Changes to VHF licence

[Dan Tribe]

I've just had an email from Ofcom telling me that changes are being made and I now have to comply with ICNIRP and EMF.
I've now idea what that means, can anyone who understands radio let me know if I have to do anything?

 

[Black Sheep]

Unsurprisingly there's a couple of threads already:
EMF
Ofcom license changes

I'll suggest to the mods that they do some merging.

 

[Topcat47]

I have received an e-mail from the RCA regarding my "license". The only ones I have are a TV License and my Marine radio License and as the only one that transmits is my VHF Radio, I think it refers to that. I'm not a radio engineer so I'm reasonably unclear regarding its implications. My VHF is about 12 years old, it's a Cobra. My HH transmits @ ~ 3watts so it's exempt and my ship mounted one has an antenna at the top of my mast. It transmits (I think, the handbook has long gone) at 5 or 10Watts at full power. The guidance talks about transmitters licensed tom operate above 10W. Does this mean I can forget about it or is there something else I have to do?

 

[stuartwineberg]

Got the same. Extremely unhelpful message full of vague info and a link to an emf calculator which I think is supposed to define the safe distance from your radio. Tricky when you’re holding it. I await more comments.

 

[Black Sheep]

I have received an e-mail from the RCA regarding my "license". The only ones I have are a TV License and my Marine radio License and as the only one that transmits is my VHF Radio, I think it refers to that. I'm not a radio engineer so I'm reasonably unclear regarding its implications. My VHF is about 12 years old, it's a Cobra. My HH transmits @ ~ 3watts so it's exempt and my ship mounted one has an antenna at the top of my mast. It transmits (I think, the handbook has long gone) at 5 or 10Watts at full power. The guidance talks about transmitters licensed tom operate above 10W. Does this mean I can forget about it or is there something else I have to do?

There's another thread or two in Scuttlebut, but my very cursory reading agrees with your interpretation:
1) No need to do anything at the moment anyway unless you want to take part in the consultation
2) If you do need to do anything, they'll tell you the changes to your licence, but:
3) I agree your handheld is too few watts, and
4) Your masthead antenna is highly (geddit!) unlikely to affect anybody (even though I'd expect your main VHF to be more like 25W?)

I'm suggesting to the mods that they consider merging the threads...

Edited to add quote, so as to give context, after merging of threads (thanks, Rod the Mod!)
Also to add that I think there's a requirement to have paperwork, so add:
5) You are supposed to keep records to show that you have ascertained your installation doesn't put anybody at risk. This might imclude operating procedures (eg instructions by the set) to ensure no operation with anybody within the restricted zone.

 

[ProDave]

I received the same email but thought it could not possibly be related to the marine licence, it must have been in relation to my ham licence. Of course it does not state which one it is supposed to apply to.

I suspect it is something best quietly ignored, but if someone understands what they are trying to say please do let us know.

 

[DanTribe]

Unsurprisingly there's a couple of threads already:
EMF
Ofcom license changes

I'll suggest to the mods that they do some merging.

Oops, sorry hadn't spotted those.

 

[Hoolie]

I used the calculator and got a "safe" distance of 1.1metres for the radar and 1.6metres for the 25w VHF. I guess it's just not a problem for mast-mounted antennas.

 

[Black Sheep]

Oops, sorry hadn't spotted those.

No criticism intended - one of them was started very shortly before yours, so possibly wasn't there when you started typing, and the other easily missed because of its title.
Another two or three have appeared since then...

 

[Halo]

I thought the government required its agencies to communicate in comprehensible English. The message is anything but ! I expect it is technically correct but may as well be in Ancient Greek !

 

[Marmalade]

Agree - very techy and not at all easy to get to the bottom of. Followed loads of links and finally found a helpful bit - I'll summarise my understanding:
- you will have to ensure that your radio antenna doesn't come within a certain distance of the "general public". This is not just anyone on your boat and does not include people working (doesn't say why).
- There's a spreadsheet so you can calculate the required distance for your radio
- the inputs are: the power you transmit at, and the frequency
- I input 25W and 162mhz - the answer (safe distance) was 1.6m
- As my antenna is mounted atop the mast - 20m in the air...I comply

Does that align with others' understanding?

 

[Never Grumble]

- I input 25W and 162mhz - the answer (safe distance) was 1.6m
- As my antenna is mounted atop the mast - 20m in the air...I comply

Does that align with others' understanding?

Yes mine is the same.
Confused re my radar and AIS transponder.

I was going to mount the latter on the push pit rail but the calculator is suggesting safe distance is 0.71m? I also read through the Digital yacht brochure which said that needed to be mounted 3.5m above the deck to meet RF exposure requirements. Perhaps I'll be buying a splitter after all.

Not sure about the radar as not sure how much power my ancient Furuno pushes out.

 

[ProDave]

Agree - very techy and not at all easy to get to the bottom of. Followed loads of links and finally found a helpful bit - I'll summarise my understanding:
- you will have to ensure that your radio antenna doesn't come within a certain distance of the "general public". This is not just anyone on your boat and does not include people working (doesn't say why).
- There's a spreadsheet so you can calculate the required distance for your radio
- the inputs are: the power you transmit at, and the frequency
- I input 25W and 162mhz - the answer (safe distance) was 1.6m
- As my antenna is mounted atop the mast - 20m in the air...I comply

Does that align with others' understanding?

So no field to enter the antenna gain?

I wonder what distance it would come out with at 144Mhz, 400W into a 10db gain aerial?

 

[Tradewinds]

Agree - very techy and not at all easy to get to the bottom of. Followed loads of links and finally found a helpful bit - I'll summarise my understanding:
- you will have to ensure that your radio antenna doesn't come within a certain distance of the "general public". This is not just anyone on your boat and does not include people working (doesn't say why).
- There's a spreadsheet so you can calculate the required distance for your radio
- the inputs are: the power you transmit at, and the frequency
- I input 25W and 162mhz - the answer (safe distance) was 1.6m
- As my antenna is mounted atop the mast - 20m in the air...I comply

Does that align with others' understanding?

My old Icom-700M SSB HF tranceiver uses the insulated backstay as an aerial (as do many) - that's going to be interesting.

 

[Moderator]

Threads merged as suggested. The reports of #1 in each thread made it relatively easy to find them - thanks. I've left a forwarder where the PBO thread was which expires after 24 hours.

Regards,


Rod

 

[doug748]

Agree - very techy and not at all easy to get to the bottom of. Followed loads of links and finally found a helpful bit - I'll summarise my understanding:
- you will have to ensure that your radio antenna doesn't come within a certain distance of the "general public". This is not just anyone on your boat and does not include people working (doesn't say why).
- There's a spreadsheet so you can calculate the required distance for your radio
- the inputs are: the power you transmit at, and the frequency
- I input 25W and 162mhz - the answer (safe distance) was 1.6m
- As my antenna is mounted atop the mast - 20m in the air...I comply

Does that align with others' understanding?

Out of my depth here, how does it compute with mobile VHF jobbies, with the aerial right next to your earhole?

My AIS says it pushes out 2 watts about the same as some handhelds.

.

 

[Alicatt]

So no field to enter the antenna gain?

I wonder what distance it would come out with at 144Mhz, 400W into a 10db gain aerial?

you have to deduct cable losses from your 400W then for 10db you multiply by 10, so if you have lossless cable then your 400W = 4kW = approx. 20 meters

Ahh they have changed the calculator since last night, EMF calculator - Ofcom

 

[pvb]

It's just Ofcom indulging in pointless box-ticking, and we're paying for it!

 

[st599]

Agree - very techy and not at all easy to get to the bottom of. Followed loads of links and finally found a helpful bit - I'll summarise my understanding:
- you will have to ensure that your radio antenna doesn't come within a certain distance of the "general public". This is not just anyone on your boat and does not include people working (doesn't say why).
- There's a spreadsheet so you can calculate the required distance for your radio
- the inputs are: the power you transmit at, and the frequency
- I input 25W and 162mhz - the answer (safe distance) was 1.6m
- As my antenna is mounted atop the mast - 20m in the air...I comply

Does that align with others' understanding?

Working in this context is meant to be someone with knowledge of the dangers of RF.

The input to the spreadsheet is not power out of the transmitter, it's the EIRP power out of the antenna. You need to factor in antenna gain and cable losses.

You may have an issue if you were transmitting when dried out next to a quay or in a lock, but otherwise probably OK.

 

[st599]

Out of my depth here, how does it compute with mobile VHF jobbies, with the aerial right next to your earhole?

My AIS says it pushes out 2 watts about the same as some handhelds.

.

Your AIS is only transmitting for about 1/300 of the time so the average power will be lower.

To work it out, you need to convert your transmitter power in to dBW.
Add the Antenna Gain (in dBi)
Subtract the Cable Loss (in dB)
Convert back in to W
Multiply by the percentage of time you transmit in a 6 min window (use your worst case)

Put this number in to the Ofcom spreadsheet with 156.8MHz as your frequency of interest.

Really surprised that Ofcom are expecting this from users

Converter for dBW <-> W dBW (Decibel-Watt)