Sunday, November 29, 2009

receiver comparison

Short test this morning, all about receivers again. Usually, if there is no special experiment going on, I have my little diodes doing the receiving for my grabber. And so did those during the night, when we stopped the experiment on 20m.
Due to the 20m experiment, the AOR AR3030 (with Collins filters) still is close to the grabber computer. Thus, a quick look to compare the homebrew direct-conversion receiver to the commercial product. Same antenna (G5RV-jr), same matching, just another receiver.
Here's the result:

Some short explanation, around 0745z I decided to have a look on the grabber to see if something is dripping in. I reckoned that the brightness setting for the spectrum was a little on the darker side and therefore adjusted to the level I usually use. Around 0806z the receivers were exchanged, and sensitivity levels needed adjustment. Since both receivers deliver quite different a.f. levels, the spectrum on the d.c.-RX is essentially black at 0805z, this is due to the working of spectrumlab, whenever you used this software before, you will know what I am writing about.
The AR-3030 show a slight warming up curve, fair enough, I was off all night.
As for sensitivity and noise, I don't see much difference...
To me this is a very satisfactory result, given the d.c.-rx cost a fraction of the commercial receiver equipped with the finest of filters'.
I could, and probably will, give the FRG-100 a shot, however, the FRoG is not equipped with a narrow bandwidth filter.