Built my first antenna and doubled my coverage

Welcome! Glad to see you made it here. :smiley:

Hi, all. I build first antenna :slight_smile: one circle 50km, i can see planes up to 350 km. Coco antenna make from 12 segments (11,6cm each), i found thicker cable than RG59, but feeder cable its RG59 about 10 metres. USB TV dongle i buy from china, pay 11 euro :slight_smile: everyting working perfect, later i buy Raspery, shorter cable more dbi.

flightaware.com/adsb/stats/user/DeivisSaldukas

Welcome to the forum. Great work on your antenna. You have very good reception. I’ve made a couple of colinear antennas but neither one had as good reception as my ground plane.

One type of antenna I haven’t tried yet is a dipole. Very easy to make. I’ll put this one on the roof this afternoon and see how the performance compares to my ground plane.

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??? :angry:
I will have to test this by making a dipole with 68mm each limb.
Then 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. :angry:

Welcome to antennas in the real world! I think you’ve got the right idea – build a few and test them, and let the numbers decide. This is how things were done in the days before computer models and simulations. Some of us “older” farts still think that actually building things and testing them is a good way to go – and when the thing on the test bench (or on the pole in the air) gives results that are different from the simulation/model… Well, the thing on the bench is doing what it’s doing.

An orthogonal observation – SWR is very important for transmitting; less so on receiving, at least with SWRs less than 3 and at these frequencies.

One of the nice things about what we’re doing with ADS-B is that the antennas are reasonably small and easy to construct (well, tolerances are tight at these frequencies). And with tools such as PiAware, we have a common set of measurements to tell us how things are going.

A technique I’ve used in my ADS-B experiments is to select another PiAware feed close to me that seems to have stable and similar numbers and use that station as a reference. I compare my systems performance to that reference station using the daily reported FlightAware stats. That way I have a chance of figuring out what’s going on as the base numbers change from day to day. I’m not left wondering if the number of positions reported or aircraft sighted went down because the change I made decreased performance, or the decrease was because there less traffic and fewer birds overhead that day.

For example, tracking my station performance against the reference shows that the reference on a day to day basis has 80% - 82% of the position reports of my station, and 94% - 97% of the aircraft spotted. These percentages stay within those ranges even as the overall numbers change from day to day. When I change to a different LNA, for example, and see that positions reported percentage shift to 78% - 80%, that shows I’ve made a small (but measurable) improvement. That small improvement shows in the reference comparison, even though the day-to-day numbers may vary substantially, such as the normal traffic variations over a weekend.

I respectfully suggest you’ll need to do something like this to keep from losing even more of your sanity, as you’re dealing with small changes.

Keep good records, let us know what you learn, and have fun!

bob k6rtm

Good evening, Bob -

Are you still working on this? If so, I’m starting to get interesting in building another receiver to put up on a local mountain. I’d love to be a guinea pig for the project! :slight_smile:

Cheers and 73 - Jon N7UV

Jon–

Short answer: don’t hold your breath.

Longer answer:

In my voluminous spare time (I’m part of a startup), I’ve been researching different parts. This idea, like most, is a cross product of time and money. Right now I’ve got a little time but very little money. If our startup gets funded (soon, and I hope it does), I’ll have money but for a while I will have no time!

Most of the parts are easy – high pass and low pass filters from Mini Circuits, HFCN and LFCN, very low insertion loss, small (1206 size, practically huge for surface mount), not too expensive. LNA is easy. The problem is sourcing the SAW. Not in stock, 8 - 14 weeks lead time, and expensive. Makes the ones I’ve ordered from Eastern Europe at $10 each feel cheap. Maybe they are?

But do we really need a SAW, if the front end filtering is good enough? If the SAW isn’t needed, it’s easy (well, other than the issue of a controlled impedance pcb layout, which is kind of important for this)…

Most of the parts and subassemblies are available now, on eBay or other sites – the LNA in kit form or assembled, PCBs for the Mini Circuits filters. Small hindrances – Mini Circuits minimum orders on parts, and doing surface-mount assembly. The assembly part isn’t an issue; I do surface mount assembly at home using a modified toaster oven; that’s a well traveled path. Minimum orders are just an issue of money (which our startup is searching for).

There’s a fundamental question – what’s the product? Best I figure it currently, it’s an assembled surface mount PCB that has at least input bandpass filtering and an LNA. Bonus points for fitting into standard enclosures. The pcb assembled with parts shouldn’t be too expensive. The machined cases with SMA connectors are expensive. The whole pricing issue… Is this a Tindie project?

I’m rambling again, big surprise… One of the things I can do, and will start on the weekend, is running an experiment to see just how much that SAW actually helps, setting up a system without one and tracking it against one that has one.

I’m also investigating ways of having the pc board designed for me. Our startup uses some very nice 4 layer boards. I know what the layout costs are, and what our fab runs cost. It’s a lot higher than OSH Park!

cheers–

bob k6rtm

Sounds a lot like this:

lna4all.blogspot.com/

I had mine with 5 element as design shown here. It is working nice.

Making an inexpensive 1090MHz ADS-B collinear antenna - YouTube)

It wouild be ideal if it had pads for a pair of Mini Circuits filters (LFCN, HFCN) in the input – 1206 sized, lower cost and lower insertion loss than a SAW. I’ve e-mailed Adam asking if he would consider doing a revised board…

bob k6rtm

After seeing a link either here or on the PlaneFinder forum, I’ve ordered a HABAmp (http://ava.upuaut.net/store/index.php?route=product/product&product_id=85). MiniCircuits LNA and a SAW.

Not cheap at ~$90 delivered to Phoenix, but the specs appear pretty good. I’ll let everyone know how well it works once I receive it. It will be setup in an area with several cell sites nearby.

Welcome to the neighborhood, scholztec -

I just had lunch with a buddy of mine down near where you station reports. Your station is doing extremely well, especially if you’re really where it reports!

Cheers and 73 - Jon N7UV

Since I made my first spider/ground plane I have yet to make another antenna that can equal its performance. So I decided the only way to see if that first spider had any magical qualities was to try to duplicate it and run it side by side with the original. This is the new one. Two spiders, two Pi’s, identical but separate amps and coax. May the best spider win!

Well, a guy can always wish. :smiley:

I started looking for a nice low-loss filter design, which took me which then took me to a site where someone had designed and made a microstrip hairpin for 1090 MHz. That made me break out my old copy of Ansoft SV to look at designing a hairpin filter, which then took me to personal CAD routing and milling machines on eBay, bit sizes, etc., which then made me reconsider the whole thing again :unamused:

In any event, I look forward to more of the good work that you’re doing.

And, I think I will try setting up the 1090-mutability on my second RPi. I followed that thread from OBJ and it sounds like it’s settled down and become pretty cool!

Cheers and 73 - Jon N7UV

I exchanged e-mails with Andy, proprietor of LNA4all, inquiring about a spin of the board incorporating a pair of 1206-sized Mini Circuits filters. The good news, he replied quite quickly. Also somewhat good news, he already has boards for a pair of Mini Circuits filters (HFCN, LFCN). The bad news, he doesn’t think the volume would justify the work to redo the LNA board layout and the stencil they use for machine production. A stainless steel stencil for a reasonably sized panel is around $400.

When I come up for air again, I’ll look at pcb layout tools that let me do controlled impedance layout. Don’t know if Eagle (the free version) will let you do that.

Haven’t gotten a reply from the other guy, Chuck, who sells LNAs on eBay.

On my own antenna front, the re-purposed 950 MHz vertical works a treat, bringing in numbers around 33% larger than the discone – and that’s with an inferior LNA and SDR! Max range has also increased.

Haven’t decided what to do about swapping out the discone for ADS-B use. I’ve got another mast at the other end of the house, that one with a 2 meter eggbeater on it, as well as a bunch of other crap. Leaning to swapping out the eggbeater and putting the 950 MHz vert in its place. The other interesting thing about using that mast is that the cable is accessible in the attic (the discone cable isn’t; it’s above out bedroom which has a cathedral ceiling), so I could cut the cable and move the whole receive chain plus Pi up to the attic, cutting out about 40 feet of 9913 feedline – that’s worth a few dB! The downside is that 9913 takes special N connectors and is a pain to work with. But you only have to do it once.

bob k6rtm

That antenna you got, would it happen to be anything like this one? http://r.ebay.com/9LK31k

It lists a freq range up to 960MHz, so it’s not too far off. Did yours have any specs on it?

Justin

That one looks pretty close. Mine didn’t come with the mounting hardware – it was in a box marked “Antennas $23” – most of the contents of the box were WiFi (2.4 and 5.6 gig). This is the kind of electronics surplus place where if something is in a marked bin, the marking is usually way off…

bob k6rtm

Hello, I’ve been reading this thread for awhile with great interest. I’m not a big build it yourself person for many reasons, but I have great admiration for those of you who do that stuff. Perhaps you might be able to steer me towards a piece of software, hopefully freeware, that will let me see the strength of signals I’m receiving near the ADS-B frequency of 1.090 GHZ. For about a year now I have been using first a regular ADS-B dongle and more recently a better receiver, microADS-B. The setup I’m using is that receiver to about 50 feet of 9913 Belden coax and ½ wave ground plane about 30 feet off the ground. Surprisingly I rarely receive signals further than 50 to 60 miles. Occasionally I will get some over 75 miles and a few up to a little over 100 miles. I’m in the Midwest and the terrain is relatively flat in all directions. So I’m trying to figure out what is limiting my reception. Most users who have similar antennas and cable setups seem to get much more distant signals. I’ve had suggestions to try and reduce the signal strength as it could be overloading the receiver as well as suggestions to add an amplifier to get higher signal strength. I don’t think overload is the problem, the receiver does have a SAW filter built into it and is a better quality than a simple $20.00 dongle. The cable could be a factor I think. What I’m thinking of doing is using the 50 foot USB cable that has an active repeater to get the signal from the receiver if I put it in the attic, much closer to the receiver. Since I’m not really a home brewer like many of you I’m trying to do this relatively inexpensively. All of this may not be possible at a price I want to spend.

So I think the best place to start is trying to find out just what kind of signal I’m receiving. Does SDR# have the capacity to show signal strength at certain frequencies? Will installing it overwrite the driver I need for the receiver I’m using? From what I’ve read about the program it does require installation of a Zadig driver.

Any and all suggestions/opinions are greatly welcomed and appreciated.

Thanks, Dan

Try hooking the receiver directly to the antenna like they show on microADS-B’s website. At least for a few minutes - then you should be able to determine if your cable is the issue. It’s easier to try things out in your backyard and not in the attic until you get it working - then move it to it’s permanent home.