Mag Mount Antenna's Whip Replaced By V-Stub Wire Collinear

abcd567 · September 7, 2020, 8:32pm

This H & V plot of Radiation curve is not related to polarization or electromagnetic field’s H & V components.

Horizontal curve shows how the gain varies when transmitter (aeroplane) moves in a circle with the antenna at center of the circle. Say starting in North
N >> NE >> E >>SE >>S >>SW >> W >> N .
For a properly designed antenna, this curve should be a perfect or near-perfect circle.
Vertical curve shows how the gain varies when transmitter (aeroplane) approaches the antenna from say 250 nm to almost overhead. When aeroplane is at 250 nm, the straight line between antenna and aeroplane is almost horizontal. As the areoplane approaches antenna, the elevation of this straight line increases, and when plane is nearly overhead, this line makes almost 90 degrees from horizontal.
Ideally this curve should by like mathematical character infinity ∞ .

abcd567 · September 7, 2020, 8:47pm

I have now included SO239 in Spider’s simulation. This I have done by adding a 1" x 1" (25mm x 25mm) square in Spider’s simulation. The SO239’s flange provides a small horizontal ground plane, which brings down SWR from 2.4 to 1.3

Copy-paste the code below in a text editor like Notepad, save the text file, and change text file’s extension from `.txt` to `.maa`

Spider on SO239
*
1090.0
***Wires***
25
0.0,	0.0,	0.0,	0.0,	0.0,	0.067,	2.000e-04,	0
0.0,	0.0,	0.0,	0.0125,	0.0,	0.0,	2.000e-04,	0
0.0,	0.0,	0.0,	0.0125,	0.0125,	0.0,	2.000e-04,	0
0.0,	0.0,	0.0,	0.0,	0.0125,	0.0,	2.000e-04,	0
0.0,	0.0,	0.0,	-0.0125,	0.0125,	0.0,	2.000e-04,	0
0.0,	0.0,	0.0,	-0.0125,	0.0,	0.0,	2.000e-04,	0
0.0,	0.0,	0.0,	-0.0125,	-0.0125,	0.0,	2.000e-04,	0
0.0,	0.0,	0.0,	0.0,	-0.0125,	0.0,	2.000e-04,	0
0.0,	0.0,	0.0,	0.0125,	-0.0125,	0.0,	2.000e-04,	0
0.0125,	0.0,	0.0,	0.0125,	0.0125,	0.0,	2.000e-04,	0
0.0125,	0.0125,	0.0,	0.0,	0.0125,	0.0,	2.000e-04,	0
0.0,	0.0125,	0.0,	-0.0125,	0.0125,	0.0,	2.000e-04,	0
-0.0125,	0.0125,	0.0,	-0.0125,	0.0,	0.0,	2.000e-04,	0
-0.0125,	0.0,	0.0,	-0.0125,	-0.0125,	0.0,	2.000e-04,	0
-0.0125,	-0.0125,	0.0,	0.0,	-0.0125,	0.0,	2.000e-04,	0
0.0,	-0.0125,	0.0,	0.0125,	-0.0125,	0.0,	2.000e-04,	0
0.0125,	-0.0125,	0.0,	0.0125,	0.0,	0.0,	2.000e-04,	0
0.0125,	0.0,	0.0,	0.0613,	0.0,	-0.0488,	2.000e-04,	0
0.0125,	0.0125,	0.0,	0.0433,	0.0433,	-0.0488,	2.000e-04,	0
0.0,	0.0125,	0.0,	0.0,	0.0613,	-0.0488,	2.000e-04,	0
-0.0125,	0.0125,	0.0,	-0.0433,	0.0433,	-0.0488,	2.000e-04,	0
-0.0125,	0.0,	0.0,	-0.0613,	0.0,	-0.0488,	2.000e-04,	0
-0.0125,	-0.0125,	0.0,	-0.0433,	-0.0433,	-0.0488,	2.000e-04,	0
0.0,	-0.0125,	0.0,	0.0,	-0.0613,	-0.0488,	2.000e-04,	0
0.0125,	-0.0125,	0.0,	0.0433,	-0.0433,	-0.0488,	2.000e-04,	0
***Source***
1,	0
w1b,	0.0,	1.0
***Load***
0,	0
***Segmentation***
800,	80,	2.0,	2
***G/H/M/R/AzEl/X***
0,	20.0,	0,	50.0,	120,	60,	0.0

gtj0 · September 7, 2020, 8:58pm

Ignore my V/H field thing. I wasn’t thinking straight.

The 25mmx25mm square is exactly what I did. I was just about to do the 8 leg version and thr double 4 leg version. One thing I noticed is that MMANA does NOT like crossing wires for the connector flange. You have to draw them as individual wires with the center being the start point for each.

I let the optimizer do its thing and came up with a 0.0692 vertical length, 0.0473m radial length (not including the flange) and a 146deg from zenith angle.

WAVE LENGTH = 0.275 (m)
TOTAL PULSE = 121
THE LOWEST POINT OF ANTENNA = 6.961 M
FILL MATRIX...
FACTOR MATRIX...
PULSE   	  U (V) 		  I (mA)		 Z (Ohm)		SWR
w1b    	 1.00+j0.00    	 19.99-j0.01    	 50.02+j0.03    	1.00
CURRENT DATA...
FAR FIELD ...
NO FATAL ERROR(S)
0.14 sec

I did use Fe wire, real ground and a 7m elevation.


*
1090.0
***Wires***
13
0.0,	0.0,	0.0,	0.0,	0.0,	0.0692,	8.000e-04,	-1
0.0,	0.0,	0.0,	0.0125,	0.0,	0.0,	8.000e-04,	-1
0.0,	0.0,	0.0,	0.0,	-0.0125,	0.0,	8.000e-04,	-1
0.0,	0.0,	0.0,	-0.0125,	0.0,	0.0,	8.000e-04,	-1
0.0,	0.0,	0.0,	0.0,	0.0125,	0.0,	8.000e-04,	-1
0.0125,	0.0,	0.0,	0.03895,	0.0,	-0.03921,	8.000e-04,	-1
0.0,	-0.0125,	0.0,	0.0,	-0.03895,	-0.03921,	8.000e-04,	-1
-0.0125,	0.0,	0.0,	-0.03895,	0.0,	-0.03921,	8.000e-04,	-1
0.0,	0.0125,	0.0,	0.0,	0.03895,	-0.03921,	8.000e-04,	-1
0.0125,	0.0,	0.0,	0.0,	-0.0125,	0.0,	8.000e-04,	-1
0.0,	-0.0125,	0.0,	-0.0125,	0.0,	0.0,	8.000e-04,	-1
-0.0125,	0.0,	0.0,	0.0,	0.0125,	0.0,	8.000e-04,	-1
0.0,	0.0125,	0.0,	0.0125,	0.0,	0.0,	8.000e-04,	-1
***Source***
1,	0
w1b,	0.0,	1.0
***Load***
0,	0
***Segmentation***
200,	40,	2.0,	2
***G/H/M/R/AzEl/X***
2,	7.0,	5,	50.0,	120,	60,	0.0

abcd567 · September 7, 2020, 9:04pm

This is exactly how I have done the 8-leg version with SO239 flange. I have posted the .maa file above, so you can use it (save you some time in doing the geometry yourself). Run optimization with whatever settings of ground, elevation, etc you want.

gtj0 · September 9, 2020, 10:12pm

V-Lad likes the cold and ice:

V-Lad:

Mutant Spider:

abcd567 · September 9, 2020, 10:33pm

Your results show that the V-Stub receives 50% more aeroplanes than the Spider.
Your trial run proves another advantage of V-stub over U-Stub: In U-Stub, the entire length of two parallel wires gets short-circuited by rain drops and/or snow, and performance drops drastically. In V-Stub this does not happen (except at very small portion at tip of the V).

gtj0 · September 9, 2020, 10:48pm

I think I’d have to 3D print a backbone or exo-skeleton for it before putting it up on the roof. Even with the stiffer steel wire, it was flapping around in the wind the other night. It’d also help maintain the V gap over time. Still it’s doing really well! Congratulations!

abcd567 · September 9, 2020, 10:54pm

Thanks for all your efforts to make it & test it side-by-side with a Spider.

SweetPea11 · September 10, 2020, 4:05am

Which metric shows 50% more aircraft?

abcd567 · September 10, 2020, 4:28am

Please compare these two side-by-side “Aircraft seen/tracked” graphs.

SweetPea11 · September 10, 2020, 5:52am

I did.

I observed that one averaged 42 over the period and the other averaged 33 over the apparently same period.

This is an increase of approximately 27%.

How did you measure 50% more?

Thanks,

S.

abcd567 · September 10, 2020, 8:01am

I did not measeure, but made a quick visual assesment, my mistake.

You are right that if calculated by “Average” figures in graph it works out to be 27%.

However using “Average” figures is not very realistic. The realistic way is to run the two stations for one or two days, then compare the 24 hr “Totals”, i.e. “AIRCRAFTS REPORTED” and “POSITIONS REPORTED” each day.

geckoVN · September 10, 2020, 8:17am

More time is better, but the two graphs show exactly the same time period, so any differences should only be due to differences between the stations.

SweetPea11 · September 10, 2020, 10:32am

Why not?

As it appears that @gtj0 provided data for the two trials over the exact same time period. (Well done)

A rash assumption on my part leads me to believe that the Average is derived by dividing the total number of aircraft by the elapsed time.

As the time period is the same therefore the ratio of the Averages gives you the ratio of the Number of Aircraft over the same time.

Also, this is the number of Aircraft actually counted at the receiver and not the approximate number counted by Flightaware. There are quite a few Aircraft locally that are counted locally but not included by Flightaware such as all the Police helicopters, a number of private and corproate jets, some military and some that are just not reported by Flightaware by request.

I asked a simple question and I apologize for impugning your mathematical prowess.

abcd567 · September 10, 2020, 3:03pm

No need to apologize. Your approach & logic is correct, mine was wrong. Thanks for correcting me.

Nitr0 · September 10, 2020, 5:59pm

The V-Stub looks really good there, well done. I’m super interested in seeing a comparison between that and the FA antenna now for your location. It would be a great side by side for those pondering self creation vs. purchase.

gtj0 · September 10, 2020, 6:31pm

I can set that up tomorrow.

gtj0 · September 11, 2020, 7:08pm

So now it’s V-Lad vs Big Green Stick (FA 1090)…
Equivalent cables, radios, connectors, dump1090 settings, etc. Optimal gain was 44db for both antennas.

V-Lad:

Big Green Stick:

It’s V-Lad FTW!

DISCLAIMER: Once again, these results shouldn’t imply that there’s anything wrong with the FA 1090 antenna. It does imply that @abcd567 is very good.

Nitr0 · September 11, 2020, 8:03pm

Wow! The V-Lad blows the FA antenna away for your location. Not even close judging by the above. Thanks for running that comparison. Goes to show how location changes everything.

wiedehopf · September 11, 2020, 8:08pm

The FA antenna seems to be susceptible to some forms of interference.
Curious if a filter would reduce the difference.

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Mag Mount Antenna's Whip Replaced By V-Stub Wire Collinear

Copy-paste the code below in a text editor like Notepad, save the text file, and change text file’s extension from .txt to .maa

Related topics

Copy-paste the code below in a text editor like Notepad, save the text file, and change text file’s extension from `.txt` to `.maa`