And.... the NE602

If they didn't cost'd me around 3 Eur each I had slammed the hammer over them....
The NE602 is giving me a little of a trouble, I change the hf-radio product detector from the SBL-1 to an NE602 based. Problem is I started using the same schematic on the K2 but without the cristal filter betwen the MC1350 and the NE602, tryed the Minipig 10 and also the Malta 40 schematic (both qrp radios) but it's not easy to interface the NE602 at least to get maximum performance. Best result so far was an output transformer on the MC1350 with midle power supply coupled to another transformer on the input of the NE602.

Unless I get better result soon will revert back to the SBL-1, the price is not that diferent. I have to say on the schematic of the Malta 40 qrp I didn't used a Toko coil but made the IF transformer with an FT37-43 toroid. The main problem is with some combination of values I have a big wistle sound on the output, I gess is overdriving the NE602. In the future will try to replace the MC1350 also, it's noisy has hell... but it's simple to make and I never designed anything better :-)

Anyhow changed also the bias on the first preamp after the first mixer.

Schematics involved:

Minipig 10
http://www.kitsandparts.com/minipig/mp10.gif

Elecraft K2
http://www.elecraft.com/manual/ELECRAFT%20K2%20Owner%27s%20Manual%20Rev%20G%20WEB.pdf

Malta 40
http://www.karinya.net/g3txq/malta40/malta40.pdf