Post AdDJ5JEnCB69S9PSOu by kr1st@mastodon.radio
(DIR) More posts by kr1st@mastodon.radio
(DIR) Post #AdDJ5DI7IuBz0iv1kW by kr1st@mastodon.radio
2023-12-26T19:34:20Z
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Santa brought me Quansheng UV-5k(8). A YTer in a recent video said he couldn't recommend this HT because it was "dirty" and showed a screenshot of TinySA Ultra from which the viewer was to infer that the radio was not satisfying FCC requirements.The FCC requires harmonics to be 40dB down from the fundamental and the video showed that the second harmonic was "only" 38.8dB down. I'm including a screenshot of that video.Time to do some measurements! #hamradio #amateurradio1/4
(DIR) Post #AdDJ5EMPKRDcKJvy4m by ndz@noagendasocial.com
2023-12-26T21:19:47Z
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@kr1st is that the Quansheng you can update the firmware on to listen to 10 meter USB ?
(DIR) Post #AdDJ5FJxl0rDJ1nWu8 by kr1st@mastodon.radio
2023-12-26T19:34:56Z
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Judging by the gain (-40dB) and attenuator (21dB) settings on his TinySA I suspect he did an antenna to antenna measurement, meaning he used some sort of antenna attached to his TinySA to pick up the signals radiated from his UV-5k. The FCC requires measurements on the feedline to the antenna. That means you need to use a coupler. I'm a bit puzzled that when he measured a number so close to FCC specs he didn't suspect his measurement method before declaring the radio "dirty". 2/4
(DIR) Post #AdDJ5HF4cA8PGRWeYq by kr1st@mastodon.radio
2023-12-26T19:37:06Z
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In my test setup I inserted a Narda 30661B coupler between the HT and a dummy load, and then connected the same TinySA Ultra with a 20dB attenuator to the coupler. See the attached image to see the test setup. Note that the coupler is a microwave coupler and that the sensitivity rolls off below 700 MHz. What this means is that the sensitivity lowers as you go lower infrequency, so the measured differences between the fundamental and harmonics below 700 MHz are *larger* than measured. 3/4
(DIR) Post #AdDJ5JEnCB69S9PSOu by kr1st@mastodon.radio
2023-12-26T19:39:12Z
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When you look at the image of the TinySA Ultra, the second harmonic is 45dB down from the fundamental frequency (146 MHz), and the 3rd harmonic is 49dB down. The UV-5k(8) was transmitting at full power on 146 MHz.It looks to me that the radio is satisfying FCC requirements. If you find error with my assumptions or method, please let me know. I'm just an amateur, not an RF engineer. I'm in it to learn!4/4