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Old 11 December 2005, 09:17   #21
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I had a white plastic one. That fell to bits and had to be glued back together, then it was okay.

Then I got one that was about a meter length of straight whip antenna. It was old and i kept losing the meter lengths. They were a bugger to find on their own.

Now I've treated myself to a RIB Raider one that I picked up cheap. To make sure I don't lose anything off it once its been fitted I'm going to cable tie the antenna to the base, so that if it undoes itself I won't lose the damn thing in the sea.
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Old 11 December 2005, 13:52   #22
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I have 2 x Pacific Aerials on the A-Frame -

http://www.pacificaerials.co.nz/marine/vhf.htm

I can't remember which model they are, but they're 1.8m. The local electronics company I bought them off have installed them on the police ribs along with icom radios and they don't have problems, so I went for the same setup.
Reception is excellent - they beat the little aerials most ribs have on them for transmit/receive quality.

Main concern when I bought them was that they might snap, cos the aerials themselves don't bend much before snapping. However, with them I bought 2 mounts which flex plenty when attached to the a-frame. There was an option to buy stainless mounts, but they transmit too much shaking into the antennae and ultimately fracture them.

Finally, they look damn good

-Alex
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Old 12 December 2005, 05:32   #23
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Hi Alex
Have you Co-Phased the two antennas?

Shaggy
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Old 12 December 2005, 08:21   #24
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Twigs

Alex do you get much interferance between each antenna when you Tx on one ?
Or is the 2nd a spare?
I have run multi radio set ups for ages now, personnaly and for work. Ideally you need to get horizontal and vertical seperation between the antennas in the same band / frequency. I know thats easier said than done with an A-Frame, if you can get about 1.5m horizontal and the antenna vertically clear you should be ok, this VERY rough and ready, there are full calculations on the radio Ham websites.

If you want a really good antenna for VHF then try Procom's marine VHF range, but be sitting down when you look at the prices
Jelly
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Old 12 December 2005, 09:26   #25
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Quote:
Originally Posted by Alex Brown
Finally, they look damn good
in a boy racer, go faster stripes, fluffy dice kinda way if its the radio controlled toy boat look you were after...
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Old 12 December 2005, 10:44   #26
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Quote:
Originally Posted by roycruse
in a boy racer, go faster stripes, fluffy dice kinda way if its the radio controlled toy boat look you were after...
....Or 10ft of clear plastic tube with 12ft of floppy wire trailing out of that and Tyco splashed down the side!
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Old 12 December 2005, 11:49   #27
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You are asking a bit too much of any antenna on a rib if it is only base mounted. That's not so say you can't get away with it. However, if you mount a good quality nylon base on the side of the A-frame and then support the antenna casing further up using a non-metallic support, it'll be fine for many years. To prevent an impedance mismatch, you need to keep the separation between the antenna and the stainless steel of the A-frame 40mm or greater. This works out nicely because a sideways mount gives a good spacing. The extra support needs to be about 200mm above the mount. Beware of cheap nylon mounts from China...pish. I am presently using stainless mounts, they look smart but they are a mistake. If you want to have the extra gain from a 3db antenna, a good solution is to mount it using a rail mount and an upper support with a greater vertical spacing between them for normal use and slide the lower mount up the A-frame to get it clear of the steel should you ever need the extra range in an emergency. I use this sytem and it works well. If you have access to an SWR meter, you will be able to adjust the vertical position of the antenna against the A-frame and you'll find good positions where the loss is almost insignificant. You can then use this position for normal operation.
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Old 13 December 2005, 16:06   #28
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The two aerials in my case do two different things. One is attached to the Icom 503 VHF, and the other the Icom DS-100 DSC Controller. At the time, there was no Icom unit out that combined DSC with VHF in one unit, so I went for the 503 which is a great radio to use (I'd previously had the 501, and we have 501's at work too with no probs).
Working things this way, if the main aerial were to snap, I can swap the cables over to the other pretty quickly in the console.
The base mounts are both nylon - the aerial bases are stainless which screw onto the nylon base to keep the aerial rigid, but allow the mount to flex.

The main reason for getting these aerials was signal - one thing most ribs do not have is height - putting them on the side, but up top of the humber a-frame which is quite high anyway, they stand very tall above the vessel and give very good signal. Having been next to other ribs with the smaller aerials, I frequently pick up stuff they don't - for that reason, I'd go with these aerials every time.

edit: my aerials weren't cheap - nor the mounts - like most things, you get what you pay for. I would however be expecting to be changing the nylon mounts in the next 6 to 8 months cos they're exposed to the sun all the time, and I'd rather change em than loose the aerials - they will have been on the rib for over 3.5years at that time.

-Alex
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Old 13 December 2005, 16:13   #29
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Quote:
Originally Posted by roycruse
in a boy racer, go faster stripes, fluffy dice kinda way if its the radio controlled toy boat look you were after...
boy racer? - no.....

practical, yes.

they just look smart on the a-frame mounted like that amongst the radar reflector.

-Alex
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Old 13 December 2005, 16:33   #30
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Quote:
Originally Posted by Alex Brown
boy racer? - no.....

practical, yes.

they just look smart on the a-frame mounted like that amongst the radar reflector.

-Alex
I agree they are probably very functional - I just found it quite comical that you should comment on their appearance - something that I would have thought (hope) didn't even enter in to most peoples heads when choosing their antennas.

What an aerial looks like i thought was reserved for the CB fraternity who call their aerials names like "Silver Rod" and "Thunder Pole"
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