Bitx40: ~ Replacing the Raduino with the N6QW controller!

Say What: Replacing the Bitx40 Raduino?

12-07-2019 ~ Pearl Harbor Day

Let us not forget what happened 78 years ago today. On a sad note there are but three remaining survivors of the original USS Arizona crew and only one will be attending the commemoration ceremony.

Many have sacrificed to make this the Land of the Free and the Home of the Brave! 


I have now added switching of an linear amplifier to the PTT circuit so I can run 600 Watts with my "reworked" Bitx40.  Two 1N4148 diodes and a 12 VDC SPST relay make it all happen. Running a bit more power does help.

My latest project now on my website...


I call my Bitx40 "Maggie May" since she has been passed around a bit and before transmitting I specifically looked at the Bitx40 documentation. Shazam -- The bias was at Zero and not set to 100 Ma, and there was no drive as such. Fixing those two provided 10 Watts of solid power output on 40M. I cranked it back a bit since it would see some heavy duty cycle operation on WSPR. 

My offer stands: any one wanting to dump their Bitx40 -- a crisp $10 Bill and shipping costs from a US address is my offer. C'mon guys rid yourself of that former play toy and let N6QW work his magic. 

Send me an email to the address on the masthead if you would like the sketch code. 

N6QW, Pete the Radio Genius

12-03-2019 ~ Digital Modes with the Bitx40 and the N6QW Controller.

Raspberry Pi3 and (not seen) N6QW Digi Controller being used with the Bitx40 and N6QW's Raduino Replacement.

A couple of key comments 

  1. This shows I must be close on the USB offset as both FT-8 and the WSPR were dialed in on their normal frequencies
  2. I did not transmit on either WSPR or FT-8 as you must modify the Bitx40 Microphone input circuit. The Bitx40 uses an electret microphone which typically has a DC bias voltage on the input pin. As I did on The Paesano, I added a Data Port -which is nothing more than a 3.5 mm stereo jack that has a 10 NF cap in series with the microphone port to provide DC Isolation. That has yet to be done. Works perfectly on transmit see last chart.
  3. So for those of you who have "put away" your Bitx40, with a few changes you can do "The Digi Dance" with your rig.
  4. My offer is still open if you would like to dump your Bitx40 -- a crisp $10 bill plus shipping and I will take it off your hands.
  5. WSPR on the Bitx40 with N6QW Arduino Controller.

  6. After three hours both transmitting and receiving

The Bitx40 being heard In Brazil and Sout Africa! Nice!

Stay tuned to this space for more exciting Bitx40 Modifications -- may be even 6 Meter SSB.

Pete, Radio Genius


Pete N6QW


Is this like blasphemy, heresy or on par with the Ukrainian Bribery scandal? No, it is none of those just a practical matter. 

In a recent Soldersmoke Podcast #215 the fact was made known that the Bitx40 was no longer in production. I then said if anyone wants to sell me one for about $10 contact me. That offer is still on the table!

Well my good friend N2CQR sent me one that had been passed around a bit (you know like Maggie May and the high school football team). Well when I connected all I soon discovered that Raduino was not providing any RF. The pot tuning also left me wondering even if it did work would I be happy.

So I took some parts, took some software and when you know stuff you can do stuff!

I started 1st with a 5 MHz PTO from a Drake TR-7 and that was to quickly establish that the main circuit board worked and was the Raduino the only problem. That was accomplished. 

Next was to get a basic Nano and Si5351 to produce the LO signal which was also to prove that my LO was correct and that a first stab at the BFO frequency was at least in the ball park. Keep in mind that not all Bitx40's are exactly alike. I think initially depending on Uma's crystal sorting there could be as much as 3 BFO frequencies.

Finally after passing the LO test I added the BFO. This test proved that the LSB BFO is very close but I may need to tweak the USB -- next phase. To introduce the BFO signal (since the LO is done through a two pin header) I had to uncouple the crystal and inject the BFO into the base of the former oscillator transistor. I am using a custom made for Pete Si5351 PLL's that has isolating caps on the outputs built into the board. Your may not so include a 10 NF on your output other wise you may smoke the transistor or your Si5351. Add the BFO signal at the junction of R102, C104.

Recapping my Raduino Replacement has 2 VFO's, USB/LSB and a Tune Tone. Did I mention the cool Green LCD?

The long term plan is a 6 Meter SSB transceiver using an outboard Transverter. Stay tuned and try to catch up.

Pete N6QW

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