Need help to amplify my VHF marine radio for fishing offshore/ increase range

[xrayengineer@cfl.rr.com]

Hello, I have a problem that I knew the amateur radio community would probably be able to help with.

I am a recreational fisherman, and recently I was involved in a situation where VHF marine radio communication was falling a little short in range, and and EPIRB had to be deployed.

In the future, should a dire situation develop, I would like to be able to extend the range of the VHF marine radio to transmit and receive further than I currently can get with my 8 foot antenna mounted about 8 foot off the water and my standard 25 watt vhf marine radio. I understand the legalities of the 25 watt limit, but I am only talking about a life or death situation, not regular chit chat.

I have been looking at a few amps that supposedly will take a 25 watt input and amplify to 100-200 watts, depending on the model.

I am assuming this would substantially increase my transmit range. However, probably do nothing for my receive range.

Is this a good solution? Would I need a different antenna or upgraded cables?
Would the amp still allow the signal to feed the receiver when not transmitting? Is there a amp that can boost both transmit and receive signal?

Can anyone recommend a good solution for communicating more reliably at 40-60 miles offshore? The boat is 27 foot open console, so VHF is really my only choice. Would a taller antenna make a substantial difference?

Here is a link to an amp I was looking at, any advice would be appreciated:

vhf amplifiers 156-161 MHz

Regards! Jim

 

[Robb]

I would invest in a fine antenna and ditch the amp idea. A real quality antenna up high as it can be mounted would be far more effective. That's a fact; and that is what real radio operators do first before going to more power as a solution. It might not be the answer that you were looking for; but it is the right answer.

I've talked to Australia several times with 25 watts and a premium antenna when conditions allow. The antenna has always been the most important part in Ham or hobby radio - and always will be.

I would take the time and re-evaluate the antenna situation first. Spend some for a nice antenna - then see what happens then.

 

[packrat]

I have to agree with Robb. Also, an amp wont do anything for the receive side, and communication is a two way street. The EPIRB is for just that sort of situation, which will occur once in a lifetime anyway. If you find yourself in the Life or Death situation more than once as a recreational fisherman, you are just being foolish.

 

[W5LZ]

An amplifier would give you an increase in range. No telling what that increase would amount to, and I certainly wouldn't count on that 40 - 60 miles. Getting that antenna up higher would probably be your best bet. Which says nothing about the legality of an amplifier, which I'm not familiar with.
I'm afraid I'd have to agree about the, "Don't get into those kind of situations!" thingy. If you do that more than once or twice, you need to re-evaluate what you are doing, you know?
Not much help, sorry 'bout that.
- 'Doc

 

[Beetle]

Getting the antenna up higher is going to be much more beneficial than throwing more power at the problem. If the two antennas can "see" each other, you'll have communications with remarkably low power over open water. If the antennas CAN'T see each other, it could be because the signal is overshooting the other station.

Can you hear the shore station, even if you can't talk to it?

 

[Happy_Hamer]

Not to change topic, but maybe you can post what happen that emergency beacons were used, I just like interesting stories is all.

Also, I would invest in quality coax and connectors, I have used some of that white marine coax, some of it is not so good. Times Microwave LMR-400 with the sealed Times Microwave PL-259. I mean, marine radio is not "recreational" it can be the difference between life or death, eliminate as many deficits as possible in my opinion

 

[Happy_Hamer]

i was curious,

RG-8X 25 feet at 156.800 MHz = Total Run Attenuation(dB) 1.2

LMR-400 25 feet at 156.800 MHz = Total Run Attenuation(dB) 0.4

May seem negligible,,,,,,,,life and death thing come into play

http://www.timesmicrowave.com/cgi-bin/calculate.pl

 

[office888]

Would a taller antenna make a substantial difference?

YES YES YES!

The top three things that dictate range are antenna height, antenna type, and wattage...in THAT order.

Get that antenna as high as you can. A 3 element vertical polarity yagi tuned for Marine VHF, on top of a TV antenna rotator would do even better than a regular old omnidirectional vertical antenna. It'll provide some selectivity too, you can focus your RF energy towards shore, rather than radiating in a 360 degree circle. Lastly is wattage. First off, you want to make sure you're using quality coaxial cable. For short runs less than 20 feet, LMR240 is perfect. For runs great than 20 feet, LMR400 is a better choice. Once you've got that sorted out, an amplifier is the last thing you add. Ideally with an integrated preamp.

 

[packrat]

Going to look pretty funny with a tower, rotor and yagi on that 27' sportfish. Guess you could climb the tower to spot fish.

 

[Happy_Hamer]

A 3 element vertical polarity yagi tuned for Marine VHF, on top of a TV antenna rotator would do even better than a regular old omnidirectional vertical antenna.

The problem as I see it, the upside of a yagi could also be a downside.

Imagine pointing that yagi toward shore, and not pointing at a receiving station, behind you.

During an emergency, you want your signal out as much as possible. An omni directional signal could get that signal to possibly a close by boat, so I would avoid the yagi.

 

[packrat]

Not to mention that a yagi has a narrow signal beam and boats roll!

 

[office888]

Not to mention that a yagi has a narrow signal beam and boats roll!

Not to mention that a yagi has a narrow signal beam and boats roll!

I don't think the boat roll would be a huge problem with a 3 el. You've got about a 60 degree wide beam, that covers about 30 degrees of elevation in front of you.

As long as you're not out in 45 mph winds, you'd probably be okay.

The only times I'm out on Lake Michigan though, it's pretty calm.

By all means though, don't throw out the vertical though. Keep both! Throw in an antenna switch and you're good to go.

Although I'm not quite sure what kind of mast you'd use on a boat.

At the very least though, get that antenna as high in the air as you can, and upgrade to better coaxial cable. That shakespear coaxial stuff is twice the cost of LMR400, and delivers half the performance.

 

[xrayengineer@cfl.rr.com]

Thanks for all the great replies! I agree wholeheartedly about the once in a lifetime event, however, that does not make you want to be less prepared after a bad event. If anything now, more prepared.

There was a question about whether I can hear the shore stations, and yes, very often I can hear shore stations that have to be close to 60-80 miles away.

The situation was a fishing trip about 40 miles offshore from the East Coast of Florida. Nice calm day and the motor (a two year old outboard) dies! Broken timing belt! Water too deep to anchor, so a drift anchor was immediately put out. There was plenty of fresh water on board, with decent seas and weather for at least the next 24 hours. A float plan was filed and the latest time to contact the folks back on shore was 8pm. It was around 2pm. For the next several hours the VHF radio was used to try to hail assistance, but to no avail. We were not able to hear any other boats or shore stations response if there was one. Cell phones, of course not working either. At around 7pm we knew that some folks were going to start getting worried soon, and at around 9pm we were sure that some type of phone calls and possible search were getting geared up. We had drifted about 7 miles North of our predicted float plan fishing area. At around 10pm, still no luck with radio so it was decided that a search may very well be underway (it wasn't) and to assist in the search some flares were launched. Still nothing all night, and finally in the morning we we around 14 miles north of our float plan fishing area, we decided to set off the EPIRB. About an hour later, a coast guard person hailed us by vessel name on the VHF channel 16. We responded with the situation status and location, and a commercial tow boat was summoned.

What was odd was we did not know the details of the EPIRB response. We assume that the satellite picked up the signal, and the coast guard made contact with us from a boat that was close enough for us to hear, but we never saw them.

We felt bad about setting off the EPIRB since it was not exactly life or death. But if I could have reached to shore via radio we could have perhaps saved some trouble.

It seems that the consensus is to get the antenna higher and use the top quality cable. Without being ridiculous, how high off the water should the antenna be in order to reach land? Or is it even possible? Also, What would be a top quality antenna? I assumed that inside all of them was just a length of copper wire and the real money in a nice VHF antenna was all on the outside mounting hardware and finish quality.

I would just like to know that communication is still possible without having to get SSB or a sat phone.

thanks again for the help!

 

[Robb]

The highest point that you can get the antenna safely with the best coax available (little to no db loss = Times/Microwave LMR-400).

You must remember, that 151mhz is a line-of-sight frequency. A six foot tall man on the surface of the ocean can only see 8 miles due to the curvature of the Earth. So; how high is your antenna at this point?

You are right about the antenna materials. Is it a 5/8 wave antenna; that would be ideal. Is it in decent shape? Corrosion? Has it been specially tuned for the lowest SWR at the frequencies you are using? All of your equipment grounded together?

 

[xrayengineer@cfl.rr.com]

The highest point that you can get the antenna safely with the best coax available (little to no db loss = Times/Microwave LMR-400).

You must remember, that 151mhz is a line-of-sight frequency. A six foot tall man on the surface of the ocean can only see 8 miles due to the curvature of the Earth. So; how high is your antenna at this point?

You are right about the antenna materials. Is it a 5/8 wave antenna? That would be ideal. Is it in decent shape? Corrosion? Has it been specially tuned for the lowest SWR at the frequencies you are using? All of your equipment grounded together?

The VHF radio has the negative battery lead connected to it for power, of course, and the antenna only has the coax cable connected to the VHF radio. That is the only "grounding" in the system.