SDR: Not working

[millsey]

Hi Sarma,
I am 5 years your junior then !! I have checked the frequency at the output of the 74AC74 and it remains fixed at 25.92687MHz. I am now becoming convinced that the CY27 is faulty. I connected my Oscilloscope to the SDA and SCL pins, and when I vary the frequency in the Elektor tuning software I see negative going pulses on both pins. So I can conclude the FT232 is working I guess.
I have not bothered connecting the audio yet, until the CY27 frequency can be made to change it is pointless. I will consider ordering another CY from Germany this time.
I have used a 200x electronic microscope and cannot see any problems with connections or shorted pins.
I will keep you updated. Are we the only two people using this forum ??
Regards
Millsey

[millsey]

Hi Sarma,
Have changed the CY27 and can actually now get the osc to change frequency, but oddly I seem to be getting a 15MHz test signal instead of 5MHz. At least I can now see some light towards the end of the tunnel. I have had no success in connection it to my PC soundcard yet, but at least I have solved one problem. I'll report further news when I can.
Millsey

[sarma]

Hi Sarma,
Have changed the CY27 and can actually now get the osc to change frequency, but oddly I seem to be getting a 15MHz test signal instead of 5MHz. At least I can now see some light towards the end of the tunnel. I have had no success in connection it to my PC soundcard yet, but at least I have solved one problem. I'll report further news when I can.
Millsey

Sorry for late reply, Millsey !!
It is nice that you replaced the chip. Perhaps you are measuring harmonic as your frequency counter may be having higher gain. once you reduce the front end amplification of the measuring device, you might read the fundamental 5MHz.

for your ready reference, I am attaching a table of test results across the band , the LO output measured after 74HC 74
now you may select other channel number (in3) and go ahead to tune from aerial, wish you all the best

[millsey]

Hi Sarma,
Working at last ! Have managed to hear some MW stations and Shannon Volmet, but there is so much noise and interference it's not quite what I had expected. Using the G8JCFSDR software. Need to change the decoupling caps to ceramic as I used polyester ones and I think this may help. Not as good as my Softrock receivers that are very sensitive and quiet, but at least it does something now. Thanks for your ongoing assistance.
Millsey

[sarma]

Congratulations, Millsey !!!

I am getting things fine. Never had much of Noise, unless QRM is bad . especially the DRM signal is like CD quality. I saw some reports that in UK and other places where power line modems are used for remote metering etc, the Noise in unbearable.
But as you said, SOFTROCK works same time silent, the SDR needs to be checked perhaps !!
I too tried Softrock but the pnp/npn based crystal oscillator gave trouble and the board was partially SMD . I kept it on hold.
Incidentally which model you have?

The advantage of Kainka's SDR is that, it could be software tuned across the entire band.

Regrading sensitivity, perhaps the 0, 10, and 20 db gain adjustment helps.
You can even try a better component at the Op amp instead of TL084.

I am presently using an active miniwhip antenna designed by PA0RDT. performance is almost like LW antenna with no much space needed. If you did any mods , you may try to upload a note with a photograph, Millsey.

[Elektor Editor]

congrats Millsey -- persistence pays.

The SDR Preselector described in the December 2009 edition may also prove useful in getting better reception. I know it did here at the Elektor lab location, which is abominable in terms of SW reception.

Jan