I'm lucky that my job gives me access to a spectrum analyzer. I wanted to compare the effect of two different antennas, because it seemed like I was getting lower range on the second antenna. The proper tool would be an RF power meter, but I don't have one of those. The spectrum analyzer isn't perfect for that job, but it does okay. I thought y'all might like seeing the results.
The first antenna is this iBCrazy BlueBeam whip (LINK).
... and the result:
A classic analog transmitter's spectral shape, with a peak at -43 dBm. Distance between the antenna and the spectrum analyzer is about three feet.
The second antenna is this "stubby" cloverleaf from Surveilzone. (LINK) I bought this antenna because I wanted something that was low-profile to my Popwing, so that it didn't get knocked around and bent up in transport.
... and the result:
Peak power here is also -43 dBm. But RF energy is about area under the curve, not just peak power. So let's put them one on top of each other with a little transparency.
How about that! The $5 antenna from SurveilZone appears to be putting out a bit more energy than the $30 antenna from iBCrazy. On the other hand, the vast majority of the difference is in the side lobes, at about 25 dB down from peak. In real-world conditions, at the edge of coverage where it really matters, this energy would be below the noise floor, and the difference is really moot.
Bear in mind, now, that this is NOT anything close to a rigorous test, so keep your pitchforks sheathed. Nevertheless, I think one safe conclusion is that if my range is decreased on the stubby antenna, it's not because the antenna itself is flawed. Maybe it's due to shadowing from the fuselage of the plane or something.
The first antenna is this iBCrazy BlueBeam whip (LINK).
... and the result:
A classic analog transmitter's spectral shape, with a peak at -43 dBm. Distance between the antenna and the spectrum analyzer is about three feet.
The second antenna is this "stubby" cloverleaf from Surveilzone. (LINK) I bought this antenna because I wanted something that was low-profile to my Popwing, so that it didn't get knocked around and bent up in transport.
... and the result:
Peak power here is also -43 dBm. But RF energy is about area under the curve, not just peak power. So let's put them one on top of each other with a little transparency.
How about that! The $5 antenna from SurveilZone appears to be putting out a bit more energy than the $30 antenna from iBCrazy. On the other hand, the vast majority of the difference is in the side lobes, at about 25 dB down from peak. In real-world conditions, at the edge of coverage where it really matters, this energy would be below the noise floor, and the difference is really moot.
Bear in mind, now, that this is NOT anything close to a rigorous test, so keep your pitchforks sheathed. Nevertheless, I think one safe conclusion is that if my range is decreased on the stubby antenna, it's not because the antenna itself is flawed. Maybe it's due to shadowing from the fuselage of the plane or something.
