UHF aerial mount position?
Submitted: Sunday, Aug 11, 2024 at 18:22
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Member - bungarra (WA)
I have always mounted these on the bullbar of successive vehicles over the years.
The last 10 years the bar has been decorated with both the UHF and a mobile phone antenna, one each side...have been told that's not legal in some states but never had an issue and after a while you don't even notice them through the windscreen.
I am now changing vehicles and the new GME antenna that came with the XRS pack is only ~ 600mm. Half the length of previous ones...I assume GME know what they are doing and that its functionality is not compromised.
I have seen some on a triangular mount near the window / mirror on the driver's door on a 300 series, keen to hear opinions if this position would impair their performance?
My thoughts are that perhaps it might be a small improvement for signal behind and in front of the car as it might be an advantage that time when vehicles are travelling basically straight behind and reception is static or weak when compared to vehicles in front when you can hear transmissions for ages coming towards you long before they come in view. Being on the side of the vehicle perhaps it might be a small improvement for those behind ...... unless the proximity to the vehicle mass is a negative?
If others have no negative comments, I might consider the UHF there and the mobile phone on the passenger's side bullbar.
Appreciate hearing from you
Reply By: Member - McLaren3030 - Monday, Aug 12, 2024 at 07:05
Monday, Aug 12, 2024 at 07:05
Hi Bungarra,
Firstly, let me state that I am not a “Radio expert”, and there are others on this
forum that are.
In the days of AM CB Radio, the ideal position of the antenna was in the middle of the roof of the vehicle, with UHF radios, the same principle applies. Having said that, it is not always convenient to place an antenna in the middle of the roof.
If you take the option to mount the antenna on the Bull bar, the centre of the bar is probably the best location as there is certainly less movement in the centre of the bar than there is on the outside ends of the bar. You can also get “folding” antenna mounts that can be placed on a roof rack, gutter or Bull bar.
Remember, the length of the mast is not as important as the length of the antenna wire that is wrapped around the mast. Having said that, it is important to have the top of the antenna above the top of the vehicle.
Macca.
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Reply By: Tony W - Monday, Aug 12, 2024 at 08:10
Monday, Aug 12, 2024 at 08:10
"I have seen some on a triangular mount near the window / mirror on the driver's door on a 300 series, keen to hear opinions if this position would impair their performance?"
Yes it will.
It is about as bad a spot as it can get. But it does sell aftermarket accessories becasue it looks pretty cool. These are all designed by metal work companies, not radio companies for a reason. On a bull bar is a bit, but not a lot, better. UHF CB antennas should be at least a wavelength away from metal ( about 70 cm) or you will drive the SWR up. Bad Ju Ju.
Up as high as possible without any obstructions in the horizontal plane is the right approach. Independent ground antennas don't need to be in the middle of the roof. Cheap, or even homemade fold-down brackets solve the problem of hitting car park roofs.
If you do go ahead it will work but with limited range.
You can see how large the effect is. FInd a local repeater to
test the antenna on the roof. You'll ge much better range.
But if you just want to talk to buddies in a convoy 1km or so apart then you probably wont notice it.
AnswerID:
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Follow Up By: RMD - Monday, Aug 12, 2024 at 09:58
Monday, Aug 12, 2024 at 09:58
I am puzzled as to why people think having a transmitting aerial obscured from being able to do it's task of RADIATING a SIGNAL and receiving it too, is OK. IT ISN'T.
If anything metal is in the path then it cannot be as it should be. Bullbar mounted only transmits best sideways and front. Forget rear. At side of vehicle, the aerial gets immediate signal reflection from the VERY close vehicle, and really only shines out one side.
You can make a folding bracket out of a LARGE HINGE and have an R clip to make it easily removed so as to fold the whole lot rearward, ie, within 10 seconds.
Mine is a piece of angle aluminium held with a 6mm socket head screw. If needed to be down, I use a T handle hex driver to remove the screw and fasten it in the down position. takes more than 10 seconds though. Hardly ever have to do it.
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Reply By: qldcamper - Monday, Aug 12, 2024 at 10:51
Monday, Aug 12, 2024 at 10:51
This is a regularly visited can of worms.
So as not to intentionally contradict other replies I have not read them ...yet.
My answer is put it anywhere that it is not close to anything metal above its base.
UHF is not intended for long range comms,
A 600mm antenna will work as
well as a hollow tube with a 600mm bit of wire inside it no matter how long the tube is, some only have 300mm of wire inside.
The best position for it is where ever it's practical for your particular set up, it won't be the electrically perfect position but for all intensive purposes it will do what you want it to do unless your expecting more than the mode is designed to do.
If you think it's going to come in handy to save your life then get something else, if you just need it to talk to other traffic within say 10km then antenna position won't make a big difference as long as it's in free space and not lower than the surrounding metal structures within about 300mm.
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646333
Reply By: Member - Broodie H3 - Monday, Aug 12, 2024 at 11:58
Monday, Aug 12, 2024 at 11:58
Good morning Bungarra, Just as thought in my 200 series, I have a GME radio and the antenna is stuck on the inside of the wind screen. It still works exactly the same as it did when the radio was in the ford
ranger with the antenna on the bull bar, same range same good reception. we have not had any transmission or reception issues with it. I don't have a bull bar on the cruiser as I don't do the night drives that I use to do, and we are generally parked up by 4pm. so the position of the radio antenna is only used for taking to truckies, and if we are travelling with friends . we were in convoy coming back from Carrawine
Gorge , and spaced about a Kilo meter apart there were for in the convoy and we were tail end Charlie, and we had no problem talking to the leader even when going through the hilly country. the best part about having the antenna on the screen nobody knows that you have a radio in your car, until you talk to them. we tow a 23ft caravan, even when we were leader we had no problems talking to tail end Charlie. now we don't have any antenna problems. just to give you another option for your antenna
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Reply By: Gronk - Monday, Aug 12, 2024 at 17:04
Monday, Aug 12, 2024 at 17:04
Just bought a new cb radio ( Uniden )with a 640mm antenna ( 5db )
The 600mm one you bought may
well be a 2.1db one, which is good for hilly terrain, but less good for long range.
Mine will be going on a bonnet hinge mount, so yes, most of the rearward signal may be compromised, but for a 4wd that isn’t going to be used just for outback travel, and also doesn’t have roof racks, a roof mounted one is out of the question.
Everything is a compromise, so we just have to make do with what we have.
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Follow Up By: qldcamper - Tuesday, Aug 13, 2024 at 07:31
Tuesday, Aug 13, 2024 at 07:31
If it works it works.
Compromise is something social media forgot long ago......it has to be 200% perfect these days.
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