I was puzzled for a while: why is my northern coverage so good when my antenna is placed at a south-facing window?
As you can see in the tar1090 coverage overlay image below, my direct path to the south is heavily blocked by a neighboring house right in front. Naturally, I expected poor reception in that direction.
However, it turns out that very same neighbor’s house is acting as an unexpected passive reflector! The signal bouncing off the building is actually boosting my coverage toward the north (the shadowed side of my house) much better than the direct path. Sometimes, a physical handicap can work entirely in your favor.
Have any of you experienced quirky multi-path or obstacle-reflection magic in your own setups?
In my limited expertise on this band, I believe the reason must be something else.
Except for very close aircraft, the received signal is too weak for a building to act as a reflector. Furthermore, for that to happen, the building’s construction material is crucial. Concrete and brick won’t reflect a weak signal; they’ll absorb it. However, if the concrete is reinforced with steel rods or any other material, its metallic nature allows it to act as a reflector.
If the building’s structure consists of steel pillars, they wouldn’t absorb the signal but would reflect it. Glass would simply allow the signal to pass through, attenuating its strength, although I’m not sure what to say about glass reinforced with metallic particles.
I also think that for that to happen, the building across the street would obviously have to be taller than yours, and those aircraft wouldn’t have to be very far away.
This is really interesting, but as I said, I’m giving my opinion using logic; I don’t know if it applies in this case, in that band and with weak signals.
I’m thinking about something else, which might not make much sense, but I know perfectly well that in other bands, humidity in the air causes signals to behave differently; for example, tropospheric ducting is proof of that.
I don’t know if the humidity between the two buildings could be affecting it, or even the humidity covering the building across the street. I know the humidity in Japan very well…
Perhaps this theory isn’t as reasonable as the one I mentioned in my previous answer.
You should look for another possibility instead of signal bounces.
That’s a very logical analysis, but interestingly, I see a similar phenomenon with a GPS dongle placed right next to my aviation antenna. Even satellites that should be shadowed behind my own house’s roof are reliably caught.
Here is a quick look at my xgps screen (connected via gpsd on my local machine). It seems environmental reflections and multipath are quite potent in practical, real-world indoor setups, beyond pure textbook theory!
Unlike ADS-B or GPS reception where multipath and reflections can sneak around obstacles, the satellite signals here strictly follow line-of-sight — beautifully proving that my southern view is indeed blocked, and the northern ADS-B coverage really is the result of special reflection magic!
Update: Wait, spoke too soon! Just caught a fresh pass from the north on TinyGS as well. Looks like reality is always full of surprises, and radio waves love to defy textbook expectations. Happy tracking, everyone!
Could be ducting, or some interesting multi-path/reflection magic!
Here is a snapshot of the raw packet list. As you can see, it’s not just a single lucky hit—there are multiple frames coming through consistently. Real-world RF is full of surprises!
@abcd567 Thank you for sharing that! When I saw your post and sketch about the Toronto airport reception behind those high-rise buildings, I literally slapped my knee in total agreement.
It’s amazing how real-world RF completely shatters textbook assumptions through glass reflections and multipath magic. Seeing your documented case gave me absolute confidence in what my own setup is experiencing. Thanks for keeping the discussion so insightful!
Great, as always, but I still maintain that ordinary glass doesn’t reflect any signals. If we’re talking about Toronto, I’m assuming it’s insulated glass, which contains a significant amount of metal, and although I wasn’t sure, you’ve confirmed that it reflects the signal, which makes sense. In a traditional Japanese house, there’s no steel, or if there is, it’s in very small quantities, and they don’t have special glass.
If what our friend SHIRAKAMI is experiencing are indeed signals coming from the opposite direction, I’d bet more on weather conditions and some kind of ducting effect (look at the image):
Shifting gears a bit to look at the big picture from an RF perspective—how do our usual targets compare when we break down their altitude, frequency band, and transmission power?
I put together a quick comparison chart for TinyGS (LoRa satellites), GPS, and Aircraft (ADS-B):
It’s fascinating how vastly different these environments are, yet we pull them all into our home setups through windows and walls! What are your thoughts on how these different frequencies and link budgets behave?
For ADS-B at 1090 MHz, I thought the aircraft transponder power was more like 50 Watts. It should also be noted that there are two antennas on aircraft with ADS-B transponders one on top and one on bottom of aircraft. The one on top is for transmission to LEO satellites.
Well, Radio waves are non-ionizing radiation, so the only effect to the human body is possibly localized heating. For example, having a cell phone upside your head. Most ham radio operators have probably experienced RF burns from touching the wrong thing in a transmitter or transmitting antenna!
What the heck is going on here. I have deliberately pointed my antenna at the neigbours balcony across the yard who live at the top floor = > 350km without line of sight at the opposite side of which i can actually see something. Choose your reflecting obstacles wisely.
Looks like yesterday really was a textbook example of a temporary ducting/propagation anomaly. It’s amazing how volatile and shifting these 433 MHz paths can be day-to-day. Has anyone else tracked similar “ghost” openings in their TinyGS logs?
Just caught a fresh pass from the north on TinyGS as well. Looks like reality is always full of surprises, and radio waves love to defy textbook expectations. Happy tracking, everyone!
