Convert your uBITx display to an I2C Display

Andy KB1OIQ has posted a file on the [BITX20] IO Group files page: kb1oiq_i2c_mod.pdf that describes the hardware and software modifications that he performed on his uBITX to free up digital pins on his arduino.  You will need to be logged in to the Group page to access the file.

Andy converts the LCD to use the I2C bus, thus freeing 6 Arduino digital pins for other uses.   Only very minor modifications are required to the Raduino sketch (and you will need to install a different library).  He documents every step involved with photos.   Well done!

[EDITOR Comment – removal of the two pull-up resistors on the additional board and direct connection to the I2C A4 and A5 ardunio pins should suffice without use of a level converter board.  However, the cost of adding in the level converter is negligible and will work well!]

Reference

New Software Release for TFT Colour Touch Screen

VU2SPF – Dr. SP Bhatnagar (India) and VE1BWV Joe Basque (CD)  are pleased to announce the initial public release of the UBITX Colour Touch Display Controller v2.72u.   
This is essentially  the same as the one for BITX, but modified to work with the UBITX.   The new software provides  a Colour Touch Display Controller with a no menu approach  to control your ubitx .
More info  can be found in the following locations:

The website contains information on how to download the code.

Features:
  1.  Low cost for parts – Suggested parts –  1 atmega2560 – approx $8.00US, 1 Addafruit dds Si5351 – $10.00  –  2.8 TFT  touch colour display     $12.00 US
  2. All bands, band selectivity, USB LSB  -Works well with digital modes
  3. All Display buttons are touch control – and no menus
  4. Any button can have a physical button and a TFT touch or any combination.
  5. 100 memory channels
  6. Tunable BFO’s
  7. 3 VFO’S – A  B  and  MEM
  8. USB / LSB
  9. TX  timeout control
  10. Touch TX button and or physical TX control – for ptt mike or digital modes (vox input low)

Next : New Feature – Working on adding  CAT Control

Connections diagram

Joe VE1BWV subsequently uploaded the connection diagram to show how the Arduino Mega 2560 connects to the display, the si5351a and the main board.

Typical current draw on the uBITx

Greggory N5WLF  observes that he gets in the range of 1.4-1.8 amps current draw on transmit, SWR depending and asks if this correct.

Feedback from the group suggests that:

  • on receive current draw is around 0.16A for an unmodified uBITx; and
  • on transmit it runs around 1.4-1.8 amps depending on the SWR.  On high SWR the finals can draw up to 2.2A approximately.A 2A fuse on the TX line and 0.5A on the main board seems about right in order to protect your uBITx.

Reference

BCI filter in the RX line

Nick Pullen VK4PLN has inserted his 3 stage BCI filter into the RX line.

Filter Details: https://groups.io/g/BITX20/wiki/uBITX-AM-BCI-Filter

Nick cut the trace either side of the new HPF board, exposed a bit of the trace and jumpered onto that.   You need to cut the second trace from the PA side (3rd trace down from the 45MHz roofing filter with the crystal).

Taken from the top trace to the bottom in the photo below, starting from the relay on the left and the PA circuit on top:

1: TX pwr to the PA circuits via R89
2: RX path (between K1 and K3 relays. (CUT AND INSERT HERE)
3: TX pwr to the LPF bank.
4: RX pwr to the receive circuit (R18,R38…)

Nick picked up GND from the 2 unused caps C216 and C210 as can be seen in Nick’s photo above.

Reference

IRF510 bias current

Jerry KE7ER says:

“Farhan recommends 100ma for the push-pull IRF510’s on the uBitx. More is better, you get into a more linear region of the FET. But more means more power getting sucked from the battery if portable, that power gets dissipated as heat in the FET’s.  I’m going with 100ma.

“With a 500ma quiescent drain current when using a 24v supply, each FET is dissipating 24*0.5 = 12 Watts.   That’s a lot of heat. Back off to 100ma and it is only 24*0.1 = 2.4 Watts.   Which still seems plenty.

“You want to be very careful when adjusting IRF510 gate bias trim-pots, take it too far and the IRF510’s might be trying to dump 100 Watts or so.”

Note that a Mitsubishi D16HHF1 in push-pull requires a higher bias current setting (perhaps 250 mA or 300aA).

Damaging your Raduino

A post fromJustin KN4FAW reminds us all that it is VERY VERY EASY to damage your Raduino.

Justin says “So, I assembled my Bitx40 kit, at this point it was just wires laying on my bench. I wired up the function button, tested, everything working great. Accidentally touched the ground from function button (orange wire) to 12v while moving stuff around. Now my LCD only shows squares, and I can not tune the radio.  Am I screwed?”

Answer: Yes.

Watch out for the two orange wires on the two different connectors.    Check and double check your wiring before powering on.

Justin isn’t the only one who has done this.  Several other group members fessed up to doing the same, or similar.   Arduino Nano pins are not tolerant of 12v.  There are many other ways to destroy an Arduino Nano pin.  You can read about 10 ways to destroy an arduino here.   There may be quite a few more ways as well …

Mike Hagen WA6ISP comments:

“I recommend in building these radios that you change all ground wires to Black and all Power (5 or 12V) to Red. Reserve these colors for just 2 purposes. You can use the wires you remove for additions.

“Leave the molex pin on them. I have a lot of spare Brown ones. I can’t stand an Orange wire being B+ (the term for us old Valve guys)! 26AWG stranded works great.  I purchased a bunch of colors at All Electronics. Molex pins can be acquired at Tayda and Mouser.

“You don’t have to be in such a hurry and blow things up. Check your wiring several times. You could even make a connector chart with J numbers and pin numbers with the associated wire color.  Match it up to what is on HF Signals. It may mean you catch a mistake and save a lot of trouble shooting?”

Reference

Update on Martin AE7EU Top Board

 
Pictures: Front panel:  Headphone, Microphone, Encoder (from uBitx kit), 4 pushbuttons, AF gain, uBitx standard display.
 
Rear Panel:  +8V input, +12V (or ‘PA’) input (switchable), RF output, Teensy micro USB (CAT), PTT, Key, DSP Audio (from Teensy3.2), Linear control.
Martin AE7EU provides a detailed update on getting his “top board” working:
1) Mechanical clearances are okay.  Front panel mic/headphones need to move up by about 0.15″ to be flush to the encoder/display level
2) .1″ headers are misaligned, just needs adjusting in the gerber files, shouldn’t be too bad.  Big ‘PITA’ will be wiring directly to the uBitx on the first run for power, and since I only care about single power supply, this mod will only be roughly tested.
3) Messed up on a few pin headers on the front panel; mostly in that the pins from the AF gain resistor interfere with the main PCB, requiring that they be sanded down.  A 0.062″ move is all that’s needed.
4) BoM was heavily not optimized.  Optimized out a bunch of components to make everything 50-ohm, 1k, 2.2k, 5k, 10k, and 100k resistors, 0.01uF caps (minus one required 1000pF cap), and removed a bunch of 0.01uF caps that can be replaced with capacitor arrays, but some testing with the new values will need to be done.  Board is populated with optimized values.
5) Footprint for HC595 is incorrect, but usable.  Too narrow footprint, component wider.  Failure due to rushing out the door with the design before checking the footprints on a printout (didn’t have the component in hand).
6) Display module is actually the limiting factor for overall height.  A smaller display module, and the whole thing could fit in 1.25 (right now, designed for 1.5″)
7) PA Gain cutout is slightly off; still useable with a phillips head screwdriver though.
8) Incorrectly specified Aluminum electrolytics; changing to TH in next design, all 10uF
9) Found the RTC battery was almost fully discharged… will have to check out current consumption when not plugged in, it’s probably trying to run the CPU full tilt.
10) Need to change $1.5 PV36W 20-turn pots to 3/4 turn TX33 pots ($.10 each or whatever)
11) Optimize mods comes next after powerup and verification.
12) Need to verify winding orientation of the SWR bridge
Reference

An annoying fault (solved)

John  VK2ETA raised a request for help on the group list on 24 January after spending over a week trying to figure out an issue he had with his uBITx.

The problem

John built his uBitx around a manpack configuration with an external side mounted heatsink, no connection at the back, and room for an autotuner.  The issue he had was strong audio tones inside and outside the passband on receive, typically up to 15khz.

He attached an audio recording and took some audio spectrum snapshots made by placing the phone’s microphone near the uBitx speaker.  The tones were often near or above the level of the decoded signal which makes them impossible to ignore.  The frequency of the tones did not change significantly with tuning up or down, or going through the menu items except when passing over the “CW Speed” option.

After doing all the normal things you would expect, such as redoing the factory alignment and BFO adjustment several times, nothing changed.  He changed out the power supply (with three alternatives), he checked the voltage on the Radiuno: 5.01VDC, added capacitors from the Radiuno 5V rail to ground (470uF, 0.1uf mica, no change), power supply rail to ground (470uF, no change), and added 1nF between the  casing of the Arduino crystal to ground (which produced a shift in tone, but no reduction in amplitude).  He modified the software where I would shift the frequencies of both the first and second oscillators by the same amount, thereby leaving the received frequency the same. The result was no change in frequency of the annoying tone. So only a BFO frequency change produces a shift in tones.

Needless to say John was right out of ideas and welcomed input from the group.

Group responses

Jerry KE7ER immediately responded:

Your best bet might be to either replace the nano or replace the 16mhz crystal on the nano.  It might be possible to shield and filter the nano sufficiently somehow, but that would be tough.   It could be that HF Signals would consider replacing your Raduino.  You might ask them.   Do you have somebody nearby you could swap out the Raduino with, to see if the problem follows the Raduino?

There were a number of other responses from group members, and other group members had observed similar issues with tones inside the filter passband.

The problem solved

On 2 February 2018, John announced to the group that he had solved the problem:

“I bought a cheap Arduino on eBay and after some struggle I changed the Nano, re-programmed it and all came good. The tones within the passband are gone and the ones outside the passband can be eliminated with a careful choice of BFO frequency.  Also the tuning noises have disappeared.  So it must have been a bad Arduino.

“As an interesting aside, when chasing this issue I changed the first two mixers VFOs thereby changing the alignment between the 45Mhz filter and the 12Mhz one. I noticed that the default values produced a signal around 8dB lower than when “re-aligning” the two passbands.

“If anyone is interested I can share the code for this test (I simply re-assigned the RIT menu item and had an extra variable which was added to the first two VFOs so that the net received frequency stayed the same, but the first IF was shifted correspondingly).

“Please note that I found the removal of the Arduino a challenge and resorted to cutting the edges out of the Arduino board with a Dremel.   I cut the plastic spacer between each pin to be able to de-solder each pin individually.”

“Since I have mounted the display remotely and have space in front of the Raduino, I opted to use female headers so that I can plug/unplug the Arduino, just in case.”

It turns out that Jerry KE7ER’s advice was spot on.   Afterwards he commented:

“Could be that the old arduino had a faulty 16mhz crystal.  But that thing is tiny, swapping in a different crystal would be tough. Could also be that the ATMega382P processor had a faulty oscillator.”

Ashhar Farhan from HF Signals has since commented on this fault:

“Since we noticed these problems, we do check for the presence of these tones. Our pass test includes viewing the audio spectrum at 5v/db, 625 hz per division setting of FFT on rigol. We set the carrier so that the audio passband is inside two cursors at 300 hz and 3000 hz. Then we check for any spurs upto 15 khz that are above the noise floor. If these tests pass, we move to the next test of transmit outputs on 3.5, 7, 14 and 28 mhz. These tests are a part of the firmware being shipped.

“I suspect the 16 mhz crystal must have aged. There are two things you can try. First is go into the bfo settings and move it slightly so the spurs go away. Second is to add some capacitance to the 25 mhz crystal, about 10 pf. There is a third way too, which is to program the si5352 initialization code to enable a different load capacitance on oscillator. I havent tried the third method myself.

“Very often, closed commercial designs tend to ignore or bury design faults. Open source proceeds with acknowledgment and fixing these to make the system better. As the saying goes, given enough eyeballs, all bugs are shallow.”

Reference

Relay K1 mod

Fred PE0FKO asks a question about relay K1 after looking at the very nice schematic of the uBITX.

“The K1 relay is used for the RX and TX power switching and also for connecting the antenna in RX to the LP filter.   On RX (and TX) the LP filter is also a connection to the TX power amp by C80, that will give a (very) small load on the antenna signal at RX and a mixer (Q90 diode BE) for strong received signals?  Could it be improved by switching pins 12 and 14 of K1 and connecting pin 16 of K1 to C80 (removing the connection to the Low Pass filter)?”

Jerry, KE7ER responded:

“It’s a good idea to make use of K1-16 to disconnect Q90 during receive.  This would also protect Q90 from local QRO transmissions into a local antenna,   The similar Q13 on the Bitx40v3 is often blown in such situations, even when the rig is powered down.”

Alf Baranda asks:

“Can it be the Mod that I have highlighted?”

Of course it is the same mod!   Alf goes on to  attach images with the signal paths in the RX and TX modes.

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