Monday, October 12, 2009

Noise Blanker

I was playing with my new Computer/Radio. The latency in the new computer is 45 microseconds down 10 times from the core 2 duo machine. As I was measuring latency I was monitoring 160 CW and a terrible noise came on:

You can see the noise as a jagged regular wideband saw tooth of about -90 dBm. I get this noise intermittently. I live out in the country, and we are all on well systems as opposed to county water, and I believe it to be from a well pump motor from one of my neighbors. I flipped on the NB and here is what I saw:

Noise 100% eliminated and you can see stations that otherwise would be obliterated pop out of the noise. Look closely at the noise still visible in Skimmer. It looks like an increase in background snow on the display. The signal that goes into Skimmer is the raw I/Q data not the processed data that is displayed on the panadapter. Hence you can still see the noise in Skimmer even though every trace of it has been eliminated in PSDR. This is the advantage of this kind of radio system. The signals are processed in a kind of virtual time that is "near real" so you can do many things to the signal (like remove all the noise) that enhances the human-system experience. This is one blanker that really works!! Notice that you can not see the signals in Skimmer that you can see in the panadapter with the blanker on. The noise is intermittent enough and the blanker works so well I haven't even tried to spot who's pump is the culprit.

Here is a shot of "normal":

Here you can see Skimmer and the panadapter are seeing the same signal. Very interesting display. With the NB on there is no distortion added so even the weakest MDS signal is unaffected by the NB. Notice the S-Meter reading in each screen shot. These readings tell the story. With the NB engaged there is no difference in my 160M MDS between noise and no noise

I finally have all the basic accouterments loaded on the new computer finishing with Tortoise SVN. I made an image of the partition using Acronis, and now I can return to a pristine condition in about 10 minutes by simply reloading the image of the partition. I like to do that every so often and Acronis works great for that purpose.

Here is a copy of my usual desktop when I am operating:

I have PSDR, DDUIL, Skimmer and 4 of the DX lab suites applications open as well as Firefox, and some tray applets like Google talk. SpotCollector which is the DX lab cluster program is connected by telnet to 3 spotting sources. In the past having this much internet activity (SpotColector, Google Talk, and Firefox as well as email) has caused the % processing utilization to sore. With this rig I have never seen it more than in the low teens.

This computer makes this radi0 and all the rest of the other applications that I like to have open play so smooth, its a delight.

73 W9OY