Spurious Emission Measurement on stock uBitX
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Hi, all.
Attached is a PDF file which shows the results of measuing spurious emission on my uBitX which I haven't modified its hardware/software at all. Here, in Japan, the spurious emission should be less than -50dBc and so the list indicates I can use my uBitX with a Pi-C antenna tuner, but not on 15m unfortunately. This time, I checked only the CW transmission beccause I had a problem to measure SSB case. It would be very much appreciated if someone could advise to me. To measure the spurious emission on SSB, at first I need to saturate the PA output by the mic input of so called "pseudo voice" that is 1.5kHz sine wave, and when the output is saturated by increasing the input leve, then 80% of the input level will be used to measuer spurious emission, the Lab guy explained to me. However, uBitX output won't be saturated which means I couldn't observe the flat level of PA output as increasing the input (pseudo voice) level, but suddenly the output level falls down to a few mW. The Lab guy said it would be because uBitX didn't have an ALC - Auto Level Controller of the mic input. So please advise to me how I can saturate the output (PA) level with such a "pseudo voice" input? Maybe bring an external mic compressor? However, how can I observe the flat level of PA output? Thank you for reading my long email. Hope someone can help me. If you are interested in screen shots of the spurious analyzer, feel free to email me. BR, // hiro, JJ1FXF |
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Iz, Thanks for reading. No, I didn’t insert any LPF but only the simple pi-tuner was there btw uBitX and analyzer, because I thought pi-tuner might work as a kind of BPF. There will be a possibility to suppress the spur emission if I add a LFP but what I observed was the spur of 28MHz with AT was OK but 21 MHz was not. So maybe I need some drastic solution, I suppose. Here is a manual of TRIO AT-200 antenna tuner, if you are interested in it. Yes, I’m planning to do like what you did. So I already got AA-30.ZERO antenna analyzer. Thanks for your comments. // hiro, JJ1FXF 2018年8月18日(土) 0:30 iz oos <and2oosiz2@...>:
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Allison san, Thanks for your info. I tried some apps from Apple Store and seemed any of them might be OK. I will plot the PA output level as increasing the volume of iPhone. // hiro, JJ1FXF 2018年8月18日(土) 2:59 ajparent1/KB1GMX <kb1gmx@...>: Hiro san, |
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Looking at the “strongest spur frequency” column, 42.4700MHz spur was -41.1dBc at 21.2250MHz row. However, with AT, the 42.4700 spur was dropped to only -45.6dBc which tendency is different from other bands. Then looking at the 28.8500MHz rows, 14.4270MHz spur was observed as the strongest without AT, but 43.3000MHz was the strongest spur with AT. Maybe this Pi-C AT does not work efficiently above 30++MHz? I don’t know. So additional LFP which cuts above 30MHz may be a good trial. I’ll do it next time, maybe after casing my uBitX. // hiro, JJ1FXF 2018年8月18日(土) 5:21 iz oos <and2oosiz2@...>:
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HIRO, JJ1FXF