mk tank

What type of antenna do you have.

Is it a fibre glass type whip

Is it a metal rod, as the metal ones are usually a bit shorter.

Rays correct in his comment regarding the tune to length.

Effectivly a antenna is a pice of wire that is cut to the required frequency - i have made antennas out of fencing wire in the past.

If you use a (GPI) Ground plan Independant antenna, you dont need to earth the roof Rack.

On the new 80 channel radios, the first 40 channels are the same freqs as the old 40 channel rigs. But the radios are now operating in a 12.5 Khz channel plan compared to the old 25 Khz channel plan. This means that the radios are transmitting 1/2 the deviation (voice).

Basically you dont get the same freq response - but uhf cb's are not design for high fildality music - speach will still be ok.

The extra 40 channels are in between the old channels.

When purchasing an antenna, you will hear terms of 3db, 6db, 4.15dbi, 2.15 dbi, 9db, 8.1 etc.

Some manufacturers use db other use dbi (because it looks better)

Db - refers to the gain compared to a ¼ wave roof mounted antenna.
Dbi – refers to the theriacal gain of an antenna in a free space vacuum. To compare antennas, take 2.15 of a dbi Antenna. E.g. – an 8.1dbi antenna = 6 db gain antenna.

What does gain do?

An antenna with a gain of 3 dB gain, means that the Transmitted (radiated) power is 3 dB higher (twice as much) – gain is logarithmic.

E.g.
A uhf CB is transmitting 5 watts into a 3 db gain antenna; therefore the radiated power is 10 watts
A uhf CB is transmitting 5 watts into a 6 db gain antenna; therefore the radiated power is 20 watts

Impact of having higher gain antennas

I always use a balloon to explain the impact of gain on the radiated energy, with someone stepping on it and gradually flattering the balloon.
0 db – the balloon is round and provides the best all round coverage – ideal for mountains
3 db – the balloon is ¾ round and provides the good all round coverage – ideal for mountains
6 db – the balloon is ½ round and provides the best compromise for mountain driving and driving on the flat
9 db – the balloon is ¼ round and provides the best for driving on the flat - dessert driving)


The higher the gain the bigger the antenna.

For further reading look here http://www.lakecomm.com.au/Antenna-Prop.html (im not asscoiated with this site)

here is my contibution?

All antennas once installed should have there VSWR (voltage standing wave ratio) checked. The factory pretuned antennas may be faulty, the connector may be faulty the location of the antennas may be affecting the antenna.

A vswr check will indicate of the antenna is ok, plus you can "tune" the antenna for best operation.

I have found the UNIDEN antennas to be very flimsy and they move around a lot while you are driving.

I would adviod using a 80 channel rig until all people are running 80 channels, as dependent on the receiver design of your 80 channel rig, the rig may block somee one transmitting on a old 25 Khz rig. The first 40 channels for both rigs are the same.

Im a radio tech

I used to work for the big M, but now back with the goverment

The most comment problem I see if guys doing there connectors incorrectly.

Can we have a forum for communication issues