We didn't go looking for a donut hole in the propagation pattern. It was a surprise that Bob discovered only through the use of more precise analytical software.
Ric,
A surprise that Bob discovered? Made possible by more precise analytical software? Really? I’ve been through this donut-discovered-how? issue several times on this forum. Perhaps a review of it is in order.
In the
Radio Reflections - NR16020 second world flight dorsal V antenna thread, I gently introduced the topic of mis-modeling the dorsal V antenna in the closing sentences of my
second post to the forum.
I did this because I could see that in their published papers and forum posts neither Mike Everette nor Bob Brandenburg understood the antenna.
I brought up the mis-modeling issue as a direct question in
Reply #24 of the same thread.
My question, and the following replies, went like this:
Chuck to Ric -
Bob Brandenburg's papers, and forum posts between 1999 and 2009, are quiet on this point, but there are a number of hints in them that he did model the dorsal antenna as a V with the source in one leg. Did he?Ric to Chuck -
I'll ask him.Bob to Chuck –
I modeled the dorsal antenna as it existed, not as a variant of any generic antenna. The model uses the entire feed wire, including the run from the transmitter to the fuselage penetration point. The first sentence artfully avoids answering my question. The second sentence relates to his model at the time of my question—
not the one he used in the papers that prompted the question.
I think it would be worthwhile for you to read through to the end of that thread.
I broached the mis-modeling issue again in
Reply #10 of the Radio Reflections – 3105 Donut thread.
That post provided what I believed to be the real revelation behind the 3105 Donut. It was
not a change of software that revealed it—it was Bob’s finally getting the antenna model right. To show that failure to see the so-called dimple in the antenna pattern could not be attributed to MININEC-based software when modeling the antenna close to ground, I dredged up the oldest (1986) version of MININEC that I could find and modeled the dorsal V antenna at 12 inches above ground. Twelve inches is very close to ground. The dimple was very much present. This was on 24 Jan 11.
Nearly 8 months later, same thread, Bob
commented on my back story, saying that both versions of the antenna modeling software he used showed the dimple, and that the dimple was never an issue. I accepted his account. But read on.
Our exchanges continued to the end of thread. I’d recommend reading those posts, too.
In
Reply #26 I returned to the donut back story, pointing out the contradiction between what Bob said in 2009 and what he was claiming in 2011. (My words to Bob:
In 2009 you said the "dimple" was revealed when 4NEC2 (NEC-2-based antenna modeling software) replaced NEC4WIN95 (MININEC-3-based antenna modeling software). In 2011 you said the dimple was never the issue--both software programs showed it. Please explain.)
In Reply #27 he deflected the comment, declaring the dimple issue to be a matter of dimple
degree—not whether it was seen or not.
I cited an
example from his
The Post-Loss Radio Signals: Technical Analysis paper, where the pattern he described contained no evidence of a dimple at all.
Bob’s response to that was “
That was eleven years ago, Chuck. What's your point?”
I answered: “
My point is that you would have the general reader think that, because you now understand a thing, all the papers you authored reflect that understanding. They don't. The excerpt I gave from your The Post-Loss Radio Signals: Technical Analysis paper is one example.”End of review.
I’ve provided an attachment to illustrate the radiation pattern at 3.105 MHz when the antenna is mis-modeled (source in starboard leg of the V) and when modeled correctly (source in the wire interconnecting ground with the starboard leg of the V). The two patterns were modeled over perfect ground with MININEC-based MMANA-GAL. The height above ground of the source in the left plot is the same as that for the junction of the lead-in wire with the starboard antenna leg in the plot to the right (7.4 feet). Gains along the X-, Y-, and Z-axes are given. A second set of gains is given below the right-hand plot to illustrate the difference when modeled with NEC-2 software rather than MININEC-based software. The difference is insignificant.
Note: The attachment is for illustration purposes only. Gary LaPook continues to make reference to some antenna gains I gave in one
post as if they were some grand analytical handiwork of mine. They, too, were provided solely for illustration; namely, to show that MININEC-3 itself was perfectly capable of revealing the dimpled pattern, and a significantly dimpled pattern at that—even at 1 foot above ground.
What the pattern might look like at 1000 feet above seawater, which is the real consideration, is an altogether different matter. I provided an illustration showing the effect of reflections off a smooth sea surface as an attachment to
Reply #21 of The 3105 Donut thread.
Chuck