Handheld vhf question

[itsonlymoney]

What is the transmission / reception distance of a 2w handheld vhf ?
Ian

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[Alistairr]

I think it depend on wether its transmitting to another handheld or a base station.

But in general my Handheld going ship to ship is usually good for about 5miles or so. Thats in the hilly surroundings of LL, would be better if nothing in the way.



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[ccscott49]

Aren't handhelds normally 5 watts? MIne works fine up to about 15 miles, its an icom euro thingy.


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[itsonlymoney]

Maybe the one I saw was a cheapo then cos it said 2w. Think it was a "Cobra" summat.
Ian

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[Alistairr]

My Simrad works off 1w at Lo power, and 5w at Hi power, Usually i have it set at Lo.



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[whisper]

Yes, it is a cheapo. I also saw the ad. somewhere.

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[Solitaire]

The general rule of thumb is that all handhelds have two power settings- 1watt & 5watt. Tx distance will depend on how "high" the set is!Operating on a powerboat at say about 2-3 metres distance won't be much more than say 5 nm's but it will depend on the height of the receiving antenna.. Rule of thumb for a fixed set tx'ing at 25 watts using a 10metre antenna to a 100 metre antenna will be 30-40 nm's.

The Cobra set advertised at £49!

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[itsonlymoney]

Just found another one. An ICOM 5W for about £53 I think it was on marine superstore. Probably a better buy. As long as I get coverage of around the 5mile mark it should be ok.
Ian

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[Solitaire]

ICOM is a better bet. You will have both (1 and 5 watt) power setting on that. Note though, the manual will tell you not to relie on it in an emergancy. H/H's are not a substitute for a fixed set really. As I said the tx distance will vary greatly depending on how high you tx from and how receiving anttenna is.

VHF is line of site.

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[steverow]

VHF relies mainly on line of sight, so therefore the height of the antenna, and conversely the height of the receiving station antenna are far more important than the power level. It is also affected by "path attenuation" ie buildings and structures in the way causing signal degradation and reflections.
Therefore when you are in the marina or very close to land, power becomes more important to overcome these problems, but less so when you are out at sea, where there is a clear path,within the horizon, between you and say the CG station.


Steve.

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[Oldhand]

It should work over line of sight distances from typical handheld location, i.e. down on deck and not up a mast. However, if there is a lot of radio traffic, i.e. channel 80 in the Solent, you may have difficulty in getting heard over more powerful but distant transmissions.

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[Solitaire]

"where there is a clear path,within the horizon"

Now here is an interesting point! How far is it to the horizon? Becomes very relevant when using a handheld.





And B4 anyone asks - I do know the answer/forums/images/icons/laugh.gif

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[BrendanS]

Depends how tall you are, and e.g. if in a rib, or up on a flybridge! Trick question

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[Solitaire]

No trick! But .............................................?

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[BrendanS]

If your eyeballs are 2m above water, you can see rough 3 nautical miles
at 4m it's roughly 4 nm
at 6m it's roughly 5 nm

You can usually see futher than this though, due to refraction.

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[steverow]

When radio engineers talk about the horizon, we mainly talk about the "radio horizon" which is in fact a little further (maybe 25%) than the line of sight or "eye horizon".
Also as frequency increases the radio horizon diminishes, which is why a UHF handheld at 400+MHz will only give a range of about 6 or 7 miles, as opposed to a Marine VHF at 150Mhz which is capable of ranges between 10 and 35 miles.
Power certainly does help. It is likely to make your signal better heard and more intellegable. But there is a rough rule of thumb, that if you cant hear anything at all on VHF at 1 watt then 5watts is unlikely to make a substantial difference.
There is another Law in radio physics that states to Double your distance you have to QUADRUPLE your output power. (within the radio horizon).
Dont also forget the role of the Receiver in all this. You can have the most powerful transmitter known to man, but if your RX is deaf, it aint a lot of use.
So look for a set with an RX sensitivity spec of better than 0.5uv (microvolts)
for 10dB quieting (SINAD)

Steve.

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[Solitaire]

Yup - give or take. Interesting question when doing courses, answers are usually > 20 miles as standard. Mind you that is at Level 2 - but had some equally interesting answers from those doing Advanced Level PB courses. I had a Level 2 instructor who had been past by a well known IOW operation who could not write a LAT and LONG - but that's another story!

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[Solitaire]

That has been duly copied and pasted! Thank you. Just goes to show - you never stop learning.

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[BrendanS]

Having done II, Advanced and YM theory, I've had a few chances to get it off pat now! <g>

I'd have put the answer much higher before having done the theory bits

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[JonBrooks]

Well worth checking everyones radios at the boat show.
There will be lots of special offers running.
I know one company that will suprise you all on its pricing for the boat show!! ))

You will be able to get a decent fully waterproof hand held for just over £100!

I gave a talk to yacht club last night, there were lot of negative comments about really cheap radios, people are worried that they are "too cheap"!

Regards

<hr width=100% size=1>Jon Brooks
Marine Dealer Manager
Icom UK Ltd.
01227 741741