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

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

A uBITx alternative: the BITx40

It is a while since uBITx.net featured a story on the BITx40.

Jerry KE7ER posted the following on the BITx20 IOGroups list:

“Most traffic in the forum is now all about the uBitx, a very capable rig for all of HF.  Those put off by the need for mods to reduce harmonics and spurs on the uBitx should consider the simpler BITx40.”

http://www.hfsignals.com/index.php/bitx40/

Usable out of the box, only issue is that the stock firmware shifts around occasionally by 50 Hz due to noise when reading the tuning pot
with the Nano’s Analogue to Digital Convertor.

Jerry recommends Allard’s basic BITx40 firmware, requires no mods, fixes the operating frequency drift issue, adds a number of other new features. Some minor hardware mods are optional, adding the Function switch is a good idea.

https://github.com/amunters/bitx40

If so inclined, Allard’s  bitx40_raduino_2  firmware adds even more features, though does require some minor mods:

https://github.com/amunters/bitx40-raduino-v2

Jerry notes that the Bitx40 is a very good deal at US$59.  Being a single band 40m rig it does not have the complications that come from the wide band approach of the µBitx.

Bruce KC1FSZ is also a fan of the BITX40/20 architecture and has had good luck on other bands. One thing he did was to create a “mainframe” of the core of the design (see the manhattan breadboard style construction above) that starts right before the first mixer and ends right after the product detector/balanced modulator.

In his experimentation it seems like 90% of the modification are happening in the “peripherals” around the core (different LC filters, different PAs, different bands, different audio/mic configurations, different software, different enclosures, etc.) so I am able to cover more ground without needing to re-build the inside of the inside every time.

Bruce’s core uses two SI5351 ports so the BFO is tunable just like the VFO making it easy to fool around with different IFs, filter widths, etc.  He also based the chain on the W7ZOI TIA amp which seems to improve performance a lot. There is a bit of the uBITX design incorporated  in his bottom up construction.

The crystal filter is on a daughter card for easy swapping in and out .  He is using ADE-1 mixers on both sides, which are easily and cheaply obtained on eBay, and adjustable gain VFO/BFO buffers (a la N6QW LBS design). The core is 100% symmetric so it’s quick to build and test.

MVS Sarma notes that “try using the  3 transistor bi-directional amp version and see the performance difference. A friend has indicated that the noise level comes down.  You could even try with single dual gate MOSFET in each direction.”

Reference

Belt and braces filtering of a BITX40 power supply

Akira JJ1EPE had spuries on his BITX40 at 75kHz.

The modification for suppress the spurious signals provided by a friend involved the following steps:

1) Add 3.3uF electrolytic capacitor to VCC line of Arduino board

 

2) Add 0.1uF x 2 bypass capacitors to the VCC line (fuse point)

3) Insert high frequency choke of about 100 uH in the power line of Arduino

4) Connect the minus line of power supply line to the ground


5) Connect the minus line of BITX40 main board to the chassis ground


6) Add 0.1 uF × 2 bypass capacitor to VDD of BITX 40 board

7) To prevent common mode noise, add 0.01uF x 2 bypass capacitor to the power connector

This series of steps could equally well be applied to the µBITx if you have noise from your power supply and want to get rid of it with a very thorough strategy.

Reference

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.

Reference

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.

Reference

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?

MAX9812 Mic Pre-Amp conclusions

David N8DAH has been testing the MAX9812L Mic Pre-amp module on his BITx40.  In theory this should improve the gain and signal quality.

David says “So far its working ok at best I sound a bit robotish.”

“I am TXing at around 20w with my amp. I took the audio out through a 10uf dc blocking cap to the bitx40 mic in.  I powered the board from a 9v just for testing.  R136 is about 1/4. If you use a pre-amp you should adjust this lower or you will cause one heck of a noise on tx.  I am not yelling or shouting to get audio out now but not sure I like the audio in any case.

This is without the pre-amp … with the audio files from Michigan to Milford PA websdr

This is with the pre-amp …

David has decided he “might just stick with the slight yell to get the audio out. I like the idea of not having to shout but do not like the audio from this version of preamp”.

Others may think differently.  Mike ZL1AXG thought his “more robot-like” voice was more intelligible because it was more “punchy”.

Jeff AD6RH says:

“I used another mic housing with a DPDT switch and wired it so voltage is supplied only when PTT is engaged. I am using a CR2032 3v button cell. It seems to work fine, but I have not compared the stock vs. preamp mic with anyone on the air yet. It definitely has more average power on the watt meter. I can hear some peaks come thru the speaker when transmitting. I may try installing a pot to dial back the gain.”

Reference

BITx40 Software

For those wanting to upgrade the stock BITx40 the favoured option is to use the software developed by Allard PE1NW.  This is a well worked over piece of software and is used by 100’s if not 1000’s of BITx40 owners.


Allard’s firmware options can be found here:
https://github.com/amunters/

 

You need to choose between his Bitx40 and Bitx40-raduino-v2 branches. Both take some minor hardware mods which Allard has documented extremely well.   His version 2 drives the BFO from the si5351 on the Raduino
instead of using the stock analog crystal oscillator for the BFO.

Reference

BITx40 – Essential Mods

Fantastic BITx40 build from Glenn VK3YY

Jerry KE7ER notes that the schematics on the hfsignals.com website for the Bitx40 are final but not necessarily correct.  He then goes on to talk about some of the variances and essential hacks.

This website is dedicated to the uBITx.   However, so that everybody who also has a BITx40 doesn’t miss out entirely on the occasional “gold nugget”,  some interesting articles about the BITx40 may appear from time to time on this website.   Jerry’s comments on the variation between the published circuit diagram and the actual board currently in production meets the “gold nugget” standard.

Differences between the BITx40 Board as manufactured  and the manufacturer’s Circuit Diagram

  • The two modulator diodes D15,D16 plus balancing pot R106 got replaced by a BAT54s dual schottky:  https://groups.io/g/BITX20/message/33385
  • All those BC849’s?  Have always been MMBT3904’s.
  • L5 and C103 of the BFO are missing, the BFO is at just about the right frequency if the crystals are matched without any adjustment.  Usually.
  • L4 in the VFO is not stuffed on the board, meaning the analog VFO doesn’t oscillate.  The VFO comes instead from the si5351 PLL chip on the Raduino through the Bitx40 connector labeled “DDS1” in the schematic.
  • T6-4 is tied to C142 and R144, U3-3 is tied only to the 12v rail labeled “TX”, schematic does not show that clearly.
  • RV1-2 is not connected to U3, the schematic drawing is just a little tight there.Otherwise, Jerry thinks that the schematics on HF Signals are correct, reflecting what is currently being shipped.   Nothing has changed in Bitx40v3 boards shipped since Dec of 2016.

Changes that should ideally be made to the BITx40 Board

He then goes on to note that he thinks there are a few things that perhaps should change:

  • D7 and C130 should be across the coil of relay K1,  D8 and C164 are correctly across the coil of K2
  • R141 is currently a 1/4 Watt 10 ohm resistor, should be 1/2 Watt as have been reports of it burning out.
  • The surface mount MMBT3904 at Q13 could be replaced with a through-hole version of the same part, the 2n3904, as it must dissipate a fair bit of power during transmit.  Even with the radio off but hooked up to an antenna, a nearby QRO transmitter or electrical storm can blow Q13.

Essential mods

And finally Jerry suggests the following as essential mods for all purchasers:

Note that he suggested adding an incandescent lamp, which can be quite effective:
https://groups.io/g/BITX20/message/21901