SA612AN (NE612) based
direct conversion receiver for 15440 KHz

It's quite simple to produce DRM demonstration receiver
using SA612AN double balanced mixer/oscillator IC. Of course the
receiver doesn't give high perfomance results but under good receiving
conditions it could show quite nice results, over 25dB SNR is not uncommon.
Sometimes it's doing job well but sometimes it doesn't work at all.

I'am using 15432 KHz crystal oscillator which is tuned to 15428 KHz.
Sines 15.440KHz signal is feeded through band-pass filter and then
it's mixed in SA612 to produce 12 KHz IF. That's it!
The IF signal is transferred to soundcards Line-in/Mic connector.
Dream DRM open source software receiver is practical with this
receiver because it makes possible to chance center frequency little bit
from 12 KHz. You can find pictures below and some
screenshots about receiving tests.

[First realisation]


Screenshots from Dream and DRM Software Radio

Reception results 25.2.2004 09:15 - 10:09 UTC

[FRG-100 / SA612RX reception compare]
Here is reception compare with FRG-100 communications receiver using
the same antenna. As you can see, FRG-100 won the game easily but sometimes
SA612 receiver gave almost error free audio, hi :-).

 Click here to get compare log




This configuration is same like above, but it uses ELV
 20 MHz DDS. First test showed that over 30db
SNR can be achieved when listening Sines 15.440 KHz

[Click for fullsize picture]


15440 KHz receiving results 24.11.2004
08.02 - 09.54 UTC


Otso Laakso / OH2GAX