22 July 2023

The sBITX - My maiden voyage into the art of homebrewing. Part I

     Every once in a while a new product comes out that you just got to have. While you are drooling over the listed features you think to yourself "Wow, not only are the NSA, CIA, Homeland Security and Girl Scouts of America flex their financial and covert might at tracking every move and thought that I make, so does HF Signals out of India." When  Ashhar Farhan VU2ESE announced the sBITX I couldn't help myself. I'm a big fan of HF Signals. They are the ones that sell the most famous electronic creation of Farhan VU2ESE, the BITX series of radios. I have the BITX 40, uBITX (pronounced MICRO BITX, not U BITX), and the Antuino. So when Farhan announces a new project, well that is clickbait for me. I have to check it out. 

    A simplified description of the sBITX is a uBITX and a Raspberry Pi 4 computer get together and some magic happens. 

    The following is a list of features of the sBITX as borrowed from the HF Signals website:

Home station, at home

  • The big compact: Although compact, it has the largest display shipped with a transceiver, a capacitive, touch screen of 7 inches.
  • All software to run modes like FT8, RTTy, PSK31 is integrated into the radio, without any messy configurations, setup, etc. to deal with.
  • It switches soundlessly from transmit to receive and between bands due to its electronic filters and T/R.
  • Band-stacking VFOs with 4 memories on each of the 8 bands, 9 convolution digital filters for the best audio experience. 
  • High-performance electronics with a passive-FET front end, 8 crystals filter, and a low phase noise, temperature-compensated crystal oscillator. 
  • The built-in, editable macros that make it a breeze to work DX or compete in contests. 
  • Add an HDMI monitor or use the browser from your PC/tablet to have a large-screen experience of all the features of this amazing radio. 
Go POTA, Go SOTA, Go Wild
  • The sBITX will neatly slip into your backpack with its compact size of 10 inches X 6 inches X 2 inches and weight of under 4 pounds (less than 2 KGs) with room to spare. With its 40-watt transmit output, it is the most powerful radio you can put into your backpack. 
  • It is armed with an XT60 power connector that you can use with lightweight 3S LiPo batteries to provide hours of field operation (The receive current is 600 mA, the transmit current can go up to 8A depending upon the drive settings.)
  • The built-in mic and the onscreen keyboard, macros makes it easy to operate all modes, voice/digital or CW without a key, mic or an extra computer in the field.
  • It has an accurate real-time clock to time FT8 transmissions and log the contact made. 
  • The built-in logger eliminates the need to carry the logbook too. 
High-Performance Radio
  • Bulletproof hybrid superher with passive-FET KISS nixer.
  • Brickwall crystal filter with 8 crystals.
  • 80 db close-in dynamic range, 90 db wide dynamic range.
  • Low phase noise, temperature compensated reference oscillator.
  • 30-40 watts output on all bands from 80 M to 10 M
  • Transmit IMDR of 30 dB (from PEP levels)
  • Silent, fanless operation
  • Noiseless electronic T/R and band switching.
  • Built-in 2 tone transmitter to tune the antenna and measure IMD
  • Built-in FT8 that works out of the box
  • One-touch operation. Touch to call CQ or start the contact.
  • Automatically logs all the QSO's into the built-in logbook. 
  • Built-in, high accuracy, real-time clock. 
CW/RTTY/PSK31 with logging and Macros
  • Totally noiseless, fast electronic T/R without noisy relays.
  • Built-in N1MM style Macros support Running and S&P
  • Uses Fldigi with its high-performance decoder in the background.
  • Raised cosine CW keying with perfect shaping.
  • 9 ring-free Convolution filters from 3 KHz to 100 Hz.
  • Use the onscreen touch keyboard or add a USB/wireless keyboard for effortless CW sending. 
  • The sBITX uses convolution SDR technology and a 7-element crystal filter to provide superb sound quality with punchy clarity.
  • Built-in microphone and touchscreen PTT as an alternative to plugging in a mic
  • It works with any other mic (standard audio jack)
  • Transmit IMD of 30 db
  • Receiver with variable receiver bandwidth from 3KHz to 1.8 KHz.
  • Built-in two-tone generator to align external linear amplifier or tune your antenna
Logger and Logbook
  • The sBITX has a logger and a logbook with RDMS support.
  • N1MM style logger with macros and automatic logging of contacts with the frequency, mode, time, automatically filled in.
  • Use macros on CW/RTTY/PSK to send out standard messages with the press of a button/key.
  • See the spots, DX clusters on the radio with built-in telnet to DX Clusters, Reverse Beacon, PSK Reporter, etc.
Hackable Code, Skinnable GUI
  • Full source code, circuit and explanations on github.com/afarhan/sbitx
  • Write custom apps in javascript without learning SDR coding. 
  • Open source, hackable SDR written in C
  • Develop your own skins in UI in HTML/CSS/Javascript
  • More modes and functions planned
    Hopefully, all of that information will give you a general understanding of this great and wonderful radio. See here is my situation. I'm disabled. My back has all kinds of trouble. As a result, I have to spend about 90% of my time in bed. So because of this my shack is a plastic table that is on the side of my bed, set up so that I can operate my radio from bed. Then from decades of me having to be at work by 0500 I have a habit of waking up early. Well my beautiful bride is a night owl, about the time that I am waking up, she is going to bed. Being respectful of my wife's sleeping, I try to keep the volume on the down low. So I wear headphones and earbuds when watching TV. Having to keep quiet puts a pretty good kink in operating radio while the XYL is sleeping. Because of the noise I have to be regulated to the digital modes like FT8. Well, lately I have been addicted to CW. Because of my poor hearing I use an app on my cell phone to decode the CW as a backup for when I miss something. To do this the cell phone has to be able to hear the CW signal from the radio. So I can't do CW while my wife is slumbering because of the noise. Looking at the sBITX, with the feature of decoding CW itself and tons of other stuff makes this an ideal radio for me. I could go from FT8 to SSB without having to unplug an interface and its cables. I also love to operate portable when my health allows it. With the sBITX I will be able to take my radio, a computer, and just about everything else I need in one small box. Not a truckload of stuff.  
    To be honest, when I heard about the sBITX it kind of made me mad and depressed. Like I said, I'm on disability, and with my low disability paycheck, I have to support my wife, my 20-year-old Autistic son with Aspergers Syndrome, and a 16-year-old daughter that I'm putting through countless drama classes because she wants to be an actress and I am doing all that I can to help her achieve her dreams. It's like I now get to go on one of those internet gatherings of like-minded people, like the BITX 20 io Group, and see those that are more fortunate than myself and are able to get this wonderful radio and then tell everyone how great it is. It is something that is out of my reach and why? It's because I sacrificed my body and my health to provide for my family. This is also the reason why I don't do Facebook very much. I get to see all of my friends and family go on these vacations and do all of these things while I am sentenced to life without parole to my bed. It sucks more than a warehouse full of vacuum cleaners. I would like to live my life also. It may be hard to understand but I'm alive but I'm not living. 

    Then from stage Left, Ashhar Farhan came into my life. He is well aware of my station in life. Even so, he got me to believe that I too could have this great little radio. I can have one by making it myself. When an amateur radio operator makes something themselves we call it homebrewing. Ashhar convinced me that I can build the all-mighty sBITX at a fraction of the cost of buying one. Ashhar first developed the BITX with the goal of having people build it themselves. Then it became another rig for people to buy. He has the same idea as the sBITX. He would rather have people build it themselves than to send out the credit card numbers in exchange for a finished radio. 

    I don't remember how it happened but yeah Ashhar got me to believe that I could build the sBITX myself. Now my experience in homebrewing is limited to making different kinds of radios. I have no history in electronics at all. If I can completely build a fully functioning sBITX radio then hopefully it will inspire others to build their own. 

    My mission is to try to learn every aspect of the sBITX and share it the best that I can here on this blog. As of right now, I need to learn a lot. Right now the only parts that I have to go towards this build is a Raspberry Pi 4 (4gb RAM) and a monitor for the Raspberry Pi 4. When Ashhar designed the sBITX he made everything open source. So everything, including the OS that is on the RPI is hackable This radio isn't just soldering a transistor to a resistor. It's about learning the code, knowing what electronic component goes where and why. Like I said, I plan on sharing everything here on this blog and on the BITX 20 io group. I'm gonna tell you right off the bat. I AM BAT POO CRAZY! That being said you can and should expect lots of failures and lots of laughs from me. In fact more failures than successes. When I fail at something I want to know why it failed and what can I do to fix it. You learn more from mistakes than you do by never failing. If that is the case then I should be a genius. I should be Aaron the Great. lol

    So PLEASE subscribe to this blog so that we can go forth on this Journey together and keep slugging away. We will succeed as long as we Don't Stop Believing. (See what I did there?) We are gonna show those street light people how to build an sBITX. Anyone can comment so please do so. You can also email me at Aaron@K5ATG.com
Check back often for updates, or just subscribe so that you will know when this blog is updated. 

Aaron K5ATG

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