|
|
 |
 |
 |
 |
|
Battery Re-Radiating
Antenna Review (GARATX/GARATB) |
20th January
2002 |
|
|
Review by
Dave Burrows
Purchase From
PC-Mobile
|
|
One popular accessory for many it would seem is a
re-radiating antenna. Re-radiating antennas aren't that expensive.
They start at around £30, and although they don't look much, they do the job
well. All re-radiating antennas need to be powered. Until recently,
most have had to be powered by the cigarette/accessory socket which has been a
problem for many. Now
PC-Mobile have recently designed
and brought out a battery operated re-radiating antenna. The need for
re-radiating antennas is because many car manufacturers are creating UV coated
windscreens. These and other devices fed through the windscreen like
heater coils, metal flakes can all cause a signal drop in GPS signals, and a
re-radiating antenna will help boost these signal levels back up to what they
should be enabling you to have your GPS Receiver inside the car in the dry, and
still receive adequate signals to be able to use street routing software.
|
|
The
PC-Mobile re-radiating antenna
comes in two parts. First the active antenna that you see on the right
that sports a magnetic base so you can fix the square antenna block to the roof
of the car, followed by a 3 meter long cable which should give you enough cable
to run it inside the door and conceal the cable quite adequately on most cars
and the cable terminates in an MCX or BNC connector depending on the one you
need, the one we reviewed terminates in an MCX connector which is standard for most antenna
sockets.
You then have the second part (on the left) which is the battery
box which houses 3 x AA size batteries, a power switch and a blue led that
lights up when switched on.
|
 |
|
This has a 1 meter long cable that ends in a hardened loop
cable. This is the internal antenna and needs to be fixed to the GPS
Receiver you currently have. Now most people may have concerns that the
only using 3 batteries may be an issue, and that they need to be replaced on a
very regular basis.
PC-Mobile says that under normal
use, Rechargeable Ni-Mh batteries should last for around 100 hours, and using alkaline
batteries you should expect to see 200 hours use. This means if you're
looking at commuting 2 hours a day, and switch the unit off after every trip,
you should expect to see the batteries last up to 100 days using alkaline
batteries!
Most of the accessory socket re-radiating
antennas require to be within 45cm of the GPS Receiver, due to the design and
power, the PC-Mobile re-radiating
antenna prefers to be as close to the receiver as possible. In the
prototype version we received, it came with an elastic band, although this might
sound primitive, it works well and allows you to secure the loop to the GPS
receiver. If you have a Navman sleeve, then you could place the loop over
the antenna that sticks out of the sleeve. |
|
The active antenna is
like the one supplied with many re-radiating antennas, and very similar if not
identical to several add-on active antennas that can be purchased for many GPS
receivers, including handheld receivers like Garmin's.
The antenna itself is
a SM-76 and currently sports a low current of between 2.5v DC and 5.0v DC.
The base of this antenna is magnetic, and quite a strong one at that. Many
readers have a concern whether or not these active antennas will fall off the
car at high speed, and I can definitely say there's no chance of that.
Once you place this on the body work of the car, it's difficult to get it off!
It clings beautifully to the bodywork. |
 |
|
I think I have a coated windscreen, do I need a
Re-Radiating antenna ?
This is
a question we are receiving a lot of. People with 4 or 5 sat signals on
average knowing there are a maximum of 12 satellites they can pick up think they
may be having problems. The easiest way to test this is, acquire a fix
in-car like you normally would do, then move the GPS receiver out of the car
onto the roof. Now see if your GPS signal increases by 2-5 satellites.
If it does, then you may be better off having a re-radiating antenna in-car.
Are re-radiating antenna's any good for in-car use
?
Check
out some of the pictures below. These tests were performed inside a house,
where you usually don't receive GPS signals. You'll see from the first
three screenshots show no signal lock at all |
|
Fig 1
|
Fig 2
|
Fig 3
|
|
Now
compare the above screenshots with the ones below. These below were taken
using the
PC-Mobile
re-radiating antenna. You'll see that
the signal has quadrupled and we can now receive a 4 satellite lock! Quite
impressive!
|
|
Fig 4
|
Fig 5
|
Fig 6
|
|
PC-Mobile are
selling this as a complete unit at the price of
$52.50 for the MCX (GARATX) connector version (£32.54) or $52 for the
BNC (GARATB) connector version (£32.23).
If you already have an active antenna
that terminates in the MCX or BNC connector, then you can just
purchase the battery box (seen below) at the price of $25 MCX (£15.50)
or $24.90 BNC (£15.44).
If the 3 meter cable is also not long
enough,
PC-Mobile also
sell 3 meter extension cables for both connector types on the
GPS Antenna Page.
|
|
Please note, even if you are
receiving a 4-5 satellite 3D lock, you may not experience any greater
signals. First test by moving your GPS receiver out of the car
to see if your signal increases. If it doesn't, then purchasing
a re-radiating antenna will probably not do much for your signal.
If you would prefer a re-radiating
antenna that is powered by the cigarette/accessory socket check out
the following review:-
|
GPS-RRAD-45
|
|
|
 |
 |
 |
 |
|
|
