I have 3 RPI’s using mag mount antennas in different window sills. I have found my best window reception is using a 10" steel cake pan with the antenna stuck in the center of the pan. The pan sits right in the window and has fairly decent reception. Without a ground plane the reception is very poor. What do you folks use for your mag mount antenna ground plane?
KB4ERT
Trial Run Results for Four Sizes of Ground Planes
Trial Run Results for Three Types of Whip Antennas
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Can diameter: 100mm, height: 65mm + optimized whip antenna.
I have a RPi3, a FlightAware Pro Stick Plus (blue stick), a Uputronics ADS-B SAW filtered preamp and a 3dBi 170mm mini mag mount centre loaded whip designed for 1090MHz. It is all sitting on a windowsill inside the house upstairs. The preamp is powered over USB from the RPi. The mag mount is sitting on top of a Kenco coffee tin.
I started with the mag mount just sitting on the windowsill as there is some metal underneath the UPVC which the mag mount can slightly stick to, so this was providing a reasonable groundplane. My range was reasonable, getting positions from up to 100NM away.
After a few weeks I added a metal lid similar to the one shown in abcd567’s photo 1 of 2. Performance dropped so I reverted to the mag mount just sat on the windowsill.
Next I ordered the preamp and that made a nice difference, I was pulling in positions over 100NM. It’s an excellent quality bit of kit, I recommend it.
I once again tried a metal lid, and I also tried a paint tin but they both reduced performance.
After a while I did a bit of googling and found the antenna discussions on here. I discovered that in the UK, Kenco coffee tins are about the right diameter and are also magnetic. I made a crude spider but cut the legs a little short (I measured from the edge of the overlapping mag mount base, not the edge of the top of the tin). However performance did improve and I caught positions further out towards 150NM.
I then changed to the same Kenco coffee tin but fully intact and vertical shown in the first photo. This has given a fantastic result. I am in the north west UK and I am now seeing aircraft on Skyview just outside the M25 by Luton, down by Bristol, at the Isle of Man, over the North Sea 10NM off the east coast, and up in Edinburgh. These are 130-150NM away. I know I’m not dreaming because I’ve drunk so much coffee!
I think the tin is acting as a really good, perfectly sized capacitively coupled groundplane, and the combination of the Pro Stick Plus and the Uputronics preamp are working well together with this to extract maximum messages from what is being received.
I considered cutting the tin down to 69mm but I don’t want to risk ruining what I have. I’ll give it a go when I next have to buy a tin. I’m also reluctant to cut the coax down to a shorter length as it’s all nicely heat shrunk and lets me move it around if I want to experiment.
Moving on from the mag mount I intend to get the FA external antenna and I think that same Pro Stick Plus and preamp combo will really let me extract the most performance without signal to noise penalty from its higher gain.
Here is my stats page https://flightaware.com/adsb/stats/user/chrislfa#stats-68549
Comments or suggestions for improvement welcome! I’m enjoying seeing how far I can push this internal setup for maximum range.
Regards,
Chris
@chrislfa
ENJOY EXPERIMENTING! This is fun!
I’m very pleased with my Kencotenna! I’ll compare it with a Stellatenna over the next few days, just as soon as I’ve finished drinking them.
Try the roof of the car as well.
