Technique for removing relays on a uBITx

Gerry recently changed out the relays on his v3 µBitX.  He had trouble getting the wick to remove all the solder, no matter what iron he tried and how much flux he used.   So he tried another method.

There are a number of low-temperature solder products, the most famous/common, being ChipQuik. These are basically an alloy that includes indium or gallium.   When added to a solder joint, this drastically lowers the melting point. You can melt the solder at each leg of a device, and by the time you have gotten to the last leg, the first will still not have set, making it easy to pull free the device. The risk to both the device and the circuit board will be greatly reduced.  If anyone is having difficulty, or is apprehensive about replacing the relays, this represents a good approach.


New BCI Filter Kit from KitProjects (N8DAH)

David N8DAH from will have BCI kits out in the next week or so for the BitX radios as well as other direct conversion receivers that suffer from close AM stations.

The drop off of the filter kit is right at about 3MHz.

These filters will cost 5$+ shipping.  They come with 3x toroids and 4x capacitors.  This would be a good kit to learn about toroid construction for those that have not had a chance as yet to try winding your own.

These filters are RX ONLY and should not be placed in the TX path.

David’s website will have detailed specifications and instructions for both the Bitx40 and uBitx radios on it shortly.


Remote access to your uBITx

There have been quite a few posts recently on the BITX20 list about remote access to your µBITx.   There are a number of ways to achieve this, but Jens (KM6ZJV) has provided a useful summary of how he has achieved this using a v5 µBITx connected around the clock to a Raspberry Pi 3 used as an FT8 monitor.

Jens  can access it from anywhere on any device (laptop, iPhone, iPad) with VNC and OpenVPN.

A big advantage of this setup is that the radio is always ‘ready for action’ – even if I have only a few minutes time to transmit (FT8 or FT4 or FS8).

As others have mentioned, the Raspberry PI comes pre-installed with VNC.

Using OpenVPN

OpenVPN can easily be installed with:

OpenVPN allows access to the Raspberry Pi VNC server with the same IP address / portnumber used in your in your local network (without a VPN connection). OpenVPN client applications are available for all major platforms.

Of course, once you have established the OpenVPN connection, you can access any other  part of your home network (fileserver, printer, etc.) as well – not just VNC running on the Raspberry Pi.

Jens does not not recommend directly enabling a port to connect to the Raspberry PI VNC server, instead enable a port to connect to the OpenVPN server.

Using Teamviewer

Frank KJ5WI suggests an alternative in teamviewer host.

Teamviewer host on the Raspberry Pi from the above link will allow a remote connection without opening anything. When the webpage opens, scroll down and watch for the pi logo on the right side.  Frank says that the Sun City Georgetown amateur radio club uses Teamviewer for remote access to their club station radios.

KM4UDX took a bit to get both computers trusted and set up… one running on Ubuntu/AtomicPi and the other Win10/oldlaptop. But he says, “it works!”

The  screen capture above from his win10 laptop controlling the AtomicPi with ubuntu controlling his V4 uBITX running WSJTX and completing a JT8 QSO.

Don KM4UDX is thrilled to have remote control!

After his initial success, he switched to FL-Digi and this works as well sending the keyboard via the link to FL-Digi text input window. However, if the uBITX audio output level is set too low from the last time he physically adjusted the speaker volume, then he has no way to change/increase the uBITX output level to make Fl-Digi happy.

Challenges with remote operation on the µBITx

Don sees the real advantage from complete visualization of the transceiver (.e.g. Flex).  If he had all of the uBITX functions on the screen, then the volume controls would be screen sliders allowing adjustment of all functions via the remote control.

The first challenge is how to adjust the uBITX volume levels in software through some sort of interface.

The second challenge is not seeing the RF output levels.  While you can adjust the drive level remotely, the impact on RF power output levels is not known, and could result in harmful emissions.


Adjusting your BFO offset using audio spectrum analyzer software

In adjusting the BFO  you have to be careful to not transmit both the signal AND the carrier.  If the filter has been shifted too far, it is possible to have the carrier transmitting unintentionally. Roman K7TXL found this out while trying to transmit FT8 signals.  He found two spikes on his SDR.

In his experience he has found that the only reliable approach, that doesn’t involve complex test instruments, is to download and use an audio spectrum analyzer program.

Roman uses SpectrumView by WD6CNF.

SpectrumView software

WD6CNF Audio Spectrum Analyzer runs on the Windows operating system and has the following features:

  • Analyzes audio from 10 Hz to 20 kHz
  • Takes an input from a microphone or wave file
  • Has variable displays
    • Fast Fourier Transform (FFT) display
      • Variable sample rates (8000 Hz, 11025 Hz, 22050 Hz, 44100 Hz)
      • Variable transform sizes (1k, 2k, 4k, 8k)
      • Upper and lower limits adjustable
      • Continuous, averaged, peak hold
      • Selectable foreground/backgrounds
      • Variable markers (2)
      • Save a reference plot, compare with the foreground plot
    • Time display (oscilloscope)
      • Triggered sweep
    • Waterfall display (color or B/W)

Alignment procedure from Roman K7TXL

  1.  Disconnect antenna from ubitx, or better, find an unused part of the band with just hiss, no other signals
  2. Run audio out from ubitx into PC/Mac/Linux audio in
  3. Run spectrum analyzer and configure it to listen to the audio in
  4. Turn up volume on ubitx until levels are reasonably high but not clipping in the spectrum analyzer
  5. For the ubitx 5 (not the earlier versions), you will want to set the BFO somewhere around 11.055-11.056 MHz as a starting point.
  6. I am going to presume that you started with the BFO frequency on the high side, say 11.057 and you are lowering it. As you do so, you should see on the spectrum analyzer that the noise’s high frequency roll off frequency increase. At some point it will no longer get any higher no matter what you do with the BFO value. The point you want is right as you touch that max value. You might have to back off and watch the max value decrease, then adjusting again until you find the maximum.
  7. Save the BFO frequency using the PTT where you get maximum high frequency response. Roman found that the BFO frequency was about 1.5-2 kHz lower than the frequency where he got the most “bass” response in his headphones, thus the final result had less bass response.
  8. If you have an SDR, you can double-check your results: Run ubitx into a dummy load and have an SDR with separate tiny (or no) antenna nearby, either run WSJT-X “Tune”, or a single frequency of audio into the ubitx mic. The SDR will likely be sensitive enough to pick up stray RF (even with the dummy load) and you should be able to see only one, not two spikes on the display (make sure you zoom in maximum to a narrow bandwidth view).

After this adjustment, Roman has managed to make a few longer distance FT8 contacts, i.e. Seattle to Alaska on 40m.


LF homebrew for the uBITx

Olivier has connected his uBitx  to  a homebrew converter (using an NE612) (see schematic attached) and PA0RDT’s mini whip just to see what he could find on the VLF bands.

He  made RX tests on DCF77 on 16.4Khz (Norway) with good results so I think it will be nice on 17.2Khz from Sweden.
Olivier has also provided a link to a short video, “Listening to BBC4 on 198 KHz” from the north of France.

Reducing the audio gain on a v5 uBITx

Roman provides a no-soldering hack to reduce the audio-stage gain on a v5 (current model) µBITx.

Power off the BitX before starting…

1. Observe which end the notch on the body of the 386 is facing
2. Remove 386 carefully from socket (i.e. use tiny screwdriver pull up chip body incrementally back and forth from each side)
3. Gently lift either pin 1 or 8 90 degrees so it is horizontal. These are the pins closest to the notch, that is, in each line of four pins, the pin at the end of each line closes to the notch.
4. Reinsert the 386 into the socket in a straight down manner until firmly in place, ensuring that all remaining 7 pins go into their proper slot (and don’t bend accidentally due to misalignment). Make sure that the notch on the 386 is facing the same direction that it was when you removed it.

Try it out by turning on the BitX – there will be less hiss added to the audio (this is especially noticeable in headphones)


Too much RF up the spout

Jonas SM4VEY posted on the IO GROUPS BITX20 list that his µbitx hadn’t survived field day operations After Jonas discovered his transceiver was dead he connected a dummy load via a power meter as an antenna.

The power meter showed 2 w power into the 50 ohm dummy whenever another nearby station transmitted into a nearby antenna.

His poor µBITx was now as deaf as a brick and provided (almost) no power out on transmit.    Jonas mused “What should I suspect first?”

Constructors made a number of suggestions.  Jonas reported the fixes as follows:

“After replacing the 1st mixer diodes the RX came to life again and I could hear -120dBm signals which represented an improvement of around 30 dB.

“I then started measuring the signal levels before and after each amplification block in the TX path and found Q90 having less signal after, then before.  I replaced Q90 with a leaded transistor and the µBITx now works normally again.

“I’ll look at adding 2 reversed (one each way) diodes to ground from the RX line before the 1st mixer. I’m not sure these will survive 2W though…”


Important  Information provides help for constructors:  Preventing catastrophes and providing guides, fixes and modifications for your µBITx.  We are an information site only and not associated with HF Signals.

WARNING:  As shipped, your µBITx  v3  or v4 board will probably not be compliant with emission requirements.  It has been found to generate spurs and harmonics.  There are now simple fixes available to address these issues.  Make sure you apply them prior to operating the transceiver on an antenna.

CAUTION : If you power up the µBITX without the pull-up resistor the µBITX is likely to go into CW transmit. Make sure you install the 4.7k pull up resistor on the CW key pin!

v3 Board?  – There are known issues with WX brand TDA2822 chips (U1): Read this.  Earlier UCI and later socketed TDA2822 are not affected.   You will probably want to do the audio pop mod at least.

v4 Board? – If your audio is distorted see this article.  Note that audio output is reduced over the v3 board.  If you use a low impedance speaker you may need an additional amplifier module (LM386, TDA2822, etc.) to get adequate volume. The audio pop mod is not required on v4 boards.

v5 Board?  – It is too early to say as yet whether this is compliant, but early indications suggest that some boards on some bands may not be fully compliant, but they are a lot closer to compliance than v3 and v4 boards.  At 30dB down or more your spurs and harmonics will be in milliwatts!

SHIPPING:  µBitx orders were shipping within one or two working days of being ordered. You should receive a shipping notification through PayPal once your product has been shipped. You will not receive any other email.

BITX QSO DAY:   Every Sunday – 3PM & 7PM Local Time – 7277 kHz in North America, 7177 kHz elsewhere.