An Origami Case for the uBITX

Mitani Misaru JE4SMQ’s ubitx has been built in an ORIGAMI paper case (15 cm square) which cost just 100JPY(about US$1).

Mitani did not use an Encoder with a push switch but substituted a separate push switch for the encoder button switch.

Ver1.00R software has been installed and modified as follows:

1. The uBITx transmits on the Japanese Amateur bands only.   If you tune out of the band the PTT/CW Break In simply doesn’t work. This is required to meet Japanese regulations.

2. The BAND Select mode follows the Japanese Band Plan.

3. In CW mode the Mic PTT is used for keying. This is always in straight key mode. If a Paddle is connected the keyer can be used by adjusting the menu menu setting.


SSM2166 (Mic amplifier and compressor) as Audio AGC?

Henning Weddig DK5LV says he is in the process of using an op amp and SSM2166  on his “original” BITX40 as a way of achieving an audio AGC function.

This op amp has a  gain of 10 (20 dB) and an audio AGC system.   He purchased a pcb from ZL1CVD with the DIL chip via ebay years ago.  Unfortunately ZL1CVD does not sell this pcb any more…

The SSM2166 has a dynamic range of 60 dB, the opamp in front of it is intended to replace the first discrete amplifier after the demodulator and will amplifiy the audio into a range the SSM2166 can handle.  The SSM2166 has a provision for outputting an AGC voltage (an RMS output) and this may be able to be used for driving an S-meter.

Others are thinking along the same lines.  For example, Glenn VK3PE says:

“I’m thinking along the same lines. I built a Mic amp version using the SSM2167 and thought it might work also for the Receiver. It’s essentially the module seen on ebay but I’ve added a level pot on the output side.”

Meanwhile Alex PA1FOX comments:

“I am using the AGC from the original uBitx design, but found the time constant of 1uF and 100k to be far too low. This makes it a very fast AGC, not producing a nice sound with voices. I changed to 1.5 uF and 4M7 and now stronger stations are nice and clear (they ‘push’ the noise level down ) and the gain comes up nice and easy when the QRG is clear. I think I’ll keep it this way.”


Optical Rotary Encoders

José CT1KFN asked  about possibly changing out the mechanical rotary encoder for an optical encoder due to quality limitations of the supplied uBITX encoder.    As an example he referenced this one he found this one on ebay.

The responses were clear:   “Using one of these will present challenges for the Arduino Nano.  It can’t keep up with the number of pulses per revolution that an optical encoder like this will generate”.

However, Michael KM4OLT says:

“After I saw the post and responses I was wondering too…  I ran across this article that might help.  If nothing else it helps with managing fast digital writes.

Quadrature Encoder too Fast for Arduino (with Solution)



Top Band (160m) with uBITx

Bill Richardson NG1P has reported on his modified uBITx on 160m operation using a doublet antenna.

“Doing some testing with my uBitx on 160m with a 160m LPF attached to the output. I’m seeing about 15 Watts out but the current draw is running very high at just over 3 amps. So not usable on 160m at the finals will blow I’m sure. The bias stays normal so it’s something else?

“Doing the same test on my Bitx40 on 160m I see about 10 Watts out and the current is about 1.5 amps and very usable.”

John AD5YE responded with:

“I think that what you are seeing is the “normal” variation in the output of the MOSFETs. Some are better than others at RF.  Gordon’s suggestion to turn back the drive is probably the right answer.

“Alternatively, you could turn down the gate voltage a bit, but that would probably introduce compression distortion. Or you could increase the size of the heat-sink and see how it goes.

“Probably the wisest thing to do is both turn back the drive a bit and increase the heat-sink. Some, but not all, IRF510’s are capable of 20W or more on 80m. you might happen to have some good ones. The key lies in the harmonic generation and the heat-sinking. Note that what you are seeing MAY be from UHF oscillation included in the signal. Be very aware of that. Check your output very carefully. “

Bill reduced his drive to overcome the high current, and reports:

“I turned the output down to about 8 Watts and I have made 4 contacts on 160 with great reports. I will add a larger heat sink to be safe. “

So the uBITx works fine on 160m with an outboard LPF to remove unwanted harmonics from the transmitted signal.


Fixing low SSB drive (updated)

Anders SM5NNO has drawn attention to a published fix for low levels of drive on SSB with BITx transceivers from Mr K P S Kang  (VU2KR / VU2OWF) on this blog.   While the mic gain fix relates to the BITx40, it translates readily to the uBITx.


An update

André PA3EIV confirms that the above fix (by Mr. K P S Kang VU2KR works 🙂

He changed the value of R65 to 4K7 and the value of R63 to 10 Ohm using 1206 surface mount components (desoldered from scrap prints).

He now has, on normal voice volume, 10 watt’s out on 20m.  RV1 is turned counter clockwise for about 75%.   André uses a Baofeng microphone.


New software release v2.00b from W0EB/W2CTX

A file has been uploaded to the Files area of the group.


Uploaded By: Jim Sheldon <> </>

Latest NON I2C release from W0EB/W2CTX – ubitx_V2_00R contains totally restructured menu system – SPLIT is working – slight rewiring of CW Key Jack is required but this VASTLY improves the CW keying – full instructions are included in the PDF manual — see README.TXT in the zipfile for change details. File has been replaced due to newer instruction manual contained in the zipfile.

You can access this file at the following URL:

You may need to log in to the website IO Groups site to access the file.


Download the file directly from

Instructions for W0EB and W2CTX uBITX V2.00R software



Jim W0EB provided a further post on the [BITX20] Group list that gives a bit more detail on this v2.00 release:

“We have totally restructured the menu to make it much easier to use.  The Nano’s CPU cycle usage has been optimized for vastly better CW (a minor front panel wiring change is necessary to use this software).  Split is working (you do NOT have to be in transmit to change the transmitter’s frequency) and though not available yet CAT is being worked on.   We are not promising CAT anytime soon but we’re trying to implement it and keep CW working right.  (Not an easy task with a Nano but we want to keep from having to change out the Nano for some bigger card).

“Due to an easy programming trick, the keyer’s dash paddle AND the Hand Key/external keyer connection has been moved to the same wire as the SSB PTT on the Raduino’s digital connector (the orange wire).  This is possible since we don’t normally use the CW key or paddles when in SSB mode and we don’t use PTT when in CW mode.

“The menu item CW:Key or CW:Pdl selects whether or not the line is used for the hand key or dash paddle.  This requires a minor wiring change and either a short adapter cable to be built for the hand key/external keyer or a separate hand key jack be added.  Either way it’s an easy mod.

“This change gives the analog A7 input back to the guys wanting it for an “S” meter or power/swr metering.  The blue wire (A6) remains as the dot input.  Since we don’t have to select a specific threshold voltage on A6 for dot/dash/hand key and just determine key up or key down, the 2.2K and 10K resistors are no longer needed and the CW paddles work MUCH better.”


An RF based AGC design from K P S Kang

K P S Kang VU2KR / VU2OWF has an item on his blog showing an RF AGC for BITx designs.  The AGC is apparently very effective at calming those 9+20dB signals that on the uBITx will damage your hearing!

The design is for the BITx40, but can be readily adapted for the uBITx – probably not at the antenna (because it is best to avoid diodes at the front end of the uBITx), but at the 45MHz IF stage.  Are there any takers to adapt this design for the uBITx?

Nice looking case

Sajeesh VU3PSZ shows off his new uBITx case design alongside his older BITx40.   A nice pair of rigs.   His blog item shows all the details, including a home made jig to achieve the folds in the aluminium.   This is definitely worth a look if you are considering a home-brew aluminium case for your uBITx.


Front panel layout ideas

Vic WA4THRI always enjoy seeing how others have built their BitX’s and has pointed out ideas that others might find useful:

1. Almost everyone places their tuning control to the right, but if you place the Raduino to the right you can easily update and play with the software by just plugging your computer into the USB port [EDITOR:  With a penetration on the right hand side wall of the enclosure for insertion of a mini-USB-B connector.]

2. It is hard to beat the value of the Banggood EF01 instrument case. If you turn it upside down and eliminate attaching the hard plastic feet you have a smoother mounting surface for circuit boards and can use the vent holes for a speaker grille.  Add some stick-on soft plastic feet on the “new” bottom.

3. Using the second line of the BitX display to label switches and controls saves having to find a way to place labels on the front panel.