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Old 12 January 2003, 12:49   #1
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Where to mount aerial ?

I have purchased an Icom 401 and aerial at the boat show and need some advice. My Zodiac pro 550 will not take an A frame so I think that the aerial will have to be mounted on the center console. Any thoughts or help would be appreciated.
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Old 12 January 2003, 13:43   #2
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Scotty

Although my boat has an A-frame it always prudent not to have long wires scatered on the boat.
Both the GPS and VHF aerials are mounted on the port and startboard side of the consol of the boat as is shown in the attached photo.
Hope this info helps.

PS Since then I also put a compass in the middle but there is not interferance by either the GPS or the VHF.
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Old 12 January 2003, 14:44   #3
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Reception ?

Will the reception be ok if the aerial is only as high as the console ?
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Old 12 January 2003, 14:51   #4
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Scotty

So far no probs with reception.
Until transmits and receives 100+1%!!
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Old 12 January 2003, 15:28   #5
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Scotty

Have the same problem myself at the moment. I have a Selva 460 which can take an a-frame but i am against putting any more weight at the back. I also have the 401 which was fitted by the dealer but not put into the console. It was just put on the bracket and fitted to the console with a very small whip AE. I have found this to be very poor indeed.

I have therefore been to to my local shop and bought one of those big AE's as seen on bigger boats. I think this will provide a far better AE. I don't see the point of having a fitted VHF and losing the power available with a poor AE. To that end i have invested in a bracket to fit the AE to the centre console. I have decided to fit here as i think this will give me more height which is better for VHF. I could have put it on the back where the A-frame goes but not as high and is still putting weight at the back.

The AE and bracket is made by Glomex which i found a bit expensive but worth it as it sorted my problem. Their web is www.glomex.it and the bracket i got is the RA166.

I will post a pic when i have finished the job.

Hope this helps.
Regards

Stuart
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Old 13 January 2003, 05:31   #6
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Aerial,

Stuart,
What aerial do you use with this bracket ?
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Old 13 January 2003, 11:02   #7
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Scotty, I've got a 485 Cherokee and, although it's got an A frame I (for various reasons) decided to mount the aerial on the consol. I've got a 6ft f/g aerial on a ratchet mount on the starboard side, just above the tubes. No probs. Remember that some aerials don't like the wire being shortened, so plenty of room to coil it inside the consol.
Phil
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Old 13 January 2003, 15:11   #8
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Scotty,
Attached a pic of where i put it. (just got to wire it up!)

The whip i got i just asked the bloke for their advise and got the one that is about 2m in length. The higher the better for VHF but not big as to look stupid !
Rgds
Stuart
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Old 13 January 2003, 16:41   #9
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Hi folks

For my 2p's worth

Where Manos has mouted the antennas might be good for cable routing but ALL antennas MUST be mouted away from conductive items, which includes items which hold water as salt water is conductive. (dont forget people are maily salt water . )

To work correctly and idea siuitaion would be where no conductive items are within a wavelength of the antenna, on the same level, about 1.9 meters for VHF and about 25cm for GPS. If items are placed closer than this they tend to de-tune the antenna making it a poor antenna. This leads to poor GPS fixes, shorter VHF range etc.
This can be hard to obtain but most of the loss if when you go below half these values, a half wale length.

The other key thing mainly for VHF is height. The higher an antenna the better the reception.
Mounting on a pole is good, but you must get a antenna that does not need a groundplane, which most do, if you going to pole mount it.

If i didnt have a A frame i would go for a transom mounted pole about 3-4 foot high and go for a antenna with about 3dBi gain (the ones about 3-4 foot long).

A good check but not always 100% is to use a SWR meter the reflected power should be 1.5:1 or less.
This is only a guide as a dummy load with give you 1:1 but will not radiate much !!.

Also Phil, there should no reason not to shorten a coax feed antenna as long as you make good job of fitting the coax plug.

Anyone wanting more info on specific instalation drop me a PM

Have fun

Regards Gary
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Old 14 January 2003, 16:53   #10
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antenna

Scotty its worth noting that good aerial connections are vital, transmitting on a vhf with no aerial connected can damage the unit , a bad connection will give the same result, as far as I can remember total impeedence of the aerial and cable is 50 ohms.Rember vhf is line of sight no matter how big your aerial is , a transom mounted Glomex might be the way to go for your Zodiac , also note that the fine for operating or posessing vhf radio equipment in the Republic without the licence is 25000 euro gav
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