db Rating on UHF Antenna

Hi All,

I've done a bit research on the how the shape of the coverage changes with the different db ratings on UHF antennae. The higher db rating extend further but are less suited to hilly areas.

I have one of those configurable antennas from GME and was going to set it to 9db for the trip up to Cairns to get more distance.

Just wondered if anyone has any experience using a 9db antenna in the open country.

Thanks in advance.
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Reply By: apwaddo - Thursday, Jun 18, 2009 at 22:43

Thursday, Jun 18, 2009 at 22:43
If by configurable you mean you have a two part antenna where you physically change a long section (9Db)for a short section (4Db) in my experience you will find a dramatic difference between the two antennas.
In brief - the 'long' section gives brilliant coverage in 'open' country but it bloody useless in 'hilly' terrain.
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Follow Up By: Member - OzGazza - Thursday, Jun 18, 2009 at 22:52

Thursday, Jun 18, 2009 at 22:52
Yep thats the one - great feedback thanks.
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Follow Up By: warfer69 - Friday, Jun 19, 2009 at 00:39

Friday, Jun 19, 2009 at 00:39
6db i found works well for both,hilly and open,find i dont change down to 4db much anymore....

RFI CD900 is a great aerial

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Follow Up By: Sand Man (SA) - Friday, Jun 19, 2009 at 07:20

Friday, Jun 19, 2009 at 07:20
I agree Warfer,

I use a RFI CD63-71-50 which is a 6db stainless steel whip antenna.
I can exchange the 800mm whip with a "rubber stubby" for around town.
This I do on the Jack as the antenna is mounted on the roof gutter. I don't really need extended range around town as there are too many wankers using the UHF band.

For my newly purchased Colorado, I intend reverting to a bonnet mount location and the standard 800mm stainless steel whip and ground independent configuration will give me excellent coverage.

Bill.
Bill


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Follow Up By: Holden4th - Friday, Jun 19, 2009 at 18:22

Friday, Jun 19, 2009 at 18:22
The AE409L antenna from GME has a -6dB section and a -9dB section, interchangeable. I always use the -6dB and it's worked wonderfully so far.
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Reply By: olcoolone - Friday, Jun 19, 2009 at 10:06

Friday, Jun 19, 2009 at 10:06
I don't see why people have to keep changing antennas all the time when the terrain changes?

There are so many variables that come into play when receiving and transmitting, we don't live in the ideal world.

Get a good quality 6dB antenna and leave it alone.

But then people will buy the cheapest 1-2 watt UHF handhelds and tell you they work wonderfully and they don't have a need for a better one.

Then when it comes to antenna gain people think differantly.

I think people become to anal about it.

But then again it's no different to what I do, I take 6 different types of tyres (yes thats right 30 tyres in total) when going away so I can constantly keep changing them when the road road conditions change!....so I suppose it is no different to some one wanting to change antennas all the time to suit the terrain.

AnswerID: 370853

Follow Up By: Dennis Ellery - Friday, Jun 19, 2009 at 11:44

Friday, Jun 19, 2009 at 11:44
30 tyres - you're pulling my chain! - How do you have room for the rest of your gear?
Regards Dennis
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Follow Up By: StormyKnight - Friday, Jun 19, 2009 at 13:29

Friday, Jun 19, 2009 at 13:29
Thats why I have a ULP/Diesel Prado since you never know which is going to be available out bush...but changing tyres thats just ridiculous!
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Follow Up By: Bonz (Vic) - Thoughtfully- Saturday, Jun 20, 2009 at 10:02

Saturday, Jun 20, 2009 at 10:02
30 tyres? Thats NOTHING... MY 1500w inverter puts out 246 different volts cause I am not sure which one I will need for the terrain I an traversing
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Follow Up By: Boobook2 - Saturday, Jun 20, 2009 at 19:02

Saturday, Jun 20, 2009 at 19:02
olcoolone, I am not sure what you are on about. I have 3 different gain antennas for 2, 2.5 and 3 km ranges. Once I heard some kids swearing on the UHF from 5 km away. It is great. ;-)

To be honest I don't even get why you need a UHF apart from group travel work and talking to trucks / caravans 200 meters away.

As you say get a good 4.5 - 6db and you are fine.
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Follow Up By: olcoolone - Sunday, Jun 21, 2009 at 14:40

Sunday, Jun 21, 2009 at 14:40
Some people get carried away with small detail.

Yeah i also do the same with driving lights...differant shapes, sizes, colours and wattage for differant driving conditions....

Took 5 hours to travel 17 kilometers on night...we had rain, snow, fog and 7 differant types of terrain....had to stop every couple of kilometers and change lights......lucky I suppose I didn't have my 6 types of differant tyres on board as well or it would of taken 11 hours.

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Reply By: MEMBER - Darian (SA) - Friday, Jun 19, 2009 at 11:55

Friday, Jun 19, 2009 at 11:55
Yep - I too reckon that the + - 6db area as a compromise for most conditions is a good idea - it is true that the high number radiation patterns work much like a very wide flat pancake with line of sight being very important. The low numbers work more like a ball, with better local penetration into obstacles. Another factor that was important learning for me was that rigid antennas are better - the flexible whip unit I had once (GME - with 3 wires and black / blue phasing coils) flopped around that much that the signal would (of course) sometimes be directed way up in the air (and the people we were trying to comm with insisted on staying on the ground :-o).
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Reply By: Member - OzGazza - Friday, Jun 19, 2009 at 13:55

Friday, Jun 19, 2009 at 13:55
Thanks Guys
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Reply By: Shaker - Saturday, Jun 20, 2009 at 13:44

Saturday, Jun 20, 2009 at 13:44
My GME AE409L "configurable antenna" kept snapping witht he corrugations.
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Reply By: Stu & "Bob" - Sunday, Jun 21, 2009 at 17:45

Sunday, Jun 21, 2009 at 17:45
I have been using the same AE409L antenna for the past 12 years. I have always used it as the 6db antenna and find that it gets out and receives well.

Prior to that I had a 9db fibreglass whip mounted on the bullbar. It was roughly 2.4m long, I just forget who made it, but I bought it new in 1985. It worked really well in the open downs country around Longreach and Winton, with mobile to base comms on simplex still possible around 100Km (no repeaters around then). The base antenna was a 12db gain that came in 3 sections that had to be glued together before we put it up on the aerial mast.
The UHF radios were (mine still is) Sawtron 999 units.

HTH

AnswerID: 371203

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