Re: [Flexradio] Interesting behavior when connected to a dummy load

[Eric Wachsmann - FlexRadio]

Title: Interesting behavior when connected to a dummy load

Jeff nailed this one on the head.  The jumping around is because when spur reduction is turned on, the radio hardware is only tuned every ~3.051kHz.  We do the fine tuning using a software oscillator.  Also worthy of note is that we use an 11kHz IF.  So what you are seeing is the junk around DC on the left side of the spectrum.     Eric Wachsmann FlexRadio Systems     -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Tim Ellison Sent: Friday, December 02, 2005 11:23 PM To: flexRadio@flex-radio.biz Subject: [Flexradio] Interesting behavior when connected to a dummy load   I was testing tonight into a dummy load and noticed some very peculiar behavior. When connected to the dummy load on 14.179 MHz (USB)  I see the noise floor (signal) in the panadapter as a flat line from -10K to +10K  Hz at about -145 dBm.  That looks good to me Now I change frequency to 14.178 MHz and I see the signal rise to -130 dBm between -10K and -9.5K Hz.  It is flat at -145dBm across the rest of the spectrum.  Looks like more noise on the low end.  Not so good. If I change the frequency the to 14.177 MHz I see the signal rise to -113 dBm between -10K and -9.5K Hz. It is flat at -145dBm across the rest of the spectrum This shows a *lot* more noise. Here come the strange part. I change the frequency to 14.176 MHz and the signal looks just like the signal on 14.179.  Flat across the entire spectrum at -145 dBm. By changing  the frequency down one kHz to 14.175, I see the signal that looks like 14.178 MHz.  A small rise to -130 dBm at the low end again. If I decrement the frequency down an additional kHz to 14.174, I see the signal that looks like 14.177 MHz.  A large rise to -113 dBm at the low end again. This pattern repeats itself through out the entire 20 meter band.  The rise in the noise floor is a little less in magnitude at the very bottom of 20 meters (14.050), but by the time I get to 14.150 the rise in the noise floor is back to approximately -110 dBm. I checked other bands and it exhibits this behavior on ALL bands.  Always a three kHz stepping to repeat the pattern. Anyone have a clue what might cause this behavior?  I'm using the Delta 44 with the breakout box eliminator. -Tim --- Tim Ellison Integrated Technical Services Apex, NC USA 919.674.0044 Ext. 25 / 919.674.0045 (FAX) 919.215.6375 - cell Skype: kg4rzy