Single-ended relay board for existing LPFs 

Gordon has been testing out his mult-relay single ended board.  The concept here is that the existing LPFs and relays are reconfigured on the µBITx main board and the ends of the LPFs are connected to a new daughter board attached behind the LPFs and relays to provide for greater RF separation between LPFs.

And this photo shows the cuts made to the top of the board:

And showing the connections to the add-in board

And a different view showing the wiring to the main board:

And the relay power on connections:

The results seem promising.

A separate board with all LPFs mounted on the external board  (e.g. this one) would not be much larger overall and would require fewer connections to the main board.

A document with all the explanations of how to create this modification, including photos of traces to cut can be found here.


Long distance contacts on the uBITx

EI Frank asks: “So what’s your personal best distance on SSB?”

  • EI Frank – 380 km’s (236 miles) on SSB, with an End Fed half wave wire on 40m with a uBitx
  • iz oos – New Zealand, ssb 3w qrp with the Spanish ILER20. I logged that as an ordinary qso. I was not in the States of course… But in Italy. New Zealand is exactly on the other side of planet earth from my qth. Just let me say that if you hear anything around s9 or more if you use a qrp you can have a qso, of course it will be more difficult during a pile up. So give up FT8 and come back to cw-ssb!
  • Don ND6T – First SSB contact with new uBITX was with JE6EHP on 20m with an end-fed random wire. Nice long chat. Well over 8,000 Km.
  • Joel N6ALT – worked a station in Antartica from his QTH in Oregon USA, a distance of 10,455 miles, on a Bitx17A running 8 watts into a EFHW antenna. He has the QSL card to prove it!
  • Pete VK3YE  –  About 2600km on 80m – with a half-collapsed wire antenna
  • Don KM4UDX – so many of you have gone really far. I am but a grasshopper. But it might be fun to get other distance records? I was pleasantly surprised to see this.
  • Doug Wilner – The K1JT modes sure do give you a high action to watt ratio.  I have FT8 QSO’s between USA and ZL on just over 4w which is 13,176.51km (8,235.318 miles). On my raspberry pi WSPR rig I have reports from ZL as well and that is on .1w.
  • Brent Seres – I managed southern Ontario to northern Brazil with my bitx40 on 40cw and end fed wire

LPF board from Nick VK4PP

Nick VK4PP (earlier he was VK4PLN) has come up with a small circuit board for mounting replacement LPFs (or the existing LPFs removed of scraped off your µBITx).

A topside view:

And a bottom side view:

Posting of the boards has resulted in lots of comments on layout and we can look forward to further enhancements of the design.


Update on fixes for uBITx spurs and harmonics

The number of posts on the BITX20 IO Groups list hasn’t gone down very much over the last month,  but the ideas that swirl are all about potential fixes to the µBITx spurs and harmonics.  And a new problem has been identified … very poor intermodulation results.

The µBITx is simply not putting out the nice pure signals we would like.   We are now trapped in a pattern of waiting for the  “magic bullet” solution to our woes, but sadly this seems unlikely to result.   There are just too many issues that need to be resolved.

Somewhat understandably after months of exciting developments, new contributions from constructors with substantive mods and hacks making the whole package sing are now no longer emerging.  We had become somewhat used to regular exciting new updates on processor or screen additions, or simple fixes to niggly issues (such as low audio, or distorted audio, or the annoying pop on toggling between RX and TX), and now we are becoming a bit more despondent about those more serious problems of compromised output.

Some progress is being made in solving spurs and harmonics.  We know that the built-in LPF filters and relays in the output stage can simple be disconnected and bypassed by adding a new external filter set (e.g. using Hans G0UPL’s filter board and filter kits for LF through VHF) on the antenna output.  After doing this the rig should work just fine on CW operations on all bands.   Of course, it may need either a hack to the firmware to get automatic band switching to work, or we can just use a rotary switch.

Alternatively, there has been work on modifying the filters in situ.  By changing the relay switching logic (e.g. mounting the relays under the main board and rewiring the switch points) and at the same time adding a second set of relays on an add-in daughter board we can restore effective functioning of the existing LPFs.   They work fine, but the switching system creates unwanted blow-by.  However, this involves quite a bit of hacking on the main board that many constructors may baulk at.

And none of this solves the issues with the spurs on SSB on 15m and above, that requires yet another fix of a second filter board at the output of the 45MHz mixer, and then there is the probably unrepairable issue with intermodulation products are probably way above what would normally be expected.

So where does this all leave us?   We have had a lot of fun on the journey to date.  We all acknowledge that most of the fun has been in the journey, but what’s the point in a journey that has no end?

Should we wait a bit longer hoping for a fairy godmother and a magic bullet solution to appear?   We  could spent more money to acquire the new QRPLabs transceiver  kit when it comes out (hey, all bands all modes and around US$150!)?    However, we already know that Hans G0UPL won’t release the firmware source code – therefore, there will be no add-ons and feature enhancements unless they come from Hans.

We could now just bite the bullet and hack our µBITx to turn it into a CW rig?  But it is supposed to be a phone rig as well.

Hold in there a bit longer, the “magic bullet” may eventuate.  Who knows? And I am sure there are plenty of other projects under the workbench for you to get on with in the meantime.   At this QTH there’s a couple of mag loops under construction (Teensy controlled) and a bench power supply project …

Problems exposed on uBITx sans filters

Warren WA8TOD, who has now relocated his µBITx to the top shelf (of abandoned projects), but he has provided us with a series of shots of the output of the µBITx on different bands, with no LPF filters in place.  These show the raw product coming out of the µBITx and put in full view the problems with the 45MHz filter and the harmonic generation in the power amplifier.

80,40,20 meter CW
– Power level set on each band individually to 5 watts
– Green display line represents the -43 dBc threshold
– Second harmonic on both 80 and 40 is somewhat problematic as are odd harmonics out to 13th

80,40,20 meter SSB
– Power level set on each band individually to 5 watts CW then 1 kHz tone input level adjusted to produce the same 5 watts
– Green display line represents the -43 dBc threshold
– Second harmonic on both 80 and 40 is somewhat problematic as are odd harmonics out to 9th

17, 15, 10 meter CW
– Power level set on each band individually to 2 watts
– Green display line represents the -43 dBc threshold
– Harmonics can all be removed with a simple 34 MHz LPF. The filter included in the uBitx is more than adequate

17, 15, 10 meter SSB
– Power level set on each band individually to 2 watts CW then 1 kHz tone input level adjusted to produce the same 2 watts
– Green display line represents the -43 dBc threshold
– 17 meter spurs represented by markers 1 and 2 are problematic because only a close spaced, single band BPF can be used to remove them.
– 15 meter spurs at the low end need to be addressed.
– A single filter cannot cover these bands because of the close spaced 17 meter spurs.


3.2″ Nextion display files for CEC v1.097 Beta

With each new releases of the CEC firmware and CEC Nextion firmware,  Ian KD8CEC provides constructors with 2.4″ and 2.8″ versions of the NExtion firmware.    Meanwhile, a bunch of other Nextion screen users eagerly await adjustments to the firmware that will work with their particular screen size (3.2″, 3.5″, 4.3″, 5″ or 7″).   Adjustments have to be made for each screen size.

Darren VE3XLT has helpfully converted the current beta for the larger 3.2″ screen.

Files for downloading can be found here:


Here’s a video of the display in use so you can see its features



Low power on 80m?

Allison KB1GMX notes that if you have a v4 board and experiencing low power output on lower bands (80m and 40m) you may want to check the emitter of Q90 to see if a .01uf or a 470pf or 220PF is there.

There was a change to lower the value from .01 to 470 pf to level the output
power so 80M wasn’t 15-20W when 20m was maybe 8 watts output.

Some have experienced  that low bands work very poorly with a 470pF or 220pF capacitor.  You may want to increase the capacitor back to 0.01µF or perhaps 1000pf.


QRP-Labs bringing out new Txcvr


Hans, G0UPL ( produces a range of QRP kits, including his well regarded QRP CW rig, the QCX.  He has been working on a new SSB kit (in fact all modes, AM and FM as well as digital modes) that will be released later this year.  The new rig will be modular, 10w output, and initially available as a 40m transceiver only.

A later module will add 10 LPFs that will set it up for use on all HF bands (including 60m).  Expected costs are around US$75 for the 40m only kit (no enclosure) and around US$150 including all bands and enclosure.

The photo above shows the small size of the new kit (seen alongside the QCX).  The photo below shows a glimpse inside.


Biteensio with LCD touch screen coming

Jim W0EB is working on a 2.8″ touch panel for the triumverate’s BITeensio.  That will make four different alternative touch screen options for constructors:  VU2SPF Mega2560 attached 2,4″ LCD (first up way back in January),  KD8CEC Nextion screen (in a range of sizes from 2.4″ to 7″) , BiTeensio 2.8″, and the long awaited JackAl (in 5″ and 7″ sizes).