Uhf Aerials?

[dklyne454]

Hey guys,

I posted this question earlier today in the auto electrical section, but since it has only had a dozen views i guess not many members look in that section.

So since my issue needs to be dealt with rather hstily, here is the link.

If you know anything at all about this topic, please lend a hand.

Cheers
Daniel

http://www.outerlimits4x4.com/ftopic160926.php

[macca81]

why does the issue need to be dealt with hastily? you have already bought it...

[PJ.zook]

Youre first mistake was buying anything from Dick Smith when you needed specialist knowledge. Youre options are basically you can try it out and see if it suits youre needs, or you can return it and buy one from the likes of Scalar or Prestige.

[dklyne454]

Whilst i have already bought it, i am hitting the road in 10 days, so if i need to swap it or return it.... then i need to do it quick .

Cheers

[Fishin' Dave]

Antenna design theory is very complicated.
There are lots of variables that change the gain.
To simplify - the gain of an antenna is rated over a theoretical ‘0’db gain antenna called an isotropic radiator.
Vertical ‘stick’ antennas are limited in the amount of gain they can produce, it is dependent on:
The design - ¼ wave / ½ wave / 5/8 wave (the physical length of wire used to make the antenna) and the ground plane – mounting position on the metal (vehicle)
Quality of construction, thickness of wire ect etc also plays a part.
One way to produce gain is to make the radiation pattern directional.
This theoretical gain (its radiation pattern) is then highly dependent on its ‘ground plane’ – the metal it is mounted to.
Dick Smith staff would not be able to advise you, but I do not think they sell junk antennas – the brands I have seen there are reputable.
An a radio engineer… my advice would be to mount the antenna as high as you can on the vehicle and make sure the base has a good connection to metal.
The ‘lobe’ – direction of gain of the antenna – should then be front to back / elongated in the direction you are travelling.
If you wanted a more omnidirectional radiation pattern – ideal for twisted mountain roads, then you might be slightly better with less gain antenna that has a a less directional lobe.
Read this slowly so it sinks in – Provided it is installed correctly, the biggest influence on antenna performance is height!
I have designed and built my own mobile antenna - a base loaded 5/8 wave ground plane antenna, (it has the lowest angle of radiation) and mounted it mid point at the highest part of the vehicle.

- My 2 bobs worth

Dave

[dklyne454]

Thanks Dave for your help.

It's good to know that there are people who know what's going on

Much appreciated
Daniel

[PJ.zook]

Outers suprises you sometimes, everyone knows something about everything, but there are few who arent just talking out theyre ass.