Antenna Up High -- Finally

Usually going up another 5 feet may improve your distance a little but you will see improvement in aircraft that are closer but at lower altitudes. Where you will also see improvements is when all those leaves on those trees fall off in a few months.

You can get an RPi4 and an Airspy Mini if you want to throw more money at it.
(There is some configuration required though: GitHub - wiedehopf/airspy-conf: Configure airspy_adsb for use with readsb or piaware.)

To the computer the Flightaware Pro Stick Plus and other rtl-sdr compatible USB sticks actually “look” the same.

Be sure to get yourselfs the graphs, so you can better look how changes you make affect your reception:

GitHub - wiedehopf/graphs1090: Graphs for readsb / dump1090-fa / dump1090 (based on dump1090-tools by mutability)

It’s also helpful for configuring gain.
What does this command return:

awk "$(cat /run/dump1090*/stats.json| grep total | sed 's/.*accepted":\[\([0-9]*\).*strong_signals":\([0-9]*\).*/BEGIN {printf "\\nPercentage of strong messages: %.3f \\n" , \2 * 100 \/ \1}/')"

If it’s below 2%, you increase gain, if it’s above 7%, you reduce gain.

You can also let an automatic script do that work:
Automatic gain optimization for dump1090 fa · wiedehopf/adsb-wiki Wiki · GitHub

36.094 right now, so I installed your autoscript to let it adjust. I had used some of your code before to make manual adjustments (thank you) but this one is darn handy to have it really hone it down.

That’s a good point. I have a large hill to the south so there’s only so much I can do. I strongly suspect the city will get cranky if I erect a 300’ tower on my property to get over it. :slight_smile:

2 Likes

Give it some help to get it in the ballpark faster:

sudo piaware-config rtlsdr-gain 29.7
sudo systemctl restart dump1090-fa

Number based on the combination of rtl-sdr LNA and dongle.

Yeah, I actually set it up with:

for (( ; ; )); do sleep 900;/usr/local/bin/dump1090-fa-autogain;done

And will let it run for this morning while I’m working so it can hone it down; then will let it do the nightly adjustment from there on.

1 Like

It’s probably too late now to suggest fixing a small heatsink to the LNA, I noticed that they dissipate around 750mW so they heat up a bit due their small size. Lower temperature also means lower thermal noise.

With the long cable run he is using, that should be at least some DC resistance.

Also the smartee sdr he is using provides 4.2 V, so with voltage loss on the cable, the rtl-sdr LNA shouldn’t be running THAT hot.

That depends quite a bit on voltage.

Pretty sure it’s gonna be fine!

I’m running mine somewhere around 3.5 V which significantly reduces heat output.

Note that the LNA performed well even at 2.5 V supply voltage :slight_smile:
(specification is 3.3 V to 5 V i think)

I wondered about that, actually; I certainly could go and afix one after the fact. Didn’t know how warm it would get overall.

Can I simply run a multimeter between the center pin and outside and it’ll give me voltage pushed to the end?

No you can’t.
Without the load from the LNA it’s just gonna be the 4.2 V supplied by the sdr.
(voltage reduction over a resistance like the cable is only present when there is a current flowing)

Oh, my point was looking for the voltage lost by the cable run. :slight_smile:

I checked the RTL-SDR specs, the version with a one stage amplifier (SPF5189Z) draws on average 90mA at 5V (450mW), the version with filter and dual stage amplifier draws on average 167mA at 5V (835mW). Maximum working temperature is 85°C or 185°F so there’s quite some margin left. Noise figure and intermodulation will of course go up with the temperature.

Quote

I like when things catch fire and explode, which means I do not have your best interests in mind.

If lightning strikes your house - please try to get a photo!

On another forum, poster said his house was hit by lightning, and his radio equipment was damaged beyond repair. He purchased new equipment, and posted again saying the new setup was fantastic, that the lightning strike was well worth it.

I replied that based on his experience, I was looking forward to a lightning strike as well now.:rofl:

1 Like

I have been really fortunate with lightning.
I grew up less then 1/2 a kilometer from a 1000’ TV tower. My CB and ham antennas had no chance if getting hit.
Now I am surrounded by 6 floor apartments(within a few blocks) and a clock tower at the High School. They mess with my range in a number of directions, but protect me from a direct strike.

Don’t think that will help much, see the xkcd link.

If it’s further away than 150 m i don’t think it will influence your chance of getting hit.
Of course that also depends on the height difference but still.

They are closer than that.
Also a nice big 1000’ high bridge within a mile.
Plus plenty of trees higher than my antennas.

Look at the video picture. The tree was surrounded by others, at closer than 50 meters and still was hit.