ADS-B DIY Antenna

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ab cd

Senior Member
Latest findings ....

I've adjusted the tap between 18mm and 28mm in 2 mm steps. The best position seems to be about 26mm but there is very little difference between any of the positions. I made a 2.5mm thick plastic template and used that to form the stub wires so they are all similarly spaced.

In your diagram above you have the stub lengths of 67mm whereas the tap length is 69mm. How important is the 67mm? My 6 element has stub lengths of 68mm but the tap is 69mm.

The 6 segment Franklin has a small range benefit (~10 nm) over the 4 segment but not as much as I expected. I'll try folding the stub wires into a circle today.

Many thanks
Dave
Please see this page to get an idea of mechanical construction for outdoor Franklin:

http://www.lesaunier.com/htm/franklin1_eng.htm
 

ab cd

Senior Member
.......In your diagram above you have the stub lengths of 67mm whereas the tap length is 69mm. How important is the 67mm? My 6 element has stub lengths of 68mm but the tap is 69mm...........

Many thanks
Dave
The dimensions of Stubs between segments:
It's total length (2 horizontal+1 vertical parts) should be half wavelength i.e. 138mm.
So it can be 67.5+5+67.5=138 mm, or 67+4+67=138 mm or 68+2+68=138 mm etc etc....

The dimensions of Central Stub (to which cable tap is connected & which is used for Impedance matching):
It's horizontal length should always be quarter wavelength i.e. 138/2 = 69mm.
So it can be 69+3+69=141 mm or 69+4+69=142 mm or 69+5+69=143 mm etc etc....
69+5+69 gives a better SWR than 69+10+69.
69+3+69 gives a better SWR than 69+5+69.
i.e. lesser the spacing of Central (impedance matching) stub's wires, better the SWR

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trigger

Member
Hi ab cd,
Once again, many thanks for your comprehensive reply. I think antenna design is beginning to sink in ;) 3 weeks ago I thought any length of copper wire was able to pick up every frequency. I now know better.

The Franklin on the Lesaunier website is beyond my capabilities so I'll stick to an indoor version in my loft.

I'll post any updates when I have them.
Dave
 

ab cd

Senior Member
........3 weeks ago I thought any length of copper wire was able to pick up every frequency. I now know better.......
Dave
Your belief that any length of copper wire was able to pickup every frequency is 100% right.
What you missed is that the output (received signal strength or Gain) is greatly enhanced at a particular frequency. This is the frequency where the length of wire matches the wavelength of that frequency. Each frequency has a particular wavelength.

wavelength = speed of radio waves/frequency
speed of radio waves = 300,000,000 meters per second

wavelength = 300,000,000 meters per sec/frequency in Hz

at 1090 MHz (1090,000,000 Hz), the wavelength is 300,000,000/1090,000,000 = 0.275 meters or 275 mm
half wavelength = 275/2 = 137.5 mm say 138 mm
quarter wavelengt
h = 275/4 = 68.75 say 69 mm

if you want to receive a signal of 150 MHz (150,000,000 Hz), its wavelength is 300,000,000/150,000,00 = 2 meters. Hence a half wave segment of 2 meters/2 = 1 meter will give maximum output at 150 MHz, although it will receive all other frequencies including 1090 MHz, but at much lower output (low gain).

By the way, it is not only copper wire which picks up radio signal. Any metal, as well as any object which conducts electricity picks up radio signal.
Since our body is also a conducting object, we also pick up signals of all radio frequencies existing around us. Have you ever noticed that if the telescopic antenna of your FM Radio is in fully collapsed position, you may receive some stations weak, but if you touch the tip of telescopic antenna, the reception improves.
 

trigger

Member
Hi ab cd, thanks for your last post.

I've made another 6 element Franklin and I was VERY careful with the measurements. The new one has an extra 30nm so from my location in Oxfordshire, I can see planes over Brittany. I'm very pleased with the performance.

Many thanks for your support and encouragement.

I might be able to source some copper pipe used for feeding oil for domestic heating. I see another project :cool:
 

ab cd

Senior Member
Hi ab cd, thanks for your last post.

I've made another 6 element Franklin and I was VERY careful with the measurements. The new one has an extra 30nm so from my location in Oxfordshire, I can see planes over Brittany. I'm very pleased with the performance.

Many thanks for your support and encouragement.

I might be able to source some copper pipe used for feeding oil for domestic heating. I see another project :cool:
Congratulations. Your diligence brought fruit.
How about posting pictures of new antenna and screenshot of coverage?
Talking of another project, why not try adding an in-line amplifier?

in-Line Amplifier:
http://www.ebay.co.uk/sch/i.html?_sacat=0&_from=R40&_sop=15&_nkw=satellite+in+line+amplifier&rt=nc&LH_BIN=1

DC Power Inserter for inLine Amplifier:
http://www.ebay.co.uk/itm/DC-Line-Power-Inserter-/161044085914?pt=UK_Sound_Vision_Other&hash=item257ef9bc9a
 
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ab cd

Senior Member
Hi ab cd, thanks for your last post.

I've made another 6 element Franklin and I was VERY careful with the measurements. The new one has an extra 30nm so from my location in Oxfordshire, I can see planes over Brittany. I'm very pleased with the performance.

Many thanks for your support and encouragement.

I might be able to source some copper pipe used for feeding oil for domestic heating. I see another project :cool:
The 4 segment franklin antennas has theoritical gain 7.5 dBi if made very precisely; crudely made may have as low as 3 to 5 dBi
The 6 segment franklin antennas has theoritical gain 8.5 dBi if made very precisely; crudely made may have as low as 4 to 6 dBi

By making VERY precise 6-segment, you ended up from crude 4-segment 3 dBi to precise 6-segment 8.5 dBi, and obtain an advantage of 8.5-3 = 5.5 dB

Now try using an amplifier of 20 dB gain and you get an advantage of 20 dB, 4 times what you have gained by making a precise 6 element antenna!!

in-Line Amplifier:
http://www.ebay.co.uk/sch/i.html?_s...kw=satellite in line amplifier&rt=nc&LH_BIN=1

DC Power Inserter for inLine Amplifier:
http://www.ebay.co.uk/itm/DC-Line-P...?pt=UK_Sound_Vision_Other&hash=item257ef9bc9a

See below picture of my INLINE AMPLIFIER SETUP. I am using a 13-18 dB RCA Amplifier and a home-made Power Inserter:


inline amplifier setup.jpg



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ab cd

Senior Member
...........I think antenna design is beginning to sink in ;) 3 weeks ago I thought any length of copper wire was able to pick up every frequency. I now know better.........

Dave
I have run a frequency sweep (i.e. varied frequency over a range) for a 1-meter Center-fed dipole as an example case for you.

1-meter center-fed dipole.png


The plot of Gain vs Frequency & SWR vs Frequency show that:
Although this antenna will receive signals at all frequencies (as you have correctly believed), it gives the best Gain (2.71 dB)+SWR (1.26) combination at only one frequency i.e. 143 MHz.
It also shows that another frequency i.e.443 MHz it gives a good SWR (1.26), but Gain is much lower (0.64 dB) than Gain at 143 MHz.
Also the Radiation Patterns are distinctly different at 143 & 443 MHz.

What is relationship between 143 Mhz & 1-meter?
At 143 MHz the Wavelength = 299,000,000/143,000,000 = 2 meters
Wire (Dipole) length = 1 meter
Hence a center-fed Wire gives best response at the frequency where length of Wire is equal to 1/2 wavelength.

See Sweep Plot results below:

SWR at 143MHz & 443MHz : 1-meter Dipole
1-meter dipole SWR vs Freq sweep.png


Gain at 143MHz & 443MHz : 1-meter Dipole
1-meter dipole gain vs freq sweep.png


Radiation Pattern 1-meter dipole at 143 MHz
1-meter dipole pattern freq 143 Mhz.png


Radiation Pattern 1-meter dipole at 443 MHz
1-meter dipole pattern freq 443 Mhz.png
 
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trigger

Member
Hi ab cd,

Thanks for the above - interesting.

I'm running some plots at the moment so will post later. Do you have Google Earth on your PC? I've been converting the plot files to .kml

I've also purchased the amplifier and power inserter you recommended. Does it matter what voltage you use to power the inserter? I'm not sure I have a 15 volt one.

Regards
Dave
 

ab cd

Senior Member
Hi ab cd,

Thanks for the above - interesting.

I'm running some plots at the moment so will post later. Do you have Google Earth on your PC? I've been converting the plot files to .kml

I've also purchased the amplifier and power inserter you recommended. Does it matter what voltage you use to power the inserter? I'm not sure I have a 15 volt one.

Regards
Dave
Yes I have google earth & .kml works fine.

I posted a link to ebay listing 43 different inLine amplifiers. I dont know which one you have ordered. If you have receieved it, please post a camera picture of it's front plate on which all details are written. If you have not yet received it post the link to ebay page for this item.

Generally satellite amplifiers are rated for 14 to 18 volts, but work ok on any voltage between 12 to 20 volts. Your 15 volt supply should be ok. However it can be confirmed when I see the label of the amplifier you got/ordered.







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ab cd

Senior Member
If you do not have an electronics parts shop nearby, you can order Splitter, Capacitor & Inductor on Line very cheap, but will have to wait 1 to 2 months due to surface/sea shipping from China:

1 Pc 2-WAY CABLE TV SPLITTER 5-900MH - FREE Standard Int'l Shipping - US $1.49
http://www.ebay.ca/itm/2-WAY-CABLE-TV-SPLITTER-5-900MH-Digital-Analogue-Satellite-Coaxial-Out-Connector-/280766417601

30 Pcs 220pF 50V Ceramic Disc Capacitor - FREE Standard Int'l Shipping - US $0.99
http://www.ebay.ca/itm/30-Pcs-220pF-50V-Ceramic-Disc-Capacitor-Free-Shipping/321028278208

10 Pcs 4.7 uH Inductor 1/2W - FREE Standard Int'l Shipping - US $1.49
http://www.ebay.ca/itm/10-x-4-7uH-4-7-uH-0307-COLOR-RING-Inductor-1-2W-3-7MM-/330452964551
 
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ab cd

Senior Member
.....I've also purchased the amplifier and power inserter you recommended. Does it matter what voltage you use to power the inserter? I'm not sure I have a 15 volt one.

Regards
Dave
VERY IMPORTANT: DO NOT connect power spply without first inserting a DC Blocking Capacitor between Amplifier and Antenna..

The reason is that Franklin, Slim Jim, and J-Pole antennas all have a shorted stub, through which DC will short and fry your inserter & DC Adaptor.

If you do not have a capacitor, you can use 2nd power inserter between amplifier and antenna, but WITHOUT connecting DC adaptor to it. I will post a drawing showing how to do this.


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trigger

Member

ab cd

Senior Member
Hi ab cd,
Power inserter http://www.ebay.co.uk/itm/DC-Line-Power-Inserter-/161044085914?ssPageName=ADME:L:OC:GB:3160
Amplifier http://www.ebay.co.uk/itm/SAC-20dB-IN-LINE-SATELLITE-AMPLIFIER-SIGNAL-BOOST-LOW-NOISE-4DB-MAX-BUYME-/120963222204?ssPageName=ADME:L:OC:GB:3160

I recently bought a bag of mixed capacitors from Maplin (Radio Shack).
Thanks for the warning about the power amp and the shorted stubs. I'll wait for your diagram.

Plots will be posted later today.
Thanks
Dave
If you have capacitor, then all you need is a TV Splitter housing to connect capacitor between antenna & amplifier. See below camera photo of my setup which shows a home-made power-inserter on one side of amplifier & a home-made dc-blocking-capacitor on the other side of amplifier:
DSC02844R.JPG
 
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trigger

Member
Hi ab cd,
Once again, thanks for your assistance. The bits from ebay should be delivered today.

OK, it looks like I can't attach .kml files so I've renamed them to .txt. You should be able to rename them back to .kml

Let me know if this doesn't work.
Regards
Dave
 

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ab cd

Senior Member
Hi ab cd,
Once again, thanks for your assistance. The bits from ebay should be delivered today.

OK, it looks like I can't attach .kml files so I've renamed them to .txt. You should be able to rename them back to .kml

Let me know if this doesn't work.
Regards
Dave
Files did work with Google Eatrh after changing from .txt to .kml
wow! Great. Congratulations.
Sure with amplifier the circle will expand to 450 kM (250 nm).
Waiting for your results with amplifier.
 

trigger

Member
SETUP WITH DAVE's EQUIPMENT

View attachment 143

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Hi ab cd,

All the bits came yesterday so I've set up as shown in the diagram above. I could only find a 12v power source so I've used that. Without the power switched on I get almost no signal from the antenna. When the power is switched on I get roughly the same range as I did without the amplifier in line. Do you think the lack of range with the amp is due to the lower voltage? You mentioned that the amplifiers work best at 15v - 24v

Thanks
Dave
 
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