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Bob, Thanks for the thorough comparisions. Very often, we are at the limits of measurements with these instruments. A professional Rigol 815 is my priced possession though I often get by with just the Antuino. - f On Fri, Nov 17, 2023, 9:55 PM Bob Benedict, KD8CGH <rkayakr@...> wrote: I uploaded to the files section a pdf on what I have been seeing while measuring the spectrum output of my sBITX V2. Nothing I have is officially calibrated and I am not an RF engineer, so take it with a large grain of salt. |
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Thanks very much, Bob!? ?Those look like they generally agree with what I found (after correcting for the problems with D20/D21).? ?You and I also see some increase in the noise spectrum around the fundamental, and some spurs that are right around the limit, but the low pass filters are doing a fine job on the harmonics.? ? Thanks also for including the KX3 for comparison!
Great job! Gordon KX4Z |
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The KX3 is a direct conversion transmitter. It has a single oscillator at the tx frequency. It will have no spurs, only the harmonics, and the push-pull power chain can null the 2nd order harmonics very well. The reason we didn't opt for it was that the IMD as well as the images are not very well controlled. For instance, on sbitx the opposite sideband is non existant. On kx3, -55dbc is your best case. - f On Fri, Nov 17, 2023, 10:15 PM Gordon Gibby <docvacuumtubes@...> wrote: Thanks very much, Bob!? ?Those look like they generally agree with what I found (after correcting for the problems with D20/D21).? ?You and I also see some increase in the noise spectrum around the fundamental, and some spurs that are right around the limit, but the low pass filters are doing a fine job on the harmonics.? ? Thanks also for including the KX3 for comparison! |
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thanks for those insights.? ?Fascinating the choices designers make! gordon kx4z On Fri, Nov 17, 2023 at 11:52?AM Ashhar Farhan <farhanbox@...> wrote:
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Bob Benedict, KD8CGH