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Author Topic: NR16020 second world flight dorsal V antenna  (Read 34149 times)

Chuck Varney

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NR16020 second world flight dorsal V antenna
« on: January 04, 2011, 10:56:33 AM »

Mike Everette's research report on NR16020's radio gear gives the length of the dorsal V antenna for the second world flight as 54 feet (two 27-foot legs). Do drawings exist that show the legs that long?

In 2008 I used two Harney drawings in Amelia's Shoes to estimate lengths of the dorsal antenna component wires. While trying to err on the long side, I settled on leg lengths of 25.7 feet. Even allowing for the inconsistency between the side and planform views, I can't make the legs longer than 26 feet.

I realize this is of no interest to anyone who isn't trying to analyze the antenna, but the leg length matter is a lead-in to comments I have regarding what Mike E. says about both the original and the lengthened dorsal antennas. This forum may not be the place to do it. Off-line perhaps?

Chuck Varney
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Martin X. Moleski, SJ

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Re: NR16020 second world flight dorsal V antenna
« Reply #1 on: January 04, 2011, 11:37:14 AM »

Mike Everette's research report on NR16020's radio gear gives the length of the dorsal V antenna for the second world flight as 54 feet (two 27-foot legs). Do drawings exist that show the legs that long?

Not drawings.  All of the information about antenna variations, known and surmised, are in text.

I've tried to summarize the variations in "NR16020 Antennas".  Let me know if the article needs correcting or extending.

Quote
I realize this is of no interest to anyone who isn't trying to analyze the antenna, but the leg length matter is a lead-in to comments I have regarding what Mike E. says about both the original and the lengthened dorsal antennas. This forum may not be the place to do it. Off-line perhaps?

It seems to me to be a perfect topic for the Forum.  If folks don't like it, they don't have to read it.  We could also create a new board just for radio discussions, if you'd like.
LTM,

           Marty
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Chuck Varney

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Re: NR16020 second world flight dorsal V antenna
« Reply #2 on: January 04, 2011, 02:25:29 PM »

Thank you, Marty.

I wasn't prepared for a "text only" response to my dimension query. So the hard data exists in the form of statements like "moved the mast from Sta. 176 to Sta. 129.5" ? And Bill Harney then used them as guidance for his drawings?

My opening comment to the page you linked relates to the third sentence under Bell Labs installation: dorsal Vee, which reads: "This length did not include the lead-in wire which exited the aft fuselage through a feed-through insulator and connected to one leg of the Vee at a point a few feet from one of the vertical stabilizers."

I think there's considerable photographic evidence that shows the lead-in wire exited the starboard fuselage through a feed-through insulator in the cabin roof near station 239 and went forward to connect to the apex of the Vee. Two photos in the Purdue collection (b10f7i22 and b12f9i2) show the connection of the lead-in wire to the Vee quite clearly.  (I have links to them, but they're each three lines long and I hesitate to dump them into this post--and I don't know what html tags are supported in these posts that would allow me to make them shorter).

It's the second sentence, coupled with the fourth sentence, that prompt my primary comments to Mike Everette's dorsal antenna write-up. These are: "The antenna was, therefore, a total of 46 feet, doubled back onto itself." and "This antenna was, then, already 15% longer than optimum;. . ." He makes like statements about the revised antenna in his research report, substituting 54 feet for 46 feet.

In each case, Mike is comparing the total length of the horizontal V portion of the antenna to a reference antenna length of 40 feet. The problem with that is twofold:

1) The V portion is just that--a portion of the antenna, not "the" antenna". The antenna also includes the lead-in wire (runs from the V to the feed-through insulator), the interior wire from the lead-in to the transmitter, and the wire from the transmitter to the airframe. These latter wires cannot be disregarded.

 2) The effective length of this antenna configuration can be much shorter than one might think. To a first approximation, it equals the length of wire that runs from the airframe to the farthest point on the V. As an example, suppose you have two 27-foot legs and a 7.5-foot "feed-line" that runs from the airframe, through the transmitter, and connects to the V at a point 9.75 feet aft of the apex. The approximate effective length is 7.5 + 9.75 + 27 = 44.25 feet (not 54 feet or 54 + 7.5 feet). In this ideal case 17.25 feet of one leg is inactive and can be ignored.

I want to emphasize the use of approximation in 2)--but it's an approximation that may have been used by a technician tasked with sizing an antenna in the late 1930's. I've found two variants of the approximation from the early 1940's. They each differ slightly from the wording in 2), and make for a bit shorter estimate. One measured from the transmitter output terminal; the other from the feed-through insulator. Applying the latter method to the dimensions I'd derived from drawings in Amelia's Shoes gave 40 feet as the estimated length. This may be just an interesting coincidence. (I have no great confidence in my dimensions, a situation I'm hoping to improve via this forum.)

An upshot of all this is that, sadly, the dorsal V as used on AE's Electra cannot be computer-modeled simply as a horizontal V with the source positioned in one leg of the V. Doing that defines a totally different antenna.

Chuck Varney
« Last Edit: January 07, 2011, 06:47:36 AM by Chuck Varney »
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ken jay brookner

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Re: NR16020 second world flight dorsal V antenna
« Reply #3 on: January 04, 2011, 06:12:05 PM »

chuck, and all..

the whole airframe needs to be modeled as part of the antenna--not trivial to do.

kenb
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Ric Gillespie

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Re: NR16020 second world flight dorsal V antenna
« Reply #4 on: January 04, 2011, 06:29:54 PM »

For a more in-depth discussion of the radio propagation issues see Bob Brandenburg's "The Post-Loss Radio Signals: Technical Analysis"
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Chuck Varney

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Re: NR16020 second world flight dorsal V antenna
« Reply #5 on: January 04, 2011, 07:38:26 PM »

chuck, and all..

the whole airframe needs to be modeled as part of the antenna--not trivial to do.

kenb

Ken,

Roger that on both counts. After a couple months of daily attacks on the problem in 2008 I concluded that short of having a $50K antenna modeling package and a super computer to run it on--plus an aircraft installation to use for validation--I couldn't really be confident in any of the results. I found that for the antenna on a simple wire frame model of the Electra, I could move, add, or remove one wire from the airframe and markedly change the calculated input impedance.

Chuck
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Chuck Varney

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Re: NR16020 second world flight dorsal V antenna
« Reply #6 on: January 04, 2011, 07:59:01 PM »

For a more in-depth discussion of the radio propagation issues see Bob Brandenburg's "The Post-Loss Radio Signals: Technical Analysis"

Ric,

I have indeed read that document, and all Bob's other papers. In addition I have recently re-read all his archived posts that even remotely relate to antenna modeling--from his first on 1 April 1999 up through 2009.

Chuck
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Martin X. Moleski, SJ

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Re: NR16020 second world flight dorsal V antenna
« Reply #7 on: January 04, 2011, 09:19:16 PM »

Thank you, Marty.

You're welcome.

Quote
I wasn't prepared for a "text only" response to my dimension query. So the hard data exists in the form of statements like "moved the mast from Sta. 176 to Sta. 129.5"? And Bill Harney then used them as guidance for his drawings?

I actually don't know what Bill's full sources were, so I have to revise my statement: I personally have only seen and collected text about the variations in the antennas.

Quote
My opening comment to the page you linked relates to the third sentence under Bell Labs installation: dorsal Vee, which reads: "This length did not include the lead-in wire which exited the aft fuselage through a feed-through insulator and connected to one leg of the Vee at a point a few feet from one of the vertical stabilizers."

I think there's considerable photographic evidence that shows the lead-in wire exited the starboard fuselage through a feed-through insulator in the cabin roof near station 239 and went forward to connect to the apex of the Vee. Two photos in the Purdue collection (b10f7i22 and b12f9i2) show the connection of the lead-in wire to the Vee quite clearly.  (I have links to them, but they're each three lines long and I hesitate to dump them into this post--and I don't know what html tags are supported in these posts that would allow me to make them shorter).

"How to insert images into posts."

"How to insert links into posts."

I'm going to stop replying there for the moment.  Paw through those two posts and put up the links to the photos, if you would be so kind.  I've just come back from N.C. and am only spending a few minutes assessing e-mail and the like.  When you give me the links to the photos, I'll edit the offending line and indicate that there is a difference of opinion.

I'll also open a "Radio Roundup" board and move this thread over there.
LTM,

           Marty
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ken jay brookner

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Re: NR16020 second world flight dorsal V antenna
« Reply #8 on: January 05, 2011, 07:43:48 AM »

Chuck,

Just curious; what modeling program are you using?

I know you said that removing a wire from the wire frame changed the impedance, but did that alter the pattern appreciably?

In a practical sense, it's probably sufficient to model a representative wire antenna over ground (using the appropriate ground conductivity figure) at the approximate height.  Not as thorough, for sure, but this was the peak of that solar cycle and the Electra was at the edge (or at times over, possibly) salt water.  These two variables make up for a lot of deficiencies!  :)  

I think the point is to see if there's a workable path at the right times with the correct power level..  I think there was.  It's another data point, but if the modeling shows no path, that doesn't necessarily mean that one did not exist.  The ionosphere doesn't always behave as modeled and then there are other propagation modes that can't be easily predicted such as ducting or skewed, and others that might have been in play.

As an aside, I've read Bob's papers and found them informative, but if I recall correctly he gives his antenna gain figures in dB (I'm thinking about the gain of Betty's antenna, here) and I've been wondering whether they're dBi or dBd?  Probably, I missed this somewhere...

kenb

« Last Edit: January 05, 2011, 08:08:10 AM by ken jay brookner »
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Chuck Varney

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Re: NR16020 second world flight dorsal V antenna
« Reply #9 on: January 05, 2011, 08:22:25 AM »

Quote
 Paw through those two posts and put up the links to the photos, if you would be so kind.

Marty,

Thank you for showing me the link and image insertion methods.

Here are links to the two Purdue collection photos that show the feed connection at the V apex for the first world flight dorsal antenna configuration (bottom wire in each photo goes back to the feed-through in the cabin roof near Sta. 239):

Photo b10f7i22

Photo b12f9i2  

Chuck
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Martin X. Moleski, SJ

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Re: NR16020 second world flight dorsal V antenna
« Reply #10 on: January 05, 2011, 09:16:23 AM »

Thank you for showing me the link and image insertion methods.

Thank you for the links!

I've added them to my synopsis:

"NR16020 Antennas."
LTM,

           Marty
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« Last Edit: January 05, 2011, 05:07:05 PM by moleski »
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Chuck Varney

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Re: NR16020 second world flight dorsal V antenna
« Reply #11 on: January 05, 2011, 02:54:47 PM »

Just curious; what modeling program are you using?

Ken,

I've primarily used MMANA 2.03, which is MININEC 3-based. To see a NEC-2 result, I've used NEC-2 for MMANA. a program that accepts a MMANA file as input, converts it to NEC format, then runs a NEC-2 engine on it.

Quote
I know you said that removing a wire from the wire frame changed the impedance, but did that alter the pattern appreciably?

I was primarily fixated on impedance prediction, so I didn't pay a lot of attention to patterns (that was to be the next phase), but I would expect no significant change in pattern in response to removing or adding a single wire from a wire frame comprising several dozen or more wires.

Quote
In a practical sense, it's probably sufficient to model a representative wire antenna over ground (using the appropriate ground conductivity figure) at the approximate height.

That may well be so, but I wanted a "flyable" model, one that could be set near ground or in freespace.

Quote
As an aside, I've read Bob's papers and found them informative, but if I recall correctly he gives his antenna gain figures in dB (I'm thinking about the gain of Betty's antenna, here) and I've been wondering whether they're dBi or dBd? 

I presumed dBi, but Bob will have to be the one to answer your question.

Chuck
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ken jay brookner

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Re: NR16020 second world flight dorsal V antenna
« Reply #12 on: January 05, 2011, 04:56:13 PM »

Thanks, Chuck.  I appreciate your comments.

I've not used MMANA, though it looks interesting.  I use either EZNEC or 4NEC2.

Best,

kenb
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Chuck Varney

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Re: NR16020 second world flight dorsal V antenna
« Reply #13 on: January 06, 2011, 08:42:41 AM »


I actually don't know what Bill's full sources were, so I have to revise my statement: I personally have only seen and collected text about the variations in the antennas.

Marty,

Can you tell me what the current consensus of the TIGHAR Team is regarding the location of the second world flight dorsal mast?

Here are some options that come readily to hand:

Sta. 129   Page 16 of TIGHAR Tracks Vol. 11, # 3     

Sta. 129.5  Mike Everette's research paper 

Sta. 125  Notation on Harney drawing of NR16020, port side

Chuck


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Martin X. Moleski, SJ

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Re: NR16020 second world flight dorsal V antenna
« Reply #14 on: January 06, 2011, 09:34:56 AM »

Can you tell me what the current consensus of the TIGHAR Team is regarding the location of the second world flight dorsal mast?

Here are some options that come readily to hand:

Sta. 129   Page 16 of TIGHAR Tracks Vol. 11, # 3     

Sta. 129.5  Mike Everette's research paper 

Sta. 125  Notation on Harney drawing of NR16020, port side

I don't know what the consensus is.  I wasn't aware that there was a discrepancy.   :-\ 

I've added your question to the article on "NR16020 Antennas."

I've also found that the same article already had Ric's answer to your other question about the feed point.
LTM,

           Marty
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