This is a rather nice µBITx build from Dennis N8GGI.
Dennis says, “Finished wiring up the UBITX today and downloaded the KD8CEC firmware. I took my time with the case. Old retired industrial designers still like to design (and build).
“I added a keyer circuit which has a speed pot…I don’t like to run through menus to match someone’s speed. I also added a Hi-per-Mite audio filter which really makes it a nice CW rig.
“First 40 meter CW contact was New Hampshire from my QTH on Lake Erie in north central Ohio. Second 20 Meter CW QSO was from Portugal getting a 559 report using a tri-bander at 60 feet. I tried 20 meter SSB and worked the gulf coast of Florida with a 5×6 report. It’s a great little radio! Now I still have to tackle the TX pop and try to tame down the sidetone volume issue. I hope the 1,500 watt linear doesn’t get lonesome from lack of use.”
And what lies beneath the paint! The “see-through” version! Dennis says, “Kinda looks like the old ‘visible V-8’ from the ’70s.”
Many constructors have had issues calibrating their µBITx.
To begin with, you have to figure out how to get into the expanded “Settings” menu. Push on the encoder, and select “Settings”. Wait for the menu to exit automatically. Then press the encoder again and in turning the dial you should see the additional menu items displayed.
Jacob AG7CT has documented the steps he takes to calibrate his µBITx:
Tune to WWV on the dial
Enter menu
Turn setup on
Reenter menu turn to and select calibrate
Zerobeat the WWV carrier. (May be difficult if BFO is too far off.)
Click PTT.
Click encoder, select set BFO.
Zero the sideband off WWV.
Click PTT to set.
Click encoder, turn setup off.
Wait more than 10 seconds to ensure setting are saved before removing power.
Bill K9HZ who we have already reported had developed a relay control system driven by the Low Pass Filter I/O lines. In addition, Glenn VK3PE has also come up with a circuit that could be adapted using a digital potentiometer module to be driven by the Raduino using a digital I/O line.
Relay drive control
Bill K9HZ has now drawn up the circuit he used to allow for relay switching of drive levels by band grouping, driven by the LPF band grouping I/O lines of the Raduino. No firmware mod is required to deliver even drive power across all of the bands.
RV1 in the yellow circle is the existing drive pot in the uBITx. Remove it and connect the wires from the relay as shown. Q17C, Q18C, and Q19C references connect to the transistor Q17, Q18, and Q19 collectors. Then set RV1A, RV1B, RV1C and RV1D on the basis of the appropriate band grouping selected to keep the power out flat.
Digital drive control
Glenn VK3PE has come up with an old circuit that could be used to work with a digital potentiometer module to use as adrive control set by the NANO firmware on a band by band basis.
The original drive control, RV1, would need to be removed and a few parts added, along with a digital pot (I2C control) in place of R3 below to form an attenuator in the RF path.
With some careful work it should be possible to design a small PCB that fits into the holes vacated by RV1, either vertically or horizontally.
The schematic is from page 62 of the book by Randy L. Henerson on designing a Transveiver. Its a very old book (1997) ISBN 0-07-028263-3
1. Encoder PCB
This pcb will save you from the clutter of wiring up the encoder.
2. USB.D9. PCB
Use this board if you wish to. if you do not want to use this board then cut a small plexi glass sheet and close the open area.
3.Power Connector PCB
The DC Power supply connections are easy to install with a board to assist. The On/Off switch, Fuse, IN4007 diode and power connector are mounted on a small board again removing wiring clutter.
Care has to be taken in mounting the On/Off switch, as excessive use of soldering heat or bending of the pins on the switch may damage it.
Sunil says that he will be making further improvements in the µBITx products to make it easier to wire in kit components into the case.
Bill KC5SB has been using his “black beauty” µBITx on the FT8 digital mode and has already worked a station in Brazil with no problems. Bill has installed a fan because he spends a lot of time on digital modes. The display has been replaced with one with a blue background (goes better with black) and the unlabelled switch on the back is for the fan – high, off, low.
The case can be purchased here. It has, of course, been painted.
Nigel G4ZAL has just finished his µBITx build and modded it a little in readiness for adding additional boards/hacks.
He cut the track feeding the TDA2822 and fed it with 5v from a little Radio Control UBEC. At the same time, he removed the 5v regulator on the Raduino and fed that from the UBEC as well. You can see from the photos that he has added a little ‘bus’ for picking off further 5v supplies as required.
His installation looks pretty snappy in the well used Banggood case
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And the µBITx is already hard at work on 40m using the FT8 digital mode:
Bill Schmidt K9HZ suggests there is a false supposition here that you must tune under full power. It is considered a good design to tune with just the amount of power needed in order to tune… not full power. This can very easily be implemented on the uBITx with a relay that substitutes in a “Tune RV1” set for a much loser tune power.
List members suggested options for simple external antenna tuners for the µBITx transceiver. The list of potential tuners below (organised by type) is not intended to be exhaustive, but illustrative of the choices available.
The LDG Z-100Plus tunes with only 100mW of power. It holds eight AA batteries internally, making it ideal for portable QRP operation. Small, light weight and self-powered.
However, Rahul VU3WJM found that the match at low power levels was inconsistent. He had to reduce the resistors in the ADC sample line for QRP operation.
Dave K8WPE prefers a small Z match like the Emtec, 4SQRP tuner, GQRP tuner, etc. At the home QTH, Dave uses an MFJ 300 watt roller inductor tuner.
He says that the reason he likes manual tuners is he can look at the numbers on the dials and if they are different from what he usually sees he knows he has antenna troubles, i.e. an antenna down, ice coated, wrong antenna, a short somewhere. With the automatic tuner it just tunes and you don’t know if its the antenna or the tuner that is making your transceiver happy. And even at 5 watts or less we can fry an IRF510.
Allison KB1GMX suggests the ZM-2, 4Sqrp, SLT, and L-tuner all work. The 4sqrp, L-tuner, SLT, and Elecraft T1 are in use in Allison’s QRP rigs for power up to 10W. For higher power a home-built L-tuner easily takes 100W. Those get used for the inverted L and the 160M Inverted V as all the other antennas are 50 ohm resonant removing losses though a tuner and coax.
Allison says, “By far the best antenna is a matched one. Second best is any needing a tuner.”
Nelson KG7GYS has built his µBITx into “a box I had bought for some project over a decade ago and never got around to using”.
He ordered a speaker grill from Amazon for about US$2.50. He decided, like many of us, to use a pot with switch from his junk box in order to have a standard size shaft (it came out of an old Radio Shack CB set). The knobs are from an old Henry Tempo One (Yaesu FT-200). The speaker is from his junk box, as is the 12vdc fan.
We all want to know what the heck all that test gear does!
Rob AG5OV says, “If you are like me and not having a lot of luck with SSB QSO due to the recent crappy conditions or want to debug your apparent low voice output the Reverse Beacon Network can come to the rescue.
“RBN listens for CW CQ’s and reports who heard them. For the uBITX you can add in Ian’s (KD8CEC) wonderful firmware and even without a key you can send a message via the Automatic Key Memory function and see both who can hear you and what your uBITX output actually is under ideal conditions.”
Edited the Auto CW memory to “TEST DE <YOURCALLSIGN> TEST DE <YOURCALLSIGN> #” (the # is the prosign for AR)
If the TX/RX delay isn’t high enough you will flop back and forth with annoying clicks when you aren’t interactive anyways, I set mine to 1000ms and 400ms.
Tuned to the CW/Data area of a band and set to either CWL or CWU
What he discovered is interesting. He was being heard and maxing out at about 1.2a @ 12.0v on CW compared to his 800ma @ 12v for voice (while “eating” the mic.
He has figured out that, besides conditions, the audio input side of the world is letting him down. He has ordered an assortment of 1206 SMD resistors and a package of replacement electret mics (both from Amazon) to see if he can fix the problem. We will be waiting to hear the results.