Another uBitx Add-on PCB.

Nick VK4PP

Im loving the cheap and easy EasyEDA/JLPCB boards and simple web designer.
This time its a CW filter similar to the QCX and HiPerMite. I take no credit for the design, just copied it and added a switching relay.
I ordered 10 boards at $10 posted. love it!

73, Nick VK4PLN.

Kelly Jack

Nice.  Are you selling these boards?


Simon VK3ELH 

Nick VK4PP

Maybe, if they work ill put the extra ones up with my RadionoI2C boards....

Nick VK4PP

Just FYI:

Center Frequency: 700 Hz
Bandwidth: 200 Hz
DC Power: 5VDC
GAIN: Upto 20dB via R11 and R12 + trimpot.

Resistors 1206 SMD:
R1 33k
R2 33k
R3 1M
R4 47k
R5 47k
R6 36k
R7 36k
R8 10k
R9 750k
R10 10
R11 100K
R12 100K

Capacitors 1206 SMD:
C1  0.1u  104
C2  47n   473
C3  36n   363 (33n + 3n3 mount on side together)
C4  1n    102
C5  39n   393 (33n + 5n8 mount on side together)
C6  1n    102
C7  2n2   222
C8  2n2   222
C11 0.1u  104
C14 220u  Electrolytic

Relay OMRON G6S-2-DC5
200K/100k trimpot

R11 and R12 are optional to parallel the 200k trimpot to make it a logarithmic 100k.
Or just use a linear 100k pot.

Use a switch connected to 5V to turn on the filter.
This powers the opamp and switches the relay feeding the audio into the circuit.
When off the relay just passes the audio straight through unfiltered



Thanks for the suggestion Nick,

BTW... I’ll buy one of those boards if you sell em. 
I’d considered tacking a relay onto a Hi-Per-Mite but yours would be more elegant. 

Let me know. 

Pete WK8S 

Nick VK4PP

Nick VK4PP

HI All.
Boards arrived today, I will assemble one and test. Hoping to feed it into an audio spectrum analyzer to provide some idea of its exact performance/response. I will ship them out to folks who have ordered ASAP.
Might be a delay, we have an impending cyclone in the area and I've taken down my antenna, I'd like to test it in the uBITX with a real signal...

Thanks. Nick

Nick VK4PP

Ok, some results:

Nick VK4PP

To my ear the lm324 gave a better result than the TLC274...

I'll start posting out the boards.

Nick VK4PP

Board complete: