The PTT switch is mounted in the pen housing on a small piece of perf board.
It is built very well and super light. Only 4 screws hold the whole thing together yet it is very strong and rigid. Very ingenious.
The radio weighs 2 pounds. Joel did not leave the display mounted to the main board as it would make the display not centred and too low on the front panel. He built a short flat extension cable out of a female and male header.
CLK0 (BFO) is fixed at 11996500 Hz, maybe 500Hz below the 12MHz filter’s 2000 Hz wide 3dB passband.
CLK1 (second local oscillator) is fixed at 56995000 hz for USB and 32995000 hz for LSB. You can find those three numbers in the file ubitx_20.ino at lines 166, 163, 164 respectively.
The VFO is used to select the operating frequency Fop according to these formulas.
Fop = VFO – (CLK1-BFO) so:
VFO = Fop + (CLK1-BFO) where CLK1 is around 45 MHz + 12 MHz
Fop = VFO – (CLK1+BFO) so:
VFO = Fop + (CLK1+BFO) where CLK1 is around 45 MHz – 12 MHz
To receive a 7.2MHz LSB signal (where 7.2 MHz is the frequency of the suppressed carrier), the VFO gets set to:
7200000+(32995000+11996500) = 52191500 Hz.
That formula gives an exact result, not an approximation.
USB vs LSB
The BFO corresponds to the carrier frequency of the station being received or transmitted. The 12mhz filter is always above the BFO, so within the 12 MHz IF it allows through only the upper sideband.
The VFO is always above the 45 MHz first intermediate frequency, and so always inverts the sidebands.
A carrier at 7200000 Hz would get translated to:
VFO-Fop = 52191500 – 7200000 = 44991500 Hz
A lower sideband at 7198500 Hz would get translated to:
52191500 – 7198500 = 44993000 Hz
In this example we assume the lower sideband is generated from a single audio tone into the mic of 1500 Hz. We have chosen 1500 hz because it will land in the middle of the 12 MHz filter’s passband, assuming the filter has a 3 dB passband that’s 2000 Hz wide and the BFO is 500 Hz below that passband. The actual range of frequencies passed will be 500 to 2500 Hz. Those assumptions of 2000 Hz and 500Hz might be off by a couple hundred Hz.
Likewise, a high side CLK1 of 56995000 Hz for USB always flips the sidebands when translating to 12 MHz, however the low side CLK1 of 32995000 Hz we use to receive the 7.2 MHz LSB signal does not.
Sunil VU3SUA who is an active BITX20 list constructor has a business (Inkits) selling enclosures and electronic components for the Indian domestic and international market. Sunil is now shipping his µBITx case. This is a high quality metal case that is available in several colours: Maroon, Black, DA Grey, Siemens Grey, and Blue.
As you can see this is a very professional looking case. The case will be in high demand initially and is, therefore, only available on pre order.
Sunil’s website says that the first batch of pre order bookings has now ended and shipping has started (15th March 2018).
We should see reviews of this product shortly on the BITX20 list.
Bookings for the Second Batch of pre order booking open now. The shipping of second batch will start by end of March or Starting from 1st April 2018.
The universal case for the µBITx costs US$34.99 with worldwide shipping via India Post costing US$20. For a DHL courier service there is an additional charge of US$15.
New releases for both variants of the W0EB/ W2CTX firmware have been recently announced by Jim W0EB. This includes the version that works with the existing Raduino configuration (but requires minor rewiring of the CW key) and the upgraded display using I2C (using the W0EB/W2CTX RadI2Cino card or your own mod).
Ron W2CTX reminds us that if list emails stop arriving you will need to go to the BITX20 Group website and click on the “UNBOUNCE” to get them started again. This can happen if your Internet Service Provider goes offline for a few hours, or your email box is full and bounces emails.
VK3DAN has a µBITx and as soon as he received it he was busy modding it for a 20×4 (2004) screen. This sort of screen is easily substituted on the Raduino, but to use the extra display space requires modding the firmware.
Dan has added band readout, his callsign, etc. It also incorporates the CW sidetone fix, CAT system and various fixes written by Ian Lee KD8CEC. This firmware version won’t work with the 16×2 (1602) screen provided with your uBITX kit. You will need to have purchased a 2004 type screen to replace your stock display. You will also need to edit ubitx_ui.ino to change the callsign to your own.
Rod KM6SN found that WSJT-X running on some versions of Linux would not work well with the µBITX. The problem was the Hamlib FT-817 protocol was not successfully connecting to the uBITX at startup.
For the past two weeks Rod has been working with Bill Somerville, G4WJS (developer of Hamlib) on the issues. He explained the nature of the problem, and provided CAT link protocol logic analyzer traces, and did bench testing of new Hamlib code Bill provided.
Bill took a lot of time out of his schedule to work on this, and it has borne fruit, having now identified the area that needed changes, provided modified software, and stayed with the problem through quite a few iterations of testing.
Rod and the rest of the digital mode enthusiast community will no doubt be grateful for Bill’s persistence.
The Hamlib FT-817 protocol has been modified to resolve the problem, and there should be an official WSJT-X release for Linux including this patch soon.
Details will be posted on uBITx.net when the new WSJT-X version is available.
“For my part I don’t know if it’s hard code developer or more mad hacker, but it is fun. Here is a picture of the latest addition, an L-Network ATU built in the uBitx case, driven by two servos and controlled by an Arduino mini pro linked over I2C to the Raduino.
“It is now working well (80m to 10m) but needs cleaning up, shields (just to make sure) and a nice display of SWR and Power on the LCD. More details to come.”
Ron, W7HD, was very interested in the servo control code and components and wiring as he would like to adapt this idea to handle a pair of servos for an az-el rotor for his satellite Arrow antenna, which only weighs about 1-2 pounds. Then he just needs to add a bit of code to show the actual antenna position and he’ll be all set!
Ron suggests another adaptation of this project would be to remotely tune a magnetic loop antenna. One of the problems you run into when trying to tune a loop is that your body affects the tuning.