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Author Topic: Factors influencing radio propagation  (Read 58112 times)

Ric Gillespie

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Re: Factors influencing radio propagation
« Reply #30 on: December 11, 2011, 06:14:49 PM »

I'd suggest that you wait for the facts before deciding which ones are ugly.
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Chuck Varney

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Re: Factors influencing radio propagation
« Reply #31 on: December 11, 2011, 07:45:14 PM »

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
« Last Edit: December 12, 2011, 10:03:31 AM by Chuck Varney »
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Ric Gillespie

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Re: Factors influencing radio propagation
« Reply #32 on: December 12, 2011, 10:07:07 AM »

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.

What's your point?  Mine was that no one went looking for a "donut" in an attempt to find further support for the Niku hypothesis.  If I mis-stated or over-simplified how the donut was discovered I apologize and thank you for the clarification.  The important thing is whether there is reason to believe that Earhart was farther away than has been traditionally assumed.  Bob says yes. Gary says no. What do you say?
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Chuck Varney

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Re: Factors influencing radio propagation
« Reply #33 on: December 12, 2011, 01:01:38 PM »

Bob Brandenburg has not yet published his paper on the donut hole.   . . .  Once Bob has had a chance to get his paper written and published, any skeptic with the ability and inclination to buy the software and check his calculations will be able to do so.  Replication of results is the essence of scientific investigation.

Ric,

While we await Bob’s paper, there’s something else that might be done that also relates to propagation and checking calculations. The recently published Catalog and Analysis of Radio Signals includes the results of hundreds of propagation calculations. No details of how they were done are given.

A person (a skeptic, if you wish) with the ability and inclination could review the method if you were to add an appendix to the catalog to provide a single complete calculation example. Message 142, the Betty Klenck case, is one of general interest. Use it for the example.

How to provide the information without investing a lot of time? Enter the parameters into ICEPAC that gave the lowest reception probability, and do a screen capture of the input screen. Follow this by selecting Run – Circuit, and saving icepacx.out, a small text file containing the results. Repeat the procedure with the parameters that provided the highest reception probability.  Post the two screen captures and saved files. Add any explanatory words considered necessary. If you wish to be thorough, you might post any unique antenna files that were used.

Without such an appendix, a person with the ability and inclination might ask a few questions and gain enough information to make some  comments.

Chuck
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Ric Gillespie

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Re: Factors influencing radio propagation
« Reply #34 on: December 12, 2011, 01:16:54 PM »

The recently published Catalog and Analysis of Radio Signals includes the results of hundreds of propagation calculations. No details of how they were done are given.

A person (a skeptic, if you wish) with the ability and inclination could review the method if you were to add an appendix to the catalog to provide a single complete calculation example. Message 142, the Betty Klenck case, is one of general interest. Use it for the example.

I think you'll find what you're looking for in Harmony and Power, Probability Tables, and Antenna Diagram.

It's also worth noting that the calculated probability was not a determining factor in assessing the credibility of any reported signal.  We set no threshold of probability. Rare events do happen.
« Last Edit: December 12, 2011, 08:11:04 PM by Martin X. Moleski, SJ »
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Chuck Varney

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Re: Factors influencing radio propagation
« Reply #35 on: December 12, 2011, 03:57:52 PM »

What's your point?  Mine was that no one went looking for a "donut" in an attempt to find further support for the Niku hypothesis.  If I mis-stated or over-simplified how the donut was discovered I apologize and thank you for the clarification.

My point was perceived dishonesty, mainly—and not relating to you.

Quote
The important thing is whether there is reason to believe that Earhart was farther away than has been traditionally assumed.  Bob says yes. Gary says no. What do you say?

I say it’s a difficult problem to solve, involving both ionospheric and direct propagation from a source three wavelengths above a high conductivity surface. I’ve seen no evidence that it’s been done.

Chuck
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Chuck Varney

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Re: Factors influencing radio propagation
« Reply #36 on: December 12, 2011, 04:17:07 PM »

I think you'll find what you're looking for in Harmony and Power, Probability Tables, and Antenna Diagram.

No, actually, I’m looking for what I suggested: a complete example—from ICEPAC input to ICEPAC output—for a message in the Catalog and Analysis of Radio Signals.

Can I tell anything from the pages you cited? I think so. In Harmony and Power the input powers are way off, and the antenna efficiencies look suspiciously like those for the mis-modeled antenna I’ve railed about. (I know the source of the powers and have commented on that paper.) The probability tables show ICEPAC being used as a daily program, which, to my knowledge, it’s not. It’s likely that daily sunspot numbers have been used, and there’s little to no correlation between daily sunspot numbers and the ionospheric state. The 15-minute time granularity is mysterious. ICEPAC is an hourly program. All the probabilities are calculated to 15 decimal places (the equivalent ICEPAC output, Reliability, is to 2 decimal places). The probabilities have up to 13 significant figures, calculated from ICEPAC output parameters that don’t exceed 3. There’s no explanation for how the probabilities are calculated. The antenna diagram is just that, a diagram. It’s not the antenna definition file that ICEPAC would use for it.

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It's also worth noting that the calculated probability was not a determining factor in assessing the credibility of any reported signal.  We set no threshold of probability. Rare events do happen.

I understand that.

Chuck
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Ric Gillespie

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Re: Factors influencing radio propagation
« Reply #37 on: December 12, 2011, 04:30:55 PM »

Chuck,

I'm not qualified to judge your criticisms of Bob's work. I do know that Bob disputes them. ICEPAC is not proprietary to Bob Brandenburg.  The research tools and required information are readily available for you to run your own calculations.   Then you can publish your own analysis of the LOP donut hole and I'm sure Bob will be happy to critique it.
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Irvine John Donald

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Re: Factors influencing radio propagation
« Reply #38 on: December 16, 2011, 08:53:53 PM »

Well said as usual Jeff.  The methodology in this case is really for the experts to ruminate over. This falls into Gary's profession where much time and effort is expended to determine WHO is an expert witness. We have no provision for this in a forum format so we are each left to form our own opinions on just who is an expert in what field. This leaves room for getting it wrong but sane, reasonable thinking people can usually work it out for themselves without getting into fisty cuffs.
Respectfully Submitted;

Irv
 
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Heath Smith

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Re: Factors influencing radio propagation
« Reply #39 on: March 01, 2012, 04:53:25 AM »

I was just curious if anyone has done any work on the radio propagation and location probability map theory? Are you still out there Chuck? Have you done any more work in this area? I would really like to get my hands on some kind of data for approximating where AE might have been based on the various signal strengths reported.

I do not have a background in radio so I am lost when it comes to creating such maps. I tried seeking out different radio propagation programs that use simple dipoles and found DX Toolbox and VOACAP for Windows. DX Toolbox indicated no signal loss while the VOACAP application suggested that there was a decrease in the signal to noise ratio the closer you were to the transmitter. Since I do not know what I am doing, this is probably incorrect anyhow.

All I have at the moment is the Waitt Institute report where they try to do curve fitting based on the reported signal strength and the estimated distances. While it probably has limited value, it is the only estimate I have at the moment.

Thanks in advance.
« Last Edit: March 04, 2012, 11:08:08 AM by Heath Smith »
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Irvine John Donald

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Re: Factors influencing radio propagation
« Reply #40 on: March 01, 2012, 05:55:43 AM »

Heath. Do you mean like the 3105 donut theory paper found at http://tighar.org/Publications/TTracks/2008Vol_24/1008.pdf. In the Ameliapedia section of the forum?  Bob Brandenburg has done lots of radio analysis for TIGHAR.
Respectfully Submitted;

Irv
 
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Heath Smith

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Re: Factors influencing radio propagation
« Reply #41 on: March 01, 2012, 02:49:43 PM »

Irvine,

Yes along those lines. I am looking for a chart that describes signal strength as estimated by the crew, a signal strength with a scale to units like signal to noise ratio and distance on the X scale. I believe the doughnut hole article that you posted just shows where they should have been at the 19:12GMT where the crew recorded the signal strength 5.

I believe Bob Brandenburg is still working on his study. I was hoping to find something to work with in the meantime.
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Heath Smith

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Re: Factors influencing radio propagation
« Reply #42 on: March 01, 2012, 03:39:53 PM »


This is the type of info I was looking for:

The Post-Loss Radio Signals: Technical Analysis
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Heath Smith

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Re: Factors influencing radio propagation
« Reply #43 on: March 04, 2012, 11:03:25 AM »

I have been reading the Post-Loss Radio Signals page and have a couple of questions for the radio experts.

In the paper, there seems to be an attempt (in a round about way) to create a translation of signal to noise ratios to the signal strength reports recorded in the Itasca and Howland radio logs.

For example, and I may be reading this incorrectly, there are end points that are established where a signal strength 5 is interpreted as a 16Db SNR or greater:

Quote
3). Note that the question mark in the 2013 GMT log entry indicates uncertainty about what was said in the parenthetical phrase, suggesting that the SNR was below the 100% intelligibility level, and thus somewhat below that implied by the “S5” estimate of signal strength. This suggests that the signal was sent from a distance consistent with an SNR of at least 16 dB.

I believe also that at the low end of the scale (S0?) an SNR of 13Db is given:

Quote
4). Note that Table A1 shows 200 miles as the maximum distance from which the 2013 GMT signal could have been sent. At that distance, the 90th percentile SNR was 13 dB, indicating a signal that was readable less than 10% of the time. Given this maximum distance, a ground speed of 115 knots along the LOP since 1912 GMT implies that Earhart’s maximum distance from Howland at 1912 GMT was 83 miles. A ground speed of 130 knots implies that her distance from Howland at 1912 GMT was not more than 68 miles. It is interesting to compare these distance limits with the 80-mile maximum CPA value derived from the SNR of the 1912 GMT signal.

5). Note that at 2115 GMT, Earhart’s next scheduled transmission time, signals on 3105 kHz were unreadable beyond 100 miles, and were unreadable at any distance after the 2100 hour. Therefore, 2013 GMT was the last time at which the Itasca could have heard a signal from Earhart on 3105 kHz.

I also read an interesting post from the 2001 archives by a Mr. Mike Everette titled "Signal strength quantifiers". Maybe I am reading Mike incorrectly but it seems he is suggesting that any attempt to translate the radio log signal strengths to any sort of meaningful distance relationship is not possible. While Mike seems to praise Bob's work he also seems to be railing against the entire notion of inferring distance to signal strength (1-5) relationship whatsoever because this is completely subjective.

But is that not precisely what is happening in the technical analysis by Bob Brandenburg? Did I miss something else here? I find the data very interesting but at the end of the day it seems that this analysis is doing exactly what Mike suggested cannot be done.

I am not trying to stoke a debate about the validity of the analysis but was hoping that this could start a meaningful discussion over whether a distance to signal strength relationship can be defined given all of the detailed information about the antennas and radios involved.

The only conclusion that I can draw from the analysis is that for an S5 to be received this suggests a maximum range of 80NM and given Mike E.'s statements I am curious to know if even that can be given any label other than an well-educated guess?

Any thoughts / advice appreciated.

PS- A signal strength to distance relationship, in a 2D model map is exactly what I was hoping to find and/or create.
« Last Edit: March 04, 2012, 01:47:36 PM by Heath Smith »
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Gary LaPook

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Re: Factors influencing radio propagation
« Reply #44 on: April 16, 2012, 03:26:54 AM »

Too bad Earhart didn't have one of these.

BTW, when we were ferrying out of Canada to Europe we had to stop in Moncton Canada where the government inspectors checked that we had the required equipment on board. We were required to have two ADFs and what we carried as the second one was just a portable radio, similar to the one in this ad, and the Canadians were satisfied with that. We were also required to have HF radios but I remember being in Moncton with a group of eight planes going across and only one of our planes had an HF. We had to do radio checks with the tower at Moncton with our HFs so we eight pilots stood in a line next to the one Cessna 172 that had the HF radio. "Moncton tower, Orient Air One, Radio check, over."  "We hear you lima charlie." Next guy in line handed the mic, "Moncton tower, Orient Air Two, Radio check, over."  "We hear you lima charlie" and so on down the line. The Canadians knew exactly what we were doing, we were parked directly under the tower and they could look down at our line of pilots holding the mic. Of course the boss of our outfit did bring "presents" to those hard working Canadian controllers.

I remember taking off from St. John Newfoundland with a flight of four Cessna 172s, it was night and the ceiling was only abut one thousand feet. We planned on flying in formation across since only one of our planes had an HF, we wanted to take off close to each other so that we could formate after punching up through the clouds. We had the planes lined up on the runway and the first guy got cleared to take off. The controller could not clear the next guy to take off until IFR separation of one thousand feet vertical was established. So the first guy lifts off and as he is flying past the tower window  he radios "Orient Air One out of one thousand for one zero thousand." Now it is on the controllers tape recording that the first plane has reported climbing past the magic one thousand foot level so he clears the next plane to take off and so on down the line. Obviously the controllers knew that we had not climbed out of one thousand as we were going past his window but his ass was covered, he had it on the tape.  Yep, it's good to bring "presents" to controllers if you want better service!

gl
« Last Edit: April 16, 2012, 03:51:49 AM by Gary LaPook »
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