FlightAware Discussions

Raised aerial 7ft and in the clear

I did not, at least not manually. But you’re correct, it is/was set to “2”

No idea what caused this. Probably the setting via FA ADS-B Portal
Changed it back to “1” now and restarted dump1090-fa, but the location is still the same.

Anyhow, i can live with it :slight_smile:

Oh the default is different for the piaware sd-card:

# https://github.com/flightaware/piaware-support/blob/master/scripts/generate-receiver-config
lappend dump1090config {JSON_OPTIONS="--json-location-accuracy 2"}

With a piaware sd-card modifying the /etc/default/dump1090-fa configuration doesn’t do anything. (says so right in the file)

1 Like

I simply changed the location by a few meters :wink:

Don’t do that, that’s really bad for MLAT.

You could for example use a Raspbian Buster Lite image, then you can change the location accuracy setting.

I wonder if piaware would overwrite the configuration file if you made it write-protected.
Change /etc/default/dump1090-fa, save it and change it to read-only:

sudo chmod a-w /etc/default/dump1090-fa
1 Like

Maybe an idea. Will test it once i have SSH access

I can post some quick comparisons now, this is comparing the MTG feeder to mine. It’s normally ahead of me by around 150-200 aircraft/day and 150,000-200,000 message/day.

Yesterday isn’t a good comparison because my mast was down for a couple of hours with the aerial horizontal but just look at the difference today with still a couple of hours to go.

MTG aircraft:

Me aircraft:

MTG positions:

Me positions:

This is quite an incredible increase in both positions and aircraft. All I have to do now is work out some way of keeping it up there in the clear when the Hexbeam goes back.

That’s pretty significant for a seemingly small change in antenna position. Maybe it’s just lifting it clear of some obstruction. Perhaps if you ran the heatmap script in both positions you could see where the gain is coming from.

Look at the first picture, the stub mast is blocking it.

What about the house in the background or in another direction, any of them able to block reception?

Anyhow, the flatter the area the more increasing height is gonna give you in return i think.

I’m surprised that the stub mast is having such a big effect, but then I suppose it is quite close to the antenna. Assuming that’s the sole cause, perhaps offsetting the antenna horizontally would help - it would reduce the angular size of the mast from the viewpoint of the antenna

This thread about Aerial reminds me the wire aerial (similar to the one in sketch below) at my grandfather’s home. The aerial was for his 6 valve (vacuum tube) LW/MW/SW radio. The radio was double the size of a modern large microwave oven :slight_smile:

wireae

1 Like

I had something similar for my crystal set.

Back then, once the local broadcast AM radios went off at midnight I could hear just about the whole world on that wire (but I also had an earth).

Yes, I remember way back when RFI was essentially non existent.

S.

On the same frequency.:wink:

Nope, the aerial in the previous position had a clear view in all directions, except where it was blocked by the stub. Bear in mind that a 2" steel pole that close to the aerial is going to be quite a good block for weak signals in that direction. What it might be worth me doing if I have to move it back is look at the signal strength heatmap and use that to decide which corner of the main mast I fix it to.

That’s a possibility as well - The further away I get it, the smaller the effect will be. That does mean getting some complicated mounting system though which may be tricky. I’d much rather see if I can somehow keep it high. I’m thinking perhaps separate the aerial from the feeder box as that will make it easier to get higher. Of course, then I’ll have a run of cable back into the box which I don’t have now.

if you look on the first picture, you can see I have exactly that! It’s an inverted L aerial, the feed point is at the bottom of the mast with a smartuner, the aerial goes up through the insulator you can see leaning away from the mast and then off to a 20’ pole at the end of the garden. I use it for top band through to 30m.

There are trees, houses further away from you that block the lower angles to horizon.
Higher you go, lower those angles become, more planes you can pick from far away - if there are any that far.
As for the pole being a blockage - planes will “fly” past that shadow, and still be counted. You’ll lose just a few positions, unless the plane flies directly towards the antenna from that direction.

To me, raising the antenna did the same thing - propelled me on the “top” of my 25 mile radius list.

I made a video a few years ago… This is from about 2ft higher than the feeder was situated and is about 5ft lower than it is now. It goes all the way from north to north in a clockwise direction and then back anti clockwise, pausing at 270, 180 and 90 degrees. The huge tree to the east isn’t there any more.

As you can see, I do have a good view :slight_smile:

1 Like

Did you post your set up here? I could not find it with a quick read.

It’s a Pi3B+ with an Airspy Mini, an RTL-SDR LNA and an FA aerial.

Marconi’s aerial :slight_smile:

Oops … sorry, Marconi’s aerial was a vertical monopole.

Marconi_transmitting_station_Poldhu_Cornwall_1900

1 Like

Well I’m sure he had more than one aerial but yes, the quarter wave vertical on a decent bed of radials is a good, solid aerial. The low angle of radiation makes it good for DX although it’s generally more susceptible to noise than a horizontal aerial. Mount one over sea water and the angle of radiation is lowered even further due to the pseudo-brewster effect.
I know this because when we go out on the Radio Caroline ship and run our special event stations, we largely use quarter wave verticals (monopoles), strapped to the hull as a ground and they work incredibly well. We do hang dipoles too.

And before anyone asks, no I can’t mount a feeder on top of that mast :smiley:

5 Likes