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fibber
12-11-2006, 02:27
What is the current thinking as to the most economic (cheapest) radio to convert for DRM. I'm not talking the cost of the IF board ($15-$25 USD) but the cost of an off the shelf radio. Anything under $50 that would be reliable enough to bother with?

I guess the Kchibo KK-DRM01 sort of died or was so poor it didn't make it too far? I was really hoping for some kind of $25-$35 USD radio with 12K IF out!

simone
12-11-2006, 10:52
Hi Chris,
there are cheap radios that can be modified for DRM in the sense that you get a good SNR with a clean feed. But these cheap radios usually have poor performance concerning selectivity, sensitivity, often no connector for an external antenna, etc.
So I think it is better to look for a good used (defective?) radio like a Sony SW7600G i.e. on ebay, which you can get for this price.
Did you also look at the Redsun RP 2100 (http://cgi.ebay.ca/REDSUN-RP2100-PLL-AM-FM-SW-RADIO-w-ENGLISH-LABELS_W0QQitemZ260049472507QQihZ016QQcategoryZ150 51QQssPageNameZWDVWQQrdZ1QQcmdZViewItem) which sells new for 56 USD and already has a 455 kHz IF output?
And of course building the mixer yourself saves money, I did some using a ceramic resonator, parts were below 5 €.
Simone

fremsley
01-12-2006, 09:58
Hi,

you could build an oscillator to directly mix down the DRM signal. I have build one based on the schematics from:

http://www.b-kainka.de/bastel3.htm

which works quite well. I use a simple 150 cm telescope antenna, but with this little machine I sometimes get a SNR of 25 dB for the Deutsche Welle on 3995 kHz. And I live in the centre of Berlin with a lot of electric smog around!

Since the above web page is in German, here are some translations:

The coils are wound onto a 9-10 mm tubes with a ferrite screw, 20 turns of 0,7 mm isolated copper wire. 'Abstimmung' means 'tuning', 'Rueckkoplung' means 'feedback' or 'oscillator power'. The radio I have built has a coil of 12 turns of 2 mm copper wire on a PVC tube (30 mm diameter) without ferrite and a variable capacitor of 2x 500 pF. If you can not get an old variable capacitor, you should have a look at the third schematic. However the BB212 varicap is quite expensive (6,20 Euros at the local store -- approx. 7,50 USD) and you'll need a potentiometer with a gear for tuning.

Best regards

Saulius
01-12-2006, 15:26
Greetings

You may try schematics 1...17 and other from this link
http://www.smail.lt/~ncss/regen_info/Simple DRM Receiver on bipoliars.html

Very simple DRM receiver:
http://www.smail.lt/~ncss/regen_info/Creating_simple1.GIF

Latest with quadrature output DX receiver :
http://www.smail.lt/~ncss/regen_info/Creating_simple16.GIF


Best regards;

Saulius.

fremsley
01-12-2006, 16:05
Hi Saulius,

thank you for the links! I'll try to build the I/Q receiver when I'll find the time. With the simple Audion it's often tricky to tune to a station in the 49m band without having another station on the mirror frequency.

Best regards