On Fri, Jun 19, 2009 at 9:04 AM, Ray Andrews, K9DUR<k9...@rnacs.com> wrote:
> Theoretically, if you had an A/D capable of a sampling rate of 40 MHz or so, > a communications link with the bandwidth neseccary to handle the resulting > data stream, and the CPU power required to process that 40 MHz bandwidth > digital stream in real time, it would be possible to display the entire HF > spectrum at one time. Of course, you would also need a monitor a couple of > hundred feet wide to make the display useable....hi..hi. Seriously, an A/D > with these capabilities would be prohibitively expensive, the required > communications link does not exist with the current technologies available > in the PC environment, and the processing power is also beyond the > capabilities of PC-type computers. But, theoretically, it is possible. > > 73, Ray, K9DUR Actually this is not too difficult. If you have an ADC capable of digitizing 0-50 MHz, and enough RAM connected to it to store a block of data, say 8192 samples, then it is possible to display any bandwidth on the panadapter from 0 - 50 MHz. This data needs to be sent separately from the real time demodulated data stream, but since an update rate of 20 - 30 frames per second is enough to make the panadapter look "real time" to the human eye, the bandwidth required to send this data is reduced by a very large amount. You cannot concatenate the 8192 sample blocks into a larger block to increase spectral resolution, though, since only the samples in each block are contiguous - from block to block they are not. The spectral resolution you get is dependent then on the storage size of the RAM connected to the ADC. You can apply averaging to the blocks though. You can get much larger blocks by increasing the storage size of a block. This is how QS1R and SDRMAX2/3 are capable of displaying any bandwidth from 0 - 50 MHz on the panadapter and switching between them on the fly. Regards, -- Phil Covington Software Radio Laboratory LLC Columbus, Ohio http://www.srl-llc.com _______________________________________________ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
