Ludwig, thank you for your help on these QMX+s. Perhaps I should have started my own topic and will do so in a few days after my USB C to USB cables arrive. I will then be able to run the tests from my Windows 10 PC.
My problem is I can¡¯t receive except for the very strongest signals, it seems they are covered by some noise.
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OPV?
My oscilliscope has no LPF, except the triggering can selectively reject low or high frequencies.
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My oscilloscope measurement was taken with a 100mhz (-3db point) scope on the audio output to the earphone connector. In particular, ?JP303 pins 2 and 5, which is next to the display board on the same side (left as I look at the front face) as the PCM1804 on my rev 2.3 board. A clip on EMI toroid with 5 turns of the stereo cable thru the core going to my powered speaker reduced the receiving noise by about half. Wierd, didn¡¯t expect that. The scope trace shows roughly a 2.2 Mhz and 220 khz and other noise, which may explain some of the noise reduction with the toroid.
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Lets do this, so you can use this topic to help N6QP Michael. I will open a new topic in a few days after I get the PC measurements with the new cables. I apolgize for any distraction.
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Bob NQ5P
