ADS-B DIY Antenna

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ab cd

Senior Member
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
1. Without power, Amplifier REDUCES the signal strength. It is quiet normal that you got no signal when amplifier is there, but power is missing.

2. The Amplifier are rated to operate on voltages of the Satellite Dish LNB. Most dish LNB operate on 14V to 18V. The amplifiers have some tolerance, so they operate from 12V to 20V. Your 12V should be OK. A bit higher voltage (e.g. 15V) may somewhat improve the range.

I am surprised to note that you get roughly the same range with & without amplifier. This is strange. Something is wrong.
 
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ab cd

Senior Member
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
Dave, can you please post some camera picture of your setup? Closeups to clearly show details may be helpful to sort the issue.

 

ab cd

Senior Member
Hi ab cd,
I had to take the antenna and amp down in order to photograph it. The actual distance between the dongle and the power injector is about 4 metres.

I'll refit everything this evening and report back.

Hope the images throw some light on the problem.
Thanks
Dave
Hi Dave,
Great that you have posted Photos.
Sorry, I did not know that you have installed all high up and need to take it down (mine all is at man's height & ground level).
SEEN ALL 4 PHOTOS. APPARENTLY ALL SEEMS OK.

Just two things which are not very likely to be wrong, but worth checking:

1) Is DC positive connected to Center Wire and negative to Braid/Body of Inserter? Generally in the AC/DC Adapter, the DC pin has Center Hole Positive, Outer Barrel Negative. This is shown on the label of your adapter also. I hope that the piece of Coaxial cable between DC adapter Pin & Inserter has coax center wire connected to center hole of pin & braid to the barrel of the pin.

2) The Power inserter used as DC Blocking and connected to LNB terminal of Amplifier has HF connected to Amplifier & HF+DC terminal connected to antenna. This should be ok, but we dont know exactly what circuit is inside the Inserter. In order to be on safe side, connect it the other way round, i.e. HF+DC terminal to Amplifier & HF terminal to antenna.

If all fails, try increasing DC voltage from 12V to 15V. This is a costly option as you have to purchase another adapter with higher voltage, and even then it may not bring success. That is why I kept it as last resort.
Regards,
abcd
 
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trigger

Member
Hi ab cd,
Checked out your suggestions.
The power is correctly wired up. I put a meter across the wires and the positive is on the centre core of the coax. There is also 12 volts coming out of the opposite end of the amplifier (opposite end to the power injector). I've also connected the amplifier to my satellite TV and it has increased the signal quality to 100% for all channels but with some decrease in signal strength.

I also swapped the orientation of the DC blocker at the antenna end of the amplifier but nothing changed. There are zero volts here.

I've attached 2 .kml files as .txt showing that the amplifier has little effect. One plot is with the amplifier attached and the other without the amplifier. Please note that the antenna has now been repositioned into my garage so the plots are not comparable with the ones I attached last week.

I will see if I can source a 15v supply.

Thanks for your help,
Dave
 

Attachments

ab cd

Senior Member
Hi ab cd,
Checked out your suggestions.
The power is correctly wired up. I put a meter across the wires and the positive is on the centre core of the coax. There is also 12 volts coming out of the opposite end of the amplifier (opposite end to the power injector). I've also connyected the amplifier to my satellite TV and it has increased the signal quality to 100% for all channels but with some decrease in signal strength.

I also swapped the orientation of the DC blocker at the antenna end of the amplifier but nothing changed. There are zero volts here.

I've attached 2 .kml files as .txt showing that the amplifier has little effect. One plot is with the amplifier attached and the other without the amplifier. Please note that the antenna has now been repositioned into my garage so the plots are not comparable with the ones I attached last week.

I will see if I can source a 15v supply.

Thanks for your help,
Dave
If 15V DC Adapter does not solve the problem, then there is only one culprit left: the amplifier itself - it is defective. Though this is unlikely, but it does happen. It happened with my first amplifier (unbranded), which I have purchased from eBay. Luckily I found a large electronics parts store in my town, where I found one from very reputable manufacturer (RCA) & it worked like Genie of Alladin's Lamp!!!

I purchased it from local store for $4.
It is available on ebay, but very costly (cost+shipment to UK is US $10.96 + US $15.45 = US $26.41 = 26.41 x 0.6 = Pound Sterling 15.85)

http://www.ebay.com/itm/RCA-Inline-Satellite-Amplifier-/231151991005



.
 
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jmcq

New Member
hi all:

a VERY interesting thread to say the least. i have a couple RCA D903 amps ordered, along with the caps and chokes and plan to convert my 10 section (@ 110mm) coax collinear to a single amp setup with 15v DC. i can't wait to try this out. currently, i am maxxed at 74 NM of range with the antenna hanging in the window of my 1st-floor den. here's a pic of approx. 36 hr run with my non-amped setup. the white 'max range' is what i have currently. after building my amp, i will post a comparison. might take a week or two...

 

jmcq

New Member
ab cd, can you post a pic of the label on your DC power supply or simply report the specs or it here? i am looking at 15v and 18v, but need to know the amps/mA your power supply is rated at. i'm guessing that i'll be ok with an 18v with 1000 mA or less, but want to be sure.
 

ab cd

Senior Member
ab cd, can you post a pic of the label on your DC power supply or simply report the specs or it here? i am looking at 15v and 18v, but need to know the amps/mA your power supply is rated at. i'm guessing that i'll be ok with an 18v with 1000 mA or less, but want to be sure.
Each of my two inLine amplifier units (Photo 1) take 25-40 mA .
My Power Supply Unit (Photo 2) is rated for 14V DV, 350 mA, and can easily spply 8 amplifiers.

Amplifier-RCA D903.gif


DC-Power-Adapter.gif
 
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trigger

Member
Hi jmcq & ab cd,

I've been making progress with my setup and I can confirm that the amplifier above suggested by ab cd works. I've tried 2 amplifiers which cover the frequency 47 - 2400 Mhz and they don't work in this scenario. They are however, fine for boosting a satellite signal. I bought one which covers 950 - 2300Mhz and that works fine. http://www.ebay.co.uk/itm/Satellite-amplifier-signal-booster-Sky-amp-sat-lmb-lnb-/350657754545?pt=UK_Sound_Vision_Other&hash=item51a4d4b5b1
Maybe someone can explain why?

My power supply is 12v. I've also tried a 15v supply but it is pushing out over 24v and the amplifier gets warm:eek:

I've attached an image from my Raspberry Pi this morning. Coverage is approx. 180nm

I'm using a homemade Franklin antenna. Details are in the above posts
 

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trigger

Member
Hi ab cd,
I've made a new antenna following this design http://martybugs.net/wireless/collinear.cgi I've made the 5 loop version shown towards the bottom of the page with dimensions
λ/2 of 137mm and 3λ/4 of 206mm. The whip I guessed at 190mm. I made it from 1.5mm copper wire.

The antenna is working fine and seems comparable with my Franklin. I will be running some tests in the next couple of days. The advantages are that I don't need the power inserter above the amplifier as the antenna is not "shorted" and it should be easier to mount the antenna in a tube for outdoor use.

Have you any thoughts about the diameter of the loops? I made them by wrapping the wire around a 15mm piece of dowel. Should the circumference be a fraction of the wavelength?

Regards
Dave
 

ab cd

Senior Member
Hi ab cd,
I've made a new antenna following this design http://martybugs.net/wireless/collinear.cgi I've made the 5 loop version shown towards the bottom of the page with dimensions
λ/2 of 137mm and 3λ/4 of 206mm. The whip I guessed at 190mm. I made it from 1.5mm copper wire.

The antenna is working fine and seems comparable with my Franklin. I will be running some tests in the next couple of days. The advantages are that I don't need the power inserter above the amplifier as the antenna is not "shorted" and it should be easier to mount the antenna in a tube for outdoor use.

Have you any thoughts about the diameter of the loops? I made them by wrapping the wire around a 15mm piece of dowel. Should the circumference be a fraction of the wavelength?

Regards
Dave
Thanks for posting the link to antenna page http://martybugs.net/wireless/collinear.cgi.
Had a quick look of the webpage. Initial study results are as follows. More in-depth study is required to understand it's principle & performance:

You did the right thing. This antenna's dimensions in mm are based on wavelength of Wireless LAN frequencies (2.412GHz to 2.484GHz). For ADS-B use, lengths are to be based on ADS-B frequency of 1090 MHz, wavelength 275 mm. So λ/2=137.5 mm and 3λ/4 = 206 mm

Seems to be a variation of original Franklin.
The original Franklin operates on principle of collapsing over themselves all alternate half-wave sections to nullify those section's field.

In this one instead of flat-folding, the alternate half waves are folded in circular form, giving similar result of nullifying alternate section's fields.

Quarter wave sections are added to vertical 1/2 wave sections making it 3/4 wave, reducing impedance from very high of 1/2 wave original Franklin (say 1600 ohms) to low (closer to 75 ohms), eliminating need for Impedance matching stub and adjustments.

These principles are also used in 5/8 wavelength antennas with phasing coil.

I will try to run a computer simulation to see it's performance. If the claims of author/designer are correct, then it is a better antenna than Original Franklin, as:
(1) It does not require impedance matching.
(2) It can be fitted inside a pipe, making it suitable for outdoor Installation.
(3) It is end fed making outdoor installation easier.
 
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ab cd

Senior Member
..........My power supply is 12v. I've also tried a 15v supply but it is pushing out over 24v and the amplifier gets warm:eek:.........
My power supply is rated for 14V but measured output voltage is 17V. Since it is still within the upper 18V limit, my amplifier working fine with it without getting overheated.

It is better to use newer "Switchable" type Power supplies.
Compared to old design. these "switchable" power supplies have:
(1) outputs much closer to rated value
(2) smoother output
(3) are much lightweight compared to old design (these don't have a transformer inside).

"Switchable" is mentioned in specifications & on the Label of these power supplies. If you are shopping in a store where you have these physically available, you can also tell which one is switchable and which one is old type simply by comparing their weights.

Have you ever noticed that Cell/Mobile Phone chargers are now much smaller & lighter than those say 10-15 years ago? These are switchable type.
 

ab cd

Senior Member
.......Have you any thoughts about the diameter of the loops? I made them by wrapping the wire around a 15mm piece of dowel. Should the circumference be a fraction of the wavelength?.......
Regards
Dave
In the page you referred http://martybugs.net/wireless/collinear.cgi, the author recommended to use 20mm dia coil, circumferential length = π d = 3.14 x 20 mm = 62.8 mm, approximately 1/2 λ at wireless LAN frequency 2.4 GHz.
However another page referred by above page http://cheatthezone.tripod.com/wireless/colinear.html gives coil dia only 10mm which will make coil circumference 32.4mm i.e. 1/4 λ. This is confusing.
Without any theoretical background & formulas in hand, the best way to find out is to make two antennas, one with 44 mm dia coil (circumference= π x 44 = 138mm =1/2 λ) & other with 22mm dia coil (circumference= π x 22 = 69mm =1/4 λ), and put these on trial and compare results.
 

jmcq

New Member
Hi jmcq,
I notice that you are using ADSB#. Have you tried RTL1090? On my Windows laptop I'm using RTL1090 "SCOPE" BETA VERSION 3 (153) and find it very good. Scroll down the page for the downloads.
http://rtl1090.jetvision.de/
Regards
Dave
Hi Dave. Yep, I think I have about all of them. I like the RTL1090 beta and use it to feed FlightRadar. I have two more dongles ordered and will run all 3 on separate antennae. The two new ones will provide another 1090mhz source alongside a 145mhz source for ATC audio. Components are just starting to come in, so I will be building some more this coming weekend.
 
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ab cd

Senior Member
Hi ab cd,
I've made a new antenna following this design http://martybugs.net/wireless/collinear.cgi I've made the 5 loop version shown towards the bottom of the page with dimensions
λ/2 of 137mm and 3λ/4 of 206mm. The whip I guessed at 190mm. I made it from 1.5mm copper wire.

The antenna is working fine and seems comparable with my Franklin. I will be running some tests in the next couple of days. The advantages are that I don't need the power inserter above the amplifier as the antenna is not "shorted" and it should be easier to mount the antenna in a tube for outdoor use.

Have you any thoughts about the diameter of the loops? I made them by wrapping the wire around a 15mm piece of dowel. Should the circumference be a fraction of the wavelength?

Regards
Dave
To properly compare two antennas, their performance should be compared WITHOUT AMPLIFIER.
The reason is that the amplifiers have AGC (automatic gain control). They increase gain for weaker input, reduces gain for strong input, giving fairly equal output & hence false impression that both are equal.
 
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