VHF transmitting range.

[Shiver Metimbers]

I think I have a problem with my VHF when transmitting and receiving. I can only receive and call very local stations, within 1 to 1.5 miles? What sort of range should I expect when transmitting on 1 watt lines of site? The whip is mounted on top of my mast (13 metres) Thanks in advance.

 

[MoodySabre]

Doesn't sounds too bad to me. 1 watt is at the very bottom of the handheld VHF output - most HHs transmit at 5 watts - good for 5-10 miles line of sight. A fixed VHF may be 25 watts - earlier this year I heard friends talking over 40 miles away!

 

[Salty John]

Theoretically the distance is D in nm = 1.23 times root of combined height, in feet, of transmitting and receiving aerials. In fact it is usually more like 1.4 times root etc. because radio waves can bend slightly so they can see over the horizon a little bit.
In some atmospheric conditions (tropospheric ducting) spectacularly longer distances have been noted - up to 600 miles, but this can't be relied upon. About 20 miles for two boats with 40' masts/aerials is normal.
If you don't get this sort of range the first suspect would be bad coax connections - corrosion of the connector or the cable. The best diagnostic method is to take your radio to a good aerial or take a good aerial to your radio. Then you'll know if it's radio or aerial system and you can refine the search from there.
Transmitting on 5 watts from a handheld you should get 5 miles.
Output power doesn't add significantly to ultimate range, that's determined by distance to the horizon which is a function of aerial height. But 1 watt? I think you'd struggle to be heard at all on such low power.

 

[pvb]

If you can only receive local stations, that would seem to indicate an aerial problem.

If you're transmitting at only 1 watt, it's quite likely that only local stations will hear you, regardless of how good your aerial is.

 

[earlybird]

. But 1 watt? I think you'd struggle to be heard at all on such low power.

My fixed VHF has a low power setting of 1 watt, which seems fairly standard. I find this OK for 2 or 3 miles or so, usually harbours or marinas.

 

[Salty John]

Brain fade. You're right, of course, 1w and 25w are the usual low and high power. I had it stuck in my head that they were 5w and 25w.

 

[Rowana]

I had similar problems a couple of years ago, and decided to replace the aerial and cable from the masthead to the back of the set.

I bought an aerial & cable from Salty John, poster of this parish, and the difference is nothing short of amazing. From being barely able to pick up the weather forecast from Aberdeen coastguard, I now regularly get Shetland coastguard and Orkney VTS from not too far north of Peterhead. I've even heard oil platforms in the north sea when atmospheric conditions are right.

Replace the cable would be my suggestion, even if you keep the same aerial. It doesn't last forever.

 

[Cantata]

I think I have a problem with my VHF when transmitting and receiving. I can only receive and call very local stations, within 1 to 1.5 miles? What sort of range should I expect when transmitting on 1 watt lines of site? The whip is mounted on top of my mast (13 metres) Thanks in advance.

Should be better than that, I'd have thought. My annual 'radio check' to the CG (when I've reinstalled the set in the Spring) usually gets through on 1w over 12 miles with a lump of land in between too.

 

[duncan]

Should be better than that, I'd have thought. My annual 'radio check' to the CG (when I've reinstalled the set in the Spring) usually gets through on 1w over 12 miles with a lump of land in between too.

you are probably making a bit of an assumption re the position of the receiving aerial - CG have rather a lot in different places along the coast line.

 

[VicS]

As pvb says

If you can only receive local stations, that would seem to indicate an aerial problem.

 

[AllanW]

confused now

Took the VHF licence last year. Newcomer to boating. I was given the impression that I should stick to one watt output unless in an emergency situation. On Channel 16 my fixed VHF dsc goes straight to 25 watts, which I would expect.
Can you experienced boaters tell me the correct procedure. The thought of loads of boats having a chat a mile apart on 25 watts seems a bit excessive?
Look forward to your advice.
AllanW

 

[Shiver Metimbers]

Week signal

Thanks for the help. Today, in the marina I prearranged with a friend to give me a call on Channel 69 at various distances as he made his way out to sea. At 1/4 mile I could hear him although he was breaking up and he could not hear me at all, I was transmitting on Hi. So it looks like the antenna. Salty Johns Metz Manta looks the job but the coax connection looks as it could be vulnerable to the elements, can anyone advise?

 

[richardbrennan]

I suprisingly had exactly these symptoms when I renewed my aeriel cable. I discovered that the "helpful" rigger that offered to fit the bottom plug just pushed the core copper wire in and forgot the outer sheath. Fixing this restored the range immediately so I would agree that problems with the aeriel cable and its connections would be the place to start.

 

[Rowana]

{snip} Salty Johns Metz Manta looks the job but the coax connection looks as it could be vulnerable to the elements, can anyone advise?

That's the one I have. It's been up on top of the mast for nearly 2 years now with no problems. I'll be taking the mast down this winter, so I'll be able to give it a close examination, but judging on performance, I'm not anticipating any issues. I'm assuming that you will also be replacing the cable, as in my (admitedly limited) experience, this is the cause of many problems.

Hope this helps

 

[Shiver Metimbers]

That's the one I have. It's been up on top of the mast for nearly 2 years now with no problems. I'll be taking the mast down this winter, so I'll be able to give it a close examination, but judging on performance, I'm not anticipating any issues. I'm assuming that you will also be replacing the cable, as in my (admitedly limited) experience, this is the cause of many problems.

Hope this helps

Yes, while I have the mast down I will pull a new cable through as I pull the old one out, cheers.

 

[Cantata]

you are probably making a bit of an assumption re the position of the receiving aerial - CG have rather a lot in different places along the coast line.

I certainly was - I know exactly where the nearest CG aerial is - 12 miles from my boat! (It helps being a CG myself...)

 

[agurney]

Took the VHF licence last year. Newcomer to boating. I was given the impression that I should stick to one watt output unless in an emergency situation. On Channel 16 my fixed VHF dsc goes straight to 25 watts, which I would expect.
Can you experienced boaters tell me the correct procedure. The thought of loads of boats having a chat a mile apart on 25 watts seems a bit excessive?
Look forward to your advice.
AllanW

You are correct, 1W in normal circumstances.

 

[PeterGibbs]

I think I have a problem with my VHF when transmitting and receiving. I can only receive and call very local stations, within 1 to 1.5 miles? What sort of range should I expect when transmitting on 1 watt lines of site? The whip is mounted on top of my mast (13 metres) Thanks in advance.

At that height and on 25 watt output you should get line of sight which is 20-30 km. Less, and you have an impedence in your antenna/cable connection. Sometimes the radio fades slowly (mine recently did) and transmission just fades with time - a new radio is the answer, of course.

On 1 watt, you get close neighbourhood whatever the quality of the gear. I have a handheld and always use it on 5 watt - good for marina approach etc.

PWG