[Flexradio] FW: Yikes, I got Spikes

[Joe - AB1DO]

Title: Hi all,

Hi all,   I am noticing a “strange” phenomenon, visible in all of the console versions I have, i.e. from 1.3.4 on. On the far left hand side of the panadapter display, and only when preamp is off I see the noise floor rise to a peak. To focus in on this more, I used SPEC to center what turned out to be an approx 3kHz wide central peak with many harmonic spikes:     In the above, the rig is connected to a dummy load. When the preamp setting is increased, this peak gets smaller, to virtually disappear at a preamp setting of med or higher. The preamp is the ONLY adjustment I can make that seems to influence it at all. If I turn the power to the SDR box off (after having turned the console on with it powered on), the central peak remains visible, but the harmonic spikes reduce greatly in value. When tuning up or down, the peak remains on frequency until it reaches about + or – 1.5kHz, at which point it flips to the other side, that is from –1.5kHz to +1.5kHz and v.v. It is also visible on every single band, at every single frequency. Also the peak value of –110dBm is absolute, that is if I calibrate the console to show a noise level of say –90dBm, it is not visible.   Before I go tearing the whole shack apart here in search of the interfering source, I’d like to know if anyone else has experienced this, if it is something inherent in the S/W or hardware, or if it has something to do with my settings (I recalibrated everything using Elecraft’s XG1 signal generator, but to no avail). If none of these, I’d appreciate a clue as to what I should be looking for.   My setup uses the Delta 44 and USB adapter.   Thanks, Joe