Alternative software for your uBITx

What do you know, but two new software forks for the uBITx are shortly to be forthcoming.   One is focussed on significant hardware enhancements and the other is designed for stock uBITx hardware.

A stylized red stamp that shows the term beta testing. All on white background.

VU2SPF Software

uBitx.net has already foreshadowed the 2.8″ display from Joe VE1BWV with its software from VU2SPF that is expected to be released shortly.  This software will feature full touch control along with physical optional buttons,  100 memory channels, a tunable BFO. VFO, memory selection and all bands will be selectable from the touch panel.   However, this software has still to be released.

KD8CEC software

Meanwhile, Ian Lee KD8CEC has announced his Beta release of a further update for the stock uBITx.   Version 0.30 has already been released as a final version.   However, version 0.31 is out for beta testing.

This release features CW Keying, Frequency Tune and CW performance meeting the demand for such features from users.   CW keying improvements will continue to use original hardware.  However, it is also possible to set the CW Key analogue to digital conversion range to reduce mis-keying errors that some (but not all) have observed.   Reporting of the resistance detected allows you to know your exact resistance and key contact status (in case the key needs cleaning).  These functions need testing.

The source code for frequency tuning has been rewritten.  Ian has applied a threshold parameter, speed weighting, and a step function. The problem of an arbitrary change in frequency when turning the knob should have disappeared.   When a particular threshold has been exceeded, the frequency step will begin to change,  but Ian has added some logic to prevent the thresholds from becoming unnatural.
If you want to fine-tune, turn the dial slowly and the step rate will change, getting smaller as you turn more slowly.   There thresholds are more gradual  and change more slowly, to give a more natural effect.

The tune steps now are 10, 20, 50, 100, and 200, but you can change these in uBITX Manager 0.31 (Beta release).    You can change the step rate by pressing holding down the function key slightly longer than you would normally to enter the menu. If you keep holding it down for even longer, the Dial Lock function will be enabled.

Band setting is already present in version 0.3O, with the ham band set to “region 1” as the default.   In a similar way to controlling step rate, you can change to state by pressing the function key in the band select menu for a longer time.    You can set up to 10 frequency bands in uBITX Manager to suit your country or your preference.

These new features, a description of the features and details of how to upload firmware (both source code and compiled firmware) can be found here:

https://github.com/phdlee/ubitx

Details on how to upload firmware and access firmware versions up to version 0.27 can be found here:

Ian has indicated that future versions of his software are likely to require hardware modifications.

Tuning up

End whistling into your mic with this suggestion from David GW4AKZ:

When using an antenna tuner on SSB, we could easily add a tone generator and switch to do that.

I have fitted a switchable -6db pad between the output of the pcb and the antenna socket. With the circuit switched in the worst case SWR is about 1.65 to 1 with an open or short circuit.  This prevents the finals from ever seeing a poor SWR.

Tune is easily achived with the key down and reduced radiated power when tuning up.

I use 2 watt carbon resistors 33 ohms in a t attenuator circuit. 2 in parallel to give 16.5 ohms which is close enough to the calculated value.  A relay is s used to switch this attenuator in and out.

Chris suggests replacing the 51 ohm resistors with 2x 100 ohm 3watt resistors.
REFERENCE

Another audio pop mod

Joe VE1BWV provides another audio pop mod:

You probably will want to install a pop click fix to eliminate a loud pop whenever TX is turned on and off.   This circuit uses a 1N4148 diode, a 470k  or 300k resistor, a .22 or .44uF cap and a 2n7000 MOSFET.  Joe says this works amazingly well and mounts on the rear of the volume pot as indicated below (ignore the 0.1 uF capacitor).
Reference

The first TFT display for uBITx

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.

Reference

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.

Reference
 Joe recommends the Elegoo 2.8 inch  TFT Display with pen from Amazon.com  He has ordered 4 over time and the quality has been consistent, resulting in all of them working with clear, clean, crisp displays.
The price is  around $15.00 shipped within the USA. Note that the vendor does not ship outside of North America.
The Elegoo 2.8″ display with ATMega 2560 mounted behind it in the uBITx
Arduino Module : Joe uses the AT Mega 2560 and suggests Ebay is the cheapest source at less then $10.00 with any AT mega 2560 working.
DDS module –  SI5351  module (not just the chip)- available from Ebay or Adafruit direct or from Amazon.com for around $11.00.
Joe uses female single jacks to solder to the rear of the At Mega. Access to the pins is from the rear of the atmega 2560 as the front is facing the front radio panel with the TFT display plugged directly into it.  There is no room to get access to the pins after assembly.   This method minimizes the wires from AT Mega to the ubitx board.
You can also use an interface board which VU2SPF has developed – he has the pictures, but no pcb for sale at present.
Jumper cables are as follows:
  • 1 Jumper cable (2 pin) – male to female for connection of SDA and SDC lines from AT Mega to the Si5351 DDS.
  • 1 Jumper female to female 8 pin from atmaga to ubitx board
  • 3 cables for the clocks from Si5351 to the Ubitx.  – shielded cable is best
Joe feeds the rig with 13.5 volts – using a well filtered non switching power supply.   He also uses 2 “buck” converters (around $1.50 each on Ebay).
  • The first of these gets fed the 13.5 volt, and reduces the voltage to 9v to feed the AT Mega 2560.  This keeps it cooler than running full input voltage. He also adds 2  filter caps –  one 2000 mfd capacitor on the input side, and the other on the output side, along  with a 2- 10 ohm resistor on the output in series to act as a hash isolation filter.
  • The second converter is used to feed the SI 5351 module, adjusted to 5 volts. This uses the same filtering system as above.

Joe says this results in a very quiet rig with everything nice and cool.

Reference

IRF510 failure avoidance

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.

Reference

 

Marco – KG5PRT notes from one of the stories reviewed …

… In the middle of the page:
“I destroyed many IRF510 FETs during testing. In fact I blew a small hole in one and another into several pieces. It was quite a shock when the first one was destroyed because it made a loud noise like a rifle being fired.

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.

Reference

 

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
light/LED.

Inline image 1
from: http://www.g0kla.com/scpa/SimpleCheapPA.php

Or this one:

Conclusions about protecting the IRF510 devices

Arv’s conclusions to date are:

  • Power supply current limiting (2.5 to 3A) seems to work.
  • Bias voltage shutdown on high current (3A) seems to work.
  • Driver impedance to IRF510 gate should be quite “stiff”.  Use a 50 ohm pad.
  • Use a low resistance (4.7 ohms) in series with each IRF510 gate lead.
  • Keep IRF510 leads short.
  • Impedance presented to the IRF510 drain should be 12.5 ohms.
  • RF output transformer should be 1:2 windings for 1:4 impedance transition. A Binocular core may work better…?
  • Avoid the problem by using some other MOSFET.
  • Use plastic fuses at 3A for self-healing action.
  • Fuse rig power at 2 to 3A to avoid IRF510 failures.
REFERENCE

New: µBitx CW keying fix

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.

Reference

Removing the audio pop on T/R

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.   

A complete top board for µBitx

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.

µBitx mods website under construction

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.