VHF Range

SteveHall · 05 December 2005, 19:54

Hi There,

I have a question about VHF Range,

I did my VHF/DSC a while ago and i am sure that I was told that VHF works on line of sight, and that even though your not allowed to use VHF on land it would not work anyway - as Manchester is so far away from the sea.

I was talking to a guy at work that is into his radio’s (although not vhf) he told me that it should work at home, even though you’re not supposed to do this.

I would just like some clarification on this, as it would push me quicker to the shop if it did, even though I would not as your not supposed to.

Biggles · 05 December 2005, 20:29

Hi Steve,

Not too sure of your question but the way I read it is you want to know if your Radio will work at home.

Yes it will. But it will only be able to speak to other radios operating on the same set of frequencys and for only a certain distance.

Manchester to the sea. Haven't you got the Manchester ship canal near you. Maybe they operate on Marine frequencys. If you want to listen to Marine radio I should imagine you won't be able to over that distance.

Besides the fact that you aren't allowed to use your Marine Radio on land other than for talking to crew men whilst berthing etc, VHF handsets will only transmit a couple of miles under ideal conditions and Fixed VHF sets probably 20 miles tops with a good high aerial.

Having said that if you fit a base station in your house with a 100 foot aerial who knows !!

Steve, Personally I would only use my radio at home for testing purposes. The way Radio frequencys are allocated its quite possible that the Marine ones conflict with some land based systems.

I use Radios to some extent at work and after some discussion we all agree that the 25 watts that a VHF Marine Radio can pump out is quite a lot.

Maybe somebody could enlighten us more. I see a spot for David Brooks here.

If you just want to listen to Marine Radio traffic, why don't you look at some sort of a scanner. Not that I know much about them but they can be very expensive.

Hope this helps a little.

Regards Nick R.

Jon Brooks · 05 December 2005, 20:50

David Brooks?

Is he new here?

You are never more than 72 miles from the sea here!
You can use that one if it goes quiet in the snug!

Line of sight is taken from the top of your antenna to the top of the other station.
So if you were a coastguard station with an antenna some 200 feet up your range would be preety good.

If your using your hand held then range is limited.

As suggested a scaner with a decnet outside anteena would give the best results from home, you are also then not just limited to the marine chit chat.

They take a dim view of marine radio used in land if it is not for a legit reason.

Hope that helps a bit and hopefully David Brooks can give you some pointers too

Regards

Biggles · 05 December 2005, 20:52

Jon,

Sorry No offence, Your so famous you know I meant you....

Jon Brooks · 05 December 2005, 21:20

Tis ok none taken!

Not sure famous is the right way to look at it

Regards

Jimbo · 05 December 2005, 23:10

Quote:

Originally Posted by Jon Brooks

Tis ok none taken!

Not sure famous is the right way to look at it

Regards

Definitely notorious...

Jon Brooks · 06 December 2005, 07:51

Quote:

Originally Posted by Jimbo

Definitely notorious...

Why thank you James.....I think!

Regards

osprey__viper · 06 December 2005, 08:09

When im working on the boat at home I have me radio on. Get very good reception from VTS Humber and all the BWB locks along the trent valley.

Me dad used to have a Belcom scanner at home and that was great (especially when the nice man at Lowe electronics put 0 in it shhhhh..) Made you feel you were still boating in the middle of winter!!! That said the muppet sold it with his boat

never mind. I think alot depends on atmospheric conditions and your locallity. I sometimes take me handheld with me in the truck if I know im going to be parked up near the seaside.

Simon B · 06 December 2005, 14:05

There's some sort of formula to work out your range based on antenna height, did it in my RYA VHF - then forgot it. Will have a look tonight if no one digs it up sooner.

Simon B · 06 December 2005, 16:56

Range = 2.25 x square root of antenna height in metres

This is in ideal conditions though.

ashbypower · 06 December 2005, 17:01

Looks a great formula apparently you don't need any power!!!

Poly · 06 December 2005, 17:47

I would have assumed the height of the recieving station was also important?

Neil

eupa · 06 December 2005, 19:10

i was in Nieuwport and easily picked up Dover which is about 60+ miles straight line. Aerial is about 4 meters off the sea surface??

I thought 10 miles was max with standard VHf??

Jonathan

await for comments from Jon Brooks on this.

wavelength · 06 December 2005, 20:33

When you're trying to see over the horizon then height at both ends has gotta be relevant. when you're talking to the coastguard remember you're not necessarily talking to the aerial at the named base. One of our local aerials for Liverpool Coastguard is 500ft up on Blackpool tower-which does wonders for its range! Worst place for reception on ch0 from that aerial in our coastguard vehicle is on the promenade right under the tower itself. High pressure weather also has an effect and then we start getting stations we would not normally hear.

Jon Brooks · 06 December 2005, 22:12

Quote:

Originally Posted by Simon B

Range = 2.25 x square root of antenna height in metres

This is in ideal conditions though.

Also is this with a unity gain antenna or a 3dB type?

Regards

Nick Thompson · 06 December 2005, 23:21

Quote:

Originally Posted by Jon Brooks

Line of sight is taken from the top of your antenna to the top of the other station.
So if you were a coastguard station with an antenna some 200 feet up your range would be preety good.

I called Brixham Coastguard yesterday from the River Dart at Diddisham although only a couple of miles there was a 300' hill between us & we got very good reception both ways.

roycruse · 06 December 2005, 23:36

Coastguards usually have several masts to help with coverage of their area - you could have been communicating with an alternate mast away from the coastguard station.

Nick Thompson · 06 December 2005, 23:43

Quote:

Originally Posted by roycruse

Coastguards usually have several masts to help with coverage of their area - you could have been communicating with an alternate mast away from the coastguard station.

There must be, but as far as I know the only 'external' mast is on Berryhead at 180', with the same hill in the way

David Hickman · 07 December 2005, 08:59

Nick,
Brixham CG have got an mast on the top of Dartmouth Collegeas well to cover the dart river.
So where we are ther is Exmouth, Teignmouth, Berry Head, Brixham Harbour, Dartmouth, Prawle, Rame head etc.
When we get called out to an Coastguard incident for example in Totnes, we will be using both Berry head and the Dartmouth Mast. When Brixham receive a call. they look at the Computer screen and see which mast is receiving the highest signal strength and then that is the mast they will use to reply.

A real "blind spot" near to here is Man Sands on the way to Dartmouth. That is within 1.5 miles of the berry head mast yet still because of the headland next to st mary's the signal cannot get through. I have actually acted as a relay on Ch "0" between the rescue teams on the beach and Brixham CG on a couple of occasions whilst out training.

Hope this helps.

Searider · 07 December 2005, 10:15

Parents have a boat on the Thames at Reading.

It was often possible to hear Ostend Radio!

So, if you have a handheld VHF in Manchester why not switch it on and see what's out there.

Duncan