Mike Bedford wrote:Your article is thought-provoking and I look forward to the mathematical justification which, I understand, you intend to write in due course.
Well... probably. The reason I have not yet done it is that it is not, in fact, necessary, because it is "obvious". It is certainly not novel. All I have done is to study the right parts of the right textbooks to pull it all together. I realise that refusing to explain it because it is "obvious" is, on the face of it, a ridiculous position, but what I mean is this: because the underlying theory is not novel, nor original, there is, in fact, no need for me
, specifically, to explain it. It is not my
theory! Explaining it would amount solely to my re-writing chunks of other people's text books. But... perhaps I will
get around to it sometime, although Im more interested in explaining the applications of the result.
Mike Bedford wrote:The claim, which is at the very centre of the argument, is that the Big Loop model is fallacious.
I certainly used that word; and the BL concept is
based on a fallacy, but its not really the central part of my argument. I made the point in the article that there is more than one way of looking at things and that different explanations, if they all have validity, will converge on the same reality. To that extent, I am willing to accept that a BL-type concept might have some validity but only provided its proponents can demonstrate that it converges on reality. So its over to you, really, Mike: what testable predictions on field strength and field orientation does your BL model make? And - importantly - are they the same predictions that the G-HED model makes? (If they arent - we have a problem).
Saying that the Big Loop model is incorrect could mean several things, including, but certainly not limited to:
1. That a current does not flow in the ground.
2. That a current does flow in the ground but these ground currents are not responsible for the generation of a magnetic field.
3. That the BL model is not particularly useful because analysing earth currents through multiple loops would be difficult and when, as is usually the case, the structure of the underlying geology is unknown, it becomes impossible.
Im not saying 1 or 2 (was that not clear from my article?). Im not really saying saying (3) either, but that's a good-enough approximation. Some of what Im saying - certainly in "sound bites" like in the abstract of my article - was designed to grab your attention. It might be fairer to say "the BL model serves no purpose", which is certainly true, unless anyone can demonstrate how it leads to testable
predictions of e.g. field strength and orientation.
I acknowledge, of course, that you do shed some light on these issues in the article but I did find myself re-reading it several times to appreciate what you were saying. If you are able, concisely, to clarify the basic premise of your claim with respect to the BL model, I think it will go a long way to reassuring those who have, no doubt, come to the conclusion that your suggestion is so counter-intuitive that they don’t stand a chance of understanding it.
The "basic premise of my claim w.r.t. the BL model" is that it is , fundamentally, not a "model" (i.e. a hypothesis) because it makes no testable predictions. It is just "hand-waving". If anyone wants to confer on it the status of a model/hypothesis we would be in a position to discuss it further. Until then, it is not really possible to have a meaningful discussion about it.
The HeyPhone is traditionally used with earth current antennas at both ends so, surely, the "Conduction Mode" model makes more sense than the BL model in any case? CM is more testable than BL - it is straightforward to write down the shape of the field lines and the (d.c.) electric field strength from the CM model and to confirm that they agree with the G-HED model. This would allow a prediction of HeyPhone signal strength to be made, although unfortunately, the CM model does not account for skin depth, so the prediction would not be entirely accurate. The CM model allows the magnetic field to be calculated too. This makes it rather surprising that apparently radio amateurs have been claiming that the CM model implies that no radio interference is generated because it is all "conduction". This is clearly not the case since the CM model actually implies a "full strength" magnetic field if you do the analysis properly!
Going back to my comment about "sound bites", I have said that that the current in the ground does not contribute "materially" to the operation of the antenna. This was designed to catch the attention of the reader but I think this the statement has been misinterpreted. So, to recap/rephrase what I said in the article...
- The current in the antenna, together with all the current loops in the ground contribute to producing the observed fields.
- The fields are the same as would be generated by the same antenna current flowing in an isolated electric dipole, i.e. disconnected from the ground.
- Such an antenna (isolated dipole, uniform line current) is easy to model, so it provides an easy way to describe what is going on.
So, because the earth-current description can be equated to a situation where there is no earth current, it is as if the earth currents did not "materially" affect the field. (That
is the central point of my argument - not the thing about the BL model). The salient point is that the isolated antenna I have described is a theoretical one, it could not physically exist. This is where a lot of people have misunderstood: they assume that Im saying that you can disconnect the antenna and it makes no difference to the fields. That is nonsense, of course, because if you disconnect the antenna no current will flow. It doesnt matter at all that the antenna is a theoretical one because we are only using it as a model - we are not intending to build it!
Correct me if Im wrong, Mike, but I think part of the problem is that we are discussing this at two different levels. I am interested in a scientific hypothesis, which is testable, which is why I call the BL concept merely "hand-waving". Whereas you, coming from your journalistic background, are interested in conveying the concept to lay people, to explain how it works. From your point of view the BL concept seems adequate ... and perhaps it is ... but it doesnt actually get us anywhere useful. Suppose we have a caver attempting to detect an earth current signal using a small portable induction loop or ferrite rod receiver? Clearly it helps if he knows the likely orientation of the field lines. The G-HED (and CM) model provides this (and we can test the hypothesis); the BL model does not - or at least, I have never heard a proponent of the BL concept ever describe the orientation of the magnetic field lines from this mysterious "big loop" in the ground - nor even where this big loop is actually situated!
I think it is
possible to provide a good explanation for the lay person without either a) getting caught up in the question of the "material" nature of the earth currents or b) creating a fallacious (as I assert) "big loop" in the ground. It is something we ought to try to work towards. In fact... Im pretty sure I already gave a lay explanation "in passing", in a CREG article many years ago. Perhaps I just didnt emphasise it enough at the time?
Anyway... I hope this reply helps.