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Old 21-04-2010, 07:18   #1
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Powerful Aircraft VHF Radio

I am looking to install a strong VHF (Aircraft Frequencies) radio on a yacht.

The only ones I can find so far on the net are handhelds and those tiny (and very expensive) cockpit mounted units.

I am looking for powerful output linked to a hi-gain antenna so as to maximize range from the yacht to talk to incoming aircraft on their frequencies.

Are there any fliers or communications gurus out there who know of a good “base station” type vhf radio or something that will allow us to modify frequencies to include aircraft bands for a ship board set up….

Any help much appreciated…..Thanks!
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Old 21-04-2010, 07:27   #2
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One comment on your plan for high gain antenna. This would focus the output from the radio into a more horizontal pattern, ie towards the horizon and not the sky. If you are trying to maximize contact to aircraft, potentially at cruising altitudes I think you would need to keep the gain of the antenna lower to radiate more of the signal up.
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Old 21-04-2010, 07:32   #3
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ICOM Aircraft VHF transceiver

ICOM IC-A110-05 VHF AIR BAND TRANSCEIVER BASE STATION from Aircraft Spruce
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Old 21-04-2010, 08:15   #4
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Thanks Skipmac… That radio looks perfect!

I am struggling with what type of antenna to order since it is for heli operation and they fly fairly low so as this table shows we are probably dealing with radio horizon limits.

Please correct me if I am wrong as this is a learning experience for me…. Thanks again
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File Type: pdf Ground Station Ranges 1101298.pdf (48.3 KB, 491 views)
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Old 21-04-2010, 09:20   #5
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Look at the diagram on this page http://www.westmarine.com/webapp/wcs...F-Antennas.htm and it will give you some idea of where the signal goes from the antenna for high gain vs low gain. Understand that even very high gain antenna will not send ALL of it's power horizontally, but much less of the signal will radiate at an upward angle.

Even helicopters can operate at several thousand feet and depending on the distance from your boat, a high gain antenna may radiate most the signal under them.

Also on a sailboat that rolls in the waves, a very high gain antenna will alternately send the signal into the water then into the clouds.

One way to look at it, high gain antenna is like a lens that focuses the output into an narrow disk like a saucer shape around the boat.
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Old 21-04-2010, 09:24   #6
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A question. What kind of range are you trying to achieve? Very long range then the signal spreads anyway so a little higher gain could help, ignoring the issue of the boat rolling and the power radiating downward. If you want long and short range then you do want to consider insuring that a reasonable amount of the power will go upward.
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Old 21-04-2010, 09:46   #7
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High output VHF

Why not, for about the same amount of $$ as an aircraft radio simply get an Icom 706 mk2 G which offers up to 50 watts on VHF. By removing a diode from the circuit board(yea I know) you will be able to program in all of the marine VHF freqs. Remember, while you may be pumping out 50 watts you are still only receiving signals originating from 5-25 watt transmitters.
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Old 21-04-2010, 10:08   #8
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Becker AR601 is a great unit, I have the predecessor and am happy with it. I'm not quite sure I see the need for a specific device limited to aircraft frequencies when you could get a SSB that covers all the bands.
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Old 21-04-2010, 16:38   #9
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G'Day all,

FWIW -- Using a normal VHF masthead type whip antenna and a normal marine VHF we frequently communicate with Australian Coastwatch aircraft at distances of many miles (can't see them, but it takes several minutes for them to arrive at our location). And while in the marina at Gladstone Qld, we often hear the helicopters ferrying pilots to incoming ships at a distance of twenty plus miles. I doubt if you will need anything very sophisticated to do what you want.

Cheers,

Jim and Ann s/v Insatiable II lying Lake Macquarie, NSW, Oz
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Old 21-04-2010, 17:00   #10
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Not sure what you are trying to achieve BUT marine VHF & AIRCRAFT VHF are not the same!!

Marine is FM Aircraft is AM. There is a issue with licenses as well. It is not legal to broadcast on the aircraft band from a boat. You may get approval for a fixed frequency if you are working with an aircraft operation. The different frequency bands require a separate or very broad band aerial if you are trying for only one (118-156Mhz). Aircraft involved with marine & SAR operations will be able to communicate on the marine frequencies.i.e they will call you on Ch 16. Range- line of sight so your aerial on the back rail will give you the same range to an aircraft at 1000ft as one on the top of your mast!!
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Old 21-04-2010, 18:52   #11
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Thanks Guys for the advice.

To clarify Skipmac it is usually an Augusta 109 that will be incoming. Has a range of about 500 miles and a service ceiling of about 19,000 ft.

So assuming I get the right antenna mounted 30m from sea level and use the IC A110-05 VHF what kind of range do you think this will give me if they have a similar powered radio on board and are cruising at 8,000 ft?

The yacht it will be landing on does not roll much since it is fitted with zero speed stabilization.

The reason they want to use standard aircraft frequency vhf is because the noise cancelling headsets they wear are connected to the heli’s onboard com System.

Bill, thanks for confirming that it is in the AM frequencies (118-156Mhz). Aircraft radio licenses are available for vessels having “frequent flight operations” so we are ok there.

This radio will have it's own antenna so what is the best kind to get?

The reason I am scrambling with this is that it was discussed 8 months ago and discounted. Now that the yard is building the bridge console… change of mind.... so I have to decide on a control head and design it in… promptly!

Thanks again for your advice.
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Old 21-04-2010, 19:03   #12
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Aircraft VHF

Good point Bill Good. Use of aviation VHF frequencies requires a station license unless it is in an aircraft and it is operated domestically. Never mind the legal problems you could have if you try to use internationally.

Where do you plan on using it? Once you get off shore all the aircraft making ocean crossings are on HF frequencies anyway.

As Bill Good mentioned all the search & rescue aircraft have marine VHF.
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Old 21-04-2010, 20:18   #13
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It would more normal to add the marine radio to the aircraft. But if you are expecting various aircraft then maybe the approval can be obtained. Be careful of buying aircraft aerials as they will expect to have a "ground plane" ie aluminum airframe!! when they are installed!! I would install a 1/4 wave with ground plane cut to the frequency allocated. It may be necessary to have the radio modified to prevent it being able to change channels or one which cannot change channels. @3000' 30+nm. range. 5Watts Transmitter min will do the job. A simple vertical whip on top of a wheel house? what is the installation going on? Bit hard trying to advise without knowing a bit more!!
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Old 21-04-2010, 20:55   #14
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Good to know the radio in my fabric airplane can't possibly work without a ground plane.

I've had better luck talking to a cheap handheld aviation radio than anything else on a boat. You'll need to step outside the wheelhouse or mount an external antenna, at least on a metal boat. Magnetic Base Antenna - Sporty's Pilot Shop, with the high-tech installation method of duct taping the base to something convenient, works well. Just about anything else (like DM C63-1/A ANTENNA from Aircraft Spruce) is probably better.

I've don't make it to 8K very often, but we can usually get 20 miles or so from 1500' if there isn't a mountain in the middle, and that helo probably has better radios than me.
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Old 21-04-2010, 21:52   #15
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The advise given is on the basis "free". The installation is going on a sea going ship & I have assumed a fixture to stand that environment. DM C63-1/A on top of a metal area would be OK. I would not recommend it without some form of ground plane. Good advise for any non aluminum aircraft owners any 1/4wave aerial should have a ground plane. No one said in can't possibly work. There maybe other structural components close or there maybe some ground plane even 100mph tape under the fabric.
I would still select a aerial best suited to a boat installation from land & Mobile rather than aircraft for this installation.Pelagic PM if you are still unsure.
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