Hello, I have been very interested in your project also for the physical size that seems to be small and nice. What are the real dimensions of the small box? From the picture I could not easily evaluate them.

Very good work,

Regards

Mario

Mike,

Glad you got it working OK mate. :)

Regards,

Alan

Just a note to say thanks for posting this little receiver and your help Alan. I had great fun making this and its performance is surprising.

cheers

mb

Many thanks for the coil winding clarification. The oscillator is working fine and I have now wound the ferrite ring coil.

cheers

mb

Mike,

Yes, all three windings are the same number of turns. The winding is trifilar, you twist three wires together first, then wind them as one on the core. Separate them afterwards using a meter. The dot shows the phase, pick an end all three wires from that end are the one with the dot.

Regards,

Alan

Alan,

Thanks for posting this - I will give it a try. I new to this stuff ... are all the windings 6 turns on the mixer ferrite ring?

thanks

mike

David,

I just dug it out and counted the turns; 92.

Regards,

Alan

What values did you use to get the pto to tune 3.4 to 4.00 mhz?? how many turns on the coil?? would like mine to cover the complete 80 meter band but doesnt right now.thanks alot

Erik,

I don't think the PTO will be stable enough on 20 metres, however you could try it. You could also try running the PTO at a lower frequency and multiplying it up (but this will also multiply up its instabilities), or mix it with a xtal oscillator to generate the LO.

The later is probably your best bet, say with the PTO at 4-5 MHz and the xtal higher. Add a BPF to reject the other products and isolate only the one you want. An alternative might be a sub-harmonic mixer like the Poliakov design which needs an LO at half the RF frequency, a PTO at 7 MHz is fairly stable if well built.

The rest of the circuit should work fine on 20 metres by just changing the filtering but the front-end amplifier might be improved and as the band noise is lower on 20 metres it could be worth it. If I was building this radio again I'd use a double-tuned LC filter in the front-end and probably Sallen-Key filtering in the audio amplifier.

Regards,

Alan

Hello Alan,

Ik admire the KISS approach in your projects. No difficult parts standing in the way of construction. That's very attractive to the would-be homebuilder like me.

I would like to build a decent 20m band direct conversion receiver. Can the 80m scheme be ported to 20m? Will the PTO be stable enough?

Thanks for any helpful suggestions!

Erik

ON4ADV