FW: [VHFlorida] Morning Enhancement
Mike Lewis
Forwarding this from N4IS in southern Fl about work they are doing for propagation monitoring using ADSB to identify potential 1.2Ghz openings that can happen independent of lower frequency openings.
I believe the LOS is calculated using curvature of the earth today. A next step could be to use GIS data to account for mountainous areas like the PNW.
- Mike K7MDL
From:
n4...@comcast.net <n4...@comcast.net>
Sent: Monday, March 30, 2026 1:49 PM
To: 'BR...@groups.io' <BR...@groups.io>
Subject: RE: [BRMS] FW: [VHFlorida] Morning Enhancement
Hi guys
I am following Eloy work on the Reverse Beacon ADS-B project, RBADS, and it is remarkable, fantastic job. The main idea is to show propagation spots based on the signal BLOS; Beyond line-of-sight using ADS-B decodes, they provide positioning and altitude.
I invite you to check the web server to follow the propagation in Florida, the server runs in a RasperryPI-5 it is a working in progress, the receiver in a rPI3 or 4.
My station in SW Ranches is using an Omni vertical 45”tall 9 dBi at 36 FT above ground, ½ hard line, digital filer 6 cavity 1.2 db insertion loss, 40 db preamplifier into PLOTO SDR.
The gain is necessary to see more aircraft, but Noise Figure is more important to see weak signals.
Eloy station is using a 3FT dish and the kind the same hardware, but it the antenna gain and directivity allow to see more BLOS signals.
Here is a screen shot during an opening in Florida. You can see the directory of the antenna. The white airplanes icon are BLOS, the yellow water mark is the same BLOS with a 10-minute time out.
With normal conditions you see none BLOS, just the green location of the receiver in the map.
I am experimenting with antennas and preamplifier, my receiver can see 250 miles aircraft in a regular base, but very few BLOS ones. I need to improve the NF; however, I can see more airplanes than Eloy because no directivity of the antenna here.
We still need a big opening, like a duct to better understand what we see on the screen and the correlation with actual opening to generate contacts on uW.
Today we have the APRS map on 144 MHz, and the RBADS on 1.09 GHz. We have openings on uW that does not show up on VHF. We may need more receivers to cover the East Coast, may be one every 400 miles.
My receiver can decode 250 miles (400 km) with no propagation enhancements. This kind of observation can take several months to experiment a good opening, lucky April is a good month. You can open two screens, one for Miami, and another for SW Ranches, and compare how two different antennas behavior.
Here a screen you can see not selecting BLOS. It not possible to spot opening just watching the airplanes. The color blue is weak signal, green is normal , yellow, red are strong signal, white is BLOS.
BLOS ONLY, selection >
73’s
JC
N4IS
From:
BR...@groups.io <BR...@groups.io>
On Behalf Of Mike - W3IP via groups.io
Sent: Monday, March 30, 2026 10:48 AM
To: br...@groups.io
Subject: Re: [BRMS] FW: [VHFlorida] Morning Enhancement
Here is a plot of the signal strength of ~1000 ADS-B position decodes versus distance from inside my shack this morning (blue markers). The red markers are a curve fit of "R squared" on the peak of the data. Any future signals that fall above the red markers should be enhanced by anomalous propagation (i.e. tropo). Next steps are to run a much longer duration test to see if and when signals appear above the line and to get an outside antenna up the tower a bit. The easiest test doesn't care if the plane is beyond line of sight or not - only that the signal strength is stronger than expected for the given distance.
73, Mike, W3IP
Hardware tech details - Mag mount antenna in shack > 1090 MHz band pass filter > RTLSDR Nooelec V5 > USB cable
Software - Dump1090 beast mode (the Malcolm Robb variant) >Python/Spyder - modified PymodeS and some data collection code I hacked together
From:
VHFl...@groups.io <VHFl...@groups.io>
On Behalf Of Eloy Ritter via groups.io
Sent: Tuesday, March 24, 2026 12:08 PM
To: VHFl...@groups.io;
bea...@aol.com
Subject: Re: [VHFlorida] Morning Enhancement
Buddy, great propagation this morning too. Amazing SSB QSO.
A while ago I asked on the mailing list for sources of RF that could be used as beacons. I started working on an ADS-B receiver to check propagation in the GHz range. It turns out that decoding ADS-B beyond the radio horizon is very possible and improves during an opening like what we have seen these past days.
Normally very few airplanes are decoded BLOS but the number grows during an opening. I recorded my screen to show what happened this morning.
If you want to see the data live, the address is:
Even if the server is usually on, the receivers feeding it might not be. Currently two receivers are feeding data: mine and N4IS who is still testing antennas.
73
Eloy
W4ERP
On Tue, Mar 24, 2026 at 9:02 AM Buddy Morgan via groups.io <beamar=aol...@groups.io> wrote:
This morning:
2M - nothing special
432 - nothing special
902 - maybe a little better than normal
1296 - very good signals. Eloy and Gary were wall to wall Red, on the waterfall, when I watched them work. Downright awesome!
2304 - Eloy and I moved up to 2304. Eloy's barefoot IC 905 was 20 over S-9, here in Lakeland - 191 miles.
5760 - Eloy and I went up to 5760. S-7~S-9 signals. Had a armchair copy SSB QSO, on 5760.1 Eloy made a video of the contact.
I will let Eloy tell everybody about the airplane signals, from over North Carolina, he was seeing. it is a shame nobody from the Carolinas was on, this morning.
Buddy WB4OMG EL 98
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Eloy Ritter
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Mike Lewis
I had a Pluto+ several years back but it failed several hours after first use and I moved on to other stuff.
After this looking into the email content below and talking to Carlos (N4IS) on the phone today, I took a look at what was out there for Pluto+ variety hardware. I came across a website with lab measured perf specs and comparisons between some Pluto derivatives including the LibreSDR and a PlutoSky, which has some amplification onboard. The last update was a few days ago.
General Information — Z93-Lab 1.0 documentation
Firmware for several variants is found at F5OEO/tezuka_fw: Universal Zynq/AD9363 firmware builder. There are others as well.
The discussion section of that GitHub site is an interesting read. In the Wiki section there is info how to unbrick the LibreSDR.
--
~The Voice of the Pacific NorthWest VHF Society~
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