The Virtual VRS2H relays in the µBITx are not easy to find, but there are substitutes available from Panasonic.
The VRS2H datasheet can be found here.
The first uBITx has appeared with a 2.8” TFT display. The hardware is from Joe VE1BWV and the software from VU2SPF.
The display provides full touch control along with physical optional buttons. 100 memory channels come standard, along with a tunable BFO, selection of VFO A, B or M. All bands are selectable from the front display which is a cheap 2.8” TFT touch display. Joe uses an AT Mega 2560 processor for lots of pins and better performance and an Si5351 for DDS.
Further details were given subsequently by Joe VE1BWV …
We have already done this for the Bitx40 and released software, videos etc.
Under youtube vu2spf and facebook as well as in the [BITX20] io group.
They are for the Bitx40 but the new code for ubitx has all the same features.I have 2 of my 3 Bitx running the basic same code. They work and look great.
See http:// vu2spf.blogspot.ca
This has info on the code, features, hardware, etc. The full UBITX info will be posted soon, including the arduino sketch, hardware options, where to source parts. An article in QRP magazine has just been released to subscribers.
Joe says this results in a very quiet rig with everything nice and cool.
Arv K7HKL notes that the problem with IRF510 RF amplifiers failing seems to be a recurring one for those who are not quite careful with antenna matching, bias level, and drive level.
As a way to start looking into this situation Arv performed some on-line searches to see how others were working around this problem.
There are a number of potentially useful ideas contained in those articles and discussions, but nothing that obviously applies directly to the problem of blowing IRF510 devices at only a few watts of power if the antenna is mis-matched.
Marco – KG5PRT notes from one of the stories reviewed …
Once I got tired of replacing the FETs, I built a current sense circuit, which shuts off the bias once the amplifier draws more than about 3 amps from the PSU. I think this circuit is essential. You can build it into the Power Supply or into the Amplifier. I built it into the Amplifier because the power supply, which is also homemade, does not limit until 7 amps. With the current limit circuit the amplifier now survives transmitting into any SWR from an open circuit to a short.”
He notes that the current limiting circuit has only 7 parts.
And Arv K7HKL suggests implementing this bias control circuit used by AC2CZ in his 50 watt IRF510 linear. He suggests you could probably do this using 2N3906 transistors. Arv likes the fact that it includes a warning
Or this one:
Conclusions about protecting the IRF510 devices
Arv’s conclusions to date are:
John AD0RW who has studied the CW keying issue has determined that the primary problem is that the analogue to digital conversion in the µBitx was having trouble distinguishing between “manual key down” and “dit”. This causes keying errors. For example, an ‘I’ becomes an ‘N’ when the dit paddle is held closed.
John incorporated the keyer code from W0EB and W2CTX into his personal software build, but he was determined to save the last analog input for S/power metering. So he kept the single input that detects four different levels. Actually, he doesn’t care much about straight keying so he left out the manual key resistor.
When looking at the nominal voltage levels with the provided resistors, he observed that there was only around 0.22 volts between the “dit” and “manual key” levels (1.60 vs 1.38 V). On the other hand, there is 1.8 volts between “dit” and “dah”. Errors due to fluctuations would be much more likely between “dit” and “manual key” levels.
He investigated options for resistor replacement, and in the end, replaced the 2.2k resistor with a 5.1k one. Now the nominal levels are 3.4 V for “dah”, 2.6 V for “dit”, and 2.1 V for “both”. The boundary ADC values were adjusted in the software.
He has found the results to be favourable so far in his testing, including sending a fair amount of practice code at speeds up to 25 wpm. The iambic action seems flawless and smooth.
He notes that “I might actually get good at sending iambic style someday…”. Some of us need to try this solution. Saving ports is a good idea on an Arduino Nano! It would also be helpful to know what values folk are using for the thresholds for the boundary points in the sketch.
A mod developed by Gary N3GO (and required for Full QSK) also mitigates the Tx and Rx pop/thump noises in SSB mode. This mod should work fine with the existing relays and with or without other mods, but has yet to be verified by others.
Martin Held AE7EU has been very busy designing a top tier board for the µBitx main board.
The board interfaces via the standard connectors to the main board of the uBitx. Martin’s top board adds essential features, such as speech compression, an integrated Teensy 3.2 processor, an attenuator and an auto antenna tuner. The front panel break-off from the board simplifies construction and makes the form factor as small as possible.
We look forward to seeing Martin’s report on how the board performs in practice. It is likely we will see a few changes to the board before it becomes available to purchase!
In a post to the BITX20 list Martin identified four options for release:
1) Release the board files, schematic, design files/gerbers, BoM and let someone in China clone it, walk away.
2) Same as #1, but just sell bare PCB’s.
3) Sell PCB’s with all SMT components installed, and a baggie of TH parts, toroids, and couple feet of magnet wire.
4) Sell the entire thing fully assembled ($$$).
It is likely that either options 2) and 3) will be favoured by the amateur community, based on initial feedback to Martin.
Tired of searching through the Bitx20 iogroups emails to find mods for your µBitx transceiver?
This website should make it much easier to identify potential mods for your own µBitx, and get the information you need to do the construction! It is not intended to replace the group culture, but to make it easier to reference mods suggested by group members.