RE: [Flexradio] FW: Yikes, I got Spikes

[Gerald Youngblood]

Title: Hi all,

Hi Joe,   In Panadapter mode, the red center line will be at the IF frequency of around 11KHz.  In SPEC mode the IF shifts to DC (0Hz) at the red line so that you can view +/- 28KHz from the tuned center frequency.  The reason we use the offset IF at 11KHz is to get rid of the junk near DC such as AC line noise and harmonics, 1/f noise, phase noise, etc. etc.  In SPEC mode, this junk will show up in the center of the screen without an antenna.  With the preamp on, you will cover up most of this noise, even in spec mode.  With the preamp set in the off position, the 1/f noise also goes up on the instrumentation amplifiers.   On the other hand, I have not seen a setup with spikes like that.  It appears to me that you have a VERY bad ground loop.  There is nothing in the radio that will emit fixed spurs at those frequencies.  It appears to me that those are harmonics of 60Hz AC, probably odd harmonics.  I would recommend that you work on the wiring.  Make sure that you have the computer, radio, and all peripherals plugged into the same outlet strip.  Also, make sure you your outlet strip has a good ground.  If that doesn't solve it you may need to try a UPS supply.   Finally, using the rig in SPEC mode in the OFF preamp setting would be a very rare application, I would think.   73, Gerald -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]On Behalf Of Joe - AB1DO Sent: Tuesday, June 14, 2005 9:34 AM To: Flexradio Reflector Subject: [Flexradio] FW: Yikes, I got Spikes 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