The trifilar wound transformers in the from the uBitX schematic have polarisation as indicated above. The transformers use a 6 pin IC base legend, with the pin numbering as indicated above.
uBITx manager Master Calibration settings
Nigel G4ZAL asked what people saw in KD8CEC’s UBITx Manager for their calibrations.
Nikos, SV1IYF, sent Nigel his settings, and they may be useful for others who want to recalibrate roughly to get going:
- Master Calibration 143000 => Accuracy within 3Hz @10MHz, as delivered was ~75Hz off
- USB Calibration 11996200 => Places the audio BW @ 430-2450Hz @-6dB
I ended up with said figure for USB as I only work FT8 and also the farther the crystal filter’s pass-band is shifted from zero the better the carrier suppression and the LSB sideband (which are nothing to boast about). - LSB Calibration: Not changed.
A voyage of discovery with the µBITx
Rob, AG5OV, discovered the uBITX around Christmas and promised myself that when he got his Extra licence, he would setup his first HF shack. The uBITX removed the financial barrier and two weeks after he discovered the uBITX he passed his Extra exam (50 of 50!).
Rob’s adventure was in full-swing. He was aware of the anecdote of not to QRP for your first rig, but some frustration and failures did not dissuade him easily. He decided against building his own antenna for the first go round, as the uBITX was already going to be somewhat of a variable. After all, the fewer variables, the better!
He went with an EFHW from MyAntennas, which seems pretty well regarded. He learned about configurations, gotchas of EF’s, radiation patterns and about slingshotting fishing weights over tree limbs.
While waiting for his uBITX to ship he read every single post on the BITX20 list. If there was a part number, he went and read up on it. If there was something he needed for his µBITx, he ordered it. (He now has a stash of TDA2822’s, sockets, IRF510’s, RD16HFF1’s and BN’s sitting around). He bought a new soldering iron, bought a handful of newly discovered SMD practice boards and then read some more.
His uBITX eventually arrived and proved to have the dreaded WX version of the TDA2822 chip. He was not discouraged for he had a stash of step-downs from eBay.
He rushed putting his uBITX together with a build that aesthetically belongs in class of what not to look like. He printed a mic enclosure and a double paddle (and he has been practicing his CW regularly). The rig was brought to life. There were VOICES on his radio! He tried some SSB CQs, but his output looked very low… something to follow-up on.
Next he built an audio interface (using an EasyDigi design, but without the kit) and tried some FT8 because he had two young helpers who needed to see results… The young helpers make activist investors look like puppy dogs! They don’t want to hear their Dad endlessly calling CQ, they need action!
Rob had his first uBITX QSO on FT8 last week and with his helpers they have looked at the map everyday. They worked Mexico and down to Colombia shortly after. Last night they managed a first FT8 QSO across the pond to Slovenia and Hungary on the junkyard uBITX.
Rob wrote out his story not for himself, but because all this happened when the uBITX became available and it changed a “someday”activity into a “Hmm, I can do this right now” activity. It ignited a grand adventure for himself and a couple of young men.
Next up, Rob plans to use his µBITx on CW and SSB. He has already met a local HF’er via FT8, who’s going to be his testbed for SSB and he’s been practicing for his first QRS CW QSO.
Rob extends a big “Thank you” to Ashhar Farhan VU2ESE for making the little hackable “platform of discovery” and he also extends a big “Thank you” to the community of constructors on the BITX20 List for imparting the “Yeah, I can do this” motivation.
16×2 Display Dimensions
Jim Reagan asks, “Can anyone give me the manufacturer of the LCD display? Or the exact size?”
Jerry, KE7ER responding noting that “Adafruit says they nominally measure 24x69mm, mine measures 24x71mm https://www.adafruit.com/product/181″
“The 16×2 LCD (or 1602) is a generic display and there are clones of clones of clones for this display. Who built it first has long since been lost to the mists of time, as has pretty much everything from the 1980’s. But hobbyists have taken to it because it’s cheap, and speaks via 5v logic just like the equally ancient tech of their Arduino boards. So they still get cranked out, by manufacturers too embarrassed to put a name on them. The going price on eBay is down around $1.60.”
The LCD that comes with many uBitx is the JHD 162: https://www.sunrom.com/get/526000
The dimensions shown on page 16 are 24.1 x 72.2 mm.
Those pre-preparing a front panel while awaiting the arrival of their µBITx are advised to make a hole smaller than these dimensions, just in case the dimensions don’t match. There is quite a bit of variation in 1602 display dimensions.
Reference
Linear amp conversion to Mitsubishi finals
Nik VK4PLN has been doing further work on upgrading the linear amp to Mitsubishi finals in his µBITx. He says,
“So looking good so far. I am getting these output values: (RV1 adjusted(75%) for 20W on 80/40)
80m : 20W
40m : 20W
20m : 18W
15m : 17W
10m : 14W
“No feedback, but I have yet to test a QSO on 20/15/10m…
The configuration is:
RD16HHF1 finals,
- BN42-202, but a 2:4 ratio winding giving 1:4 transformation.
- 320pf on all 7 emitter resistors of the pre-amp chain
- 330pf across the primary of the final’s winding.
- 220 ohm feedback resistor.
The finals run cool at 20+w with 330pf Mica cap. Nik is still considering changing out the driver and pre-driver transistors.
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New Arduino IDE settings
Bob N0BHC stumbled across an upload problem with an order of 5 Arduino Nanos this week.
This batch of Nanos used the CH340 USB chip and he was certain the USB driver was correct.
He found there had been a recent change in the Arduino IDE (sometime during March ’18) and to program new “old” Nanos you have to select “ATmega328P (OldBootloader)” from the “Tools – Processor:” Menu. After doing this, sketches uploaded to the Nanos just like before.
Reference
Processor upgrade to a Teensy
Stephen, KD2NDR, has been working on porting the µBitx code to a Teensy.
He has added a few other features with the new expanded memory capability. This includes an I2C 4×20 display, leaving many pins for other uses, and digital beacon modes supporting all JT modes, WSPR and FSQ. Transmission is triggered by a timer interval set through main menu.
The teensy real time clock is updated using a GPS module. Stephen plans to add an option to set the clock manually or via a serial port at a later date. His implementation also allows for dynamic setting of a maidenhead locator (4 or 6 character) based on the GPS data.
Planned features for a future build include an SD Card to store custom messages and logging for digital mode operations. He also plans to provide numeric keypad support sot that text can be entered directly along with setting the frequency. A voltage/ amps monitor for battery operation, and an. swr meter, and more is planned. Stephen promises to make the software available to constructors when he gets more time to test everything in more depth.
In commentary on the measurement of amperage, there were several suggestions for how to do this including the use of cheap “Hall effect” sensors. Probably the best of these came from Arv, K7HKL, who suggests:
” An alternative approach for current monitoring might be available. As part of a workbench system I built a dual-port DC voltmeter using an Arduino NANO.
“By using two ADC inputs I can measure voltage on both ends of a resistor and
the use the NANO software to calculate difference voltage. This lets me
manually calculate the current from resistance and voltage.
“In a captive system this approach would work because the software would know the resistance value and thus be able to measure differential voltage and from that calculate current flow through that known resistance.
“Differential voltage measuring is necessary in cases where both ends of the device being measured are at some potential above ground, because the Arduino ADC can only measure relative to a ground reference.”
KD8CEC version 1.061 with WSPR released
Ian KD8CEC has released Version 1.061 of his µBITx firmware. You can read more about it here. This version provides support for WSPR and has several bug fixes.
You can download Hex files and source code for compilation in the Arduino IDE from github here:
Ian says he is currently experimenting with various applications for the uBITX.
Reference
Gian, I7SWX, has shared a mod for replacing the TDA2822 audio amplifier. He intends to apply this circuit after other mods he is experimenting with on his uBITX.
The audio PA is the TDA2003, an amplifier where the bandwidth can be modified. His circuit is designed for 3kHz.
This circuit, with reduced bandwidth, has been tried on an FT920. It is possible that some components values may need to be changed.
It is important to note that Gian has not tried this mod as yet, but others might like to beat him to it!
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uBITx gifts to St Lucia YLs
Bill Schmidt, K9HZ / J68HZ writes, “Thanks to my friend Frans J69DS, freshly built uBITx radios were given to two well deserving young ladies on the island of St. Lucia yesterday.
“They are part of the Youth On The Air (YOTA) movement on J6 and now you can listen for them on their own radios. Getting the radios to them had its challenges but they are very happy to have them! We have more radios to give away too!”
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