VHF Antenna location

Seahusky
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Re: VHF Antenna location

Unread post by Seahusky »

That's exactly it Hunter. It's all about ease of deployment. Once the antenna is high enough and you are out on the water your range is line of sight on these frequencies. Since most of us are out in the straits or the sound we're all still in range of the CG. It's really when you go off shore 30-40 miles is where you will see the decrease in performance due to bad location of antenna.
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MacGyver
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Re: VHF Antenna location

Unread post by MacGyver »

Seahusky wrote:
Sun Mar 08, 2020 11:40 am
Andrew, that's the norm for most fitters and HT bulkheads boats of the SeaRunner, Ocean Pro, Alaskan series boats. Fitters don't understand how signal polarization works and how antennas radiate as well.

FYI: For maximum radiation from a vertically polarized antenna the antenna MUST be mounted in the dead centre of a vehicle or boat. So in other words, for a Hard Top boat it must be mounted in the centre of the roof. If it is not then it creates "lobes" in the radiated signal from the antenna. So in theory if you mounted an antenna on say the starboard bow of a boat, it's strongest field will be in the direction of the port stern direction or opposite diagonal direction. So in the centre of the roof of a boat you will have 360' of maximum field efficiency with no strong/weak signal lobes in amy direction. Of course having an antenna with a good gain also helps.

I'm going to fit a ham radio mobile station hopefully in my new boat for some fun when I am moored. Being a Ham Radio technician has it's benefits ;)
That is not true with ALL vertically polarized antenna if the antenna is using the boat as part of the ground plane then yes putting it in the center is the best place. Most vhf marine antenna are end feed 1/2 or 5/8 wave and do not need or use the boat as a ground plane.

Seahusky
I really need a life!
I really need a life!
Posts: 731
Joined: Fri Feb 05, 2016 11:16 pm
Name: Eoin
Vessel Name: Argonaut
Vessel: 2020 PC 240.
Location: Sequim, Washington.

Re: VHF Antenna location

Unread post by Seahusky »

Hi Tom.

According to my Field Strength meter it will show effiency no matter what way the antenna is grounded or in relation to the OP, proximity of radar or other units near it which affects field effiency.

On aluminum boats it is recommended to use a no ground plane antenna as it uses the water or ground mount to radiate effectively. On Fibreglass boats the grounding is within.

I've been building ham antennas for years as it's a hobby of mine and was part of my technicians license. It's a wonderful hobby to say the least.
2020 Pacific Cruiser 240 (Ordered).
Yamaha 300hp V6 DEC with Yamaha 6YC display.
Yamaha T25hp High Thrust Kicker with prop guard.
Lowrance 3G Broadband Radar.
Lowrance HDS-12 Live at helm.
Lowrance HDS7 Gen 3 at 2nd steering station.
Lowrance Totalscan Transducer.
Lowrance Link 8 AIS VHF radio.
Lowrance Point 1- GPS antenna.
Scotty 1106 Downriggers.
Discovery Bay Pot puller.
NOCO 2 bank battery charger/maintainer.
Lowrance Auto-Pilot.
Wallas 30 GB heater cooker with defrost fans.

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NovaCX12
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Re: VHF Antenna location

Unread post by NovaCX12 »

See my post here for some ideas.

viewtopic.php?f=13&t=3311
16' 190 SeaRunner ET HT
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MacGyver
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Re: VHF Antenna location

Unread post by MacGyver »

Seahusky wrote:
Sun Mar 08, 2020 10:24 pm
Hi Tom.

According to my Field Strength meter it will show effiency no matter what way the antenna is grounded or in relation to the OP, proximity of radar or other units near it which affects field effiency.

On aluminum boats it is recommended to use a no ground plane antenna as it uses the water or ground mount to radiate effectively. On Fibreglass boats the grounding is within.

I've been building ham antennas for years as it's a hobby of mine and was part of my technicians license. It's a wonderful hobby to say the least.
It’s a small world. I too am a ham, extra class license and I used to design and build wide band HF antennas for the commercial marine frequency.
I could not find where Shakespeare has a marine VHF antenna for fiberglass and a difference antenna for aluminum boats. What am I missing?

Seahusky
I really need a life!
I really need a life!
Posts: 731
Joined: Fri Feb 05, 2016 11:16 pm
Name: Eoin
Vessel Name: Argonaut
Vessel: 2020 PC 240.
Location: Sequim, Washington.

Re: VHF Antenna location

Unread post by Seahusky »

I too Tom have full licence privaleges. But I know when I fitted antennas to boats back home you had to stipulate what type of surface/material you were fitting the antenna to for maximum performance.

Never saw an antenna not work right for me yet that I installed..

Best 73's.
2020 Pacific Cruiser 240 (Ordered).
Yamaha 300hp V6 DEC with Yamaha 6YC display.
Yamaha T25hp High Thrust Kicker with prop guard.
Lowrance 3G Broadband Radar.
Lowrance HDS-12 Live at helm.
Lowrance HDS7 Gen 3 at 2nd steering station.
Lowrance Totalscan Transducer.
Lowrance Link 8 AIS VHF radio.
Lowrance Point 1- GPS antenna.
Scotty 1106 Downriggers.
Discovery Bay Pot puller.
NOCO 2 bank battery charger/maintainer.
Lowrance Auto-Pilot.
Wallas 30 GB heater cooker with defrost fans.

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