On Thu, Apr 24, 2014 at 3:31 PM,?<allgyer@...>?wrote:
You mention however that you are using HDSDR for your measurements. You can get some fantastic performance numbers if you dial the RBW back, average the noise floor, and read MDS as a 3 dB spike above the averaged noise.
I selected 2.9Hz as the RBW because it resulted in -130dBm which matches your results and makes things easier to compare for this conversation. I wasn't trying measure absolute values, just trying to prove that something could be achieved by increasing the gain factor beyond 100.
But the results will not correlate with the ARRL method. A 3 dB spike above an averaged noise floor on HDSDR will be perfectly audible but it will not result in a 3 dB S+N/N ratio at the audio output. In fact, if memory serves, there was no significant difference between S+N and N on an RMS noise meter under those circumstances.
Changing the display RBW doesn't change the bucket size of the sinc filter. If you look at the data while it's in the middle of the sinc filter, where it's in the frequency domain, you should see a better correlation to ARRL test methods. This isn't want we want to visualize as an operator though.
If you are using output RMS noise as your measurement then I can only guess that something about the Peaberry mixer/LO layout produces less noise than does the Ensemble II and, therefore, "uncovers" the op amp noise to allow for improvements.
The Peaberry V2 has a different receiver. Same parts, just a different configuration.
