Ofcom made their decision

[Solent Sailor]

It is a load of nonsense (and I worked with some EMF legal issues in a former job) but I've just done my calculation for fun (I know, but I'm like that).

Being a mobo with a fly bridge, there is a potential risk of someone being within the 2.04m that is the maximum possible distance away from the aerial under the guidelines. Accordingly, I have prepare a short notice which I will keep with the licence onboard which says that I will only use the flybridge VHF on full power in an emergency situation, on low power or when all crew are further than 2.04m away. Took about 10 mins to do.

For yachts, if you're carrying a standard VHF set, I can't see there being any question of you being in sufficient proximety of the aerial to be within scope, but check for yourselves.

 

[Alfie168]

I havn't cooked any seagulls yet with my aerial. There is just a touch of irony when an organisation called Ofcom has links in their email that don't work.

They are supposed to have simplified it from their previous unfathomable publication. I'm not convinced yet.

What is sad is that somebody has obviously put in a lot of hard work, and its fundamentally about safety from electromagnetic waves which is sensible. It just need to be communicated in a form that users can relate to and understand, and it needs to be achievable in a way that garners support and compliance, not derision and confusion.

I thought it was just me and that everybody else understood. I was mightily relieved that others were having a similar reaction.

 

[gandy]

I looked at that link ... antenna gain ... how does the average sailor measure that then?

I looked a mail order site for an aerial that looks like ours and they say it's 3dBi which sounds about right for an omnidirectional aerial.

Our fixed set on high power is 25W, with the 3dB antenna gives just under 50W EIRP. In reality less because of cable losses. So using their criteria the equipment does not have a peak power higher than 100W. If we reckon the set can't possibly be transmitting for as much as 20% of the time, then we are not transmitting at an average higher than 10W either.

 

[JumbleDuck]

So if I use my VHF once every few weeks or months it should be fine. I really ought to do a radio check at least.

I rarely use mine more than once or twice a year, and it isn't uncommon for me not to use it at all. partly because I am sullenly uncommunicative and partly because mobile phones almost always work better.

 

[Parabordi]

Anyone care to read an explain what the latest comms from Ofcom mean? It's in relation to the baffling radiation email of March, apparently it's all now finalised. I can't be arsed to decypher this one and the links didn't work anyway, but I'd quite like to be compliant so hopefully someone here has read and understood

Why couldnt they just give us a sample document to keep on the boat for a VHF and one for a Radar and be done with it.

 

[longjohnsilver]

They will apparently be producing some specific guidance for us seagoing types, but haven’t quite finished writing it yet.

Pete

Interesting, how did you discover that?

 

[Never Grumble]

I looked a mail order site for an aerial that looks like ours and they say it's 3dBi which sounds about right for an omnidirectional aerial.

Our fixed set on high power is 25W, with the 3dB antenna gives just under 50W EIRP. In reality less because of cable losses. So using their criteria the equipment does not have a peak power higher than 100W. If we reckon the set can't possibly be transmitting for as much as 20% of the time, then we are not transmitting at an average higher than 10W either.

Out of interest the aerial I bought for the AIS has a gain of 1dB at least that is what it says on the website. Also interested to know what the cable loss is?
I ought perhaps to have a greater look at the radar output.

 

[Boathook]

I have just had an email from ofcom apologising about the links and saying that they have corrected them. I haven't yet tried the links or even fully read the email. Tomorrow's task ......

 

[prv]

Interesting, how did you discover that?

I read the email?

We are also preparing a new simplified version of the full Guidance, plus specific advice for holders of amateur, ship radio and aeronautical licences. We expect to publish these documents on our website by 8 June.

Pete

 

[Bristolfashion]

Knowing bureaucracy, they are more likely to bust you for not having the assessment than for getting the calcs hopelessly wrong. Bearing in mind my (pretty much made up) operating percentages of <1% for the VHF and <0.1% for the radar, the exposure is negligible.

 

[lustyd]

I read the email?

You may be the only one who got that far. Well done sir!

I have just had an email from ofcom apologising about the links and saying that they have corrected them. I haven't yet tried the links or even fully read the email. Tomorrow's task ......

Yes, it would seem that Ofcom have inadvertently supported the idea of a second chance. If they need two attempts at explaining the rules, why would we be expected to follow them correctly on the first go? 12 year olds in 1994 could insert a hyperlink correctly, so...

 

[Rappey]

Our fixed set on high power is 25W, with the 3dB antenna gives just under 50W EIRP. In reality less because of cable losses

I tried Mark-1s link for calculator just for fun. A little confused with erp, eirp and dBW .
On another website I was reading about different coax , antenna gain and what it means in terms of signal radiation and coax such as rg58u up to rg214 and their losses.
Rg58 which comes with most antennas has a loss of -6.5dB per 100 ft at 150khz.
Transmitting at 25 w with 3dB antenna over 25 foot of coax gives 17w at antenna.
At 75ft it's 8.5w
Rg214 gives 23w and 21w at 75ft.

 

[longjohnsilver]

I read the email?



Pete

Ha, I didn’t get that far! Thanks.

 

[Seven Spades]

When cruising I would say I use the vhf in transmit mode for about 3 minutes a week, the hand held 2 minutes a year and thus far the SSB has never been used. I am not sure how I can input any meaningful data. Rubbish in rubbish out.

 

[Mister E]

Could this be a way to cut down on the radio checks?

 

[DJE]

I will happily keep another bit of paper next to my radio licence if somebody can explain to me exactly how that will make anything safer.

 

[Thistle]

I tried Mark-1s link for calculator just for fun. A little confused with erp, eirp and dBW .
On another website I was reading about different coax , antenna gain and what it means in terms of signal radiation and coax such as rg58u up to rg214 and their losses.
Rg58 which comes with most antennas has a loss of -6.5dB per 100 ft at 150khz.
Transmitting at 25 w with 3dB antenna over 25 foot of coax gives 17w at antenna.
At 75ft it's 8.5w
Rg214 gives 23w and 21w at 75ft.

Well up to Ofcom's standard of confusing communication. Do you work for them?

 

[graham]

25 watt high and 1 watt low are more or less standard on fixed vhf sets and all send on the same frequency 156 something or others and nobody would be broadcasting more than 10 percent of the time


.Does that mean we all piddle about on the online calculators to come up with the same answer?

Maybe one clever person on here could work out the safe distance for a bog standard vhf then post a link so we can all print a copy?

PS I doubt our radio broadcasts even 1 percent of the time.

 

[Rappey]

As others have already stated, using the ofcom calculator a 25w set with a 3dB gain antenna gives a person safe distance of 1.6 metres.
In reality it would seem many yachts may not transmit over 10 w at antenna due to cable and connector losses.

 

[tony_lavelle]

Glad I'm not the only one so just doesn't understand the waffle.

Ofcom's motto is "making communications work for everyone". Enough said!