Ho Ho Ho SDR

[WA1GFZ]

Tonight I went to sdradio.org and downloaded Dream software and the extra dll to run it. Dropped it on a cd and loaded it into the shack machine. I then took the 6.4 KHz baseband output from a Racal and put it into the sound card. No I/Q just single ended. This was very cool. I went on 75 and it is quite washed out. The SDR could clearly pull signals out of the noise better than the receiver standing alone. There is a couple word delay in the process. I could barely make out the radio and a couple seconds later I heard words coming out of the computer. This was very cool.
I then tried the FT1000 I/Q demodulator but the software is looking for a low IF not base band audio so it didn't work very well.  Dream is set up for a 10 KHz offset but 6.4 worked fine. 6.4 just limits bandwidth to about 12 KHz while 10 KHz would allow up to almost 20 khz bandwidth. I'm using the stock Dell internal sound card.
The nice thing about the couple second delay is you get to hear things twice if you want. Cool on the brain under poor conditions. A simple converter on any receiver to 10 KHz and a computer gets you a SDR machine and the software is free.
htere is other software out there including flex but dream with the cool spectrum display is a nice simple control panel that took all of 5 minutes to figure out.
Computer meets pw ho Ho HO

[WA1GFZ]

I just tried two more software packages "Rocky" I think has the best spectrum display But only does SSB and CW,  and I2PHD ver 95 SDR with the FT1000  base band converter off the 455 KHz IF. I need to listen to a round table QSO to see how well the PLL grabs signals after playing in the loop filter. the lock is a lot slower but cleaner output.
IF. This stuff is very cool. Next I may try my LTI base band module hanging off the 40.455 MHz first IF.

[Warren]

Hey Frank,

     Alberto and Vittorio really have some cool software, and the best part it's FREE! Try downloading SPECTRAN from their web site www.weaksignals.org, it will allow you to dig signals out that are 20+ dB below what you can hear! It's the program of choice for LF DX.

   Another great and extremely powerful program is Spectrum Laboratory by Wolfgang DL4YHF, very fancy spectral analysis program - you can define filters, derive I&Q channels, create a local oscillator and mixer and more. One application of it allows you to turn your PC soundcard into a vlf receiver!

http://people.freenet.de/dl4yhf/spectra1.html

73 & HNY Warren K2ORS/WD2XGJ

[WA1GFZ]

hi Warren,
Dream is from Alberto's web site in the DRM section. It does the best job with the RA6830 6.4 KHz base band signal. The DRM module is set up for 10 KHz. IF into the sound card. It easily tunes to 6.4 khz. The nice thing about it is the way it locks to signals off center frequency without retuning. The specrum display does not have the resolution of Rocky but Rocky has about a three word delay. I also tried Alberto version 95 software that works well. Also tried my FT1000 I/Q module but phase lock is not stable. I think my IF input may be too high so need to check it again with a pad in line. The I/Q output is almost saturating the sound card. I need to play wiith it some more. As people key and unkey you hear the pll swish to lock. Dream seems to have the same audio performance as the TCI 8174 receiver DSP. It samples the 5 KHz. IF at 20 KHz and does I/Q inside the dsp.
This is superior to the PLL method due to lock up time. The DSP is right there.
The DSP in the 8174 is as fast as the Racal AM detector. The DSP has a slight advantage of pulling audio out of a weak noisey signal. The other night 75 was dead but the dsp pulled some real weak signals out of the mud while the Racal couldn't demodulate it. I suspect the carrier was too weak to recover in the Racal.
I am planning a new I/Q demodulator to work with this software but don'tthink it needs to be a pll. The better software seems to grab the carrier and do its thing.
I got a copy of the 8174 DSP block diagrams and the DSP Does internal I/Q and is an image reject mixer. I have to go back and review the Flex to see how they eliminate the image. I'm still not ready to remove all the analog from the RX but I do have an LTI eval module that will do I/Q off the first IF which seems to make the most sense in my tiny brain.
Cables all over the shack running different signals to the computer and scope so having a ball.
Need to work on the 160 meter class e rig today and see if I can get back to qro for the net tonight.
I thing the Sherwood SE3 is a toy of the past even though it sounds good. 

[Warren]

Hi Frank,

    I have a Sherwood SE-3 that I haven't used in a long time. I could set it up to do an A/B test vs. Alberto's DSP software using the 6.4kHz output from the Racal. Not now though - I'm in a race against the clock to get my LF tuner rebuilt while I have the time and wx to work on the antenna. Also been breadbording a link coupled 160M tuner, need to get rid of the clip leads and mount it down so it is less JS!

73 HNY Warren K2ORS/WD2XGJ

[WA1GFZ]

Chuck made some changes to his S3 unit and is sounds good. you do have to change switch settings. I did more testing today and conclude my I/Q module isn't all that good I need to build something better and may not need to be a pll. None  of the software packages work better than the TCI 8174 dsp. Most have nice spectrum displays. Alberto's 95 sure picks up on drifting VFO and FM problems. I also heard one guy FM with modulation.
Cool on 160. I should be back on with the class e rig wednesday night. I rebuilt the driver stage with better output transformer ratio 2:2 from 1:2 and increased the drain voltage. Drive looks much better. I few more modes and back in the rack.