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

uBITX Mic Audio

Dave WI6R thinks that the rig only needs slightly more gain than the existing Mic PreAmp and that adjusting values to add gain is really all that is needed.  He doesn’t think it needs 40 dB of extra gain.

He has resurrected a Mic Pre-amp design used 50 years ago in the SBE SB-33 SF-1 solid state rig that first used bilateral amplifiers.   Bilateral amplifiers are used, of course, in the BITx transceivers.
This design had plenty of gain and worked with a Dynamic Mic with significantly lower output than any of the typical Electret-Condenser Microphones used today.   Also note that the Mic PreAmp was powered only when the rig was in TX and a simple diode was used to shut off the Mic PreAmp in RX with the same TX voltage.
Dave used this rig in the ’60s and doesn’t recall any “pop” when going from RX to TX or vice-versa. The “Signal Splitter” was used to isolate the TX and RX Audio.

Raj, VU2ZAP responded suggesting that simply decreasing the value of R63 would give you more gain!

Speaker Grill templates

Peter Cousins G4NJJ suggests that to get a tidy speaker grill on your EF01 or other enclosure you should have a rummage in the kitchen utensil drawer.

You may find the perfect template.  Peter used a plastic sifter lid as the holes were the size he wanted.

He drew a center line where he wanted it positioned, lined up the template, drilled one hole on the outer circle and inserted a nut and bolt, drilled a hole at the opposite end of the template, inserted a nut and bolt, and then drilled out the rest of holes in perfect place.  Hot glue allowed the speaker to be placed on the underside of the lid of the enclosure.  Done!

Oh and in case you wanted another idea for the template …  And just make sure the XYL is not aware of your minor “alterations” to essential kitchen equipment!

And if you want a variant on this theme of making a speaker grill look real classy, check out Glenn VK3YY’s website for  a ham shack alternative that won’t get you in so much trouble with the XYL:   https://vk3yy.wordpress.com/2017/01/22/bitx40-v3-and-raduino/

 

KD8CEC Software – Now up to v0.33 Beta

uBITx.net site developer, Mike ZL1AXG has been playing around with Ian Lee KD8CEC software releases and giving Ian feedback.

Mike gave the following review on the BITX20 group of v0.30:

This worked faultlessly for me, and I loved being able to adjust the step rate (I have it set on 10Hz now).

The band stacking registers and band switching is fantastic. I had intended modding the software myself to get band stacking and easy ham band switching, but I no longer need to bother! I may still add front panel buttons for band up/band down functions, but the menu band changing function is fairly handy already. It would be good to have a SPLIT function (in addition to A/B) and perhaps a limited number of programmable memories (10?).

I like the way that you can select either ham bands or general coverage RX. You go into the band change menu, and then hold the switch down for longer to toggle between modes.

I have some minor suggestions for improvement. The main thought would be to change the display of the RIT function to show the frequency offset rather than the absolute frequency (i.e. show -0.415 KHz or +0.001 kHz etc). This reflects how most people think of incremental tuning. Once you are done setting the RIT and exit the menu it would show the absolute frequency as normal on the display while the RIT still turned on. The display should, however, continue to display “RIT”/ There is a whole other line above the frequency display to show function settings on RX. Similarly you could show the keyer mode on the first line (e.g. STRAIGHT, IAMBICA, IAMBICB).

I love the way in which you have corrected the frequency display below 1MHz and opened up the RX to 1kHz to 100MHz. A shorter press allows you to set the step function. A long press on the dial switch gives you dial lock. This works well. I like the way the step speed increases when you turn the dial faster, but the dial no longer goes crazy, throwing you half a Megahertz away on outside the ham band. Well done!

The function to monitor ADC levels could be very useful for those having issues with CW keying. My uBITx has always worked fine with both manual and paddle keys. This suggests that the resistor tolerances are probably a bit narrow. My resistor values may be closer tolerance than what others have received. A check on the monitor function shows this to be the case.

I didn’t find documentation on exactly how the ADC monitoring function works. I believe it shows a continuous stream of readings on the port (0 to 1023) with 6 readings at a time. However, I don’t think you can exit from this function without turning off the rig? This allows you to press dit, dah or the manual key to get a reading for the ADC value being received by the arduino. This then allows the setting ranges to be adjusted.

If you are still fence sitting about a software upgrade you shouldn’t be! Upgrading the stock software is reasonably straight forward. Let me tell you that if you have a stock uBITx, you should definitely be downloading this sketch and increasing functionality and ease of use. It is a fine effort.

Mike notes that v0.33 released today adds several new features including some of his suggestions above.

The final release (v1.0) will be a MUST for everybody as it comes with essential bug fixes and many new features, while working with the stock unmodified uBITx.

Sunil VU3SUA kits and enclosures

Those who have constructed BITx40 or BITx20 kits will probably be aware of Sunil Lakhani’s website https://amateurradiokits.in    Sunil is known for his metal cases, but he sells other products as well.   His new uBITx case will be released shortly, and can be pre-ordered now by emailing the store with a colour preference.

The website http://inkits.in has been made to take orders from customers in India only.  This website is still not fully populated with products and some sections have still to be added.

Sunil VU3SUA says his main website for world wide customers will continue to be:  https://amateurradiokits.in

Ubitx.com

Sunil is also constructing a new website for the uBITx.  This is under construction, but keep an eye out for it on:  http://ubitx.com

ubitx.com aims to provide complete info and updates about the uBITx, sharing information with all ubitx builders.

Sunil says that “it will be similar to other group websites like ubitx.net  promoting ubitx info”.   No doubt it will have a different slant and fill a distinct niche in the uBITx ecosystem.

BITx AGC kit

David N8DAH has assembled AGC kits for BITx transceivers.  These were designed for the BITx20 and BITx40, but should work fine in the uBITx.

The AGC design was posted on DuWayne KV4QB’s site found here and used with permission. All kits will come with:

  • PCB x 1
  • Parts placement layout x 1
  • 2N3904 x 1
  • 2N7000 x 1
  • 47uf x 2
  • 1N4148 x 1
  • 100R x 3
  • 100k x 3
  • 10k x 1 this is extra for the user to play with attack or input values.
  • 2k2 x 1
  • .1uf x 2 unmarked tan

Missing parts will be replaced.   

This is the 3rd run of the boards.  Many group members have this AGC already in use.

Cost and options:

#1 – Kits 13$ shipped

#2 – Pre-built OT service 15$ shipped and tested

Write to David if you want to reserve a kit.

Reference

NB these are sold out as of 29 January 2018.

Alternative software for your uBITx

What do you know, but two new software forks for the uBITx are shortly to be forthcoming.   One is focussed on significant hardware enhancements and the other is designed for stock uBITx hardware.

A stylized red stamp that shows the term beta testing. All on white background.

VU2SPF Software

uBitx.net has already foreshadowed the 2.8″ display from Joe VE1BWV with its software from VU2SPF that is expected to be released shortly.  This software will feature full touch control along with physical optional buttons,  100 memory channels, a tunable BFO. VFO, memory selection and all bands will be selectable from the touch panel.   However, this software has still to be released.

KD8CEC software

Meanwhile, Ian Lee KD8CEC has announced his Beta release of a further update for the stock uBITx.   Version 0.30 has already been released as a final version.   However, version 0.31 is out for beta testing.

This release features CW Keying, Frequency Tune and CW performance meeting the demand for such features from users.   CW keying improvements will continue to use original hardware.  However, it is also possible to set the CW Key analogue to digital conversion range to reduce mis-keying errors that some (but not all) have observed.   Reporting of the resistance detected allows you to know your exact resistance and key contact status (in case the key needs cleaning).  These functions need testing.

The source code for frequency tuning has been rewritten.  Ian has applied a threshold parameter, speed weighting, and a step function. The problem of an arbitrary change in frequency when turning the knob should have disappeared.   When a particular threshold has been exceeded, the frequency step will begin to change,  but Ian has added some logic to prevent the thresholds from becoming unnatural.
If you want to fine-tune, turn the dial slowly and the step rate will change, getting smaller as you turn more slowly.   There thresholds are more gradual  and change more slowly, to give a more natural effect.

The tune steps now are 10, 20, 50, 100, and 200, but you can change these in uBITX Manager 0.31 (Beta release).    You can change the step rate by pressing holding down the function key slightly longer than you would normally to enter the menu. If you keep holding it down for even longer, the Dial Lock function will be enabled.

Band setting is already present in version 0.3O, with the ham band set to “region 1” as the default.   In a similar way to controlling step rate, you can change to state by pressing the function key in the band select menu for a longer time.    You can set up to 10 frequency bands in uBITX Manager to suit your country or your preference.

These new features, a description of the features and details of how to upload firmware (both source code and compiled firmware) can be found here:

https://github.com/phdlee/ubitx

Details on how to upload firmware and access firmware versions up to version 0.27 can be found here:

Ian has indicated that future versions of his software are likely to require hardware modifications.

Tuning up

End whistling into your mic with this suggestion from David GW4AKZ:

When using an antenna tuner on SSB, we could easily add a tone generator and switch to do that.

I have fitted a switchable -6db pad between the output of the pcb and the antenna socket. With the circuit switched in the worst case SWR is about 1.65 to 1 with an open or short circuit.  This prevents the finals from ever seeing a poor SWR.

Tune is easily achived with the key down and reduced radiated power when tuning up.

I use 2 watt carbon resistors 33 ohms in a t attenuator circuit. 2 in parallel to give 16.5 ohms which is close enough to the calculated value.  A relay is s used to switch this attenuator in and out.

Chris suggests replacing the 51 ohm resistors with 2x 100 ohm 3watt resistors.
REFERENCE

Another audio pop mod

Joe VE1BWV provides another audio pop mod:

You probably will want to install a pop click fix to eliminate a loud pop whenever TX is turned on and off.   This circuit uses a 1N4148 diode, a 470k  or 300k resistor, a .22 or .44uF cap and a 2n7000 MOSFET.  Joe says this works amazingly well and mounts on the rear of the volume pot as indicated below (ignore the 0.1 uF capacitor).
Reference