Sorry Allen, when you said “on my 20m one” I thought you were copying Phil’s numbers EXACTLY to check the tool was working and got different answers for the same input.
No probs Andy you don’t need to apologise tis me for being a pain in the rear
Do you get the same as Phil when you enter his numbers?
The pink cell spreadsheet indication was shown on my calculations Alan when I tried to calculate below 10 MHz. This was some weeks ago when I did my readings. I seem to recall the pink colour brought up a “tool tip” which said that a near field calculation requiring more data would be required. At that part I cleared the spreadsheet and decided to await further guidance from the RSGB experts who have more brain calls than I have. It does appear that many of us on frequencies below 10 MHz using inverted L and inverted vee antennas may need to run calculations at different power levels to determine what the safety limit is. I have a Rabone Chesterman Surveyors measure and that has been useful in taking dimensional measurements in my garden to determine how far my aerials are from neighbouring properties and fencelines. What is unclear to me at this stage for instance, with an inverted vee or inverted L is at what point do you measure from - the feedpoint, the end or half way? These aerials perform in different ways over different frequencies for example a half wave dipole resonant on its design frequency of 3.5 MHz shows its maximum current node at the centre and maximum voltage node at the end. The same aerial used on 5/7/10 MHz or higher with an ATU moves these nodes to a very different place along the wire. The feeder may also radiate! So where should the measurement be taken from? The same place on all frequencies or should the position be calculated based on the frequency. It’s all very complicated!
I’m not worried about operating portable as Mr Ofcom can’t climb hills or make an appointment to inspect you when you are there, and you can warn people off if necessary. Good old Boris Johnson “British Common Sense” will be the order of the day!
73 Phil
ah Cheers Phil seems very very complicated so methinks I’ll give it a miss as I have no idea how to do the calculations. Maybe had I been younger but now getting old I am bordering on insanity lol
Well just to make it interesting I’ll opt for the 32nd (or the 6th Monday in the month, whichever comes first).
Looks like I’m going to have to redo my calcs 
that RSGB sheet is nothing like the Ofcom one I used. Early adopters!
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yes mate
I thought the calculator did all the calculations for you …Hmmm the mind boggles lol
I sometimes wish it was more common!
Note that in the article, stage 2, it says: “The output from the Ofcom calculator is a so-called “safe separation distance” for the power level, antenna configuration, etc that you are using. If you can be sure that nobody is present within that zone while you are transmitting, then RSGB’s understanding is that you will be deemed compliant.” I don’t now if this also applies to the operator, long feeders may become de rigueur! Basically, this suggests that we should always set up in a quiet area away from the summit marker and paths, if any.
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One thing if Ofcom wish to inspect your station they will need to make an appointment. They won’t come from Baldock, Herts or Warrington (that office may have closed now under austerity measures) on the off chance you are in. Best thing though when we have the necessary tools to do the calculations, is to do them and then put them away in a drawer or on backup disk until you get the call and then refresh your memory. It’s unlikely to happen!
73 Phil
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No. This was in the earliest info on the matter.
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But would they need to visit to check that you had produced a PDF, now that they have discovered email…?
Bwahaha!
Yay for the far-flung GM summits where you can go for days without seeing another human 
But does this mean Gerald and I won’t be operating from the same summit shelter again 
?
Far as I could figure, if the “Ofcom separation distance” is less than a quarter wavelength then the field goes pink to indicate that the far-field calculations don’t actually give good answers at that distance. Ofcom’s original spreadsheet wasn’t quite so helpful.
I suspect there may also be issues with the calculations if the feed point is less than a couple of metres above ground level.
Hopefully a version handling near-field issues will appear at some point.
Don’t worry about that… we’ll just sign reciprocal disclaimers! 
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Just to confirm, having read the Ofcom notice, rules don’t apply to licensed operators, clearly they don’t care if we fry our own brains 
- or if we invite other operators to our home QTH (if that is ever going to happen again) although I guess it would be polite to point out the working conditions - but then we just love doing that at every opportunity.
Hmm, I would have thought that for portable you surely just include in your risk assessment that you stop transmitting if anyone gets within a certain distance of your antenna?
More concerning is my home setup, I have a ground mounted Hustler 5BTV which is approx one meter from the fence separating me from my happy and understanding neighbours, If I read the calculator correctly (unlikely as I don’t understand most of it :-o ) Ofcom requires a bit over one and a half meters separation for 20m CW at 100w, but because it’s ground mounted it’s shaded pink and needs a “near field assessment” :-/
On the Annex page of the Ofcom spreadsheet there’s this note:
The formulae used by the calculator are suited for power density evaluation in the far-field antenna region and overestimate the results in the near-field.
That seems to suggest that the far-field calculation will give higher separation values than a near-field one, which means the far-field separation errs on the “safe” side, so why bother with the near-field calculation. I somewhat suspect they weren’t thinking much below 100MHz when they wrote that…
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On playing a little more with the calculator, it gives a separation requirement of approx 1m across all my useable bands if I keep my SSB power at 100w or less and CW 50w or less. Sounds better that removing and reinstalling the antenna (and all the ground radials :-o ) in a less convenient location! B-)
Specifically for the SOTA activating scenario then:
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Set up away from the trig point / cairn / paths / popular areas - already a well-known recommendation in the SOTA guidelines.
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Stop transmitting if a passer-by approaches you - already basic courtesy and good practice to preserve the image of our hobby.
For anyone that is already polite, considerate and cares about the image of AR and SOTA, there is really nothing new here, is there?
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