FlightAware Discussions

Antenna on roof, what cable to use?

Yesterday I hit a record of 514.562 total received reports and 3.042 total aircraft seen and a max range of 230.8nm.
And this is WITH the piece of (white) flat coax.
Nice. :mrgreen:

I ordered the ‘old’ Pro Stick Monday afternoon; delivery date was today untill Tuesday.
But it arrived already on Wednesday.

Now I’m going to replace the cheap Ebay stick with the new Pro Stick. Tomorrow or Monday I’ll add the filter and compare results.
And search the thread about gain settings etc.

I really hope the stick and filter will improve results.

Well, it looks like the Pro Stick consumes more power than the cheapo DVB-T stick or the power supply (5V phone charger) is giving up.
The Pi’s red LED is blinking sometimes and the results I get are really poor. When I first booted up the new configurations (both Pro Stick first and later when I added the filter) results were slightly better than with the DVB-T stick but now they’re actually worse.

nl.flightaware.com/adsb/stats/user/Iemand91

I tried three versions of flat coax coming under window. Was not pleased with results, I then extended my Low loss antenna cable through a slightly open window, and my range increased well over 50 miles. I now have small towels stuck in the slightly open window. When it gets warmer, I am going to come in through the side of the house, into a cable box in wall, and then out.

I am pretty sure that the red led blinking is a sign of power problems.
You need to use a decent 2-2.5Amp USB power supply to reliability.
I have seen position report numbers triple with the pro-stick, over the non-amp dongles.
You may also want to look at the gain optimisation threads. Some people had to turn their gain down to below 40 to get the best results.

First I used this; poor results.
Then I used this; much better results. They were on par with the results without that piece.

It is indeed (according to this). Then the Pro Stick must use more power then the cheap DVB-T stick since I haven’t had this problem before.

You need to use a decent 2-2.5Amp USB power supply to reliability.

I ran the RPI3 with the DVB-T stick with a 1A phone-charger fine for months. Either the charger is getting bad or the Pro Stick consumes more power.

I have seen position report numbers triple with the pro-stick, over the non-amp dongles.
You may also want to look at the gain optimisation threads. Some people had to turn their gain down to below 40 to get the best results.

I’ll do that. When I replaced the DVB-T stick with the Pro Stick results were only slightly better before I got the power-related problems (read: a big drop in results).

Will look for a decent charger sometime this weekend.

lsusb -v will give details on power use.
My FA devices and airspy seem to want 500ma each.

I don’t have any RTL-SDR plugged in at the moment to check.

@Lemand91
I tried the link to the one that you said you used second and got good results, but I did not get anything. Could you please check the hyperlink. THanks.

I was just a link to a picture of it, but I ordered this one: amazon.de/gp/product/B00OHW … UTF8&psc=1

Please note; everything I do is still testing and finding out what’s what so no guarantees. But when I replaced the previous flat cable with this one results were better.

I put an USB amp meter in between the power supply and the Raspberry at this moment.
When booting the draw goes to about 0.7-0.8A and after a while it settles around 0.6A total.

lsusb -v says indeed the FA Pro Stick draws 0.5A.

So just something random; yesterday I broke the 800.000 total reports barrier.
I hit 819.409 total reports received. Maybe not that much compared to other sites but it’s kinda cool to break this barrier.

With the summer season only just begun; maybe I’ll hit the 900.000 barrier sometime this summer? :mrgreen:

https://c1.staticflickr.com/4/3854/33001531613_0e79b20608_c.jpg
FlightAware total reports record by Iemand91, on Flickr

I have something I can’t explain related to this. When I connect an antenna directly to my SDR or with a very short cable I get no planes, but when I add a 10’ cable in the middle I get lots of planes. I’ve tried multiple antennas, in the same rooftop location. So far, despite all knowledge saying this is wrong, a longer (20’) cheap cable tv antenna works better than thicker short cables and way better than a simple male to male sma adapter (which receives absolutely nothing). Yet that same adapter is fine if connected to a longer cable.
I can’t figure it out.

So either your SDR / RPi / power supply is noisy and feeding noise into the antenna.

Or alternatively the attenuation is reducing some foreign interference. Above a certain threshold interference will obliterate your reception. Attenuating everything in this context can improve reception because the SDR isn’t overloading anymore.

So try a filter?

One possible cause may be the short cable and connectors. I helped someone with a cable with the reverse polarity connectors, and the center conductor of the cable never touched the receiver dongle. The male cable connectors must have a center pin to work. Just a thought.

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I have a flightaware pro and a pro plus. The pro plus has the filter on it. It still won’t work with a short cable, but does improve the message rate on a long cable slightly. I also tried swapping the power supplies and the whole raspberry pi’s. The only variable that makes it work is the long cable.

@astrodeveloper described the most probable cause (it’s caught out more than a few people).

It’s not that, I’ve used the same adapters as I mentioned. I’ve also tested resistance to the antenna and ground and found no loss.

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Sorry - cant see it. What adapters are you using?
It’s the plugs on each end of the short cable @astrodeveloper was referring to.

What antenna are you using and what reading do you get?

With the RP-SMA connectors, the center pin of the male connector is a socket instead of a pin. You need to measure the resistance of center pin at the SDR dongle to the center pin of the antenna connection. This needs a low resistance, (not 50 ohms, as that is the impedance of the coax and not DC resistance). RP-SMA connectors do not provide the connectivity on the center pins, thus no signal arrives at the SDR dongle. No idea why anyone ever designed the RP-SMA connectors, as they mess up many installations. If this is your situation, you can do a fairly easy patch by using a 1/2 inch (10-12 mm) wire inside the RP-SMA connector. Cheap and easy, though the real connector is a better thing to use. Hope you get your system up and running well soon. Best wishes. I am an old ham radio / USAF retired electronics guy, just pushing electrons around in interesting projects.

SMA vs RP-SMA

WORKAROUND

Insert a piece of wire in the hole to act as a pin

RP-SMA Worksround

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