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db Rating on UHF Antenna

Submitted: Thursday, Jun 18, 2009 at 22:32

Member - OzGazza

Article Overview - UHF Radio
If you are considering a trip into Australia’s vast outback, then a UHF Radio is an important communications device to have. View Full Article...
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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Gaz.

Its the Journey!
ThreadID: 69964 Replies: 6
Views: 853 FollowUps: 9
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AnswerID: 370799   Submitted: Thursday, Jun 18, 2009 at 22:43

apwaddo replied:

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.
Reply 1 of 6
FollowupID: 638083   Submitted: Thursday, Jun 18, 2009 at 22:52

Member - OzGazza posted:

Yep thats the one - great feedback thanks.

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Gaz.

Its the Journey!
FollowUp 1 of 4
FollowupID: 638090   Submitted: Friday, Jun 19, 2009 at 00:39

warfer69 posted:



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

FollowUp 2 of 4
FollowupID: 638101   Submitted: Friday, Jun 19, 2009 at 07:20

Sand Man (SA) posted:

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.

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FollowUp 3 of 4
FollowupID: 638230   Submitted: Friday, Jun 19, 2009 at 18:22

Holden4th posted:

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.
FollowUp 4 of 4
AnswerID: 370853   Submitted: Friday, Jun 19, 2009 at 10:06

olcoolone replied:

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.

Reply 2 of 6
FollowupID: 638136   Submitted: Friday, Jun 19, 2009 at 11:44

Dennis Ellery posted:

30 tyres - you're pulling my chain! - How do you have room for the rest of your gear?
Regards Dennis
FollowUp 1 of 5
FollowupID: 638151   Submitted: Friday, Jun 19, 2009 at 13:29

StormyKnight posted:

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!
FollowUp 2 of 5
FollowupID: 638316   Submitted: Saturday, Jun 20, 2009 at 10:02

Bonz (Vic) - Thoughtfully posted:

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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FollowUp 3 of 5
FollowupID: 638363   Submitted: Saturday, Jun 20, 2009 at 19:02

Boobook2 posted:

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.
FollowUp 4 of 5
FollowupID: 638466   Submitted: Sunday, Jun 21, 2009 at 14:40

olcoolone posted:

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.

FollowUp 5 of 5
AnswerID: 370873   Submitted: Friday, Jun 19, 2009 at 11:55

MEMBER - Darian (SA) replied:

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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By the time I'm too old to go bush, I'll have all my gear set up just right !
Reply 3 of 6
AnswerID: 370897   Submitted: Friday, Jun 19, 2009 at 13:55

Member - OzGazza replied:

Thanks Guys

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Gaz.

Its the Journey!
Reply 4 of 6
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AnswerID: 371027   Submitted: Saturday, Jun 20, 2009 at 13:44

Shaker replied:

My GME AE409L "configurable antenna" kept snapping witht he corrugations.
Reply 5 of 6
AnswerID: 371203   Submitted: Sunday, Jun 21, 2009 at 17:45

Stu & "Bob" replied:

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

Reply 6 of 6

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