Improved video quality of BPSK31 decoded by Rocky from Sofrock RX/TX v6.1 on 40m.
Month: October 2007
Other SDR Software
SDRadio from I2PHD was my first introduction to SDR receivers. No transmit but a good straight forward bit of software receiver.
Here it is receiving SSB from my Softrock TX/RX v6.1.
Delta44 Sound Card revisited
I have not even tried the Softrock on my Dual Core Laptop machine. I was aware of the need for not just a decent sound card for serious SDR use. This was the ‘need’ for a new shack computer that I had been overlooking for several years.
I have just come across the following from Duncan M0KGK, I will let him do the talking.
06-Nov-2005: The Delta card has arrived, and the difference in performance is absolutely astounding. Click the pic on the right (below) to see the substantial difference in noise performance between the AC97 onboard chipset and the Delta-44.
I was going to repeat the test above with the spurs and overlay them on the graph, but this exercise proved pointless. At the same 48kHz sampling rate all unwanted images were down in the noise and could not be measured.
Quality of received audio using Softrock 40 / Delta-44 / PowerSDR is excellent. I did some back to back listening tests on CW and SSB during busy contests between the Softrock and the Yaesu FT-857D which happened to be plugged in at the time. In all cases, the readability of weak DX signals from the SDR was better. The signal to noise seemed to be noticeably better too.
The 857 is not graced with the best receiver in the world, so it’s my intention to do back-to-back tests when time permits with the FT-990 and FT-101E, both of which are (IMHO) better performers. Next steps are to get the Softrock into an enclosure and feed with an external supply.
If you are not too sure of your dB’s and analysing graphs at a quick glance there is well over 100 times more noise there.
Another very useful graph from Duncan is the noise comparisons of different sound cards. The Delta44 is the same performance as the Delta66,in fact I understand it has been optimised recently.
I am sure Duncan will not mind me repeating this. Incidentally he is the author of the KGKSDR Software. Yes I have SSB transmit working fine now, it has benn tested across town but no distant contacts have been made yet. Whereas the narrow band mode BPSK31 has produced more contacts, a nice long one with PA0MJK in the Netherlands today revealed that he too has built a RX/TX v6.1 but has not had it on TX yet.
Delta44 cards have been in short supply, I purchased mine from Dolphin Music. I was astounded by their price,service, delivery speed and after sales follow up. I told them I would not hesitate to recommend them to the radio world as a supplier.
Dolphin Music
Venture Point West
70-72 Evans Rd
Liverpool
L24 9PB
For information contact :- info@dolphinmusic.co.uk
KGKSDR Software
I looked at the Main3 Software programs on my Laptop, (prior to building the SDR) and classified them thus.
Rocky: Simple, looks nice plays the I/Q files so that had so that I could get a feel.
KGKSDR: Just about the right complexity, written for the Softrock. But hang on, that awful dancing display, it would not play my I/Q files so I could not give it a go.
PowerSDR: Quite complex having been written for the SDR100. Once again, wild dancing displays, it did play back I/Q files but signals were difficult to spot.
As can be seen from my postings Rocky was the one that worked easily on my dedicated SDR computer. It also supports decode of BPSK31 internally. I have therefore concentrated on Rocky for PSK31 and CW contacts.
I have returned to the other two in my spare moments. With a little setting up on KGKSDR I have got it to my liking and I am working on getting SSB TX going.
For now here is a capture of F6GUU on PSK31 during our contact this morning, his peak is just to the right of the vertical pale green line, I am using the CWLSB filter.
As usual Right Click on the image and select View Image for a full width display of 7.00 to 7.10 Mhz
The dB scale is quite accurate, the S meter is rather mean and needs to be set for a reference S9 signal.
Realtek HD Sound
This is a screen capture of my laptop Realtek HD sound displayed by Rocky 3.32.
I don’t use it for SDR so the input is connected to the internal mic. Background noise from the mic. accounts for some of the bump in the middle. HF response can be seen to fall off at either end of the display, there are also some large spikes, maximum output sample rate is 48KHz but it is fine for playing back a 96KHz sampled I/Q recording.
If all Radios were SDR’s
If all Radios were SDR’s how nice it would be, problem solving is made easy.
Today I put the Softrock on, tuned to my usual spot on 7.00Mhz(the PSK slot) to be greeted by a burring noise and a spiky waveform peaking 20dB above the noise floor.
On the standard HF transceiver I might have thought, just another noise on the band. With the SDR I closed the display to show the whole band. OK there are six of these peaks.
Click on the central spike to measure the difference in frequency between each. 15,650Hz ah ha television do we have a new or faulty TV in the neighbourhood? I confirmed by removing the antenna that it was coming in via that route.
My Sony portable radio was out in the car, I popped out to fetch it and tuned it to one of the peak frequencies, I spoke to my neighbour, it is not me he said. No, it was quiet around his place. Back to my house and the noise appeared, stronger near mains wiring. Up to the shack, it was stronger still, I closed down the computers and monitors, it was still there. I switched off shack mains, still there.
There was only one more thing, plugged into a separate socket, a wall wart, it powers the surveillance camera. I switched it off and away went the noise.
Please refer to my previous postings. I have been using the shack FSTV camera for off screen video of the Softrock. Hmm, I borrowed a lead from the video mixer, this left the surveillance camera un terminated, re terminated all was clear.
There may have been a clue to it being a non broadcast device, 15,650Hz, not locked to 15,625Hz line frequency.
Video with Sound
Yes the talkies are here, I promised sound, the SVHS camera was not an improvement for off screen video. So back to the Web Cam, the next step will be to use a separate computer to record the video, so reducing the SDR machine overheads.
This recording is a busy 40m with a contest on the go, SSB end.
Next a listen to some CW stations.
For now I will publish and be damned.
Rocky Spectrum Display 40m
Using Rocky on full zoom and my 17 inch wide screen monitor the Spectrum display on the 7.00 to 7.10 band segment is no lees than 2.91 meters wide.
Watch it scan from HF to LF. On a quiet night on the band.
The Computer for SDR
Time to mention the computer for Software Defined Radio.
There has been much discussion on the group recently, following a question as to what is optimum. This question sparked everything from 8 core Processors to parallel processing.
The questioner was offered.
> The offer I received comprises the following:
> Intel Dual 2 Core E6550
> Motherboard ASUS P5K
> 160 GB Samsung SATA HD
> 2 X Kingston 512 MB DDR-2 800
> Video card POV 7100GS
> Case + PS TK-1150 ATX
Optimum is of course the very best and latest computer you can afford. Adequate for Amateur use is another matter.
My own theory for a shack computer was to build a computer using last years high end, processors at the bottom of their price curve. This way I got a 2.66Ghz Celeron D machine with 1 Ghz of memory at a fifth of the price of today’s higher end, and that is including the Delta44 soundcard.
Its performance is more than adequate for what we need. In the future if I want more processor power for SDR, better will again be cheaper and I have not invested a fortune.
Orses for corses.
Rocky decoding under strong Interference
Another video. As a Fast Scan TV Operator I should be able to do better than the last web cam video, wow, sound next time we hope.
Rocky tuned to a PSK31 signal on 40m. The display width is closed to show the whole band. A creeper rolls down from the top to the bottom of the band.
The display is expanded again, decoding carries on despite a strong adjacent interfering signal.
Radio - LF/MF to Microwaves 