FlightAware Discussions

Has anyone simulated/tried a wire colinear with two single loops?

Ran across https://martybugs.net/wireless/collinear.cgi and wondered if the same design would work well for an ADSB antenna.

For the section lengths I used the 1/2 and 3/4 wavelength for ADSB, and a .95 velocity factor for my plain 2mm copper wire (12ga plain wire from hardware store), but kept the ratio of the top to center sections the same (since the top is supposed to be slightly less than 3/4), and used approx 20mm diameter for each ‘loop’. Minor adjusting of the length of the top section and the vna shows a -40db to -45db logmag and an SWR of 1.01-1.03. So it -seems- like it should be fairly decent, but I don’t know if it has much gain (since I can’t measure that with the equipment I have).

Radiation Pattern and Gain are the catch.

Even a SWR =1 is worthless if any one or both of following happen:
(1) Gain is very low
(2) Radiation pattern is drastically different from lazy eight or infinity symbol ∞

The only practical way to find out without any sophisticated equipment is to conduct a side-by-side trial run with a standard antenna such as Flightaware or Jetvison, with two antennas at same location and not more than 3 feet horizontal seperation, same type & length of coax, same dongle & filter, and same gain setting. Compare Aircraft tracked, Messages received, and maximum range.

This design has been used successfully for 1090Mhz:

G7RGQ Design Drawing from Microtronics

CLICK ON IMAGE TO SEE LARGER SIZE

Simulation results of G7RGQ

Screenshot 1 of 4 - Radiation Pattern & Gain

CLICK ON IMAGE TO SEE LARGER SIZE

G7RGQ-Pattern
 

Screenshot 2 of 4 - SWR

CLICK ON IMAGE TO SEE LARGER SIZE


 

Screenshot 3 of 4 - Geometry

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Screenshot 4 of 4 - Current+Phase

CLICK ON IMAGE TO SEE LARGER SIZE


 

DOWNLOAD SIMULATION SOFTWARE 4NEC2

https://www.qsl.net/4nec2/

G7RGQ SIMULATION MODEL FOR SOFTWARE 4NEC2

Copy-paste code below in a text file, then change extension of file from .txt to .nec

CM Simulation Model by abcd567
CM G-7RGQ wire collinear
CM rev3 by Microtronics
CM 
CM Wire Dia = 3.4 mm
CM Coils = 9mm inner dia, 1and 1/2 turns, 4mm gap between turns
CM Radiators = 4 x 200 mm
CM Lower wire = 135 mm
CM Middle Wire = 203 mm
CM Upper Wire = 188 mm
CE
SY LE = 0.135
SY LC=LE
SY ME=0.203
SY UC=ME+LC+.00675
SY UE=0.188
GW	1	100	0	0	0	0.200	0	0	.0017
GW	2	100	0	0	0	0	0.200	0	.0017
GW	3	100	0	0	0	-0.200	0	0	.0017
GW	4	100	0	0	0	0	-0.200	0	.0017
GW	5	500*LE	0	0	0	0	0	LE	.0017
GW	300	1	0	0	LC	.001184	-.003644	LC+.00045	.0017
GW	301	1	.001184	-.003644	LC+.00045	.004284	-.005897	LC+.0009	.0017
GW	302	1	.004284	-.005897	LC+.0009	.008116	-.005897	LC+.00135	.0017
GW	303	1	.008116	-.005897	LC+.00135	.011216	-.003644	LC+.0018	.0017
GW	304	1	.011216	-.003644	LC+.0018	.0124	0	LC+.00225	.0017
GW	305	1	.0124	0	LC+.00225	.011216	.003644	LC+.0027	.0017
GW	306	1	.011216	.003644	LC+.0027	.008116	.005897	LC+.00315	.0017
GW	307	1	.008116	.005897	LC+.00315	.004284	.005897	LC+.0036	.0017
GW	308	1	.004284	.005897	LC+.0036	.001184	.003644	LC+.00405	.0017
GW	309	1	.001184	.003644	LC+.00405	0	0	LC+.0045	.0017
GW	310	1	0	0	LC+.0045	.001184	-.003644	LC+.00495	.0017
GW	311	1	.001184	-.003644	LC+.00495	.004284	-.005897	LC+.0054	.0017
GW	312	1	.004284	-.005897	LC+.0054	.008116	-.005897	LC+.00585	.0017
GW	313	1	.008116	-.005897	LC+.00585	.011216	-.003644	LC+.0063	.0017
GW	314	1	.011216	-.003644	LC+.0063	.0124	0	LC+.00675	.0017
GW	6	500*ME	.0124	0	LC+.00675	.0124	0	ME+LC+.00675	.0017
GW	400	1	.0124	0	UC	.011216	-.003644	UC+.00045	.0017
GW	401	1	.011216	-.003644	UC+.00045	.008116	-.005897	UC+.0009	.0017
GW	402	1	.008116	-.005897	UC+.0009	.004284	-.005897	UC+.00135	.0017
GW	403	1	.004284	-.005897	UC+.00135	.001184	-.003644	UC+.0018	.0017
GW	404	1	.001184	-.003644	UC+.0018	0	0	UC+.00225	.0017
GW	405	1	0	0	UC+.00225	.001184	.003644	UC+.0027	.0017
GW	406	1	.001184	.003644	UC+.0027	.004284	.005897	UC+.00315	.0017
GW	407	1	.004284	.005897	UC+.00315	.008116	.005897	UC+.0036	.0017
GW	408	1	.008116	.005897	UC+.0036	.011216	.003644	UC+.00405	.0017
GW	409	1	.011216	.003644	UC+.00405	.0124	0	UC+.0045	.0017
GW	410	1	.0124	0	UC+.0045	.011216	-.003644	UC+.00495	.0017
GW	411	1	.011216	-.003644	UC+.00495	.008116	-.005897	UC+.0054	.0017
GW	412	1	.008116	-.005897	UC+.0054	.004284	-.005897	UC+.00585	.0017
GW	413	1	.004284	-.005897	UC+.00585	.001184	-.003644	UC+.0063	.0017
GW	414	1	.001184	-.003644	UC+.0063	0	0	UC+.00675	.0017
GW	7	500*UE	0	0	UC+.00675	0	0	UE+UC+.00675	.0017
GE	0
GN	-1
EK
EX	0	5	1	0	0	0	0
FR	0	0	0	0	1090	0
EN

Interesting, is the simulation software free online? The page I was referring to mentioned that it should be a single loop. If that loop needs to be 1/4 wavelength, then maybe using a single 20mm diameter loop would turn out better.

But looks like the pattern isn’t nearly as nice as the V Stub anyway :wink:

Yes, it is free of cost. You can download it from here:

Thanks! Now to figure out how to ‘draw’ a 20mm circle in that file format. :slight_smile:

Go to main menu >> Run >> Geometry Builder >> Helix.

It will create a file named Build.nec

 

20201029_174803

So this is a close match to what I’ve built. My dimensions are slightly smaller after taking .95 of these values, but it seems that is required as building with the exact dimensions here doesn’t tune at all.


image
image

CM Simulation Model by sigwx
CM two loop wire collinear
CM 
CM Wire Dia = 2 mm
CM Coils = 20mm inner dia, 1 turn, 10mm gap between turns
CM Radiators = 4 x 70 mm
CM Lower wire = 137.4 mm
CM Middle Wire = 206.0 mm
CM Upper Wire = 187.5 mm
CE
SY LE = 0.1374
SY LC=LE
SY CH=0.012
SY ME=0.206
SY UC=LC+CH+ME
SY UE=0.1875
SY GE=0.070
GW	1	10	0	0	0	GE	0	0	.001
GW	2	10	0	0	0	0	GE	0	.001
GW	3	10	0	0	0	-GE	0	0	.001
GW	4	10	0	0	0	0	-GE	0	.001
GW	5	30	0	0	0	0	0	LC	.001
GW	6	1	0	0	LC	-.000192	.001951	LC+.000375	.001
GW	7	1	-.000192	.001951	LC+.000375	-.000761	.003827	LC+.00075	.001
GW	8	1	-.000761	.003827	LC+.00075	-.001685	.005556	LC+.001125	.001
GW	9	1	-.001685	.005556	LC+.001125	-.002929	.007071	LC+.0015	.001
GW	10	1	-.002929	.007071	LC+.0015	-.004444	.008315	LC+.001875	.001
GW	11	1	-.004444	.008315	LC+.001875	-.006173	.009239	LC+.00225	.001
GW	12	1	-.006173	.009239	LC+.00225	-.008049	.009808	LC+.002625	.001
GW	13	1	-.008049	.009808	LC+.002625	-.01	.01	LC+.003	.001
GW	14	1	-.01	.01	LC+.003	-.011951	.009808	LC+.003375	.001
GW	15	1	-.011951	.009808	LC+.003375	-.013827	.009239	LC+.00375	.001
GW	16	1	-.013827	.009239	LC+.00375	-.015556	.008315	LC+.004125	.001
GW	17	1	-.015556	.008315	LC+.004125	-.017071	.007071	LC+.0045	.001
GW	18	1	-.017071	.007071	LC+.0045	-.018315	.005556	LC+.004875	.001
GW	19	1	-.018315	.005556	LC+.004875	-.019239	.003827	LC+.00525	.001
GW	20	1	-.019239	.003827	LC+.00525	-.019808	.001951	LC+.005625	.001
GW	21	1	-.019808	.001951	LC+.005625	-.02	0	LC+.006	.001
GW	22	1	-.02	0	LC+.006	-.019808	-.001951	LC+.006375	.001
GW	23	1	-.019808	-.001951	LC+.006375	-.019239	-.003827	LC+.00675	.001
GW	24	1	-.019239	-.003827	LC+.00675	-.018315	-.005556	LC+.007125	.001
GW	25	1	-.018315	-.005556	LC+.007125	-.017071	-.007071	LC+.0075	.001
GW	26	1	-.017071	-.007071	LC+.0075	-.015556	-.008315	LC+.007875	.001
GW	27	1	-.015556	-.008315	LC+.007875	-.013827	-.009239	LC+.00825	.001
GW	28	1	-.013827	-.009239	LC+.00825	-.011951	-.009808	LC+.008625	.001
GW	29	1	-.011951	-.009808	LC+.008625	-.01	-.01	LC+.009	.001
GW	30	1	-.01	-.01	LC+.009	-.008049	-.009808	LC+.009375	.001
GW	31	1	-.008049	-.009808	LC+.009375	-.006173	-.009239	LC+.00975	.001
GW	32	1	-.006173	-.009239	LC+.00975	-.004444	-.008315	LC+.010125	.001
GW	33	1	-.004444	-.008315	LC+.010125	-.002929	-.007071	LC+.0105	.001
GW	34	1	-.002929	-.007071	LC+.0105	-.001685	-.005556	LC+.010875	.001
GW	35	1	-.001685	-.005556	LC+.010875	-.000761	-.003827	LC+.01125	.001
GW	36	1	-.000761	-.003827	LC+.01125	-.000192	-.001951	LC+.011625	.001
GW	37	1	-.000192	-.001951	LC+.011625	0	0	LC+.012	.001
GW	38	40	0	0	LC+CH	0	0	UC	.001
GW	39	1	0	0	UC	-.000192	.001951	UC+.000375	.001
GW	40	1	-.000192	.001951	UC+.000375	-.000761	.003827	UC+.00075	.001
GW	41	1	-.000761	.003827	UC+.00075	-.001685	.005556	UC+.001125	.001
GW	42	1	-.001685	.005556	UC+.001125	-.002929	.007071	UC+.0015	.001
GW	43	1	-.002929	.007071	UC+.0015	-.004444	.008315	UC+.001875	.001
GW	44	1	-.004444	.008315	UC+.001875	-.006173	.009239	UC+.00225	.001
GW	45	1	-.006173	.009239	UC+.00225	-.008049	.009808	UC+.002625	.001
GW	46	1	-.008049	.009808	UC+.002625	-.01	.01	UC+.003	.001
GW	47	1	-.01	.01	UC+.003	-.011951	.009808	UC+.003375	.001
GW	48	1	-.011951	.009808	UC+.003375	-.013827	.009239	UC+.00375	.001
GW	49	1	-.013827	.009239	UC+.00375	-.015556	.008315	UC+.004125	.001
GW	50	1	-.015556	.008315	UC+.004125	-.017071	.007071	UC+.0045	.001
GW	51	1	-.017071	.007071	UC+.0045	-.018315	.005556	UC+.004875	.001
GW	52	1	-.018315	.005556	UC+.004875	-.019239	.003827	UC+.00525	.001
GW	53	1	-.019239	.003827	UC+.00525	-.019808	.001951	UC+.005625	.001
GW	54	1	-.019808	.001951	UC+.005625	-.02	0	UC+.006	.001
GW	55	1	-.02	0	UC+.006	-.019808	-.001951	UC+.006375	.001
GW	56	1	-.019808	-.001951	UC+.006375	-.019239	-.003827	UC+.00675	.001
GW	57	1	-.019239	-.003827	UC+.00675	-.018315	-.005556	UC+.007125	.001
GW	58	1	-.018315	-.005556	UC+.007125	-.017071	-.007071	UC+.0075	.001
GW	59	1	-.017071	-.007071	UC+.0075	-.015556	-.008315	UC+.007875	.001
GW	60	1	-.015556	-.008315	UC+.007875	-.013827	-.009239	UC+.00825	.001
GW	61	1	-.013827	-.009239	UC+.00825	-.011951	-.009808	UC+.008625	.001
GW	62	1	-.011951	-.009808	UC+.008625	-.01	-.01	UC+.009	.001
GW	63	1	-.01	-.01	UC+.009	-.008049	-.009808	UC+.009375	.001
GW	64	1	-.008049	-.009808	UC+.009375	-.006173	-.009239	UC+.00975	.001
GW	65	1	-.006173	-.009239	UC+.00975	-.004444	-.008315	UC+.010125	.001
GW	66	1	-.004444	-.008315	UC+.010125	-.002929	-.007071	UC+.0105	.001
GW	67	1	-.002929	-.007071	UC+.0105	-.001685	-.005556	UC+.010875	.001
GW	68	1	-.001685	-.005556	UC+.010875	-.000761	-.003827	UC+.01125	.001
GW	69	1	-.000761	-.003827	UC+.01125	-.000192	-.001951	UC+.011625	.001
GW	70	1	-.000192	-.001951	UC+.011625	0	0	UC+.012	.001
GW	71	40	0	0	UC+CH	0	0	UC+CH+UE	.001
GE	0
GN	-1
EK
EX	0	5	1	0	0	0	0
FR	0	0	0	0	1090	0
EN

@sigwx

(1) Do not waste your time in trying to adjust dimensions of a 2.4 Ghz WiFi antena to receive1090 Mhz adsb.

(2) Do not blindly believe simulation results.

(3) Forget about simulation results, and forget about adjusting SWR by trimming. Make G7RGQ antenna using dimensions on Microtronics drawing, and put it to side-by-side trial run with a known antenna (FA or Spider). If side by side test show poor resuls, then try tweaking/trimming to improve SWR.

The loops are doing the time delay, needed to change the phase of the signal, for adding the waves.
That’s what the colinear antenna does with the normal shielded portions of coax.

2 Likes

@sigwx
Your best bet is to make both the antennas i.e. your design you have posted above and the G-7RGQ rev3 of Microtronics, and do a side-by-side test of each with a standard antenna of known perfoirmance (FA antenna or Spider antenna).

Note:
In your simulation while building the coil, you have used 20 mm dia of coil (10 mm radius). Since simulation uses mean diameter of coil, the inner dia will be mean diameter - diameter of wire = 20mm - 2 mm = 18 mm

When you actually build the antenna based on your simulation (2 mm dia wire, 20mm dia of coil), make the coils with inner dia = 18 mm.

The wire collinears are very sensitive to coil dimensions.

Mean Diameter of Coil