Noob questions: receiving vhf from far away

[Rookie]

Hi

I would like to get access to listening to our local VHF stations for the recreational channels at sea but that are about 30km away from my house. Is this possible and what sort of installation would i require?

I am trying to educate myself but find all the information overwhelming not sure where or how to start. I have a VHF radio on my boat and i know the operating procedures but nothing else. If someone can point me in the right direction of where and what i should start looking at please.

Cheers

 

[KJ4VOV]

In general, VHF is strictly "line-of-sight". In practice, there are a few conditions under which it can travel further (tropo ducting, etc.) and it will go slightly beyond the horizon. What this means to you is that you'll probably need to raise your antenna higher... quite a bit higher.

30km is just a little under 19 miles so we'll work with that.

To "see" a horizon that's 19 miles away, the antenna would need to be at an elevation of about 200 feet above.

These two links may help you understand what I'm so clumsily trying to explain:

11 Tips on How to Calculate the Distance to the Horizon - wikiHow

BoatSafe.com

 

[VE6SDG]

Your going to need elevation for the antenna and most likely have to switch to a Yagi type antenna which is a directional antenna. Mind you a Yagi for the VHF freq band is going to be 6-8 feet long.

 

[KingCobra_CDX882]

to go only 20 miles..

sure you can use a high antenna
sure you can use a beam

However being on the water also gives you excellent advantage
if you are willing to mount a decent 2 meter or dual band antenna
(even a mobile 2 meter/70cm)
with radio of even 50 watts (likely even with just 20 watts)you should easily hit a repeater 20 miles away.

 

[KJ4VOV]

to go only 20 miles..

sure you can use a high antenna
sure you can use a beam

However being on the water also gives you excellent advantage
if you are willing to mount a decent 2 meter or dual band antenna
(even a mobile 2 meter/70cm)
with radio of even 50 watts (likely even with just 20 watts)you should easily hit a repeater 20 miles away.

The OP was pretty specific about monitoring the VHF marine band, not the amateur bands, and may not even be licensed. And he/she is 30km inland, not on the water at all.

Oh, and hitting that repeater 20 miles away? Most repeater antennas are mounted well above the surrounding terrain. Usually on a high point of land and/or a tall tower, precisely for the reason that it gives a wider footprint and pushes the horizon back.

 

[KJ4VOV]

Your going to need elevation for the antenna and most likely have to switch to a Yagi type antenna which is a directional antenna. Mind you a Yagi for the VHF freq band is going to be 6-8 feet long.

Could also go with something like the Elk log periodic, which is just about 2', but I think with enough elevation the OP shouldn't have any problems picking up 1 watt VHF marine band portables at that distance. I used to regularly check in to a net held on a repeater (located on top of a mountain) that was 35 miles away, using just an FT-60 and rubber duck. I was noisy but readable. If I switched the duck for an open stub J-pole with a little bit of gain I was full quieting at 5w, and a little noisy but readable at 0.5w so I think any decent antenna should work for the OP in this case, provided he/she mounts it high enough.

 

[VE6SDG]

Since Marine band freqs are all simplex and not using a repeater you could get away with a 3-5db gain omni antenna. It wont be as big of an eye grabber as a Yagi but it will still need to be up as high as you can practically get it to receive the best. The other thing to remember as well is that if your going to be transmitting from a land based radio you need a different license than the one you need for operation on a boat.

I've easily hit a repeater in the next town 115 miles away with 25w and heard it back on the linked local repeater. I was on the ridge with the local repeater at about 3500 feet with the other repeater being at about 6500 feet elevation.

 

[KJ4VOV]

He did specify "listening", so I don't think licensing will be a concern.

 

[Rookie]

awesome! Thanks for all the responses I don't intend to transmit only to listen. No repeaters for these recreational channels around here and some mountainous area in between.

So what receiver would you recommend? I hope this is going to work

 

[Comp]

Hiya!!! Sounds like any receiver that covers the marine band will be fine for you,... and a simple 3 or 4 ele yagi for 150 odd megs pointing coast ways wont hurt,...
Google 'Cheap Yagi', you will find plenty of info on an easy antenna,

Cheers, Fred

 

[NeoHam]

I see this post is a month old but.... If you go to Google Earth click Add, Path, click your location, zoom in or out, click on other location (water), title it and hit OK. Now that your path is there, right click on the path and go to Show Elevation Profile. This will show you if you need any antenna height to get over the hills.

I have an omni gain ant at 35' and I can hear ambulances calling hospitals 30 miles or more and that's with a ham antenna.

 

[Rookie]

Noob questions: reciving vhf from far away

thanks. Max elevation is 1826ft from my current location and max distance i need to be able to listen is 30 miles away