W0EB/W2CTX Firmware release v2.01R

Jim Sheldon W0EB has announced a further release of Firmware (v2.01R) of the W0EB/W2CTX firmware intended for I2C driven displays (including the newly announced “RadI2Cino” card which is an (almost) drop-in replacement for the Raduino.

This release effectively covers all the enhancements for the non-I2C Raduino released earlier (v 2.00R)

The following changes have been incorporated in the firmware:

“The CW Keyer module has been completely re-written in this version. The keyer is now totally interrupt driven which helps make the transition to CW transmit much faster and it doesn’t tend to clip the first dot as it did occasionally in past versions. This version also moved the DASH paddle input from the analog A7 input. It now shares the analog A3 input with the PTT line as normally PTT isn’t used in CW mode and the Hand Key isn’t used in CW Paddle mode or the Paddles aren’t used in CW Hand Key mode so all three can share the same input easily. This gives A7 back to those wishing to use it for metering applications. Complete, illustrated documentation on everything in this release is contained in the zip file as a PDF. Menu operation has been slightly improved from V2.00R as well. We hope you enjoy using this version. Jim – W0EB and Ron – W2CTX”

You can access the release details file as follows:


Top Band (160m) external LPF

Bill NG1P provides a bit more detail on his Top Band (160m) mod success.

“I’m having a blast on 160m I did add larger heat sinks and a pair of small fans that I can turn on and off as needed to keep the finals cool if I’m long winded or using digital modes.

“Qrp labs makes a great low pass filter kit:
Read previous news iteM

RX-TX Audio Pop Fix

Erhard Haertel DF3FY comments, “There are a lot of proposals for addressing the RX-TX audio pop with the uBITX, but none of them really works”.

Erhard has come up with his own pop-fix that involves muting the TDA amplifier during TX, turning the IC on with the 12V RX line (to prevent SSB noise in headphones during transmit) and additional decoupling for the 12V line.

Erhard says, “This fix cures all the issues”.  Write and tell us if you have tried this fix.

Anderson Powerpole chassis mounts

Dave WI6R showed off his aluminium chassis to the list, but this resulted in questions about how he mounted his Anderson 12v powerpole connectors.

The answer is that you can use either of these mounting systems (the second was used in Dave’s case):

#1 https://powerwerx.com/powerpole-connector-chassis-mount-4

Note, that the mouting clamps do not have to be mounted on the exterior of an enclosure.  They can just as easily be mounted on the inside, making the who affair look more presentable.

Experimenting with Mitsubishi RD16HHF1s

John VK2ETA has done a strait replacement of the IRF510s with RD16HHF1s in his uBITx.  You can see from the photo above that he has them installed cross-legged.   John says, “To replace the finals I simply cut the legs of the IRF510s about 3mm above the board and correspondingly cut and crossed over the drain and source pins of the RD16s to match, then soldered in place”.

What follows are the before and after values of output power and PA current that John measured.   All tests were done with the uBitx VR1 drive level in the same position of approx 60% of range.

1. IRF510s and main board at 12.1V. PA idle current checked at 0.20A total (factory setting) so assume 100mA in each final.

(For info, Rx currents: 164mA no volume, about 209mA “normal” volume).
– At 7.1Mhz: 10W, total current: 1.79A, of which PA current: 1.31A, therefore main board current 0.48A
– At 14.2Mhz: 5.5W, total current: 1.39A, of which PA current: 1.0A, therefore main board current 0.39A
– At 21.2Mhz: 2.2W, total current: 0.95A, of which PA current: 0.53A, therefore main board current 0.42A
– At 28.1Mhz: 1.3W, total current: 0.95A, of which PA current: 0.53A, therefore main board current 0.42A

2. IRF510s with 16.5V, 13.8V for main board. PA total idle current checked at 0.21A.
(For info, Rx currents: 188mA no volume, about 230mA “normal” volume).
– At 7.1Mhz: 19W, total current: 2.65A, of which PA current: 2.09A, therefore main board current 0.56A
– At 14.2Mhz: 11W, total current: 2.20A, of which PA current: 1.80A, therefore main board current 0.40A
– At 21.2Mhz: 5.5W, total current: 1.40A, of which PA current: 1.00A, therefore main board current 0.40A
– At 28.1Mhz: 2.2W, total current: 1.02A, of which PA current: 0.60A, therefore main board current 0.42A

John hasn’t managed to find a definitive reference for the safe and optimum values of the RD16HHF1s idle bias current but it seems to range from 200 to 500mA. He would not recommend long term usage of the 500mA bias used for these measurements and will reset his idle current to the 400-450mA range.

3. RD16HHF1s and main board at 12.1VDC, 250mA idle bias each (Total 0.5A PA idle current).
– At 7.1Mhz: 10W, PA current: 1.20A
– At 14.2Mhz: 9W, PA current: 1.21A
– At 21.2Mhz: 4.5W, PA current: 0.65A
– At 28.1Mhz: 5.5W, PA current: 0.95A

4. RD16HHF1s and main board at 12.1VDC, 500mA idle bias each (Total 1A PA idle current).
– At 7.1Mhz: 10W, PA current: 1.18A
– At 14.2Mhz: 9W, PA current: 1.26A
– At 21.2Mhz: 5W, PA current: 0.71A
– At 28.1Mhz: 6W, PA current: 1.11A

5. RD16HHF1s and main board at 13.8VDC, 500mA idle bias each (Total 1A PA idle current).
– At 7.1Mhz: 13.5W, PA current: 1.95A
– At 14.2Mhz: 13.5W, PA current: 1.93A
– At 21.2Mhz: 6W, PA current: 1.38A
– At 28.1Mhz: 9.5W, PA current: 1.79A

John made the following observations:

A. The RD16HHF1 produces a much flatter power curve over frequency (in his device), although it shows a dip somewhere near the 15m band.

B. The IRF510 can produce some nice power in the lower frequencies when increasing the PA supply voltage, but it comes at the price of a steep power drop at higher frequencies.

C. The bias does not seem to influence the efficiency of the finals at full power with RD16HHF1, since biasing at 250 and 500mA produces essentially the same output for the same DC power input. Assuming distortion reduces with higher bias, can we assume a higher bias (within limits) is preferable? Any risk of thermal runaway?

D. The board main current (which includes the current in the driving stages of the power amplifier) does not seem to change with frequency from 20m onwards. Is this because the gain is pretty constant? If so, most of the drop in power with increasing frequency seems to be in the IRF510s, supporting the results obtained with the RD16HHF1s.

E. With the current uBitx PA circuit the RD16HHF1 seems limited in output, but without the appropriate test instruments he can’t say where the limitation occurs.

F. When he increased the drive through VR1, he noticed that at around 40% for the lower frequencies and at around 60% for the top frequencies he gets a compression effect.   The output does not increase much more from increasing the drive level.   John left the drive gain at around 60% and got positive feedback on the voice quality on his first QSO on 40m.  He assumes that any compression/clipping is not significant at that level (but he hasn’t measured the sprectral purity).

So since his target was around 10W on 10m and 10 to 15W on 40m minimum, he is pleased to  have reached his goal just by changing out the finals to RD16HHF1s and supplying the board with 13.8VDC.   This is below the 15.2/15V stated in the respective datasheets of the RD16HHF1.

DK5LV experience with RD16HHF1s

Henning Weddig DK5LV thanked John for his intensive research on the PA stage and commented that in his experience, “the RD16HFF1 really needs a very high quiescent current of about 500 mA each, which is not good for a QRP design”.

He  goes on to say, “The output transformer plays an important role in the design. Normally a 1 to 4 impedance transformation (12.5 ohms to 50 ohms) is sufficient. Each transistor “sees” half of that impedance i.e. 6.25 ohm. The windings of the transformer must be capacitively compensated and the leakage inductance mimimised on the windings.”

“Another big issue is the choke for the supply voltage: the commonly used centre-tapped transformer without the choke is not recommended. Ashhar Farhan uses two isolated chokes, and in my experience a bifilar wound choke is the better choice.”


Lowering the height of the uBITx

Sajeesh VU3PSZ  felt that the height of his case could be reduced further as there was lots of space to spare.

He soldered a separate connector below the PCB and straightened the leads on the Raduino board so that it plugs in horizontally underneath the main board.   This saves around half an inch in the required height of the enclosure.

Reference #1      Reference #2

A nicely presented Hammond 1402 case

Dave WI6R shows off his Hammond 1402DV (V for Vented since the heat sinks are inside).

It’s tight with the Volume Control mounted in between the display and the extrusion. So the PCB is mounted as close as you can get to the right side extrusion, then mark for the display and pot, with the encoder centered between the display and right side.

Dave used his own connectors for Mic, Headphones and Paddle and a Power Pole power connection on the rear panel.  On the far left is the stock BNC antenna connector.

There was room to later mount a USB cable as show.   Dave thinks he should have centred the Power Pole connector with the USB rear panel connection, but that’s what happens when you add things in later …


You’ve got mail: a mailbox enclosure

Scott K2CAJ  was looking for a suitable metal case for his uBITX and ended up wandering down the mailboxes section of the local Lowes (a large hardware supplier to the domestic market in the US).

“They had a slim upright letterbox, the Gibraltar City Classic, for under $13.  The letterbox has a recessed back panel that limits the interior thickness to 2.5″, but all you have to do is pop the panel it off and turn it around, and you get the full 3″ of space. I added some rubber feet and used some scrap metal to hold the jacks and knobs on the same side as the board. The front lid neatly flips open to reveal the goods”, Scott said.

These cases are available in bronze and black, without any “US MAIL” detail on them.  There is a snap-on plastic fleur-de-lis if you want it, but beyond that it’s just a case.

Scott says “Now I can tell people that I got my uBITX in the mail, wah wah wahhhhh….”

RadI2cino … another Raduino replacement

Jim Sheldon W0EX  has announced the availability of the joint effort from himself and N5IB – the RadI2Cino (prounounced “Rad ee too CEE no”).  This is an almost “Drop In” replacement for the original uBITX Raduino card.

The attached PDF (N5IB_W0EB_RadI2Cino) contains the complete information on this new Raduino replacement.

In summary, the changes/enhancements that have been incorporated in the RadI2Cino include:

  • I2C is used so the 16 pin LCD display header has been eliminated
  • The LCD display contrast pot has been eliminated
  • The 16 pin and 8 pin uBITX headers are retained and connect in the original fashion
  • Arduino NANO I/O pin assignments have been rearranged to free up digital and analog I/O pins
    a) D8, D11, D12 now used for key, paddles, and PTT.
    b) D10 used for an A/B split selection button.
    c) D9, D13, A3, A6, A7 now available for other needs.
  • The LCD display is operated via an I2C bus connection.
    a) Contrast control is now part of I2C interface “backpack”.
    b) Larger, 4-line displays are supported.
  • The TO-220 5 volt regulator has been replaced by a surface mount 7805 1 amp regulator.
  • A surface mount 3.3 volt regulator has been added.
  • A 4-pin header has been added to give access to the I2C bus.
  • A logic level translator has been added to the I2C bus to protect the Si5351 clock chip.
  • Manufacturer-recommended RC de-bouncing for the rotary encoder phases has been added.
  • Provision is made for an optional dropping resistor to reduce regulator dissipation.
  • Several powering options are provided, selected by shorting jumpers.
    a) power everything through the NANO via the uBITX +12V rail**
    b) power the NANO from the uBITX +12V rail, and the rest via the 5V regulator**
    c) power everything from the board mounted 5 volt regulator.
    d) power the Si5351a from the NANO’s 3.3 V output.
    e) power the Si5351a from the on-board 3.3 V regulator.
  • Though the PC board is slightly longer, mounting holes compatible with the LCD display are retained.
  • An additional 8 pin header is added for access to the newly free I/O pins.
  • Uncommitted PCB pads are provided to connect serial I/O and NANO Reset. NANO mounting pads are intentionally oversized to allow for a low profile, machined pin, socket for the Nano.
  • Heavy use is made of silk-screened labels to identify signals and functions.

** If the optional dropping resistor is not used DO NOT EXCEED 12V when using these power options.


More boards are on order but due to the Chinese New Year they won’t be shipping until around the end of the month.

Jim asks that  all inquiries and orders be held off until after he announces the availability of the next batch.


Another Raduino replacement coming


Nik VK4PLN has been working on a simple “open source” Raduino replacement board.   He has now provided photos of both sides of the board.

It will use the Adafruit Clock board. All devices will, therefore, run at 5v.  inouts and dimensions are similar to the original so it can be used as a direct drop-in replacement, or it can be modified for i2c display and other GPIO mods.

Nik is hoping it will work out cheap (50c a board, $3 nano, $8 Si5153 board plus a 7805 regulator and a few other bits and pieces).  He plans for the board to accept either Surface Mount Devices or Through Hole devices, particuarly for the capacitors and resistors…

It is hoped that this would be a cheap easy build for a Raduino replacement. An initial assessment of costs (ex Ebay.com) is as follows:

VK4PLN RadinoI2C board : $8
LCD + Backpack : $3
Si5351 : $8
Arduino: $4
+bits : $2
= $25, not too bad.

Nik invites constructive comments and thoughts