VHF Antenna

[Steel Boat]

Hello :
I am buying an Icom M330 VHF radio for my 38’ steel troller . Any suggestions on antenna? The instruction manual says an antenna with a maximum gain of 3 db .Max RF Power is 25 watts. Advice will be appreciated. Thanks .

 

[psneeld]

This from the ICOM 330 manual....

"Icom requires the radio operator to meet the
FCC Requirements for Radio Frequency
Exposure. An omnidirectional antenna with
gain not greater than 9 dBi must be mounted a
minimum of 5 meters (measured from the
lowest point of the antenna) vertically above
the main deck and all possible personnel. "

I am sure the radio will handle up to a 9db antenna, the recommended 3db was for their mounting instructions which seem excessive.

Never ran across al VHF at 25 watt max output radio that couldn't be and often were hooked to a 6 db or 9db antenna.

Despite all the advice you will hear about line of sight and 3db is plenty...on a larger powerboat I like both a 6 and 9 db antenna. 6db for close use and the 9db for max range when I want/need it.

Distance isn't the only reason to have higher db, it is also to power through weaker transmissions.

 

[ktdtx]

I've never personally used one but I have heard positive comments about these:


http://https://www.morad.com/

 

[mbevins]

I've never personally used one but I have heard positive comments about these:


http://https://www.morad.com/

Excellent quality and service.

Sent from my LE2121 using Trawler Forum mobile app

 

[Prospective]

I really like Digital (the brand) antennas. Good quality and a nifty connector that allows you to snake the wire easily and the attach the coaxial adapter to your VHF without having to solder or crimp anything. Just thread it on.

 

[boomerang]

Hello :
I am buying an Icom M330 VHF radio for my 38’ steel troller . Any suggestions on antenna? The instruction manual says an antenna with a maximum gain of 3 db .Max RF Power is 25 watts. Advice will be appreciated. Thanks .

I briefly looked through the manual and didn't see where it said to use an antenna with a maximum gain rating of 3db. If that was the case, about 75% of the boats out there have the wrong antenna on them!
I would say, for a 38' powerboat, a 6 db ,8' antenna would be a good one if you're mounting it on top of the house.

 

[Steel Boat]

Boomerang:

Look in “Installation note “ page IX of the instructions manual .

John

 

[psneeld]

True, I did see it in the manual but it also discusses calling either the manufacturer or the retailer to explain installation of more powerful antennas.... it's not about the radio, it's about the radiation hazard of the more powerful antennas and the need for more than an ill informed "amateur" installation.

Even being a former marine electronics installer, I have never seen that only a 3 db antenna be used or instructed to mount a 6-9 db antenna well away from people... sure a couple feet but more???....

For 15 years I had a 9 db antenna on the assistance towboat within about 4 feet of me and another mounted at deck level on my trawler about 3 feet away for the next 10 years/20,000 miles. So far only partial brain frying....

 

[Comodave]

Your VHF isn’t a cell phone that you will be using for hours on end. Most transmissions are a few seconds in length and are not that frequent throughout the day. I wouldn’t be that worried about radiation from a VHF. Use a 8’ antenna of good quality. I have had good success with Galaxy HD antennas from Shakespeare.

 

[Steel Boat]

Antenna

Thanks Shawn . I will go for 6 db.

 

[Alaska Pirate]

I owned a marine electronics shop in Petersburg, AK for a number of years. We sold both Shakespeare and Morad antennas. The only failures we saw with the Morads was when they were driven under a low bridge or dropped in the saltwater. The Shakespeares...not quite as reliable.


RE: antenna gain. If the antenna is good, ie no or low reflected power, the radio will operate with no problems.

 

[boomerang]

Thanks Shawn . I will go for 6 db.

You'll be happy with that choice. Also, all the replies from others on your thread was sound advice. There's a plethora of knowledge available from experienced folks on this forum.

 

[boomerang]

I owned a marine electronics shop in Petersburg, AK for a number of years. We sold both Shakespeare and Morad antennas. The only failures we saw with the Morads was when they were driven under a low bridge or dropped in the saltwater. The Shakespeares...not quite as reliable.


RE: antenna gain. If the antenna is good, ie no or low reflected power, the radio will operate with no problems.

The radio will be happy but the OP needs to know that you always want to try to match the antenna to the boat. A 9db on a 13 whaler wouldn't perform as well as a lower gain antenna, in real world conditions.

 

[Alaska Pirate]

Nor would a 6 or 9dB at the head of a sailboat mast due to the radiation pattern. But the OP is installing the system on a 38'troller

 

[High Wire]

38’ Diesel Duck with only one VHF? How about a 4’ 3 db antenna for bridge to bridge coms on the Loop and a 6db 8 ft or 8 db 14ft on a second radio for open water. Your girl deserves some bling.

 

[IRENE]

I am a big Morad fan and current user. Pacific Aerials is of comparable performance and quality, and offers a more recreational look.

 

[firehoser75]

+1 on Morad. I used 2 of them on my Tug with good success. Around here, you see Morads on most fish boats and other commercial types.

 

[Hippocampus]

Like the 9db but the 6db maybe better for close in. Pick your poison on basis of whether or not range is a major determinant. All brands are pretty good but have had good luck with Shakespeare products. Don’t like splitters on antennas for AIS.

 

[Steel Boat]

Thanks High Wire , make sense.
John

 

[backinblue]

6db is a good compromise and should be fine for most usage w/o knowing more about your intended cruising.

 

[Circumnavigator]

I really like Digital (the brand) antennas. Good quality and a nifty connector that allows you to snake the wire easily and the attach the coaxial adapter to your VHF without having to solder or crimp anything. Just thread it on.

I second the motion. We've used Digital Antenna for years. Excellent workmanship. I don't understand why everybody else doesn't use the mini connectors.


Highly recommended.


Jim

 

[psneeld]

Possibly because many believe every connector puts RF losses in the system.

I am no expert...just passing along what I heard in the marine electronics business and read. There may be way more to it than I ever learned or understand.