ARB Bar UHF antenna reception

[jimc]

Recently had an ARB winch bar fitted to my D3 and I fitted up a GME 4003 UHF antenna to the LHS side, where ARB kindly punched a hole.

Well all I can say is reception is really really bad. I almost have to be on top of a trucking route to get any reception. Is this hole used for antenna or am I being stupid and its used for sand flag or similar?

I might relocate my antenna to the roof and see if it improves, but what a pain.

[connock]

Fitting to the roof is not a major problem and you will be able to use a smaller antenna with better reception and not have that line down all your vids/pics taken from inside of car;)
that hole makes a good sand flag holder and thats about it

connock

[jonesy63]

That antenna is ground dependent. I would be looking for a good earth at the mounting point. If it was just screwed onto the powder-coated bullbar, it may not have any grounding at all.

[Lotz-A-Landies]

As Jonesy63 says that antenna is ground dependant, so requires a good earth, not only that it requires an electrical ground plane at the level of the monopole base. The middle of the roof is ideal for a ground dependent antenna.

On your D3, the location on the side of the lower bar work will inhibit signal propagation because it has an effective vertical ground plane on the bodywork and by the height of the bonnet the electrical length of the antenna is the wrong frequency.

In theory the AE4003 will only propagate well to the side where the antenna is located.

The position of the antenna mounts on the ARB bar is why I went for the Oposite Lock bar on my D4.

What you actually need in that location is an elevated feed antenna like the RFI CD900 series CBRS Monopoles or the Mobile One RF470 series. 477MHz CB Radio Antennas (http://www.mobileone.com.au/antennas/cb477.html) if you wish to stay with GME their AE 4018 Series (http://www.gme.net.au/products/antennas/land-477-mhz/AE4018K) although I'm not happy with the spring tension on one of my GME antennas so I wouldn't buy another GME.

The elevated feed are ground independant and create an electrical ground plane at the point where the monopole attaches to the chrome/stainless base element. On the ARB bar this will be very close to the level of the bonnet, particularly if one of the antenna with the intrgral spring is chosen and will propagate well forward and to the sides with some signal attenuation to the rear quarter caused by the passenger compartment and roof.

RFI
https://www.aulro.com/afvb/images/imported/2013/03/1138.jpg

Mobile One
http://www.mobileone.com.au/antennas/images/antennaimages/F477SAN2%20web.gif

GME
http://www.gme.net.au/public/images/products/ae4018k.jpg

[jimc]

was a bit hasty with my typing of antenna type..its a 4703.

But will have a look at the raised versions suggested..and stick a flexible antenna on a roof track.

[Lotz-A-Landies]

Hi Jim

O/K that creates a different problem, thr AE 4703 is ground independant, but may have some slight warping of its propagation because of the position of its base which is overcome by its length. However a 6.6 dbi gain antenna performs best in open flat terrain because the signal propagation has a narrower angle of radiation than a lower gain antenna, it is a like a flat disk at the mid point of the stick. They are great on the western plains where they get very long range. In hilly terrain your signal may not propagate well from the bottom of a hill to the top or vica versa.

In closed hilly terrain you want gain somewhere around 3 to 4 dbi, which propagate like a giant donut around the stick.

An antenna on the roof can have car park problems.

Diana

[Tombie]

I would be checking your coax connection...

Something is wrong!

I run a AE4705 (1200mm)
https://www.aulro.com/afvb/

And dont have any problems at all...

I'm guessing a bad connection - commonly a bad solder job on the plug at the radio.

Mine has extremely good range - 20km+ and the bonus - if the tip touches something, I need to stop as its roof height.

:)

[Lotz-A-Landies]

I would be checking your coax connection...

Something is wrong!

<snip>

:)That too - take the plug off the radio, then using a multi meter set to Continuity touch one lead to the centre pole and the other to the outside of the plug or shielding: if you get the tone you have a short. If the meter doesn't have continuity use Ohms: If you get a reading you have a short somewhere.

The second test is to check the centre pole at both ends, where it plugs into the set and the centre pole on the antenna base.

[BMKal]

I would be checking your coax connection...

Something is wrong!

I run a AE4705 (1200mm)
http://www.ozautoelectrics.com/media/catalog/product/cache/1/image/390x445/5e06319eda06f020e43594a9c230972d/a/e/ae4706.jpg

And dont have any problems at all...

I'm guessing a bad connection - commonly a bad solder job on the plug at the radio.

Mine has extremely good range - 20km+ and the bonus - if the tip touches something, I need to stop as its roof height.

:)

I've got exactly the same on mine - mounted in the hole next to the left indicator.

No issues at all with range - I can hear trucks etc from many miles away. And as Tombie said - bloody good indicator of when the roof's too low for me in city parking lots.

[FenianEel]

I would be checking your coax connection...

commonly a bad solder job on the plug at the radio.


x2

That's the most common fault as Tombie said.

[jimc]

Thanks all for responses. I did have a short when I first installed, but fixed that soon after.

One thing I did was when I was annoyed with it not working and the short, I cut approx 200mm off the end of the coax. Could this be the cause?

Lotz-a-landies..How do I test centre pole at both ends? continuity test both ends..radio end and at antenna base?

Is there any protocol for testing a UHF radio...channel to use?

[FenianEel]

I cut approx 200mm off the end of the coax.
That'll be your issue. Worst thing you can do unfortunately. How'd you connect it. Was it soldered?

[Tote]

I have a wire 9db ground independant antenna and reception was atrocious when mounted on the bar so I made a 30mm pipe extension to provide a base to lift the antenna above the guard. This made a significant improvement to reception. The position on the bottom of the bar is a poor place to mount an antenna.

Regards,
Tote

[BMKal]

I have a wire 9db ground independant antenna and reception was atrocious when mounted on the bar so I made a 30mm pipe extension to provide a base to lift the antenna above the guard. This made a significant improvement to reception. The position on the bottom of the bar is a poor place to mount an antenna.

Regards,
Tote

Depends entirely on the length of the aerial. If the aerial is tall enough, whether it's mounted on the "bottom of the bar" or on top of the bar makes absolutely no difference at all.

Of course, if it's a short aerial that ends up hiding behind the guard or the body of the vehicle if it's mounted too low, then the mounting position will certainly make a difference - in this case, I'd be looking at a roof mount option.

[Tote]

Aerial is 1.3 m long
02629 - "Adveturer" 9dB UHF Heavy Duty Ground Independent Antenna (http://www.benelec.com.au/mobile_ant/02629.htm)

Made a huge difference when I lifted the antenna.

https://www.aulro.com/afvb/

Regards,
Tote

[BMKal]

Yes I imagine that it would make a difference with that style of aerial. You've raised it to about the height that we normally mount the same aerial on our work vehicles (mounted on the top of the bar).

Mine is a bit longer - tip is slightly above the roofrack when mounted down low on the bar.

I previously had it higher, but was hitting too many things with it. Reception / range seems about the same in both positions - and it's now a very handy height gauge when driving under buildings in the city (like my office). If the aerial clears - I know that I've got about three inches clearance above the roofrack (until I forget and go under with a tent or something up top) :(

At my office, I have to lower the suspension to get under the entrance. I've only forgotten once so far :o good thing it's a Windcheater steel roofrack - they're a good strong rack ;)