Problems with VHF transmission

[tgalea]

Hi All,

I recently went on an offshore trip and was quite disappointed with the range i was able to obtain with regards to VHF transmission.

At a range of 50nm i was able to recieve many stations very clearly, including other boats etc.

When it came to reply back to these people they could only recieve my transmission when i was about 5 miles away from them.

The antenna is 2 years old and wiring looks ok although i do have a joint below deck.

Any ideas of where i should start my checking ?

Thanks

Tyrone

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[JonBrooks]

I would check all conection are done up and not damaged.
A VSWR check would be a good idea to.
If all that is ok then the radio may need looking at by someone.
May have a TX fault.

But first step wolud be as above.

Hope that all helps

Regards

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

 

[Benbow]

Did the stations who eventually heard you report a 'clean' signal or one that was intermittent ?
Does the panel light dim when you press the PTT ? If yes then you have a bad power connection.

Otherwise aerial feed is the most likely culprit. Simplest way to check is to fit your emergency aerial and try again. If you have a good power supply, and alternative aerial makes no difference, then it must be the set.

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[tgalea]

Thank you for your reply.

When these people did eventually recieve my transmission they reported me to be "loud & clear"

Regards



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[tgalea]

Thanks for your reply.

The coax crimping job below deck looks a bit poor in the sense that some of the braid is actually out of the connector, etc.

Do you think this could be the culprit ? I did check for continuity across the joint and it seems ok.

Regards
Tyrone


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[JonBrooks]

Sounds like it could be suspect.
If it was me I would cut it off and start again but it will good to do a VSWR check to.

Regards



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

 

[Talbot]

perish the thought, but were you on low power?

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[Birdseye]

firts of all, your "can you hear me" test is not scientific and funny conditions can mean that it is misleading. try again - its too easy to jumpt to conclusions.

how high up is your aerial? VHF is usually line of sight transmission so a sea level aerial is prob only good for a couple of miles. but you will still hear shore stations with high aerials a long way away.

if you aerial is at the top of a sailing mast, then 9 times out of 10 the aerial will be the problem. check swr as already suggested. aerials dont seem to last long.

many swr meters will also give you a power level. if this is ok as well, then you are into problems like poor / intermittent mic connection and should send the set to be checked out. if power output is low, check the 12v feed to the set. what is the input voltage when transmitting?

<hr width=100% size=1>this post is a personal opinion, and you should not base your actions on it.

 

[Solitaire]

You beat me to it!!

<hr width=100% size=1>Boating is <A target="_blank" HREF=http://www.powerboattraininguk.co.uk>Serious Fun</A>

 

[nickjaxe]

Surly line of site, if you can here them you must be line of site to there ant, so they should here you even if your ant is low down. or am I missing the piont of line of site.

Nick.

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[Talbot]

yes you are. actually line of sight is not entirely correct, as there is some refraction on the VHF allowing a tad more range than purely visual. , but the further the range, the more power you require. thus a hand held has a very limited range, a fixed ships VHF on low power has a slightly better range (or should have if it is working correctly!) A fixed ships on full power should give you abt 20-25 miles to another ship, but the coastguard have their aerial up very high, and have a BIG transmitter thus can be heard over 50 miles away. In the solent I normally hear Portland, frequently hear brixham, and in the right places can also hear the french. doesnt necessarily mean that they could all hear me, but would suggest that my aerial is working well /forums/images/icons/smile.gif

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[MarkJohnson]

50 miles seems a long way to be able to receive any signal, let alone another boat.

Coast guards have arials dotted along the coast line, and use the appropriate one to communicate with that area.

I have a similar problem so would like to check the output. Where does one buy a SWR meter suitable for the marine VHF frequency??



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[oldharry]

Like Talbot, in the Solent I am regularly picking up transmissions from Dover Solent and Portland Coastguard, and can usually pick the French Meteo and one or two other land stations presumably round Cherbourg.

But 5 miles transmission range is not good enough and their is certainly something wrong. My 4 watt Handheld can work that distance on a good day (just!) if there's nothing in the way. The Aerial is the only variable - modern sets are very reliable as a rule, and I would look first at replacing all the connectors in the cable. The aerial itself will give very variable results depending on the design and quality. A small low gain unit can effectively more than halve the workable range, whereas a good high gain unit (6db or more) properly installed should give at least 30 miles effective range.

When I was based in N Wales, I had no problems contacting CG Holyhead some 30 miles away, even across the Lleyn Peninsular. Pronouncing local names was another matter "...thank you sir, will you SPELL your location please?"

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[alldownwind]

A few weeks ago off Whitstable we constantly heard Netherlands Coastguard (100 miles plus, and never heard before by me round here) and, once, incredibly, Portland CG who must be getting on for 200 miles away. Settled, high pressure weather at the time.

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