Archive for November 16th, 2015
A while back I wrote a post called “Why FCC tested transceivers should matter to Ham Radio operators.” As part of this post, I drew attention to testing performed by the ARRL on used ham radio transceivers. One of the highlights of this article was that the Baofeng HTs performed exceptionally poorly due to a high level of spurious emissions.
However, I recently stumbled onto an article on PD0AC’s Ham Radio blog called “Baofeng UV-5R Spectrum Analysis Revisited,” in which Hans (the author) looked into comments about the UV-5R’s suspected spurious emissions. I quote:
“But wait, we did this(link) already … 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… The only way I could replicate his [failing] results was by reducing external attenuation to such a low level that the linearity of the spectrum analyzer was compromised”
In his initial testing, Hans and Tom (PA2TSL) used a 30 dB attenuator for the spectrum testing.
So I went back to the original QST article (November 2015, page 74) and re-read it. It’s important to note that the following quote appears under the test results table on page 75:
“Specific makes and models in which the majority of the units tested were noncompliant: Baofeng, UV5R, UV5R+…”
I found the following description of their test equipment and setup:
“Our convention tests measured … using a test fixture consisting of a Bird Model 43 RF Power Meter, a Bird Model 8322 30 dB power attenuator, a Hewlett-Packard HP355C 0 to 12 dB step attenuator, and a Rigol DSA-815TG spectrum analyzer. … First, the power output … was measured using the Bird Model 43 meter. … Next, with the radio push-to-talk (PTT) button pressed and held, the Rigol DSA-815TG spectrum analyzer was used to perform a sweep…”
So, I went to the FCC’s testing setup. They’re the ones who initially gave the UV-5R a pass, so let’s see what they used to do it. Starting on page 37 of the FCC’s published test results, you can read for yourself the detailed setup and testing of the transceiver, including the directly-connected spectrum analyzer test. Note that they specifically show that the signal from the radio passes through an attenuator (if I’m reading the report correctly, the attenuation is 13 dB).
On page 76, of the QST article, Figure 3 shows a borderline result of a tested UV-5R. The attenuation displayed on the display of this figure shows an attenuation of 10 dB, below either of the previous two test setups.
Let me say that I appreciate what the ARRL does, and I don’t believe for a minute that they are unfamiliar with their equipment, but testing at the informal environment of a convention could lead to simple mistakes in the test setup. I would have really liked to see a clear spelling out of what level of attenuation, if any, was between the equipment and the spectrum analyzer. It’s also important to note that the ARRL clearly mentions in their article that this testing was performed on used equipment, not newly-manufactured units specifically submitted for testing. In light of the two previous articles I mentioned above, and the lack of clearly-mentioned attenuation between the radio and spectrum analyzer, I have to say that, in my opinion, the ARRL’s testing is inconclusive.
Your comments are welcome below. Thank you for reading.