Last altered Sunday, 29 July 2007 21:43 UTC
Testing Soundcards, Using multiple Soundcards, Two 5MHz beacon monitoring programs on the same computer.
There is a lot of software that will make a computer with a sound card a useful audio analyser.
The GB3RAL program will act as a spectrum analyser, in the tune mode it has a bandwidth of 500Hz and a 90db? range. The display is centred by adjusting "Track Freq".
A versatile tone generator is at http://www.nch.com.au/tonegen/index.html It was free for non commercial use, but now requires registration for frequent use. It will produce up to 16 simultaneous tones, sine, square, triangular and sawtooth waves etc from a soundcard. A receiver, or audio generator could be used. Before you start ensure you are getting a pure tone. I used a "Creative Audigy" sound card I found that distortion occurred when the Windows "Volume" slider was advanced too high.
Above shows my suspect on board sound system fed with two tones of equal level 900 and 1000Hz. The "mixing?" products show about 40db down.
This shows the same tones fed to a cheap PCI card. The levels of harmonics can be seen by adjusting "Track Freq" to multiples of the tone frequency.
Apart from a really strange but unconfirmed recording, the on board system produces results which resemble that of other systems but vary by around 15%. Further tests show larger differences at low signal levels. I have corresponded with Peter, he suggest that the soundcard driver may not be correct, that it may not be sampling at the rate his program tells it to (8000). He feels the results will not be compromised, my tests are not conclusive.
http://audio.rightmark.org/index_new.shtml This is a program that automates testing and reports. It can use a card in duplex mode to test itself, I have found it does not always work if the card does not produce enough output to drive itself. It can be used with one card driving another. The latest version requires registration but at the moment an earlier version is still there for download.
Spectran http://www.weaksignals.com/ a program for QRSS etc will produce a good spectrum display. Spectrum Laboratory http://www.qsl.net/dl4yhf/spectra1.html is a comprehensive audio analyser and recorder, also can be used for long term monitoring of signals within a defined bandwidth.
The Creative Audigy sound systems are of high quality. I have a LS model PCI card in my main computer and it shows good results. They produce more expensive external USB units with high specification, it must be better to keep the audio out of the hostile environment inside a computer, and they can be easily moved between computers. Note, however, if a USB card is used with a computer that has other soundcards then plugging it in and out can cause confusion. I have known soundcards jump from one application to another, before leaving the computer check that all applications are using the correct card! Further experience has shown me USB cards may not be as versatile as internal. There are some very high specification internal cards so they must cope well with the environment inside the computer.
Using More Than One Soundcard With More Than One example of 5MHz Beacon monitor.
NOTE! I'M NOT SURE IF IT IS INTENDED TO BE USED LIKE THIS! I am not sure the results are consistent.
In Sept/Oct 2004 I had been comparing reception of GB3RAL, and G4JNT using two antennas, two radios and two or more, computers.
With all Windows versions it is possible to fit multiple soundcards in one computer . Each soundcard needs to be different, well, some drivers are written to cope but the one I know of is for professional grade cards. I have had three cards running in one computer. Just run the setup program for each soundcard. Well, it can be that simple! If the cards are PCI then there are not usually too many problems. If you are given the option do not install more than the basic drivers. It is sometimes necessary to play around with resources, particularly if ISA cards are involved.
I noticed that it was possible to have two examples of GB3RAL running at the same time, the second did not actually work because the default soundcard was already in use by the first GB3RAL. NOTE:- Peter has now added a soundcard selection to the program. I retain these notes as it MAY be a way to use two examples of a program that does not include card selection.
I finally realised that if I went to "Control Panel - Multimedia (W98x) or Sounds and Audio.. (XP)" and changed the default soundcard AFTER I had started the first example, then, the second example would "connect" to the second soundcard. The first example remains "connected" to the first soundcard until it is closed. The latest program enables you to select which card is used. The "Help" gives info. "0" on line 9 in GB3RAL.DAT uses the default soundcard, "1" gives the second card. Windows XP allows different programs to share the same soundcard, make sure you check that the input you require IS being used!
If the beacon program is setup twice, given two separate folders then each of them will retain individual settings. If you are prepared to fiddle and accept there may be problems then two recordings may be made on one computer. To avoid problems the log and (image) files should be given a different name on each instance. This is still possible after Peter has modified his program to monitor three beacons. Simultaneous monitoring will show more clearly the differences between antennas etc.
Screenshot from a computer running two instances of the original single beacon monitoring program. The 3 beacon program just has more traces!
G4JNT was running one minute after GB3RAL, the noise trace of G4JNT will not be correct because the present version of GB3RAL uses readings from the previous minute to display noise level. If the RX is set slightly off tune during the GB3RAL transmission then the relative levels of the two recordings can be seen.
The frequency variation of the spectrum displays is due to the beacons not being exactly on frequency (and the receiver and soundcards may differ), G4JNT is very close to 5.290000MHz. "Track Time" had been set so the single beacon program started recording one minute later for G4JNT. "Track Rate" is not the same because it has not been running long enough to stabilise. "Track Freq" is different because of different receiver settings. Note "UTC" offset for a computer using BST.