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Author Topic: Factors influencing radio propagation  (Read 68360 times)

Michael Calvin Powell

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Re: Factors influencing radio propagation
« Reply #75 on: March 10, 2015, 12:09:44 PM »

If Wikipedia is to be believed, solar cycle 17 started in September 1933 and ended in February 1944.

http://en.wikipedia.org/wiki/Solar_cycle_17

with a maximum in April 1937.

http://en.wikipedia.org/wiki/List_of_solar_cycles
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« Last Edit: March 10, 2015, 12:12:37 PM by Michael Calvin Powell »
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James Champion

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Re: Factors influencing radio propagation
« Reply #76 on: March 10, 2015, 05:44:38 PM »

Looks like there were some solar events in 1937. I don't know how to research for more details down to specific dates.

http://www.solarstorms.org/SRefStorms.html

Appears individual "space weather" events can cause a lot of propagation changes in the MF and HF bands. There appear to be a lot of Ham tools and websites for predicting propagation based on these conditions.  I'm a ham myself, but I'm not into HF and DX communication.

James Champion - WB5KUY
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John Rayfield

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Re: Factors influencing radio propagation
« Reply #77 on: April 04, 2015, 09:20:27 AM »

I make my living by solving problems.  I work in electronic communications (commmercial 2-way radio) and have done so for 37 years.

Very often, in troubleshooting a 'system' problem, you have to take a 'reverse' approach, by ruling out the "possibilities", in order to 'narrow down' the "probabilities".  This has become more and more necessary as electronics and communications systems have become more and more complex.  And sometimes, the 'solution' or 'answer' is not necessarily what one initially thought it could even be.  I also do beta-testing of new communications products for a major communications equipment manufacturer, working directly with development engineers, where again, very often, the 'solution' or 'answer' to a problem is evasive and the only way to find it it is to "rule out possibilities" until the remaining "probabilities" are small enough that the solution or answer becomes more evident.

After 37 years of doing this, I would even say that considering "negative evidence" is very often the ONLY way to eventually solve an especially 'tough' problem.  Otherwise, the 'haystack' is just too big to ever find the 'needle'.

Considering the difficulty of solving the Earhart mystery, as a professional 'problem solver', I would say that using "negative evidence" is absolutely necessary to "rule out possibilities", in order to "narrow down the probabilities" that then can be looked for and checked.

As to 'skip conditions', if accurate details about the solar cycle conditions in July of 1937 can be found, then based on my 40 years of experience using HF communications (including the use of some HF marine band communications), I think that a reasonably accurate 'prediction' of where Earhart might have been (if her "Q5" transmissions were heard via skip propagation) can be developed.  This would be a 'range' around Howland, not a specific distance or location, but it would be information that could be used to further "narrow down the probabilities" as to where she was located at that time and where she ended up.

I just thought of a way to sum up what I'm talking about.  You can look for "positive evidence" (look for the needle in the entire haystack), or you can use "negative evidence" to rule out areas of the haystack where there is no probability of finding the needle, and then search the remaining part of the haystack for "positive evidence" (the needle).  Thus, using "negative evidence" can greatly reduce the time needed to solve a 'problem' (find the needle).  I think using information regarding radio propagation can help to 'rule out' some areas of this 'haystack'.

I thought that someone had already done some studies on this subject, but I've never seen any such information released to the public, so I don't know how detailed anyone ever got with anything like this.

John Rayfield, Jr.

Now we are both in to negative evidence, perhaps better covered in theorizing about theories.  I believe I must concede  I can not say how skip behaved on July 2 1937.   In the end I am looking for a positive result, something like Smithy's landing gear.  If you are unfamiliar, when the Lady Sothern Cross went down the only thing they ever found was one landing gear which had washed up on the beach.   It was apparently floated by the buoyancy of the Tyre.  It had brake gear with a serial number on it. 
Search under Lockheed Files Altair
Neff
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Ric Gillespie

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Re: Factors influencing radio propagation
« Reply #78 on: April 04, 2015, 09:44:48 AM »

As to 'skip conditions', if accurate details about the solar cycle conditions in July of 1937 can be found, then based on my 40 years of experience using HF communications (including the use of some HF marine band communications), I think that a reasonably accurate 'prediction' of where Earhart might have been (if her "Q5" transmissions were heard via skip propagation) can be developed.  This would be a 'range' around Howland, not a specific distance or location, but it would be information that could be used to further "narrow down the probabilities" as to where she was located at that time and where she ended up.

We're way ahead of you. Have you read the research papers on the TIGHAR website?  Are you familiar with ICEPAC? 
Go to the Earhart Project Archives Finding Aid and scroll down to Radio Distress calls.  You'll find several technical papers by Bob Brandenburg.
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John Rayfield

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Re: Factors influencing radio propagation
« Reply #79 on: April 04, 2015, 10:00:15 AM »

Thanks Ric.  I definitely want to read over those.  Excellent.

Actually, I started thinking about this (using propagation information to try to 'narrow down' 'probable location' of Earhart, back in the mid to late 80's.  I threw out this idea to someone and was pretty much 'rebuffed' with the 'argument' that radio propagation via 'skip' wasn't 'predictable' enough to be of any use whatsoever in researching Earhart's disappearance.  I knew better, but never did follow up with this idea with anyone.

John Rayfield, Jr.


As to 'skip conditions', if accurate details about the solar cycle conditions in July of 1937 can be found, then based on my 40 years of experience using HF communications (including the use of some HF marine band communications), I think that a reasonably accurate 'prediction' of where Earhart might have been (if her "Q5" transmissions were heard via skip propagation) can be developed.  This would be a 'range' around Howland, not a specific distance or location, but it would be information that could be used to further "narrow down the probabilities" as to where she was located at that time and where she ended up.

We're way ahead of you. Have you read the research papers on the TIGHAR website?  Are you familiar with ICEPAC? 
Go to the Earhart Project Archives Finding Aid and scroll down to Radio Distress calls.  You'll find several technical papers by Bob Brandenburg.
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John Rayfield

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Re: Factors influencing radio propagation
« Reply #80 on: April 04, 2015, 10:08:13 AM »

Oh, and yes, I know of ICEPAC, but I have not worked with it personally.  Most of my radio propagation modeling experience has been with VHF and UHF frequencies, using commercial modeling software from RadioSoft (with an accuracy of around 90% or better).  I'm working now with antenna modeling tools, so that I can develop radiation pattern models to use with my VHF/UHF propagation models, as well as radiation pattern models for HF antennas for emergency communications systems.

John Rayfield, Jr.

As to 'skip conditions', if accurate details about the solar cycle conditions in July of 1937 can be found, then based on my 40 years of experience using HF communications (including the use of some HF marine band communications), I think that a reasonably accurate 'prediction' of where Earhart might have been (if her "Q5" transmissions were heard via skip propagation) can be developed.  This would be a 'range' around Howland, not a specific distance or location, but it would be information that could be used to further "narrow down the probabilities" as to where she was located at that time and where she ended up.

We're way ahead of you. Have you read the research papers on the TIGHAR website?  Are you familiar with ICEPAC? 
Go to the Earhart Project Archives Finding Aid and scroll down to Radio Distress calls.  You'll find several technical papers by Bob Brandenburg.
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Neff Jacobs

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Re: Factors influencing radio propagation
« Reply #81 on: April 06, 2015, 01:14:22 PM »

John,
You may find this article from Short Wave Magazine 1937 of some use.
http://www.americanradiohistory.com/Archive-Short-Wave-Television/30s/SW-TV-1937-07.pdf
Beginning on page 7 of the PDF Around the World Radio Echos.   Apparently conditions were such on 14 and 21 Mhz it was possible to hear your own signal coming all the way round the world.  It must have been close to a sunspot maximum. This was particularly true  near June 21 and December 21 when the  most northern and southern areas were illuminated.
An interesting article on radio propagation as viewed in the 1930s anyway.
Neff
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Brian Ainslie

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Re: Factors influencing radio propagation
« Reply #82 on: April 07, 2015, 12:07:24 PM »

Forgive what may be considered a dumb question by the experts, but does propagation depend on which side of the equator one is on? A search (albeit brief) of the world wide interweb did not reveal a definitive answer. Obviously my question stems from the fact that Niku is south of the Equator and most of the other potential signals received were north of the Equator.
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Martin X. Moleski, SJ

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Re: Factors influencing radio propagation
« Reply #83 on: April 07, 2015, 12:21:43 PM »

Forgive what may be considered a dumb question by the experts, but does propagation depend on whichside of the equator one is on? A search (albeit brief) of the world wide interweb did not reveal a definitive answer.

Googling "'radio propagation' equator" brought up this discussion of "Transequatorial Radio Propagation."  From the little I've read of it, it sounds as though there are times when transmitting from one side of the equator to the other works better than transmitting to locations that are on the same side of the equator as the transmitter.
LTM,

           Marty
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JNev

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Re: Factors influencing radio propagation
« Reply #84 on: April 07, 2015, 03:07:14 PM »

The more we learn about it the stranger the world seems to be...
- Jeff Neville

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Neff Jacobs

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Re: Factors influencing radio propagation
« Reply #85 on: April 07, 2015, 07:41:41 PM »

Worth noting, I think, Transequatori Radio Propagation applies to frequencies well above those Earhart used.  Greater than 45000 kc vs 3105 and 6210 kc.   

And yes round the world echos are better heard in the Northern hemisphere in June and in the Southern hemisphere in December.

The fact 14000 kc and 21000 kc were open world wide during daylight hours suggest to me after sunrise 3105 would have rapidly dropped into short reflection/ground wave mode.  In my experience short reflections are not subjectively different from ground wave, except by theory they travel too far to actually be a ground wave.   At short range <200 miles I would expect exactly what the Itasca operators reported on 3105.   I would have expected the same on 6210.  Only once in almost 50 years have I had a complete drop out of a station on 7000kc that was within 100 miles of me.

The fact 14000 and 21000 kc were open world wide are an argument in favor of harmonics being received daylight path in Florida.

The trouble with what I call negative evidence is I never experienced a Buddhist monk until 1973.  Ergo, the monk, his brethren and the 1300 year old temple behind him never existed before May 1973.  For me they did not.  History seems  to suggest otherwise.

So my belief or non-belief in what should have happened cannot change history only color my interpretation of it.

Neff
« Last Edit: April 07, 2015, 07:45:44 PM by Neff Jacobs »
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Mark A. Cook

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Re: Factors influencing radio propagation
« Reply #86 on: April 08, 2015, 09:40:50 PM »

Great thread. Highly respect all your views. Interesting.

I made this mistake before. You can't fine tune something that never designed to be that fine tuned. Can't tune something with digital testers when its analog.   

Dealing with older radios you got to think about there technology @ that time period. They never had the proper tools or technology or it was designed to come close to fine tune them radios as we do today.

You can & will make a problem much harder trying to look @ it in todays High Tech world & not back in 1937 and what your local airplane mechanic had in tools boxes if anything meter testing wise.

I am sure A.E. had some best personal around but we are looking @ 1937 too.

Them radios was nothing like we have today.  Sometimes I think them older radio's are much better in a way performance wise.

I got real old Ham radio and hear, plus talk world wide on a good night.

No question I believe with running engine with proper elect. power, A good night she could be heard just about anywhere in world on the proper harmonics cycles .
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JNev

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Re: Factors influencing radio propagation
« Reply #87 on: April 09, 2015, 05:43:43 AM »

It might just have been so.  Too bad we can't collect all those radio signals and here them again.
- Jeff Neville

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