Friday, October 16, 2009

The Airband last!

...Not quite but enough!

Yes the Si570 kit returned from the "repair" (thank you Kees)... well it was more an operator issue than a repair, anyhow the thing works and I can finish now the airband receiver and move on to another project. After finishing the new squelch circuit (I changed from the TDA1072 to an TCA440 if) and put the boards in a box, I will consider this project done.
The receiver is not perfect but works to the minimum level I wanted, in the future probably will rebuild the input filter making it simpler.

The final circuit is similar to the ones I allready posted on previous articles so will not put again heres since I didn't draw it completly. Main features are:

Neosid coil rf filters.
BF981 rf preamplifier
NE602 mixer
Si570 VFO - kit from Kees, K5BCQ (can't get anything beter for the price)
TCA440 AM demodulator on 455Khz
LM386 (what else?) audio amplifier
CA3130 comparator for squelch circuit (shorting audio input via pnp transistor on act).

Sensitivity: enough
Audio power: enough

Here's the "beast" working, sory for the audio quality.

...there's a new Si570 VFO kit crossing the Atlantic.... but that is for another day...

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