I’m using the direction-finding application and my noise floor is a sad -69 dbm while looking at a 2.4 MHz bandwidth. I want to zoom in to about 50 or 100 KHz and lower the noise floor as much as possible, the signals I’m looking for are about -105 dBm.
What would the DAQ settings look like to do this?
Thanks!
You can use the DSP side decimation setting to improve the noise floor and zoom in to a more narrow bandwidth. A decimation value of 24 would take you down from 2.4 MHz to 100 kHz.
Thank you for this information. I should have realized this myself (I deal with SDRs for other things and always decimate down to narrow bandwidths to cut down on noise, etc.).
My concern is how much decimation can there be and not have any undesired effects on DOA accuracy, if any?
Right now I’m using the decimation of 24 (100 KHz) and that helped drop the noise floor and up the sensitivity a lot from the full 2.4 MHz. The noise floor dropped almost 20db by decimating it down that far. I’m just not sure if it can go further.
The people I’m after are using handhelds from ground-level locations. I cannot hear them directly most of the time, so I use other methods to get me “nearby” first (yagis at high elevation places is one).
When I get fairly close, I can usually hear them on a mobile radio in the car within a mile or 2 (on a very poor antenna to not interfere with the Kraken antennas), but the Kraken does not “hear” them until I’m even closer.
So the more sensitive I can make the Kraken without degrading the accuracy or causing other potential problems, the better.
I hope this makes sense.
Decimation can only improve sensitivity so much by reducing quantization noise. As long as you’re not decimating too much and cutting down the actual signal you are interested in, it won’t affect DOA accuracy at all.
The main thing that can improve the sensitivity is a better antenna and/or an LNA with low noise figure.
Your approach is correct. Use Yagis to get within range of very weak signals, then let the Kraken take over when it can.
I did some tests, and at a decimation of 2, 24, or 64, the DOA accuracy doesn’t seem to be affected, just the overall noise level goes down… so that helps with weaker signals a little bit.
I’m leery of trying to use LNA’s… even if I can find 5 of them that have the exact same gain, noise figures, etc.
It’s working good enough to do what I need. Much better than the old Doppler I used to use. The
Kraken is an amazing device.