Month: June 2018

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A new and improved audio pop fix from KB1GMX

Allison KB1GMX has come up with an improved pop fix based on the one in the v4 board design, originally submitted to the BITX20 list by Joe VE1BWV.

Allison finally got annoyed enough by the pop to fix it.

Parts count 5:

  • 2x 1n4148/914 diodes
  • 10K resistor (any value from 10 to 100K really)
  • 2n7000 MOSFET
  • 0.1 µF capacitor

Allison has added a second diode.   Why? The TX line is relay switched  and relays take milliseconds to physically move contacts. So the second diode to the T/R line from the Raduino is the fast acting “audio kill”. The second diode and parallel resistor is the hold until the relay returns to RX position.

Allison assures us that this fully mutes the rig with no pop, no thump in either transition (from RX to TX or TX to RX).

Michael VE3WMB points out that connecting to VOL-H will kill the sidetone output.   He notes that Ashhar Farhan VU2ESE has his V4 pop circuit connected at M2(R70) with the value of R70 increased to 1K ohms in order to hear the CW sidetone.

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Distorted audio v4 Main Board?

An initial report from Mike (callsign not known) of distorted audio on a v4 main circuit board was tracked down to the audio amplifier.  The v4 main board is the new board shipping from HF Signals from around the beginning of June 2018.

Mike solved his problem by bypassing the audio amp and using an output amp as indicated bottom left in the photo above.   You can see that he has also incorporated a mic amp board in his prototype.

We will be watching out (or rather listening out) with interest to see if others are experiencing the same distortion issues from the audio amplifier section.  Hopefully this is just a one-off!

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Follow up

Mike has now fixed the problem with crossover distortion.  It was a biasing issue in the audio final.

Raj VU2ZAP suggested lifting up D15 or 16 and disconnecting one end from the board. Then, solder the center and one end of a 47 or 100 Ohm preset between the two diodes.   Make sure the preset is at minimum. Power up and slowly increase the preset till distortion goes away, while also checking that  Q72  and Q73 don’t get hot when the volume is low.

 It is possible that this problem may reappear on other new v4 rigs.

Redoing the biassing as suggested by Raj VU2ZAP solved the issue.  Mike  took a 500 ohm pot and paralleled that with a 125 ohm resistor.   He  says, “The mod doesn’t look so good (LOL) but it works. One of the transistors became warm if the voltage difference due to the pot became too large. I adjusted this while feeling the temp and listening to a CW carrier”.   The setting point was where he observed low/no distortion AND low temperature.

The photo below shows how Mike fixed the issue.

Reference

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Swapping around display lines

Michael VE3WMB figured after playing around with the KD8CEC firmware for a while that he  would prefer to have the Main VFO frequency and Mode displayed in the top line, instead of the bottom line of the display and the secondary info (VFO B etc) on the bottom line of his display.

Under ‘User Interface’ of the uBitx Memory Manager application (scroll way down), checking the ‘1/2 Line Toggle’ works to swap the first and 2nd lines on the display.  No coding is required to achieve this.

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Reasonable heat output and the raduino regulator

 

 

Bob W4GHV asks how hot the regulator on the Raduino should get.

The Raduino has a 7805 regulator sticking awkwardly out of the side of the Raduino board.  Unsoldering the 7805 regulator and mounting it   on the reverse side of the board (facing inwards) can fix that little awkwardness.

The regulator also has another problem.  It gets hot!  It is fed with 12v DC input from the rig and produces regulated +5V for the Arduino Nano and the 16×2 Display unit.   The display itself draws up to 100mA.  The Nano typically draws around 35-70 mA, but it depends on exactly  what is connected.   The voltage difference between the input and output multiplied by the current is power dissipated in heat in watts (i.e. typically a bit over 1 watt).

The 7805 regulator can feel quite hot to the touch.   However, there is really no danger that it will get overheated at 12 to 13.8v input voltage and typical current draws from the Raduino unit.  Allison KB1GMX says however, “Keep it under 70C (168F) as the device has a thermal shutdown and it lives longer”.

You can share the heat around by installing a resistor between the 12vDC line and the 7805 regulator input. Skip, NC9O, added a 47 ohm resistor in the 12vdc into the regulator by cutting the trace from pin 15&16 on the Raduino. He used a  1/4 watt resistor, but calculations by others suggest a 1/2 watt or 1 watt resistor would be better.

The alternative is to remove the regulator altogether and feed the Raduino from a suitable 12v to 5v buck power supply (obtainable off eBay or Aliexpress for very little outlay) or set the output of the buck power supply to just over 7v if you can’t be bothered removing the 7805.    For those of us thinking about touch screens, this makes quite a bit of sense!

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Biteensio production boards have arrived and available now

Jim  W0EB has announced that the Biteensio production boards have arrived and been checked out.  See www.w0eb.com for details on how you can order one of these.   Remember that Vince K8ZW was the winner of the competition to name these boards.

Jim also has some breakout boards for the 1/8″ jacks that will allow them to be easily mounted and wired up without having to guess which terminal does what.  These may save a lot of grief.

Key features of this board include:

  1. uses the PJRC Teensy 3.6 as the MPU rather than the Arduino NANO
  2. plugs into the 16 pin female header on the uBITX main board just like the Raduino and the RadI2Cino
  3. the main tuning encoder, function switch and push-to-talk wiring will still be compatible with both the Raduino and the RadI2Cino.
  4. All of the extra, available I/O pins are brought out to DuPont pin headers (some on the front and some on the back of the board)  

See the board installed on the µBITx main board below:

Kits are now AVAILABLE FOR ORDER.

Prices are $12 (USD) for the bare boards to domestic US customers and $16 (USD) to international customers.

Kits which will include all parts except a Teensy 3.6 MPU, will be US$35 to US customers and US$45 to international customers. This price includes shipping (both domestic and international).

PayPal will be the preferred payment method and the ONLY payment method for international customers.

Download a copy of the BITeensio Board Construction Manual. Up to date versions will always be available in the “Documentation” directory under the W0EB/W2CTX uBITX Files link on this page.

For other details see the W0EB website.

Note that the Biteensio is not compatible with the manufacturer’s firmware supplied with your µBITx or the CEC firmware from Ian KD8CEC. The Biteensio board uses a different keying system and a different processor (Teensy 3.5 or 3.6), so you will need to use the W0EB/W2CTX firmware supplied especially for the Biteensio.

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Buy your Nextion display now!

If this display looks like it is from a commercial rig, then you are wrong!  It is  the Nextion display mounted on a µBITx!

Ian KD8CEC will shortly release his newest enhancement to CEC firmware.  His latest modification to the CEC firmware supports Nextion screens. This was foreshadowed recently on the BITX20 list.

THIS WILL BE THE MOST AMAZING ENHANCEMENT YET FOR UBITX!

If you want further proof, check out Ian’s recently prepared youtube video of the Nextion screen in operation.  His release is imminent.

Get your order in for a Nextion display immediately, as they are likely to sell out when 6000 µBITx owners twig that they really do NEED a Nextion display.  [Note that ubitx.net has no relationship with ITEAD – who make the Nextion!]

Why Nextion?

There are some very good reasons why the Nextion display is the way to go:

  • Nextion screens make it quicker for developers to provide a user-friendly interface to their product:  a separate processor controls graphics on the screen, and a Windows WSYWIG emulator can be developed for free to whip up a User Interface for the Nextion display.   The processor in the Nextion has its own control language and coding that is similar to C++
  • Users can easily hack their own display’s look and feel, by plugging into a standardised protocol between the screen processor and main processor that are connected via a standard serial port.
  • Screens come in a variety of sizes from 2.4″ to 7″.  Resizing of images and buttons is all that is required to make firmware work on a different screen size. No coding is required.  Software required is simply the Nextion Windows software and a graphics programme (MS Paint is adequate).
  • The screens come in two varieties:  a BASIC model and an ENHANCED model.  The ENHANCED model has GPIO lines controlled by the display processor and a Real Time Clock (RTC).

Nextion display units cost more than other displays for a reason.  The independent processor removes most of the burden for screen manipulation from the main processor, and it is much quicker and easier to develop the user interface and to customise it for different sized screens and to add/subtract features.   Nextion displays also include a microSD card reader.  They run on +5v DC and include a serial port.   Note that the Enhanced Model contains a battery mount for the RTC, but does not include the battery (CR1220) itself.  This is not required until you want to use the RTC.

How easy will it be to use the Nextion Display?

It will be VERY EASY to add a Nextion display to your µBITx.  Watch the video!

No hardware modifications are required to your µBITx, but you will of course  need enough front panel space to install your colour touch display of choice.  You may even need a bigger case if you want to install the 7″ Nextion display!

You will also need to download two new files:

  1. an updated version of KD8CEC’s firmware, that incorporates the interfacing protocol to the Nextion for installation in your Raduino.
  2. an image file (firmware) for insertion in the Nextion display unit.

The downloaded firmware for the Nextion needs to match with your screen size.  There are two variants for each screen size:  a BASIC or ENHANCED version of the Nextion display unit (see the discussion on which version to buy below).

This firmware needs to be saved to a microSD card (a 2GB or larger card is required).  Insert the card in the Nextion display and in powering up the Nextion display will automatically load the firmware from the microSD card into the Nextion flash storage.   Remove the microSD card when the upload is complete.

Four wires connect the Nextion display to the Raduino.  Two lines are for power, and the other two are serial RX and TX that connect to standard IO ports on the µBITx that were used for the 16×2 standard display.

Reboot your µBITx and your Nextion display should be working!

What to look out for when buying a Nextion Display

There are two versions of the Nextion Display – one developed for the Chinese market and an English language version that supports the Nextion Windows development environment.  Make sure you don’t get the cheaper, but incompatible Chinese version.  Look out for “English Version” in the marketing blurb.  This won’t be an issue if you buy from the developer (ITEAD).

 I understand a downloadable hex file will be available that works the same as the English version, for those of us who purchased the wrong model in error!  Thanks to Ian, who did it blind (also not being able to read Chinese)!

Any size will work with the CEC firmware on the Raduino end.  However, Nextion firmware is specific to  either the BASIC or ENHANCED version of the screen and to the resolution of the screen.   That said, any version can be modified to work with any other screen size with just a little bit of work on the part of the user.   You can also fully customise your screen to meet your own requirements.  Change the colours, or change the entire look and feel.  No coding is required to do this, just cut and paste the code from the supplied CEC version for each tool.

Purchase the ENHANCED model of the Nextion (for a few more dollars) if you think you will use the GPIO or RTC features in future.  The RTC could be useful for digital modes that require precise timing, or for satellite work, etc.  Additional GPIO lines could solve one of the problems with the Raduino:  a lack of spare digital ports to support customised add-ons.  For example, if you want to add 160m and switch in an additional LPF, or  if you are worried about potential spurs, you will be able to pull in bandpass filters for the high bands. In these instances you may want to spend a little more to get the ENHANCED version.

If you don’t want to wait until firmware is available for your screen size, then purchase a 2.4″ or 2.8″ BASIC or ENHANCED Nextion Display now.   These two screens have the exact same resolution, and the default version of the Nextion Firmware from Ian KD8CEC will work on both screen sizes without modification.

If you already have a different sized screen, or want to buy a bigger screen, right from the outset, don’t panic.  You may need to make some adjustments to the firmware yourself.  This is not difficult – but involves resizing graphics and moving around objects to suit the larger screen area/resolution.  Some of us are working on modifications to the Nextion firmware to accommodate 3.2″ and 3.5″ screens. Firmware for these screens is likely to be available quickly.

Screen sizes and resolutions for the BASIC models available on ITEAD’s website are as follows:

The ENHANCED versions available from ITEAD are as follows:

Most of us will choose to buy our Nextion displays from Aliexpress or eBay.

They are available in all sizes and in either BASIC or ENHANCED versions.  It is unclear which are OEM versions and which are clones.  It probably doesn’t matter.

Look for highly rated suppliers and those with higher shipping volumes.  The biggest risks are that your screen arrives cracked, or simply never arrives.  You will need some form of redress when goods arrive in a damaged state or simply never arrive, and this is where the intermediaries in eBAY, Aliexpress or Paypal can assist.

 

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Quadrature output from si5351a

The SI5351a is a key secret to the success of the BITx range of transceivers.  This chip puts out three PLL signals for the two local oscillators and the VFO in the µBITx.   Without this chip (or something similar) a double superhet design such as that used in the µBITx would require considerably more complexity, with either an analogue VFO that was prone to drift (as in the BITX20) or a PLL circuit that added cost and complexity.  The Raduino integrates a 16×2 line display along with an arduino nano and the SI5351a chip … prebuilt for US$25.

So along comes Miguel PY2OHH who announces that he as designed a new
VFO using the SI5351 and Arduino nano, which produces an output  “in quadrature” from 4.76 MHz to 220MHz.  This means is has two outputs on the same frequency, but which are 90 degrees phase shifted from each other.    Note that there is also a small frequency window that can’t be used between 144.66 MHz and 150MHz.


You can read all about the idea, and see a prototype VFO here.

So why is this such a big deal?

What you may not know is that a quadrature mixer, which requires two signals from a local oscillator fed at 90 degrees from each other, is at the core of most SDR receivers.   In an SDR receiver, there is very little “front end” analogue circuitry, with signals rapidly routed to a processor in digital form to apply filtering and band-limiting.    Miguel’s breakthrough paves the way for simple, low-cost SDR transceivers that are of low cost and high performance.   We know that Ashhar Farhan VU2ESE has said in the past that he is experimenting with SDR designs (and with a VHF/UHF version of the BITx).   Let’s hope this innovation spurs him on to produce a stunning new SDR design in kit form!

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