Baofeng UV-5R Spectrum Analysis Revisited
A few days ago I noticed some incoming traffic from a Dutch scanner forum. I could read there without registering, which made life easy. The link provided there was about the Baofeng UV-B5 review, but I also noticed something else interesting in the thread.
One of the forum members did some measurements on the UV-5R, stating that the radio was totally crap due to excessive spurious emissions and harmonics. He added a screen shot of his Rigol spectrum analyzer, probably the same model I own. This was what he came up with:
If this were correct, the Baofeng UV-5R would be the most horrible design ever. But wait, we did this already a long time ago, and the UV-5R wasn’t too bad at all. All of his bothered me enough to pick up a few of my own UV-5R’s and repeat the measurements. I tried the oldest one I have (BFB231), and a more recent one (BFB239). Results didn’t differ in any way, so I just picked one. These were the results:
So, what’s happening here?
I considered a few possibilities:
1) his UV-5R was a dud,
2) he made errors while measuring.
The answer is likely #2. The only way I could replicate his results was by reducing external attenuation to such a low level that the linearity of the spectrum analyzer was compromised.
Higher order harmonics
I’m pretty sure his faulty results were caused by a well-known factor: distortion due to higher order harmonics. When the input signal level you feed into a spectrum analyzer is (too) high, spurious images of the input signal harmonics are generated due to the non-linearity of the mixer conversion. It’s kinda like LSD to a junk; you start seeing things which aren’t there.
Bottom line: it’s easy to make any HT look bad by not understanding the test equipment you’re working with.