DC40xx Ugly Style

40 meter direct conversion receiver ugly build. Based on the progression of KD1JV's infamous DCxx Tranceiver line.

It's unique in that it uses a passive mixer and is nearlly IMMUNE to BCI!!! It uses a set of "flying" switches, in the form of a 74HC4053 IC. The switches "fly" at the desired mixer frequency. This is known as a commutative mixer. They tell me it's different from a "Tayloe" mixer.
I live near a big AM power house, and the majority of my NE602/SA612 based front-ends suffer HORRIBLY from BCI, but not with this design. It performs amazingly well I must say!

I'm still trying to get the schematic done. In the mean time here is a partial one. It does not include the VFO of the Low-Pass Filter....

The receiver "front-end" This is were the signal enters the receiver. The little yellow capacitor will be adjusted for maximum signal

"Flying" Mixer circuit using 74HC4053 switching IC. Immune to BCI. Works VERY well.
A close up of the "mixer" This is known as the "dead bug" method. The IC is glued upside down onto the ground plane and looks like a dead bug.
I am VERY happy with the performance of this mixing system!

Mixer differential output to 1st amp w/ gain of 10
Another angle of the "mixer" section. Most of the connections are made in mid-air, any connections to ground are soldered directly to to main board, which is a huge ground plane.

The AA9GG varactor tuned VFO for 7mhz
This is the variable frequency oscillator(the main tuning). I designed this first and made a circuit board for it. The pcb is tack soldered onto the main board.

40m flying mixer DC receiver w/ AA9GG VFO. The audio amp, in the foreground, is a basic LM386 configuration. The header pins are my audio out connections
I LOVE this radio!!! Performs VERY well!

That's all I have for now. I'll have to post the schematic. Actually I need to computerize it as it's hand-drawn on 2 different sheets of paper.

Back to QRP Build Page
Last updated : Thursday, August 04, 2011 9:45:14 PM
Website created and maintained by AA9GG