The Longer The Antenna The Greater The Range!
Antennas shorter than 1 metre long are for short distance only. Antennas
over 1mtr long will cover the entire 40ch on your transceiver efficiently however short antennas under 50cm long, will only work effectively on few channels.
The Thicker The Antenna The More Broadband! (channels)
The thickness of the antenna is not generally important unless there is a need to operate on a larger than normal bandwidth
(A lot more channels)
There Are Different Types Of Coating "PVC"
& "Polyolefin"
PVC - A thick coat of PVC plastic and is suitable for most applications, available in Black or White.
Polyolefin - A thick coat of Polyolefin rubber, for high quality & long
lasting finish, available in all colours
There Are "Cut To Tune" & "Factory (Pre) Tuned"
Cut to tune - These are usually tapered fibreglass types such as the (DX136SW to DX172SW) & (DX260 to DX270) etc. These antennas require the use of a SWR meter to tune them, the advantage is that you can achieve a 100% effective output.
Pre Tuned - These are usually constant diameter fibreglass antennas that such as (DX120CD to DX170CD) & (DX120FW to DX152FW) etc. These antennas do not need to be tuned as long as they have been installed correctly onto a vehicle such as a Car, Tractor, Boat, or similar, these antennas will not work as base antennas unless they are in most cases lengthened.
Some Do's & Don't's
with 27MHz Antenna
| Do - |
Test
for shorts or open circuit if possible with an multi meter or
check SWR with a SWR meter
Testing the antenna ensures
that all is in working order including the transceiver |
| Do - |
Mount
the antenna high as possible - Gutter
mount or roof is best
Centre of the roof is not
always possible but it still is the best place,
next best is on a "BMS" mount |
| Do - |
Use
a spring even if mounted on a bull bar to absorb vibration from the engine |
| Don't
- |
Use
a wire strap to earth the base - It
may damage your radio
You must earth the antenna
at the base, supplying a sufficient ground plane
area |
| Don't - |
Mount
the antenna along side any metal object - As
far away as possible
Any metal object will absorb
the radiation from the antenna, greatly reducing
its performance, you need at least 1m from a
wall or from another antenna,
if this is not possible then mount the antenna
as far away from any other antenna or metal object
as possible. |
The
main causes for poor performance with 27MHz antenna
| Poor ground plane |
You
need a suitable ground plane at least the length of the antenna as
the radius of the ground plane in area. |
| Bad SWR |
All antennas
need to be tested and if needed tuned |
| Antenna too short |
The
longer the antenna the better the performance - in many aspects
This is often the
main cause for poor performance with 27MHz |
| Antenna too low |
Antennas
need to be as high as possible - especially 27MHz |
| Antenna to close |
Antennas
will simply not work if they are running up along any metal object
such as headlights, bull bars or brick walls |
|
Click here to go to Mobile One's range of 27MHz CB Antennas