Which VHF antenna?

[ragin cajun]

Storm over weekend destroyed my VHF antenna. I have an overall length of 16ft. including the extender (8ft). Which decibel rating do you guys find the best compromise in range and voice quality for most applications? Thanks for your input.

 

[psneeld]

I always recommend a 9 and 6 dB antenna for all larger boats. One if you really need to reach out and one for close in comms..but I usee my 9dB 90 precent of the time due to where that radio is located.

On my boat the placement of the 6 dB on an extension looks just like the 9 db. Pretty much the same setup as on hundreds of sportfish the place I worked for rigged.

 

[FF]

One that folds down easily if you are in a bridge area .

As we seldom go far offshore the sail boat style "wonder whip" unit works best for locks and bridges as it will put out on restricted power (Ch 13) .

A big antenna laid down has almost no output , so if you need extreme range .a second antenna and a switch or just a hand held works.

 

[IRENE]

Morad Antennas

I once ran a work boat, which was operated by many operators on various shifts, with a name-brand VHF radio. All of us were unimpressed with the performance of the radio and 8' antenna (unknown db gain) and we routinely complained. We operated on the Detroit River, Lake St. Clair, and the West End of Lake Erie...so usually our transmissions had to go over land in an urban environment.

Management must have finally gotten tired about us complaining about the "crappy radio" and losing communications. The technicians came out and installed a Morad antenna on the same radio. The results were nothing short of amazing - we could communicate through our entire operating area with that reportedly crappy radio.

I don't currently have one, and they look a bit different. I have used them many times over the years. When IRENE needs a new antenna, it will be from Morad.

Usual disclaimer - no affiliation whatsoever, just a happy user.

 

[SteveD]

Buy Morad!

If you look at fishboats in Seattle or Alaska, the vast majority are using the Morad HD antenna:

VHF antennas — Morad Electronics

Some have a veritable farm of them at various altitudes.

They know what works and they depend on them reliable communications. Plus they are made in a small Ballard shop and are pleased to test an antenna if you bring it in. Nice people.

 

[Paul Swanson]

The difference between the two antennas is 3 db, which is a factor of two. I terms of range, you would get the same signal level at a distance of the square root of two or 1.4 times farther. However the curvature of the Earth would probably not allow that much range increase. Any particular signal will be a factor of two stronger with the 9-db antenna. The down side is that the vertical beamwidth is a factor of two smaller with the 9-db antenna. That is much more important for a sailboat that may lose the signal when heeled over. If your boat is generally upright use the higher gain antenna. The cost increment is minimal and you will get some improvement in reception.

Paul

 

[tpbrady]

Things to remember about VHF line of sight communications:

A. Height is as important as gain.
B. Connectors must be good and properly installed.
C. Don't make cable runs longer than necessary.
D. If you have more than one keep them as far apart as you can.

I have an 8 foot Digital 6 dB antenna, an 8 foot Shakespeare 6 dB antenna, and a Morad 3dB antenna. The Morad is on my AIS transponder and can receive class B targets (2 watt output) at 15 miles with some intervening low terrain and it is mounted at the same height as the longer antennas. The 6 dB antennas work out to 18 miles at 25 watts with intervening high terrain.

I like the Digital the best as it comes with factory connectors installed one of which is a mini UHF allowing the cable to be routed through a smaller hole. It is a premium antenna like the higher end Shakespeare.

Tom

 

[psneeld]

I have operated many vessels where there are 6db and 9dB antennas mounted on the 2 sides of the vessel, both relatively the same height, connected to similar radios.

The 9dB is always a standout winner in terms of transmission...reception in most cases too.

Radio theory is nice.....I have had some...but in day to day operations of vessels, which antenna is superior for general use is clear to me.

If you never plan on transmitting more than a few miles and in areas of low radio traffic, the other would be fine.

 

[caltexflanc]

The issue with the high db antennas arises in rough seas and the boat rocking around, and thus effective range can be cut down, in and out, in various directions as the boat dips. That's why the guys that are anal about it have a variety.

The Digitals and the Morads are superior in construction, having once witnessed an antenna "dissection" done by an offshore services company bidding out new gear (disclosure: my company at the time was a Digital distributor).