplified Antenna did not perform well and
was last seen in the trashcan.
Review of the Jensen JHD910
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From "J.S." (1/09): "Radio hams would probably
refer to the hidden amplified "Metra" antenna as a "coiled" or
"folded dipole". A dipole, folded or not, is always going to
be very directional and by nature is a poor choice for mobile use.
You'll see dipoles on some vehicles, but only dipoles that can be
rotated for max. signal strength (usually hams, emergency mobile
comm. vehicles, etc.). That antenna's design is inherently
weaker and so that's why they amplify it.
A regular vehicle antenna is much less
directional than a dipole. Also, radio signals are almost always
polarized vertically to match vertical reception antennas like on a
car. Also, the part of your antenna that sticks up is only
electrically half the antenna; the other half is your vehicle.
Ergo, cars fare better than bikes because of the expanse of metal
making up the vehicle half of the antenna.
To compensate, some bikers use two
antennas at the rear (theory being, to double signal capture.
The theory also is that placing them aft makes reception (or in
antenna lingo, "gain") somewhat better toward the front in the
direction you're heading."
From "J.K." (1/09): "(Here) is a link to the
TuneTrapper hidden antenna that sells quite well, mostly to
Harley owners that hide them under their front fairings. The
next time you folks do a comparison, you might check this out as