ADS-B DIY Antenna

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jepolch

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I just put together this dipole. Took about 15 minutes. I got excited about putting one up after seeing ab cd's test results above. I'll put it up on the roof in a little while. It's a beautiful day to be outside.
 

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jepolch

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And here's the dipole on the mast, circled in yellow. Yet another antenna that can't match the performance of my spider! Spider is getting about 350 msg/sec vs. dipole's 295 msg/sec. They are both at the same height (within inches), they both have the same amp, and the same length and type of coax. The difference is the power supply and injector. After a while I'll swap the power injector and power supply between the antennas and see what effect it has.
 

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giacomo1989

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I just put together this dipole. Took about 15 minutes. I got excited about putting one up after seeing ab cd's test results above. I'll put it up on the roof in a little while. It's a beautiful day to be outside.
The only fact about that dipole is the feeding line that make's the dipole longer than you would.
For better performance you should connect the dipole to the amplifier using the lesser cable you can. (0 cm :) )

PS. Indeed another neat antenna! Compliments! :)
 

Sjacket99

Member
Just FYI,
If you over have a hard time or if it's a pain to found the IP address for your Pi or anything. If you have a tablet or phone, even PC. install a app called "fing". It works pretty good. Gives the IP's and MAC address's of everything that is connected to your network.
 

jepolch

Active Member
The only fact about that dipole is the feeding line that make's the dipole longer than you would.
For better performance you should connect the dipole to the amplifier using the lesser cable you can. (0 cm :) )

PS. Indeed another neat antenna! Compliments! :)
I didn't know that. I actually made the feed line longer than my other dipole because when I used the first dipole I made (in the house) it seemed like it was directional. In other words, it seemed like the coax connector sitting right next to the dipole was blocking the signal from that direction. I have some male to male connectors coming from China (someday). When I get them I'll attach the amp as close to the dipole as possible and give it another try.

Edit: I just took a look at eBay and found that the connectors were estimated to be here already (estimated delivery Tue, Jan 13 - Tue, Jan 27) Hopefully, they'll be here soon.
 

ab cd

Senior Member
Dipole Gain & SWR vs Length of it's Limbs
Theory says SWR=1 when each limb is 1/4 wavelength (68mm)
Simulation shows SWR=1 when each limb is few mm less than 1/4 wavelength (63mm)!!
Which one to believe??? :mad:
I will have to test this by making a 68mm dipole, VRS range plot for 24hrs, trim 2mm, VRS range plot again for 24hrs, trim another 2mm, test again for 24hrs. This is driving me crazy. :mad:

dipole vs length.PNG
 
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giacomo1989

Member
Dipole Gain & SWR vs Length of it's Limbs
Theory says SWR=1 when each limb is 1/4 wavelength (68mm)
Simulation shows SWR=1 when each limb is few mm less than 1/4 wavelength (63mm)!!
Which one to believe??? :mad:
I will have to test this by making a 68mm dipole, VRS range plot for 24hrs, trim 2mm, VRS range plot again for 24hrs, trim another 2mm, test again for 24hrs. This is driving me crazy. :mad:

View attachment 1077
P

As you can see from the theory imaginary part of the impendence does not became zero at half lambda but a little earlier. So simulation is ok.. Maybe 5mm are too much....
Screenshot_2015-02-08-23-14-42.png
 

jepolch

Active Member
Dipole Gain & SWR vs Length of it's Limbs
Theory says SWR=1 when each limb is 1/4 wavelength (68mm)
Simulation shows SWR=1 when each limb is few mm less than 1/4 wavelength (63mm)!!
Which one to believe??? :mad:
I will have to test this by making a 68mm dipole, VRS range plot for 24hrs, trim 2mm, VRS range plot again for 24hrs, trim another 2mm, test again for 24hrs. This is driving me crazy. :mad:

View attachment 1077
Driving me crazy, too! What about the length of the feed line? Does that matter?
 

jepolch

Active Member
How do you see the messages per second?
Thanks,
Doug
Using dump1090-mutability. It gives more information in the dump web page. I'm attaching an older screenshot from when I had a poor antenna on Pi 3. But you will see the stats that dump1090-mutability provides.
 

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ab cd

Senior Member
Driving me crazy, too! What about the length of the feed line? Does that matter?
Well, length of feed line = distance from center of Dipole to Receiver.
It is ok to keep the amplifier at some distance from Dipole, if that is convenient.
The length of coax piece from dipole to F-connector/Amplifier is irrelevant and should not affect performance.
 

PeterPlane

New Member
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Sjacket99

Member
I've got this antenna on order from Bulgaria:

http://www.ebay.com/itm/ADS-B-omni-...for-SBS-Radarbox-micro-ADSB-RTL-/191506633936

Edit: This would have been my first choice, but it's 3 times as much:
http://www.dpdproductions.com/page_vhf_air.html#adsbout

I'll let you guys know how it works out after it arrives.

Jepolch, I'm jealous of your tower - looks nice. I live in a covenant restricted neighborhood and can't put up any external antennas.

I have one of these on the way to my door step. Hopefully I get it this week. I will also let everyone know, what I think about it.
 

ab cd

Senior Member
And here's the dipole on the mast, circled in yellow. Yet another antenna that can't match the performance of my spider! Spider is getting about 350 msg/sec vs. dipole's 295 msg/sec. They are both at the same height (within inches), they both have the same amp, and the same length and type of coax. The difference is the power supply and injector. After a while I'll swap the power injector and power supply between the antennas and see what effect it has.
What length of limbs are you using? Try trimming limbs down to 66mm. Sigh! Another trip to roof & pulling down the mast then up again :(
 

jepolch

Active Member
What length of limbs are you using? Try trimming limbs down to 66mm. Sigh! Another trip to roof & pulling down the mast then up again :(
69 mm. Yeah, it's a huge chore and I need to find a better way. I'm thinking of getting steel poles at Home Depot and putting a 40 foot mast based on the ground. Give the roof a break. But the problem is how to raise and lower the steel mast/tower. I guess some sort of hinge with a pulley system? 40 feet would be about 5 feet higher than the antenna is now. 1 inch by 10 foot steel poles are less than 10 bucks at Home Depot, if I recall.
 

jepolch

Active Member
I've got this antenna on order from Bulgaria:

http://www.ebay.com/itm/ADS-B-omni-...for-SBS-Radarbox-micro-ADSB-RTL-/191506633936

Edit: This would have been my first choice, but it's 3 times as much:
http://www.dpdproductions.com/page_vhf_air.html#adsbout

I'll let you guys know how it works out after it arrives.

Jepolch, I'm jealous of your tower - looks nice. I live in a covenant restricted neighborhood and can't put up any external antennas.
Move to the country. My neighbor raises sheep. :) (quiet, no smell)

Making those antennas must be a major cottage industry in Bulgaria. :D I'm tempted to take the plunge for one of those, too, but I'm just worried there's just a little whip inside it like the one that comes with the dongle. If anyone gets one and thinks it's a good buy, I may have to get one.
 

jepolch

Active Member
Well, length of feed line = distance from center of Dipole to Receiver.
It is ok to keep the amplifier at some distance from Dipole, if that is convenient.
The length of coax piece from dipole to F-connector/Amplifier is irrelevant and should not affect performance.
Thanks. I guess I'm back up to the roof to do some trimming. :eek: Let me tell you, I'll be 63 next month and messing with that antenna pole is hard work. I was whipped after my stint up there today. Every time I go up there I hope it's the last time for weeks. And then I'm back up there two days later!
 
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