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maxpower
07-06-2007, 11:47
Hi to all!

The computer based reception of DRM Transmisssions depends very much on the quality of the soundcards you use in your PC. I/Q-Receiver concepts, like the new SDR from Elektor, rely on that even more. So it's maybe useful to know, if your soundcard is capable for good reception.

Best test-setup for comparison would be to use the Soundcardtester from Elektor 07/05, available at AK-Modulbus (www.ak-modul-bus.de/stat/soundkartentester.html ) , explained at http://www.elexs.de/iq4.htm#tester, some other results and connection diagram at: http://www.b-kainka.de/iqrx3.htm


Please post your soundcard-test-results here for comparison.


Ok, the first results arrived and i try to make a summery here at the first post



Soundcards that should work very good with I/Q SDR's:


SoundMax soundcard, AC97, Analog Devices

AD1981B/Intel Mb/P4-2.66GHz/Chipset Intel Brookdale i845PE/W2kpro. ->
http://www.drmrx.org/forum/attachment.php?attachmentid=32042&d=1181314751,

HP-Desktop PC ->
http://www.drmrx.org/forum/attachment.php?attachmentid=32580&d=1183325069


Realtek ALC 650

Asus Mb/Athlon-1.66GHz/Chipset nVIDIA nForce2-U400/XP+. ->
http://www.drmrx.org/forum/attachment.php?attachmentid=32076&d=1181379587



Realtek HD audio driver ver alc860

onBoard intel 915glvg motherboard ->
http://www.drmrx.org/forum/attachment.php?attachmentid=32118&d=1181499697,

ACER desktop with Intel Pentium M 760 ->
http://www.drmrx.org/forum/attachment.php?attachmentid=32656&d=1183658327



Creative X-Fi (LIne in) ->
http://www.drmrx.org/forum/attachment.php?attachmentid=32091&d=1181467791



Creative Audigy-4 (in 96 kHz Sampling Rate Mode) ->
http://www.drmrx.org/forum/attachment.php?attachmentid=32060&d=1181336107




Soundcards that work good with I/Q SDR's:


Soundblaster CT 4810 ->
http://www.drmrx.org/forum/attachment.php?attachmentid=32053&d=1181334799


SigmaTel C-Major Audio

DELL Latitude D600 ->
http://www.drmrx.org/forum/attachment.php?attachmentid=32095&d=1181468535




Soundcards which you can use for start, but work less good:


Creative Soundblaster Model 9916 ->
http://www.drmrx.org/forum/attachment.php?attachmentid=32054&d=1181335067



ALS 4000 PCI ->
http://www.drmrx.org/forum/attachment.php?attachmentid=32057&d=1181335421



Creative Audigy-4 (in 48 kHz Sample Mode) ->
http://www.drmrx.org/forum/attachment.php?attachmentid=32060&d=1181336107



Creative SoundBlaster Live! Player 1024 ->
http://www.drmrx.org/forum/attachment.php?attachmentid=32079&d=1181384608



SoundMax HD soundcard

Asus P5B-E+ Mb/Intel C2D-1.86GHz/Chipset P965/XPpro. ->
http://www.drmrx.org/forum/attachment.php?attachmentid=32104&d=1181491483




Soundcards you should avoid for I/Q SDR use:


C-Media cmi 9738 ->
http://www.drmrx.org/forum/attachment.php?attachmentid=32055&d=1181335235


Realtek AC97 onBoard Soundcard

for Intel 775 Systems ->
http://www.drmrx.org/forum/attachment.php?attachmentid=32009&d=1181217746



Creative X-Fi (Mic in) ->
http://www.drmrx.org/forum/attachment.php?attachmentid=32092&d=1181467801




Note:

It seems to be that the level of image rejection can differ from one Soundcard-Tester to another one. So more or less image rejection in following posts don't need to mean weak image rejection in the real RX.


Stephan

maxpower
07-06-2007, 12:02
The first test is the Realtek AC97 onBoard Soundcard at my Shuttle FS 31 Intel Processor (Intel Celeron 3.2 GHz) SIS based Chipset Computer which is operated with Windows Vista Home Premium.

I would estimate that other Realtek-AC97 onBoard Soundcards working on Intel-775-Processor based Mainboards should perform similar.

I use the Elektor/AK-Modulbus Soundcard-Tester with a 9 Volt Batterie (19 kHz Signal) for this test. I will repeat the with the recommended 6 Volts within the next days.

As far as i can judge this soundcard uses stereo input, but it's not good in antialiasing. SNR Ratio between Noisefloor and Information-Signal seem to be ok for me eyes.

So this soundcard is maybe capable for standard DRM Reception, but not recommended for I/Q (e.g. Elektor SDR) use.


Stephan

(PS: Please write to me if you think that some of my suggestions are wrong)

mitajohn
08-06-2007, 15:01
Hi all,

Here is my test:
On board SoundMax soundcard, AC97, Analog Devices AD1981B/Intel Mb/P4-2.66GHz/Chipset Intel Brookdale i845PE/W2kpro.
Home made tester at 6VDC. The results before and after calibration show that SoundMax is good for I/Q.

dadalbinder
08-06-2007, 15:55
Hallo,

nice test result. I am able to work with the SoundMax too. Normal working is by Soundblaster Surround 5.1 USB. You have an excellent value for difference between the two channels. Should work very nice on the receiver.


As far as I see till now, Realtek seems not to be able.

Audigy 4: My experience told till now, that this is not able. Lets wait for the test-device.

Wolfgang H., 49N28, 11E00

mvs sarma
08-06-2007, 19:57
Hi all,

Here is my test:
On board SoundMax soundcard, AC97, Analog Devices AD1981B/Intel Mb/P4-2.66GHz/Chipset Intel Brookdale i845PE/W2kpro.
Home made tester at 6VDC. The results before and after calibration show that SoundMax is good for I/Q.

Hi Mitajohn,

please suggest whether the 'onboard' sound card of Intel 915GLVG mother board with ALC860 audio codec, Realteck 5.10.0.5413 software,HD audio controller and with directx 9.0C could be suitabe for DRM and SDR use. i could not assertain whether the antialiasing filter is available in the above combination and if so how to configure the same for SDR compatibility . Please help me

mitajohn
08-06-2007, 20:32
Hi mvs sarma,

Is the audio driver correct? Intel site shows this: http://downloadcenter.intel.com/Detail_Desc.aspx?agr=N&ProductID=2062&DwnldID=7525&strOSs=164&OSFullName=Windows%20Vista*%2032&lang=eng

You have to test the soundcard !

maxpower
08-06-2007, 20:33
Ok, here's my next test: My old Soundblaster CT 4810

It seems to have a good antialiasing, but image-rejection isn't as good as at johns on-board-audio (which, btw, seems to be a really excellent audio-device!)

I think it should be suiteble for I/Q operations for starting, but not the very best choice for standard-operation.

maxpower
08-06-2007, 20:38
Here's the next one: Sistermodel Creative Soundblaster Model 9916.

It doens't seem to have the same quality like the other Soundblaster model:an added carrier (low, but you can see it) is showing up on the right side of the spectrum. and i'm worried about the "foot" of the carrier-signal which is not very nice looking.

I am not sure if that would ruin I/Q reception because its not in the part of spectrum i normally would use for drm.

maxpower
08-06-2007, 20:40
This is the result of my onboard C-Media cmi 9738:

The worst soundcard i have tested! Lots of carriers everywhere...

I say: Don't use this onboard-chip for I/Q or other SDR reception.

maxpower
08-06-2007, 20:44
This is the older ALS 4000 PCI device. It's very difficult to find out best regulation for that card: if you set up volume to high, you get many carriers. If its to low, you will loose signal.

I would say: try it if you haven't got a better one, but try to change it as fast as you can. :-)

maxpower
08-06-2007, 20:56
Ok, and here's the result of my audigy-4 soundcard. I think its a very ambivalent result: I hoped and thought it would perform better, particularly in 48 khz mode.

The carrier is at about -19 kHz and the spectrum till zero is ok, but on the other side there is a carrier which should't be there at +10 kHz! The next at +19 kHz is ok again.

I wonder why i can't null the image reception out as good as mitajohn at any device i have got. Or is it the ne555 at 9 Volt which messes me up in that problem?

Next test was in 96 kHz and at that rate the audigy worked very well without any aditional carriers (but only the multiples of 19 kHZ which is ok)

I found out some strange behavior: If i pull down the potentiometer to zero many carriers appear on the spectrum. Pull it up and they dissapear...

So, in result: Can i use it for I/Q operation or does the carrier at +10 kHZ ruin the signal in 48 kHz mode. And: can i run dream at 96 kHz?
Apart from that: How can it be that two same model-devices can be as different as mine and Wolfgangs device?

mitajohn
09-06-2007, 09:02
Hi all,

Here is another test:
On board nVIDIA nForce2 MCP-T soundcard, AC97, Realtek ALC 650/Asus Mb/Athlon-1.66GHz/Chipset nVIDIA nForce2-U400/XP+.
Home made tester at 6VDC.
The results before and after calibration show that nVIDIA nForce2 MCP-T is another on board good soundcard for I/Q.

@Stephan. I believe that every good card for I/Q can be almost "zeroed", it is a bit tricky to find the best adjustment combination but it is feasible...

mitajohn
09-06-2007, 10:26
Hi all,

Here is another test:
PCI/PNP soundcard Creative SoundBlaster Live! Player 1024/Asus Mb/Athlon-1.66GHz/Chipset nVIDIA nForce2-U400/XP+.
Home made tester at 6VDC.
The results before and after calibration show that Creative SoundBlaster Live! Player 1024 is a good PCI/PNP soundcard for I/Q with some minor byproducts.

mvs sarma
09-06-2007, 11:05
Hi mvs sarma,

Is the audio driver correct? Intel site shows this: http://downloadcenter.intel.com/Detail_Desc.aspx?agr=N&ProductID=2062&DwnldID=7525&strOSs=164&OSFullName=Windows%20Vista*%2032&lang=eng

You have to test the soundcard !

I had later updated the driver

FritzWue
10-06-2007, 09:30
The Creative X-Fi works with Line In,
but cannot be better optimized with the test generator as shown.
For real life result see my next post.
The only 3.5mm input socket cannot be used if switched as Mic In.
Disappointing at that price. :(

FritzWue
10-06-2007, 09:38
First picture shows optimized Creative X-Fi result with real on air rf signal from my amateurradio transmitter received with the elektor SDR.

Second picture my little board.
At first I used unselected multilayer capacitors, the one at pin6 was +10%. The unadjusted suppression was 10dB worse than after replacement with a selected capacitor.
Sometimes the board generates spurious signals. I have to touch it from the solder side to eliminate them.

FritzWue
10-06-2007, 09:42
Yipeeh, works!
DELL Latitude D600
SigmaTel C-Major Audio

mitajohn
10-06-2007, 16:05
Hi all,

Here is another test:
On board SoundMax HD soundcard on an Asus P5B-E+ Mb/Intel C2D-1.86GHz/Chipset P965/XPpro.
Home made tester at 6VDC.
The results before and after calibration show that On board SoundMax HD soundcard is another on board good soundcard for I/Q but it has some clear byproducts.

mvs sarma
10-06-2007, 18:11
Hi all
req comments from Mitajohn please,

the intel 915glvg motherboard soundcard with realtek HD audio driver ver alc860
(described earlier-- was tested by me today.

the results before and after test are appended as jpg files.

I request for help by commeting on the suitability of this sound card for SDR compatibility.

dadalbinder
10-06-2007, 19:02
Hallo,

as far as I see, the calibration of Your soundcard is extremly able for driving the I/Q-receiver, Elektor_USB. The difference between signal and mirror signal after calibration seems to be extremly high (and suitable).

SDR, Software Defined Receivers in general do not need a soundcard capable to work with I/Q-receiving.

Wolfgang H., 49N28, 11E00

Funkerberg
10-06-2007, 19:10
Hallo an alle,

sorry für das Schreiben in Deutsch, aber in englisch kriege ich das nicht genau genug hin. Vielleicht kann es jemand übersetzten.

Ich benutze einen SDRelektor zum DRM Empfang. Den Soundkarten Test meines Onboard AC97 Sound Controler 82801BA von Intel habe ich mit diesem Empfänger gemacht. Dazu habe ich den SDRelektor und sein 5 MHz Signal (Ini 8) benutzt. Und dabei ist mir aufgefallen, das das Ergebniss sehr abhängig von der genutzten Frequenz ist!

In der Anlage befindet sich eine Datei, die die Ergebnisse von 3 bis 22 kHz zeigt. Dabei wurde zuerst die Karte bei 12 kHz mit SDRadio auf Optimum eingestellt. Danach wurde die Empfangsfrequenz im SDRelektor so verändert,
das das Eingangssignal von 3 bis 22 kHz durchläuft.

Dabei ist zu sehen, das z.b. bei 14 / 15 / 16 / 17 kHz ein großes Spiegelsignal vorhanden ist.

Die Frage ist ja nun, ob z.B beim DRM Empfang und der Lage des DRM Signals
bei 12 kHz der SNR des DRM Signal beeinträchtigt wird. Das DRM Signal geht ja in diesem Fall bis 17kHz...

http://www.knallfunke.de/forum/soundcardtest-5.gif

Müsste nicht unter diesen Bedingungen ein Soundkartentest mit einem breitbandigen Signal gemacht werden ?

Viele Grüße Rainer

dadalbinder
10-06-2007, 19:46
Hallo,

das ist ja ein interessanter und demonstrativer Vergleich!!

Ja es ist auch aus meiner Sicht richtig, daß je nach gewählter Testfrequenz die Optimierung der Soundkarte unterschiedlich ist. Es ist also keine lineare Verfügbarkeit im Frequenzband gegeben.

Je näher es an den äußeren Rand geht, umso schwächer wird der Prozess. Deshalb gibt es bei Burkhard Kainka eine entsprechende Information.

Etwas ähnliches gilt ja auch für die Mitte. Hier sehen wir auf Testbildern immer einen kleinen Signalberg. Das heisst nichts anderes, daß man in diesem Bereich auch bei der Dekodierung nicht arbeiten sollte.

Sowohl beim Dekodierer SDRadio als auch beim SDR von Peter Carnegie wird mit einer Verschiebung der Frequenz um +/- 10 kHz operiert.

Versucht man testweise in der Mitte der Nulllinie zu dekodieren, sind die Ergebnisse nicht so gut.

Ich füge einen Detailscreen des SDR bei, indem der aktive Bereich in der Mitte zwischen Nulllinie und äußerem Rand als optimierten Arbeitsbereich aktiv ist. Hier sind die Regeln zur Gestaltung der Software bei I/Q richtig eingesetzt.

Wir müssen uns auch vor Augen führen, daß "Abstimmen" bei I/Q in klassischer Amateurtätigkeit immer eine Veränderung der Filterwerte vorausgesetzt hätte, was wegen der Komplexität immer eine fast unmögliche Sache war.

Also: I/Q hat nicht den ganzen Frequenzbereich bei 48 oder 96 kHz gleichwertig verfügbar.

Ob nun mit DRMDisco 3.5.0 oder mit dem SDR arbeitet. Hier kann man bei beiden Tuning-Softwaren die Frequenzvariabilität von I/Q studieren.

Wolfgang H., 49N28, 11E00

maxpower
10-06-2007, 19:55
Soweit ich das sehe, gilt das "Ausnullen" der Spiegelfrequenz nicht nur für die "Randbereiche" des SDR-Empfangs nicht, sondern auch schon innerhalb der Bereiche, die man nutzen möchte, also zB. die, die normalerweise von einem DRM Signal belegt werden würden, das mit 12 kHz als Mittelfrequenz einen Bereich zwischen 7 kHz und 17 kHz im ZF/NF belegen würde!

Das bedeutet in der Praxis: Wenngleich ich vielleicht auch die Spiegelfrequenzen bei 12 kHz per Kalibrierung minimiert habe, so können sie dennoch im ungünstigen Fall zB bei 8kHz und auch bei 16 kHz umbarmherzig in das DRM Signal hineinhauen.

In dem Fall würde die Spiegelfrequenzminimierung zwar bei einem sehr schmalbandigen Signal helfen (zB CW oder 3 kHZ Amateurausstrahlung rund um die 12 kHZ ZF), aber ein 10 kHz oder gar 20 kHz breites DRM Signal wäre nur bei 12 kHz (Mitte des Signals) vor Spiegelfrequenzen geschützt.

Wenn ich die Softwarekalibrierung richtig verstehe, wird dabei dem einen Soundkartenkanal die eine oder andere Warterunde aufgebrummt, bis der 90 Grad Phasenversatz passt und erst dann zur Dekodierung weiter geleitet. In der Kalibierung wird festgelegt, wie viele Millisekunden das Warten dauern soll.

Wenn das so ist, ist es logisch, dass der Phasenversatz auch nur für die Frequenz passt, für die sie durchgeführt wurde. Bei den Frequenzen, die darüber oder darunter liegen, passt der Phasenversatz nicht mehr ganz genau und Spiegelfrequenzen werden damit nicht mehr korrekt unterdrückt (bzw die Spiegelunterdrückung kann nicht mehr genau errechnet werden).

Lösung könnte nur sein:

a) Hardwaremässig den Phasenversatz von 90 Grad sicherzustellen

oder

b) den Bereich, den die Soundkarte einliest, weiter aufzuteilen in kleinere Frequenzbereiche und diese jeweils einzeln in die 90 Grad Position zu versetzen. (Kalibrierung für jeden Samplebereich) Wieviel Power ein Rechner dafür benötigen würde, kann ich aber nicht sagen. Theoretisch müsste man das aber auch per Software errechnen können.

- Unter der Einschränkung: Wenn ich das richtig sehe -

Stephan

DK7JD
10-06-2007, 20:38
The aktual mirror rejection doesn´t matter so much. The sound card tester gives 90 degrees only at about 15 kHz. So even if you get only -20 dB the real result with the SDR should be ok.

Once I also saw many side carriers. It looked as if the sample rate of 48 hKz was forced on a nativ sampe rate of 44.1 kHz or something like that. This was my failed try to install a new soundcard.

Now I use anexterneal USB sound blaster with 96 kHz 24 bit. The results can be seen here: http://www.elexs.de/iq4.htm If I use 96 kHz I can seen harminics of 15 kHz. Thats ok.

Burkhard

mitajohn
10-06-2007, 20:53
@mvs sarma and all,

req comments from Mitajohn please,

From the posted screenshots I conclude that the soundcard is good for I/Q.

PS: If you want to test your souncard and the receiver for DRM follow this old link: http://www.drmrx.org/forum/showthread.php?t=780&page=2
post #71

maxpower
10-06-2007, 21:17
Hello Burkhard!

It's great to see you here! You are doing a great job to bring (Amateur- & SW-) Radio back to the people!

I'm just beginning to learn about quadrature-detectors and i've read for expample "A software defined radio for the masses" by Gerald Youngblood (http://www.arrl.org/tis/info/pdf/020708qex013.pdf).

If i read right there's a problem with direct conversion mixers: You get big image problems with image-frequencies very near to the frequency you wanted to listen to. E.g. you want to listen to 14012 kHz and so you tune the Oscillator to 14 Mhz to get this frequency to the 12 Khz ZF at the SDR-Software in your PC.

But you get also an Imagefrequency of 13 988 kHz (14000kHz - 12kHz) which you have to get rid of.

Solution is the 90 degrees second line in (the "Q"). With the "Q" you can "calculate" which of those two frequencies is the right one and calculate the other one out of the spectrum.

To reach that the phase has to "meet" 90 degrees very good. Otherwise calculating would be very difficult or impossible.

So our problem (if it is a problem) is that we think that if you "null" the imagefrequency out at 12 kHz in the spectrum, other frequencies e.g. at 9 kHz or 10 kHz or 14kHz etc. could be with little or even without image rejection. If so a DRM Signal which centers at 12 kHz would have a good image rejection at 12 kHz, but a very bad at 14 kHz if there would be a Signal at that counterpart. This is because the "meet the 90 degrees exactly"- policie is reached by retarding the "Q" some (firm if calibrated) milliseconds till it is at 90 degrees.

But this "retarding" applies only for the center-frequency and not for the whole "band" of 10 kHz that you want to use for drm.

(In our example 14012 is the center, on 13992 is a noise-signal and at 14008 kHz there is a image signal of the noise which couldn't be nulled out because we optimized image rejection at 12 khz -14012kHz)



In that case best performance of the SDR would be given if

a) the SDR gives us the 90 degrees exactly out of the box

and

b) soundcard does nothing to retard

and

c) we don't have to calibrate the SDR Software Radio out of its zero calibration-bases


Is that "theory" right?

Stephan

mvs sarma
11-06-2007, 05:50
@mvs sarma and all,

From the posted screenshots I conclude that the soundcard is good for I/Q.

PS: If you want to test your souncard and the receiver for DRM follow this old link: http://www.drmrx.org/forum/showthread.php?t=780&page=2
post #71

Hi Mitajohn,
Thanks for the comment.- in fact i assembled the sdr tester as appeared in Eleektor june07 and tested .

i am only getting ready for drm reception being located at Hyderabad in India.
we are yet to get some local transmissions. I may have to try out some DX signal- say Kuwait on 13620 KHz . this signal is reportedly received conistantly at Goa (west coast just below Bombay). How ever i coud not receive any local am transmissions using sdr till now- as i am told it can output audio of normal am channels also.
Thanks again

maxpower
11-06-2007, 13:42
Hi all!

I put a summary of the tests posted here so far at the first post of this thread.

Stephan

DK7JD
11-06-2007, 15:18
Hi Stephan,

thanks for the interesting threat!

The phase of 90 degrees is constant over the -48 kHz to + 48 kHz IF as it comes from the HC74 devider. Normally you need to adjust less than 1 degree and less than 1% of the level. So if you adjust for best mirror rejection at 10 kHz this will work also at 15 kHz and at 20 kHz.

If you change R and L in Hardware there can be a little difference campared to software swap just because the error caused by the SDR adds to the error caused by the soundcard.

Anyway, I only adjust at one point, 5 MHz. Then ther mirror rejection is ok for all frequencies.

Burkhard

maxpower
12-06-2007, 07:53
Ah, ok. So thats maybe an explanation for the fact, that some of the better onBoard Audio-Devices work much better in Image-Rejection than the more expensive devices like the Audigy and the X-Fi?!

The onBoard Soundcards have only little own processor power and give the signal as direct as they can digitized to the Main-Prozessor (and to the application which uses it).

The more advanced Soundcards (like the better ones from Creative) try to process as many within the soundcard and give out the signal maybe more late (and probably more different at left and right channel) to the main processor and his apps.

There's a standard for low-lag audio processing. It's called asio, but is has to be supported by the application - as far as i know. Maybe something like that could help for better sound processing?

dadalbinder
12-06-2007, 08:50
Hallo Maxpower,

aus den Anfangszeiten der DRM-Dekodierung gab es ja die Empfehlung, möglichst einfache Soundkarten zu benutzen. Ich denke, das hat den gleichen Grund.

Das scheint das gleiche Phänomen zu sein, was uns jetzt auch bei I/Q beschäftigt eben nur auf der Stereo-Ebene.

Hinter allen Sound-Applikationen im Rechner steht eine Menge von bisher nicht so dokumentierten Faktoren. Direkt zugreifen auf alle Faktoren einer Soundapplikation scheint bisher nur indirekt möglich.

Es gibt unter www.Audiotester.de eine Software, die es ermöglicht im OSZI dort, die Parameter einzustellen.

Weitere Hilfe könnte Virtual Audio Cable sein. Aber etwas schwierig. Lohnt sich trotzdem reinzuschauen.

Wolfgang 49N28, 11E00

mvs sarma
14-06-2007, 09:53
Hallo,

as far as I see, the calibration of Your soundcard is extremly able for driving the I/Q-receiver, Elektor_USB. The difference between signal and mirror signal after calibration seems to be extremly high (and suitable).

SDR, Software Defined Receivers in general do not need a soundcard capable to work with I/Q-receiving.

Wolfgang H., 49N28, 11E00

Thanks Mr. Wolfgang for your comments.
for the time being i can only try to receive genral AM shortwave .

I observed that with and internal loop ant , it was not possible to receive anything and perhaps may beed an amplifier.
i will have to give a try again.

maxpower
14-06-2007, 11:43
Hello Sama!

If you want to use your receiver for AM listening, i would recommend to use the G8JCF-SDR Software Radio. http://www.g8jcf.dyndns.org/
Its free to use.

It supports the Elektor SDR direct. You only have to setup some things like model (in this case the elektor sdr) and the soundcard input/output device and you will be able to listen to AM, SSB, FM... transmissions from 150 kHz to 30 MHz.

I use it with the old Elektor DRM and its working very well as a very comfortably Receiver. So you can easy test out your antenna and the rest of your equipment.

Btw: You can simply try to use some meters of wire to feed the antenna-input. maybe that gives you more input-gain?!

Regards, Stephan

dadalbinder
14-06-2007, 13:07
Hallo Sarma,

for testing the receiver You should know, that the receiver has a relatively high impedance at its entrance. Main factor is an inductivity of 220 MikroHenry. Because of that one should engage an hf-transformator from a 50 Ohm-line to the entrance of the receiver.

In general there is no need of a preamplifier.

Wolfgang Hartmann, 49N28, 11E00

mvs sarma
14-06-2007, 20:06
@Stephan and Wolfgang Hartmann,

Thanks for the suggstions. i have PCBs on hand ,for elektor SW radio with DDS and DRM(Dec06). I have to develop the software myself and a friend of mine agreed to collaborate in the development.

meantime, i had assembled the SDR model with crystal oscillator on a prototype board,employing 74HC4053 and HC74, and ne5532. Trying this assembly with SDradio ver1.00 software.

added a single stage aerial amplifier expecting to work it on internal whip ant. Now i plan to go for a SW loop ANT with a gain block and mount it in my second floor balcony and try out.

i shall get back with my observations shortly.

Thanks again,

andimik
20-06-2007, 16:11
I hope this is the right topic ...

I'm using my onboard Realtek soundcard with 48 kHz sampling frequency. It's a MSI motherboard for AMD CPUs. Here my results using In8 of USB Elektor (05/2007).

Link to the motherboard: http://www.msi-computer.de/produkte/main_idx_view.php?Prod_id=228

mjn
01-07-2007, 21:29
Hi All,

New member here. Been strugling to modify a Drake TR-7 for DRM reception, and finally have it. But, the main problem appears to have been the sound card. I started out with an AOpen AW-850, which has a C-Media CM8738/C3DX chip. I built up the NE555 Tester, and it showed spurs just like the other guy saw on the CM9738 chip. Maybe a little worse!

When trying to receive DRM, the USB edge of the signal stair-stepped down. It was worse for higher frequencies. Could not decode anything with the signal centered at 12 KHz. Was a little successful with the DRM signal at 1 to 11 KHz. Then even more successful using the undersampling - tuned the BFO so that the signal out of the detector was around 50 KHz.

Then came across your test circuit, and the SDRadio program, and gave it a try. So. Pretty much gave up on the AOpen sound card, and took it out of the computer.

The computer then reverted to the apparently excellent Analog Devices (no affiliation!) SoundMAX integrated audio. Too bad its not a 5.1 system in this computer. Which is why I put the AOpen card in the computer in the first places. So, below is the tuned up response of the SoundMAX integrated audio in this HP computer.

32580

The TR-7 has a 48 MHz two-monolythic crystal can filter that is working well for DRM, although its a little narrow. About 9.5 KHz at 3 dB down. I have the resistor network mod in the IF Selectivity board for position C, leaving only the 48 MHz filter for the real selectivity.


73, Don ...

dadalbinder
02-07-2007, 10:04
Hallo Don,

You need not to remove any soundcard from the computer.

One has only to switch between soundcard1 and soundcard2 on Your machine. In RECORD and PLAY menus or in the decoding software.

Sometimes it is usefull to have a second card for phoning and other purposes.

If Your computer has a high working frequency, You will be able to compare two cards, while the receiver is working or to engage to receivers - maybee on one antenna - to compare. In such cases change the soundcard from one receiver to the other one and vice versa.

Wolfgang Hartmann, 49N28, 11E00

mjn
02-07-2007, 17:19
Hi Wolfgang,

Thank you for the comments. But for some reason, the only sound card available was the AW-850 after it was installed. It would have been very handy to test as you suggest.

I have since obtained a SB Live! USB and after installing it, I find the SoundMAX is still available and working similarly to before installing the SB Live! USB.

The AW-850 is a PCI card sound card. Maybe that has something to do with it?

In the DReaM setup, I now have the input from the SoundMAX and the output to the SB Live! USB. This would not have been possible with the AW-850 installation, as the SoundMAX was not in the menu. Or even in the Control Panel System Hardware configuration. It just disappeared!

dadalbinder
02-07-2007, 18:40
Hallo Don,

nice information about soundcards. I had partly the same behaviour, that a certain soundcards makes a second card not to be seen on the machine.

There is a very special software called VAC, Virtual Audio Cable.

It gives the possibility to see all installed audio channels and gives the feature, to install some virtual audio cables which enables to let communicate all these installed audio-devices even with given or changing parameters.

It is a little bit abstract, but sometimes it seems to be helpful.

Wolfgang

deltaar
05-07-2007, 18:00
Hi.

My sound card is a Realtek High Definition Audio, inside a ACER laptop with Intel Pentium M 760, running at 2.0 GHz.

Here is a photo of the circuit mounted in a breadboard:

32655

SDRadio test:

32656

Cheers! :)

FritzWue
07-07-2007, 08:16
A little off topic, no IQ test, but perhaps also important:

I tried the Creative Audigy 2ZS for pure DRM decoding with 12 kHz input.
There is a problem with it I read about before somewhere in the help files of my WinRadio G303i.
The drm decoding is ok but muting the line input does not work.
That means you hear the decoded drm signal plus the hissing sound of the 12kHz input all the time.
Replaced it with a SB0060 SoundBlaster Live! 5.1 and that works like it should.

dadalbinder
12-01-2009, 22:24
Hallo,

who has experience with a not USB card of this type?

Is this model useable for I/Q-purpose?

Wolfgang Hartmann, Nürnberg

maxpower
13-01-2009, 08:30
Hi Wolfgang!

The chances are probably not very good for this model to work good as I/Q Line In, because it works with a C-Media Chip.
Until now I found no chip from this manufacturer that works well for this propose.
But the device seems to be very cheap (about 10 €) so maybe you want to give it a try anyway?! :D


Stephan

dadalbinder
13-01-2009, 18:55
Hallo Stephan and all readers,

I asked for a friend, who owns a computer with this soundcard, and is willing to start with SDR and especially I/Q-SDRs.

Thank You for the help

Wolfgang

Brendan1
16-02-2009, 23:19
I recently updated my Google Earth to the new 5.0 beta and discovered what to me is a serious flaw: upon startup, it will reset your soundcard settings and mute the line input (in my case) so that DRM reception is stopped.

This bug issue has been sent to Google already by others, and it does not appear to affect all machines the same way. Previous settings are reset so that existing sound paths are disrupted. Others reported that Mic settings were muted and changed, in my case the Line Input was muted and the Mic selected as the audio input.

My DRM reception has been completely cutoff in mid-log, and that is not very good in my book! Hopefully this will be fixed in the 5.0 full release.

mvs sarma
17-02-2009, 10:13
I recently updated my Google Earth to the new 5.0 beta and discovered what to me is a serious flaw: upon startup, it will reset your soundcard settings and mute the line input (in my case) so that DRM reception is stopped.

This bug issue has been sent to Google already by others, and it does not appear to affect all machines the same way. Previous settings are reset so that existing sound paths are disrupted. Others reported that Mic settings were muted and changed, in my case the Line Input was muted and the Mic selected as the audio input.

My DRM reception has been completely cutoff in mid-log, and that is not very good in my book! Hopefully this will be fixed in the 5.0 full release.

Now if you freshly install DRM software, it would restore while Google earth settings won't be spoiled.

Brendan1
18-02-2009, 23:24
Hello Sarma,

Thank you for the suggestion, I hadn't thought of that.

Unfortunately it didn't work here. The same problem occurs after a complete re-installation, so I think Google has some work to do. It's not a huge problem, but one that is an irritation nevertheless.