SWLing Post reader, Lee, writes:
I just wondered if you have ever seen any information about how to tap the I.F of the Tecsun 606 by any chance? I want yo use it for DRM but cannot find any info .
Love the website !
I have not seen info on tapping into the IF of any of the recent Tecsun portables. Can someone help Lee? I would be very curious how to do this myself.
you would have to command the DSP section of the chip to pass the I/Q signal rather than process it so you could process it later in the chain. Talk to SiLabs about that. Mod the chip?
Please see if this helps.Degen 1103 does the job.
”Many had a perception that DE1103 is unfit for drm converter.
Only 2 members to my knowledge worked on this. In addition to you Siber did try and succeed. he had sent few sch also to me.
I would suggest to tahe few photos of how and where you mounted the converter unit inside the radio, and how did you bring out the 12KHz IF out. as time and facilities permit , even a small youtube video would be nice. Happy that you get drm signals decoded on DE1103.
It is encouraging….
__________________
Regards,
Sarma”
http://www.drmrx.org/forum/showthread.php?t=2407
Thank you all for your help ! All very interesting stuff . Last time I attempted to receive DRM i tapped a Sangean ats909 and then built a 12 khz down converter/ mixer and that worked ok.
I notice you can buy such a mixer / converter on Ebay now as a kit
Anyway, I will try another radio but do not want to pay much, cheers !
The Si47xx programming guide p. 135 says the following:
“AM: LO frequency is 45 kHz above RF for RF frequencies 1000 kHz. For example, LO frequency is 945 kHz when tuning to 900 kHz.”
In other words the Si4734 dsp chip included in the Tecsun PL-606 has a 45 kHz IF. As there is no IF output in the chip I am not very optimistic about the possibility to tap the IF (perhaps capacitively ??).
On the other hand one could try to build a 45 kHz BFO try to induce its signal directly to the dsp chip which includes the IF stage. I would do the first experiments without modifying the radio by just bringing the BFO signal inductively or capacitively to the dsp chip. The Tecsuns signal meter should indicate whether this has been successful. If yes, tune the BFO to the edge of the passband. A very strong BFO signal level may be needed because the wirings within the dsp are very small for catching the signal at this low frequency.
Then you could try to find signals. You may need to adjust the BFO signal level and fine tune the BFO if you do the first experiments with an SSB signal. If even this is successful the next step would be taking the output signal from the earphone plug for further processing in a computer.
This is all untested – hopefully someone finds a working solution even though I think that the success is highly uncertain.
Si4734 documentation (see the Documentation tab):
http://www.silabs.com/products/audio/fm-am-receiver/Pages/si473435.aspx
Photos of the Tecsun PL-606 internals (pages 2-8):
http://fotkidepo.ru/?id=photo:693812
There is a Tecsun radio that already has a wired socket to take off the IF, and that is the Tecsun S2000. It has the socket on the back of the radio ready to go.
Yes, this is an “old machine” in conventional design.
But you will have to get a reasonable Bandwith for DRM, about 11-12 kHz. If the possible filter bandwidhts before the IF output were smaller, you will have to get out the IF before the filter(s).
The S2000 manual says that the output is meant for DRM
So this could be a reaonable way. My AOR AR-7030 has an IF output (455 kHz) behind the filter stages. I use it for a Sherwood SE-3 synch detector, the filters I have are 1,3; 2,1; 3,6; 5,2; 6,3 and 9,5 kHz, all too small for DRM. The way is to build in a convertor board in front of the filter stage, which mixes the IF down to 12 KHz baseband, 12 Khz wide, to feed a sound card.
I think the PL600, 660 and 680 are also conventional double conversion superheterodyne designs with a 455khz or so static IF.
I did bought a converter kit, connected it to my Tecsun S2000 IF output and to my laptop soundcard.
Using Dream software, I have successfully decoded DRM (Vatican, AIR).
So it is possible using the Tecsun S2000 for this purpose.
Good luck.
Best Regards,
Moshe.
Thank you Moshe for your usable idea, will also be using your idea on my S2000. 73s. Ron
According to http://www.eham.net/reviews/detail/10248 the radio uses the SI4734 chip from Silicon Labs. The data sheet is here: https://www.silabs.com/Support%20Documents/TechnicalDocs/Si4730-31-34-35-D60.pdf
In short: The chip uses a “low-IF” in a typical IQ SDR configuration. That “low IF” is not available at any pin of the chip. Nor is it specified anywhere in the data sheet.
No chance. TECSUN PL-606 is a digital DSP receiver, based on the SiLabs Si4734 chip. Those units don’t use conventional IF stages. The chip gets the HF signal and delivers the demodulated audio to the AF amplifier.
Most -if not all- actual Tecsun digital radios use SiLabs chips.
If you want a RX for DRM decoding with PC, using a SDR may be the solution for you. Perhaps the FiFi SDR about 140,- € from Germany?