ADS-B DIY Antenna

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Changed settings of modesdeco2 (addeded argument --gain 49.6 at start of arguments list), rebooted, number of planes half of dump1090-mut. see screenshots.
Stopped using modesdeco2. Now using dump1090-mutablity.
View attachment 1046 . View attachment 1047
They both use their own filtering algorithms. I know nothing about modesdeco2, but dump1090-mut uses a known set of filters? I'm searching for the right word here. My mind is still foggy from this cold. But what I'm trying to say is that it seems dump is more configurable and reading the developer's (obj) posts on FlightAware you can learn how best to configure his program. Also, he is very prompt in answering questions about his fork of dump1090. It took me a while to switch to dump-mut, but I like it and it works for me.
 
1. Which OS you are using, Windows, Raspbian, or other versions of linux?
Raspian with :

Linux raspberrypi 3.18.5+ linux kernel and custom built rtlsdr drivers from keerned repository.

2. Have you purchsed helium filled baloons recently? :D

No sir. I'm in search of thing to build a pole to put on my roof but first i've to solve the "best antenna dilemma" and solve some wiring issue that I may will have.
 
Well, another antenna and another disappointment. I put up the colinear today. It was windy and I didn't feel like I had the strength, but I got it installed. Only to find it's performing about 25% as well as my 8-legged spider. Wow! So disappointing. I dread doing all that work again, but I will have to take that antenna down and replace it with something else, probably my original cantenna.
 

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It might be the PVC pipe. Both of the coco's and this colinear were all housed in the same piece of PVC and none of them performed well. The PVC is supposed to be non-metallic, but I'm suspecting it might be the culprit.
 
@jepolch
Somebody (peterhr?) suggested putting a small piece of the pipe into a microwave oven and seeing if it gets hot. Make sure you put a vessel with water in there too so you don't hurt the oven.
 
It might be the PVC pipe. Both of the coco's and this colinear were all housed in the same piece of PVC and none of them performed well. The PVC is supposed to be non-metallic, but I'm suspecting it might be the culprit.
There's a youtube video showing a test of a ham radio J-Pole antenna and running it "free-air" vs. in different types of tubing and the result was that that the tubing significantly affected the performance. That said, my experience was the same as you, even with a free hanging colinear - it was much worse than my little quarter wave spider.
 
What do you think guys to create a blog were we can share and keep foundable all the antennas and improvements we do?

I was now looking on how to build 8-legs spider and I cannot find it.
 
@jepolch
Somebody (peterhr?) suggested putting a small piece of the pipe into a microwave oven and seeing if it gets hot. Make sure you put a vessel with water in there too so you don't hurt the oven.
I just put a 3 inch length of the same PVC pipe in the microwave (also a glass of water). After a minute, the water was near boiling, but the PVC wasn't warm.
 
There's a youtube video showing a test of a ham radio J-Pole antenna and running it "free-air" vs. in different types of tubing and the result was that that the tubing significantly affected the performance. That said, my experience was the same as you, even with a free hanging colinear - it was much worse than my little quarter wave spider.
I'll look for that. I'd like to try the colinear in "free air", but it's kind of fragile and one good gust of wind would blow it over. It's 12 gauge copper. By the way, yesterday I bought a vise and I plan to try the trick of spinning the copper wire with a drill. That would make it a lot more rigid.
 
What do you think guys to create a blog were we can share and keep foundable all the antennas and improvements we do?

I was now looking on how to build 8-legs spider and I cannot find it.
I was in the Navy. During that time, I learned that Navy stands for Never Again Volunteer Yourself. I have followed that advice religiously ever since. :D Just joking. But if anyone would like to start the blog I would gladly contribute. There's a wealth of education in this thread. @ab cd 's posts alone are worth archiving!
 
I was in the Navy. During that time, I learned that Navy stands for Never Again Volunteer Yourself. I have followed that advice religiously ever since. :D Just joking. But if anyone would like to start the blog I would gladly contribute. There's a wealth of education in this thread. @ab cd 's posts alone are worth archiving!

Searching things here is crazy. I'll search for the best platform and I let you know
 
What do you think guys to create a blog were we can share and keep foundable all the antennas and improvements we do?

I was now looking on how to build 8-legs spider and I cannot find it.
I just drew up this small diagram to show how I soldered the legs onto the SO-239 adapter. The corner legs were soldered into the holes. The intermediate legs were soldered with a little L shape to attach to the base plate.
 

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I went up to the roof and disconnected the colinear and put up the dipole I made last week. It's doing better, but still seeing about 40 less aircraft than the spider. It's a big improvement, though. At least my stats won't suffer as badly as they would with the colinear. Tomorrow I'll decide what to do next. :)
 

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THE DARK ART OF DIY COCO
Yes, well, this one wasn't a coco, but a colinear out of solid wire. I can only imagine the PVC must be causing problems. I can't believe all the antennas I've made and put in the PVC are bad and the ones that are bare are good. That would be too much of a coincidence.
 
[B
Yes, well, this one wasn't a coco, but a colinear out of solid wire. I can only imagine the PVC must be causing problems. I can't believe all the antennas I've made and put in the PVC are bad and the ones that are bare are good. That would be too much of a coincidence.
ALL collinears are very difficult for DIY. Reason: being multi element, require phasing elements between vertical receiving elements.

The phasing elements are extremely sensetive to dimensions. An error of few mm in DESIGN, or CONSTRUTION can push a collinear from excellent to poor category. The phasing element are coils (coiled whip), stubs (franklin), core wire of coax (coco).

The collinears are best when they are designed by Computer Aided Design software, followed by production using templates and precision metal forming macinary, followed by testing/trimming/adjustment with test equipment & anechoic chamber.

It seems the designer of your collinear has paid no attention to phasing coil's accuracy. The design does not include height of the coil, a very important dimension fir correct phasing.
 
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