The science behind UHF aerial placement?

[Johnboy67 Lurker Find all posts View Profile Close Johnboy67]

So is it possible to mount an antenna front and rear wired in together?

Yes you can pair antennas and increase range. A lot of Long haul truckies use this config but there are a number of parameters i.e they have to be matched, they have to be placed a certain distance apart they have to have nothing between them. You will often see prime movers with two matching antennas on the bull bar one either side, or two shortish ones on the top of their mirrors either side of the cab above roof height.

In a car situation it probably wouldn't work simply cause the car is in the way.

J

[D4D Addicted PP Member Find all posts View Profile Close D4D]

As stated best place for a UHF is on the roof, hence my install...

[SOL Find all posts View Profile Close SOL]

Yes you can pair antennas and increase range. A lot of Long haul truckies use this config but there are a number of parameters i.e they have to be matched, they have to be placed a certain distance apart they have to have nothing between them. You will often see prime movers with two matching antennas on the bull bar one either side, or two shortish ones on the top of their mirrors either side of the cab above roof height.

In a car situation it probably wouldn't work simply cause the car is in the way.

J

Johnboy67, Thank you for the reply. I understand and it all makes sense.

[DaveZ Member Find all posts View Profile Close DaveZ]

No science behind the choice or placement of mine, it's a 6dB Axis (I think) and I like the height of it because it's the same height as my roof top tent so makes it easy to gauge clearance when in the sticks.

[gumboot Avid PP Poster! Find all posts View Profile Close gumboot]

As stated best place for a UHF is on the roof, hence my install...

Intersting D4D. Did you ever have the aerial on the bullbar?. If so what sort of different you noticed?

I did see an Radio expert last week and he said, you really want the aerial away from any metal interference as well as having it clear my roofrack if possible (currently it doesn't) , as several pointed out above. He suggested like D4D the best place was higher up like on top of the roofrack but that brings a bunch of other height challenegs for most people, so they put it on the bullbar as it is more convienent generally
Cheers
Robert

[Mack Lurker Find all posts View Profile Close Mack]

I have a fair bit of experience in antennas and vehicles in my job.
To gain to best range from your antenna (both in transmitting and receiving) to roof would be the best place for it. This allows the largest ground plane (the vehicle) to increase the transmission area and positions the antenna to receive the least interruption for receiving. But but antennas should be the right length for the wave length - can get technical here so in short, a longer antenna provides much better propagation. So having a long antenna on the roof can cause lots of issues - getting snapped off by trees, undercover car parks, or the drive through at McDonald's.

So then you can look to the front or back of the vehicle.

The rear of the vehicle would be fine as long as the bottom of the antenna is above the roof of the car. If is below the roof the radio wave will only form from the area of the antenna that is above the roof.

Now to go to the bullbar mounted antenna. While this position will not get the best range, it provides the best all round performance. It allows good radio propagation to the front and sides, with some shielding to the rear. However, this shielding to the rear will not stop signals going behind, they just wont be as strong. The best part of placing it on the bullbar is that you can see it, and therefore protect it. A radio becomes a paperweight very quickly without an antenna.

Finally, as has already been stated, UHF is only short range line of sight communications. You can not bounce signals off the ionosphere, like HF (and VHF to an extent), but the radio waves can bounce off metal structures (buildings). So UHF is really only good for inter-convoy communications. If you want long range comms, use HF (good) or Satcomms (best).

[D4D Addicted PP Member Find all posts View Profile Close D4D]

Intersting D4D. Did you ever have the aerial on the bullbar?. If so what sort of different you noticed?

Not on the Prado but I have had bullbar mounted antennas before and this antenna is heaps better. The antenna is the same used on the CFA trucks, you can bend it into a U and is pretty much indestructible.

http://www.prestigecom.net.au/index....4g5t9nf5or0rq2