4' VHF antenna?

[Ronnie]

Am I kidding myself if I think I can use a 4' VHF antenna on a small, low-freeboard boat (20' bass boat, rail mounted antenna)? Seems like an 8' stick would get whipped around quite a bit in the waves. I know that more height is better, but I'm trying to be practical and also not interfere with fishing.

[Grey Ghost]

If you and a buddy have the same setup, your radio range would be 6.9 miles, under the assumption of an antenna height of 6ft.
If you have a 6ft height and your buddy has a 10ft, then your range is 7.9 miles. If you and your buddy were at a 10ft antenna height, then your range would be 8.9 miles. All of these ranges assume that you have open water between transmit and receive antennas and that you have a fixed mount radios that provide 25 watts of output power.

[Ronnie]

Thanks Grey. I was also hoping that Thom would comment on this.

[Thom]

Of course Gray got it right, he always does both here and elsewhere.

You know, this ones hard for me. I'm sure you know I'm a full fan of tall antennas mounted high and the reasons are just as well known. What occurs to me though is that everyone can't have an antenna that is tall and sure to goodness everyone can't mount one high up.

On your boat, a bass boat, no matter where you put it the thing is going to get in the way. Fish will find that antenna and lead your rod to it, you know it and I know it and every fish that swims knows it too. So while I wouldn't be to much concerned about an 8' stick being whipped around (they survive quite well on small boats on ocean waters where they get beat to death) I think it would finally bother you so much that you had to do something about it. So what's that leave. Well, to tell the truth a 4' antnna might not be much better. If you had a center console it would be easy, just mount on its side and you'd be OK.

OK, here comes the blaspheme, you might be better off with a hand held. Yikes! Well, think about it. If you stand up on your boat the antenna height of a hand held will be higher than a fixed mount 4' on a rail. Some of the hand held's around are very well waterproofed and have full day battery life as well. So that's one thing to consider. If I were in the market for one I'd pick the Standard Horizon HX350S. It has about the best waterproofing around and just as important it comes with 2 different battery packs and both an AC and a DC charger. Particularly if you are usually in an area where great distance is not really an issue you might want to consider one - and maybe as a backup even if you choose a fixed mount radio and antenna.

The next thing I would look at is an antenna that could get out of the way. Shakespeare makes a model 5246 that is a base loaded thing that has a mast that bends over if the need be. I don't care much for it but I thought I'd mention it as an option. If you can do a rail mount you might want to consider one of the ratchet type rail mounts. The only ones of these I've seen were plastic and I would avoid that because it will breake on you sooner or later but if you could find one made out of metal with a lever release it would be a good match to a 4' antenna.

There is another option too but the Ghost might want to comment on this one. You could pick up a suction cup mount 2-meter antenna. I think they are commonly available and its likely even Radio Shack carries them. You would not get good SWR out of them but I suspect you'd be under 2.0 and that, though far from ideal, isn't going to hurt the radio. You could stick it down whereever was out of the way and move it as necessary.

And that's about all that comes immediately to mind. Of course I'd like to see you with an 8' stick attached at your highest point. But of course that's not likely to be possible. I'd still give a very high quality hand held a lot of thought if I were you but in the end the fixed mount will always provide just that little bit of extra safety. Your choice.

Thom

[Ronnie]

Thanks a lot for the comments, WC-ers. Good point about the hand held. Although, I think an unattended hand held (laying on the floor or seat) may have a reduced effectiveness for "monitoring". That is, is it going to be any good if I'm not standing up while using it. Now, I'm leaning towards the 4' stick with a ratchet rail mount - I think I've seen these in stainless steel in one catalog or another. I also have some interest in being able to "recycle" this antenna onto a new CC boat, which is a possibility. I guess I could get a 4' extender if that happened.

[hawg]

ronnie...... i about got chastised for asking this about a month ago. this is on here about every other day now that i'm watching more. you got the most the most civil and honest answers i've seen. i went 4ft little giant galaxy . i hope these guys are right. whats the worst that can happen,if you go to a monster lake you borrow a 8 ftr. with the exception of lake of the woods it'll sure work anywhere in minnesota. good luck

[Grey Ghost]

I have a friend whos main bag is a Bass fishing, along with saltwater fishing when in Fl for the winter and chases landlock salmon at other times. He has rigged his Lund with a thru hull adapter in the gunnel so that he can change antennas as the occasion dictates. When he is Bass fishing he uses an collapsible antenna, like those is used on boom boxes, when he is on big water and needs to get out and touch some one he mounts his 8'.

To put all of this into prospective.

Handheld VHF radios, according to Boat US and West Marine catalogs have a range of 3 - 5 miles. Which in most cases is much less that the RF horizon. These catalogs indicate that the these devices were designed to provide communications between the boat's flying bridge and helm, between dinghies and the boat and for small boats that do not have sufficient space or facilities for a fixed mount radio and antenna and for back up comms. If I were concern about backing up my fixed mounted system, I would have dual redundant radios and antennas, just MHO. Check out Shakespeare's web site for calculating RF horizon, http://www.shakespeare-marine.com/antennas/whichant.htm.

There are three factors that need to be considered for reliable marine communications: RF output power, antenna gain and antenna height above the water (determines RF horizon). The first two parameters RF output power and antenna gain define the ERP, effective radiated power. ERP is what make it all work along with the RF horizon. The approximate ERP of a fixed mounted VHF radio (25 watts) with a 6dB gain antenna is 100 watts more or less; there are other loss factures that need to be considered for an accurate estimate. The antenna gain of a handheld is 0dB (per Raymarine) and with a 5-watt output, that yields an ERP of 5 watts. The ERP of the fixed mount system versus the handheld is 20 times better, which equates to 4.5 times more potential range. The relationship of receive power is inversely proportional to the range squared, Pr = Pt/r^2.

There is another factor that comes into play when you're near the limit of the communication range, antenna pattern. The pattern of the transmitter antenna and the receive antennas are not symmetrical across all azimuths, due to grounding effects and obstructions that are boat particular. So, your boat my have more communication range at some particular azimuth orientation versus some other.

There so many RF parameters that determine communication range, that one does not have control over, so don't worry about them. Just make the best of three; power output, antenna gain and antenna height over the water.

[Den]

The biggest thing here is how far are you going to be reaching for safety measures that you fish? if the 6 to 8 miles is far enough, then thats all you need. if you are planning on big waters you can go for the bigger antenna. as was stated in an earlier post, no matter which size you get it will always seem to get in the way, even on some larger boats. one thing i do on my pro-line center consol is drop it on a angle when i am casting, that does help when casting, and i can still pick up decent reception. good luck and good fishing
Den