Month: October 2019

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New version of Allard’s firmware for BITx40

Just as the BITx40 goes out of production, Allard PE1NW has released a new version of his acclaimed firmware for the BITx40.

This is known as the Raduino v1.29 version, and can be downloaded from here: https://github.com/amunters/bitx40

New in this release:

  • Added Roger Beep (NASA style “Quindar Tone” as used in Apollo missions).
Note that the PTT sense, RX/TX and CW Carrier mods must be installed for this feature to work.
Press Function Button 7 times to toggle this function on/off.  It’s OFF by default as some find it annoying. Others find it helpful in pile-up situations though.
Allard says “Use responsibly!”

Allison KB1GMX commented that the “Roger Beep” was not a common thing until the CB mess broke down in the early 80s and it was often accompanied with other electronic noise makers and profanity. Then that mess started moved into the lower (CW) sections of the 10M band and they got tired of freebanding.

Most of us back when that used CB found it annoying and unneeded especially for SSB. The general feeling is it was those that were disruptive or trying to feel like they were running something important doing it initially. It was especially noxious when it appeared in the 80s. Then it became a feature on CB radios (a signal that those that were modified for non CB allocated frequencies) and later Chinese made HTs.

For the Space activities (Mercury and later) it was needed as the communications were actually full duplex on the data links and you had to have some way of knowing when the other guy was done as in really did release the button and it was also to confirm the button didn’t stick as in heard in the astronauts headphone when he released  the button (or VOX). Until CB adopted it if you heard a over beep is was likely a repeater (usually ham) or space based radio (space program).

To date I know of the use of “over beep” appearing is standard communications systems, those being Space program, Repeaters, military systems that use satellite links, and CB.

It does however represent what one can do with a MPU of reasonable power and some programming skills!

Reference
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End of road for the BITX40

Ashhar Farhan VU2ESE has just announced that HF Signals has had to pull the plug on the bitx40 run.  Ashhar said, “The sales were sparse and frankly it had become a bit of a frankenstein.”

“There were too many connectors that one could plug in the wrong place.  We moved from analog VFO (that drifted due to heating of the pre-driver stage) to a raduino which wasn’t well integrated into the motherboard.”

“However, it was a big deal for us all.”

HF Signals was able to ship a full SSB transceiver for just US$50 dollars. This went over and above the ARRL challenge for a kit of parts for US$50.

It has served many well. Once you had it going, it performed pretty well.  With a triple tuned front-end and the favourite ‘down conversion’ to 12 MHz IF.

Many will miss this kit.   However, Sunil (at www.amateurradiokits.in) continues to ship the Bitx20 v3  kits, that can be modded to 40 meters.

Ashhar has indicated that if time permits and some in the group volunteer, we could update the original BITx with a more contemporary design while preserving the original’s bidirectional, single conversion scheme.

Ashhar suggests that “Until then, we will continue to see more scratch built bitxs, a kind of return to the roots.”

Reference
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Variable bandwidth crystal filter

Some time ago we featured a design from Michael N2ZDB that used a Jones filter design from TenTec to produce a variable filter passband for his BITX40.

There has been more recent interest on the IOGroups BITX20 list in variable bandwidth filters in the µBITx.

Karl-Heinz DF9RU completed a build of a µBitx transceiver and found it to be an excellent learning platform. He has been toying with a variable CW filter.

Up until now audio filters have largely been adopted by members:  either active filters with operational amplifiers or DSP filters with microcontrollers.  Karl-Heinz acknowledges that these options represent easy solutions for integration into the µBITx.

Karl-Heinz has a CW transceiver HB-1B from Youkit. This transceiver has a quartz filter of variable bandwidth.  The bandwidth can be continuously changed using varicap diodes.  The circuit diagram of the HB-1B can be found here.

Karl-Heinz was impressed by the acoustic result of the simple circuitry of his HB-1B and wondered why this alternative had not previously been used?

TenTec has patented a filter design which describes the passband curves of this filter.  A German website  also documents results on the bandwidth of these filters, which match with data from the TenTec patent.

Thierry F1HSU suggests taking a look at Tasa’s site for a tunable quartz filter  : http://yu1lm.qrpradio.com/bp%20yu1lm.htm

Ashhar Farhan VU2ESE suggests that these filter designs are merely a variation of the min -loss cohn filters. As only the coupling capacitance is varied without varying the terminating impedance, we must expect high ripple at all settings except one. What does this mean? It means that the filter will exhibit ringing and phase delays.

A better option would be a smooth Butterworth response with minimum ringing at a fixed frequency.  You can vary the BFO for shifting the audio tone. A 400 hz bandwidth will be narrow enough and yet offer a brightness that we miss in more aggressive designs.

Wes wrote a paper on this on his website www.w7zoi.net.
Ted, KX4OM reminded us of the SSB6.1 transceiver, which employs a tuneable SSB filter with tuning diodes in place of the capacitors in a min-loss configuration. The rig is a basic SA612-based design which can be found here:

Allison KB1GMX suggests looking at this design as well.  It is not new and a bit tricky but works best with lower frequency crystals.

Reference

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Monitoring your microphone level

Didier F5NPV notes that many options are possible to tune your AF level. Measurement tools like an ocsilloscope can tap directly at the output of the AF Amplifier.  Alternatively a spectrum analyzer can be very useful in monitoring spectrum quality.

It is also possible to use another RX, a SDR receiver or even WebSDR online to monitor your transmission in quite an accurate manner. When you establish the correct level  of gain required to generate a signal without distortion spikes you just need to calibrate a meter with the appropriate threshold value.

The µBITx does not have an AF level input monitoring system. It is simply impossible to know if the level applied from the microphone preamp is too high or too low.

in the picture above you will notice a little switch just below the vu-meter thatI use to monitor the AGC and AF input level.

Reference
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Large screens, digital modes, and beefy processors

A couple of constructors have been busy pushing the limits …

Digital modes µBITx in a box

Felice IK1ZVJ  project stems from his passion for digital modes. He says “The union between µbitx and raspberry works well”.   Felice combines a µBITx with  a raspberry pi and a large pop-out screen in a single portable package for use with digital modes such as FT8.

The LCD screen is mounted on an old CD mechanism to provide automatic ejection from the enclosure.

The project includes a dual power supply with a built-in power supply and battery power for portable use.  He foresees his pr  ubitx, only being used with the raspberry pi on digital modes. The raspberry pi is loaded with WSTJ-x for use on the FT8 and FT4 modes, and for FL-DIGI for PSK and RTTY.  His enclosure uses a 3U rack  (9 cmx40cmx43cm).

You can see more on his video:  https://youtu.be/TlndGOyNtVc  or you can contact Felice via email.

Ashhar Farhan is pushing the boundaries

Ashhar Farhan VU2ESE, designer of the µBITx previewed a Raspberry Pi board for HF radios with a high end codec at the FDIM (prior to Dayton Hamfest 2019).

This is for a new radio that he is building to push the limits of what his homelab capability can produce.

The story so far is that there is a very low noise 24 bit codec on a custom board that plugs into the raspberry pi. The display is a 7 inch capacitive touch screen device.

The radio is a single conversion, very low distortion superhet without any amplification before the crystal filter and triple tuned filters for each band.

Ashhar says “Nothing is casual about this radio. Even the power supply had to be included to have low noise rating.”

Reference

 

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Teensy 4.0 adapter board

Jim Sheldon, W0EB, Project Coordinator for the TSW (Triumvirate Skonk Worx) has announced that the team have successfully created an adapter that will allow the new PJRC Teensy 4.0 to directly replace the NANO MPU on their TSW Raduino Clone and on late model HF Signals Raduino boards where the NANO is mounted on the rear of the card.

The Teensy 4.0 is a much faster processor, providing experimenters with plenty of opportunities to add in features to their µBITx, including digital signal processing.   Comments suggest that the Teensy 4.0 is much faster, generates less digital noise and has WAY more programming memory.

The TSW programmer has successfully ported (with only minor modifications) the factory’s V4.3 and V5.1 software to the Teensy 4.0.  You still need to be familiar with HF Signal’s documentation for V4.3 and V5.1  as they have only documented changes in the accompanying manuals for the software.

A bare board and also a complete kit of parts for the plug in adapter is being offered for sale  and kits are also now available.

At present, kits are only being offered to US customers as the pricing includes shipping.    See the TSW website for more information.

Reference
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uBITx HD raduino bracket

Dave K0MBT has beefed up his design of the uBITx HD raduino bracket and added a two line display bracket.   He has also added an audio cable hold down. There is also a small dimensional change.

It is now a 3 part unit that can be used with or without the stock display.

Dave is offering these from his shack to yours for $15 including hardware and shipping.

Order from Ham_Made_Keys

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