Direct Conversion receiver for 80m and 40m

Receiver front view

Receiver internals

The design for this receiver is from Steve KD1JV. Some changes have been made to the KD1JV design.

Pre-amplifier, mixer and first amplifier.

I used a 74HC4066 quad switch and a 74HC04 inverter, because the junkbox did not contain a 74HC4053 at the time of building. The original BN-43-2402 binocular core has an Al value of 1275 nH/turn2. With 6 turns the primary has an inductance of 45.9 uH. If another core is used the turns count should be adjusted to get the same inductance. The secondary turns count has to be adjusted with the same factor. I used a FT50-43 with 10 turns on the primary and 2x3 turns on the secondary.

VFO with ceramic resonator.

Experiment with the variable capacitor and both series capacitors to get the band coverage you want.

700 Hz filter and auxilary output.

The main purpose of this reciever is to get coverage of the CW segment of the 40m band. For experimental purposes I added the auxilary output and an external VFO input.

AF amplifier.

Nothing fancy here, straight from the datasheet.

Receiver with loop antenna
The receiver does not have any form of pre-selection. I use a loop antenna. It's not perfect, but it works.

Archive containing the Xcircuit files (encapsulated postscript).