Well I have an attic antenna. The roof is concrete tile, over paper, over plywood (with nails as you say). I would guess the total loss is 3 to 4 dB. I have a 5 dBi gain antenna, so the effective gain is 1 or 2 dBi.
However, I think the major reason for loss of aircraft adsb messages is multipath. Signals bouncing off the furnaces in the attic or bouncing off nearby house etc. This causes aircraft to go in and out of radio shadows.
A lot of them are probably weighing in the possible effects of falling off said roof while connecting the antenna to a chimney etc⌠
And then there are HOAs, accessability, weatherproofing, etc., so in the end it is a conscious decision to put it in the attic rather than on the roof.
I think the height is the biggest factor.
Orange is RTL-SDR in the attic, blue is Airspy Mini in the attic, yellow is near a fist floor window.
My guess is the attic antennas are 20ft above the 1st floor antenna.
The graphical comparison is a interesting comparison. Thank you for that. Even outdoors I find that increments of 5 feet can make a significant difference. My mast system is made up of 5 foot sections of pipe.
Yes, the roof height and pitch can have a negative effect on interest. HOAâs are the curse in my way of thinking. Never would go there for any reason. I do all my antenna work no higher than a step ladder high off the ground now. Mast gets pushed up through a 9 foot section of Rohn Apex tower attached to the house.
Is this tracked aircraft?
Yes, aircraft tracked.
Based on the wavelength at 1090 Mhz, most roofing nails are much shorter and I suspect not a huge problem. Nails in the rafters and metal bracing will definitely affect performance of an antenna. While height is usually the best answer, I have seen dropping the antenna a bit helped with better overall performance. 5 inches can make a big difference at these wavelengths. Even a heavy rain or frost on a roof will attenuate the signals at these frequencies. If you can take a cell phone up and monitor your real time performance, you might be able to improve how well your system is working. Be careful up there.
Nice idea to avoid the inside corners on the roof to avoid the metal flashing!!!
Yes, a cell phone can be a great signal strength portable tool. I use a Wi-Fi analyzer app to track Wi-Fi strength around a house to optimize source and receiver componentâs locations. Those signals are straight line animals and donât like corners. Your cable provider doesnât normally install Wi-Fi routers in optimized locations.
