Big News! First contact made 10/4/2007 using the bitx20
The first 2 way qso using the bitx20 was with Wes, W4WEL in North Carolina. Thats 1500 miles using 4 watts and a low hanging dipole antenna! I answered his CQ and he came back to me. I was very surprised when he came back to me. We went back and forth a few time and then signed off.
Here's a link to Ashar Farhan's original article on the Bitx.
I began this project about 6 months ago. I was searching for a simple tranceiver to build and stumbled across Far Circuits on the web. While looking through the circuit boards they offered, I found the Bitx20. I had held a conditional amatuer license in the mid 60's and my rig then was a Heathkit HW32. A 20 meter rig. My interest immediately hit the maximum. I followed up with a lot of web research and about January of 2007 I called Far Circuits and ordered their 2 board set which was based on an early design and posted here Printed circuit board files
When I received the boards, that was what I received. The boards only. On the Yahoo Bitx groupYahoo Bitx Group I found a file from EB7HPM which was a great start but far from what I needed.
After some work, I soon had this.
I began building the board using a systematic approach. 1st, easily built and tested circuits.
Click on the link below to download the component placement diagrams. Warning - I believe these to be accurate but I have not assembled all of my unit using these yet! If you find any errors, please email me at kc0wox
Bitx Parts List - This is a partial parts list for the circuit boards with part number hyperlinks from Newark Electronics. The hyperlinks may be bad as this list was generated about 8 years ago.
Chassis Build Up Final build up putting the boards into a chassis. This is a picture series and not yet complete.
Audio Section Build and Test Video 140mb This is the in-depth video on the audio section It is also a basic tutorial on fabrication.
Balanced Modulator Section
Adjusting the carrier suppression
Short video on the section 2 1/2 minutes and 7 mb
Troubleshooting a mike amp problem 7 1/2 minutes 24.4mb
Amplitude and Double Sideband Modulation
This is a tutorial on modulation 12 1/2 minutes 40.5 mb
Demonstrates crystal selection, sweeping the filter using an oscilloscope, and checking and adjusting the carrier supression using a spectrum analyzer - 21 minutes long, 68mb in size
Winding a trifilar transformer video 14 minutes 46mb
Demonstrates winding a trifilar transformer. I don't believe that the core used, (T50-61), is the best for a Bitx but it is what I used for the demo. I also wound one with a T37-61 core and it appears to work ok in the board. I've ordered some T37-6 and FT37.43 cores which are the same one's being used in the upcoming kit. I've read somewhere that they are a better match.
More modulation and filter testing 7:45 minutes 24.8mb
Testing the modulator section for the source of the 2nd harmonic of the modulation frequency by substituting out the mike amplifier.
Linear Amp Testing part 1 7:44 minutes 25.3mb
Sweep testing the linear amp output filter and overall static gain testing.
Linear Amp Testing part 2 12:25 minutes 139.5mb
Sweep testing the amplifier, on-the-air listening with the receiver.