Originally posted by abcd567
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Originally posted by Rooster View Postdo you have a link to the Franklin antenna please ?
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COMPARISON OF COVERAGE OF FOUR (4) DIFFERENT ANTENNAS
WITHOUT AMPLIFIER
VERY SHORT COAXIAL CABLE (11 FEET / 3.5 METERS) BETWEEN ANTENNA & RECEIVER
1) DIPOLE: 1/2 WAVELENGTH
Dipole-halfwave.jpg
2) FRANKLIN DIPOLE: 1/2-OVER-1/2 WAVELENGTH
Franklin Dipole-half-over-half wavelength.jpg
3) COAXIAL COLLINEAR: 3-AND-1/2 ELEMENTS (EACH ELEMENT 1/2 WAVELENGTH) WITH SHORTED TOP
CoCo-3-and-half+shorted-top.jpg
4) COAXIAL COLLINEAR: 3-AND-1/2 ELEMENTS (EACH ELEMENT 1/2 WAVELENGTH) + 1/4 WAVELENGTH WHIP
CoCo-3-and-half+quarter-whip.jpg
Coaxial Collinear 1/2 wave element =1/2 x wavelength @ 1090 MHz x coaxial cable velocity factor
For RG6 cable with FPE (Foamed PolyEthylene) insulation, velocity factor = 0.8
Coaxial 1/2 wave element =1/2 x 27.5 cm x 0.8 = 11 cm
Tests for these antennas WITH Amplifier will be posted when completed.
.Last edited by abcd567; 2013-12-01, 22:03.
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Originally posted by peterhr View PostHi guys,
Is the velocity factor of a cable frequency dependent?
What is velocity factor of LMR400 at about ADS-B frequency?
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To: abcd567
Very impressed. Nice work. Much appreciated.
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Less than what?
I think we are getting tied up in technical mumbo jumbo a little here.. The antenna location is the most important factor (including your house!)
I am in the Midlands, UK... And I can see aircraft near the Irish coast... The Scandinavian coast, the edge of Scotland and down to Devon... All with a £10 dongle and 10 element coco fed with 15 metres of satellite cable, at gutter height!
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Originally posted by abcd567 View PostCongratulations.
Welcome to CYYZ ADS-B Radar community.
Sure you are going to get a great coverage with FR24 supplied Antenna mounted on the 150 feet high tower, and the Low Attenuation Coaxial cable LMR400/RG8 which you will use to hook-up antenna to receiver.
I am waiting eagerly to see your results.
I am not using equipment supplied by FR24.
Instead, I am using my own low cost equipment, much of which, including antenna, is home-brewed, and the antenna is located indoors. Even then I am getting a reasonably good coverage. Please see attached pictures of my setup:
Picture 1: Coverage Map - CYYZ area
Picture 2: 4-Element Franklin Co-Linear Dipole Antenna - Home Brewed - Located Indoors.
Picture 3: in-Line Amplifier & Bias-T (DC Power Injector) - Home-Brewed.
Picture 4: DVB-T SDR USB Receiver connected to Desktop Computer.
Picture 5: Schematic Diagram of my Setup.
[ATTACH=CONFIG]2666[/ATTACH] [ATTACH=CONFIG]2667[/ATTACH] [ATTACH=CONFIG]2668[/ATTACH] [ATTACH=CONFIG]2669[/ATTACH] [ATTACH=CONFIG]2670[/ATTACH]
It looks like two coax cables are joined into one F-connector? How did you do this? I'm waiting on my dongle and am looking into home made Antenna options.
Mike
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Originally posted by peterhr View PostHi guys,
Is the velocity factor of a cable frequency dependent?
What is velocity factor of LMR400 at about ADS-B frequency?Originally posted by andyk1 View PostLMR400 has a velocity factor of between .80 and .85 depending on manufacture. Need to see product specs for each company. Am sure you already know LMR400 is 50 ohm's. To be honest I don't know about freq dependent but I do know that LMR400 has less signal loss over longer distance.
Velocity factor is mainly dependent on Dielectric (Core Insulation Material).
Most of LMR400 manufacturers use Foamed Polyethylene and specify 0.85 Velocity factor.
Average values of VF are given below. For exact values, refer to Cable Manufacturer's Data Sheets.
VF for solid polyethylene (PE) is about 0.66
VF for foam polyethylene (FPE) is about 0.78 to 0.88
VF for air is about 1.00
VF for solid polytetrafluoroethylene (PTFE) is about 0.70
VF for foam polytetrafluoroethylene (FPTFE) is about 0.84
Attenuation (Loss) per meter is dependent on frequency, and increases with increasing frequency.
For LMR400, attenuation at 30 MHz is 2.2 dB/100 meters, at 900 MHz it is 12.8 dB/100 meters, and at 2500 MHz it is 22 dB/100 meter.
The Velocity Factor (VF) is determined by the permeability and permittivity of the Dielectric.
VF = 1/{square root of (relative permeability of dielectric x relative permittivity of dielectric)}
where relative means value for dielectric compred to value for vacuum.
Velocity factor of Vacuum is EXACTLY 1.00000000000000000000......
Velocity factor of Air is APPROXIMATELY 1.0 .....
.Last edited by abcd567; 2013-12-02, 16:11.
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Originally posted by mickopla View PostHi, With regards your Antenna
It looks like two coax cables are joined into one F-connector? How did you do this? I'm waiting on my dongle and am looking into home made Antenna options.
Mike
See the pictures below. The "Enlarged View" rectangle at top-left of picture 3 gives answer to your question.
Are you going to use in-Line Amplifier? If not, Franklin without Amplifier is hopeless because of it's high impedance. With in-Line Amplifier it gives good results.
Try half-wave Dipole also. It is simplest and shortest (2 legs, one up one down, each 6.8 cm) and has an impedance of 75 ohms which matches with impedance of coaxial cable and the Dongle. See my yesterday's post above for comparison of various antenna WITHOUT Amplifier.
The DVB-T USB Dongle's built-in pre-Amplifier is not powerful enough for ADS-B, as it is designed for Local TV reception, where signals are strong. Adding an in-Line Amplifier greatly improves Range.
Antenna-Franklin-Assembly-Steps-1.jpg Antenna-Franklin-Assembly-Steps-2.jpg Antenna-Franklin-Assembly-Steps-3.jpg Antenna-Franklin-Assembly-Steps-4.jpg DSC02576-R90c.jpgLast edited by abcd567; 2013-12-02, 01:21.
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Originally posted by abcd567 View PostIt is ONE coax + an extra core-only, inserted into shield/braid of coaxial cable.
See the pictures below. The "Enlarged View" rectangle at top-left of picture 3 gives answer to your question.
Are you going to use in-Line Amplifier? If not, Franklin without Amplifier is hopeless because of it's high impedance. With in-Line Amplifier it gives good results.
Try half-wave Dipole also. It is simplest and shortest (2 legs, one up one down, each 6.8 cm) and has an impedance of 75 ohms which matches with impedance of coaxial cable and the Dongle. See my yesterday's post above for comparison of various antenna WITHOUT Amplifier.
The DVB-T USB Dongle's built-in pre-Amplifier is not powerful enough for ADS-B, as it is designed for Local TV reception, where signals are strong. Adding an in-Line Amplifier greatly improves Range.
[ATTACH=CONFIG]3006[/ATTACH] [ATTACH=CONFIG]3007[/ATTACH] [ATTACH=CONFIG]3009[/ATTACH] [ATTACH=CONFIG]3008[/ATTACH] [ATTACH=CONFIG]3010[/ATTACH]
All the houses around me are two storey high so there are no big obstructions that would block the signal. I'm toying with the idea of an attic install or outside at roof height. Would there be a big percentage loss level having the Antenna indoors in my attic rather than outside? The Antenna height would be more or less the same.
Mike
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Originally posted by mickopla View PostThanks for the advice. Very much appreciated. I'm open to all types of Antenna and have already made the collinear antenna which is mentioned on this thread. I have ordered an in line amp to increase my options.
All the houses around me are two storey high so there are no big obstructions that would block the signal. I'm toying with the idea of an attic install or outside at roof height. Would there be a big percentage loss level having the Antenna indoors in my attic rather than outside? The Antenna height would be more or less the same.
Mike
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Originally posted by mickopla View Post.....All the houses around me are two storey high so there are no big obstructions that would block the signal. I'm toying with the idea of an attic install or outside at roof height. Would there be a big percentage loss level having the Antenna indoors in my attic rather than outside? The Antenna height would be more or less the same.
Mike
Originally posted by peterhr View PostI'd stick it outside if possible - I posted some plots a little way back in this thread that show the sharp range cutoff from 300km to 50km cause where my antenna falls in the 'shadow' of the next door neighbours roof.....
If you look at my coverage plots posted two days ago, you will notice sharp drops in coverage in many directions. These are caused by buildings higher than my antenna. My antenna therefore can not "see" horizon in those directions, and a sharp drop in range resulted. I live in an apartment, and building management does not permit installation of individual antennas on roof of the building. I am restricted to locate my antenna indoor near windows.
Sent from my N762 using Tapatalk 2Last edited by abcd567; 2013-12-02, 16:34.
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Originally posted by peterhr View PostI'd stick it outside if possible - I posted some plots a little way back in this thread that show the sharp range cutoff from 300km to 50km cause where my antenna falls in the 'shadow' of the next door neighbours roof. One I get some new downfeed and time on a nice day to do it - I'll be lifting my mast by another 1.5m section. (I have wall mounted T & K brackets, holding 2 sections of Sectional Aluminium 20' Pole Mast Set - 4 x 5ft Swaged Pole Sections Slot 1.25" OD (32mm Diameter) - bought from Delcom Systems Ltd)
Mike
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