Antenna Tuners for the uBITx

Introduction to tuners and tuning

Arv  K7HKL  suggests the type of antenna tuner depends on the type of antenna:

  • L-network for end-fed or high impedance antennas.
  • T-network for medium to low impedance antenna.
  • Pi-network for dipoles.

He suggests it is unfortunate that specifications for ATU’s usually do not include the adjustable impedance range for each band that they cover.

Bill Schmidt K9HZ suggests there is a false supposition here that you must tune under full power.   It is considered a good design to tune with just the amount of power needed in order to tune… not full power.  This can very easily be implemented on the uBITx with a relay that substitutes in a “Tune RV1” set for a much loser tune power.

List members suggested options for simple external antenna tuners for the µBITx transceiver.  The list of potential tuners below (organised by type) is not intended to be exhaustive, but illustrative of the choices available.


LDG Z100+

The LDG Z-100Plus tunes with only 100mW of power. It holds eight AA batteries internally, making it ideal for portable QRP operation. Small, light weight and self-powered.

However, Rahul VU3WJM found that the match at low power levels was inconsistent. He had to reduce the resistors in the ADC sample line for QRP operation.


From the marketing description, this unit handles up to 125 watts SSB or CW but requires only 0.1 watts to tune, making it ideal for QRP operation.

Elecraft T1

Manual Tuners

SOTA Beams Mountain End-Fed antenna tuner

Sotabeams Mountain End-Fed Tuner


Mike WA1MAD has built the Sota beam Mountain tuner.  He says, “It is easy to build, but very manual and only covers 40-17.”

Emtec ZM-2


Dave K8WPE likes the Emtech ZM-2 better as it has air variable capacitors whereas the 4SQRP uses poly variables.

4SQRP tuner

GQRP tuner

Dave K8WPE prefers a small Z match like the Emtec, 4SQRP tuner, GQRP tuner, etc.  At the home QTH, Dave uses an MFJ 300 watt roller inductor tuner.

He says that the reason he likes manual tuners is he can look at the numbers on the dials and if they are different from what he usually sees he knows he has antenna troubles, i.e. an antenna down, ice coated, wrong antenna, a short somewhere. With the automatic tuner it just tunes and you don’t know if its the antenna or the tuner that is making your transceiver happy. And even at 5 watts or less we can fry an IRF510.

Hendricks SLT

Allison KB1GMX suggests the ZM-2, 4Sqrp, SLT, and L-tuner all work.  The 4sqrp, L-tuner, SLT, and Elecraft T1 are in use in Allison’s QRP rigs for power up to 10W. For higher power a home-built L-tuner easily takes 100W. Those get used for the inverted L and the 160M Inverted V  as all the other antennas are 50 ohm resonant removing losses though a tuner and coax.

Allison says, “By far the best antenna is a matched one. Second best is any needing a tuner.”


Another nice build – we do like the speaker grill!

Nelson KG7GYS has built his µBITx into “a box I had bought for some project over a decade ago and never got around to using”.

He ordered a speaker grill from Amazon for about US$2.50. He decided, like many of us, to use a pot with switch from his junk box in order to have a standard size shaft (it came out of an old Radio Shack CB set).  The knobs are from an old Henry Tempo One (Yaesu FT-200). The speaker is from his junk box, as is the 12vdc fan.

We all want to know what the heck all that test gear does!


Testing your uBITx using the Reverse Beacon Network

Rob AG5OV says, “If you are like me and not having a lot of luck with SSB QSO due to the recent crappy conditions or want to debug your apparent low voice output the Reverse Beacon Network can come to the rescue.

“RBN listens for CW CQ’s and reports who heard them.  For the uBITX you can add in Ian’s (KD8CEC) wonderful firmware and even without a key you can send a message via the Automatic Key Memory function and see both who can hear you and what your uBITX output actually is under ideal conditions.”

What Rob did:

  1. Installed Ian’s (KD8CEC) firmware (1.04)
  2. Downloaded the Ian’s Memory Manager
  3. Edited the Auto CW memory to “TEST DE <YOURCALLSIGN> TEST DE <YOURCALLSIGN> #” (the # is the prosign for AR)
  4. If the TX/RX delay isn’t high enough you will flop back and forth with annoying clicks when you aren’t interactive anyways, I set mine to 1000ms and 400ms.
  5. Tuned to the CW/Data area of a band and set to either CWL or CWU
  6. Select Auto CW
  7. Push the PTT to send it
  8. Look yourself up on RBN

What he discovered is interesting.  He was being heard and maxing out at about 1.2a @ 12.0v on CW compared to his 800ma @ 12v for voice (while “eating” the mic.

He has figured out that, besides conditions, the audio input side of the world is letting him down.  He has ordered an assortment of 1206 SMD resistors and a package of replacement electret mics (both from Amazon) to see if he can fix the problem.  We will be waiting to hear the results.


WSJT-x release addresses Linux issues with uBITx

JP Bhatnagar, VU2SPF, has advised the list that the anticipated announcement  of a new version of WSTJ-X has been  made by Joe Taylor of the WSTJ-X development team. This mentions addressing ubitx transceiver connectivity with WSTJ-X.   WSTJ-X  has become very popular with amateur operators, as it implements the exciting new FT8 digital mode.
The full announcement follows:

The WSJT Development Group is pleased to announce a third Release Candidate of WSJT-X Version 1.9.0.  A second release candidate, v1.9.0-rc2, has been tested in the field over the past three weeks, including a public test of FT8 DXpedition Mode conducted on March 6-7.

A General Availability (GA) release of v1.9.0 will be announced at a suitable time, probably in the near future.  After that time you should stop using any -rc# release candidate.

Here’s a short list of features and capabilities added to WSJT-X since Version 1.9.0-rc2:

1. Corrected a number of flaws in Fox behavior, FT8 DXpedition Mode

2. Allow Hounds to use compound callsigns in FT8 DXpedition Mode

3. Write debugging information to FoxQSO.txt

4. Fix the “Blue Decode Button” bug

5. Allow partial processing of incoming UDP Reply messages so that non-CQ/QRZ decodes can be processed. The processing is the same as double-clicking the same decoded message within WSJT-X except that “Enable Tx” will not be enabled.

6. Send DX grid locator to wsjt_status.txt, for use by applications like PstRotatorAZ

7. Correct the display of DXCC status of KG4 calls

8. Updated copy of cty.dat

9. Updates to documentation

10. Updated Hamlib functionality including changes to the Yaesu FT-817  back end that allows the uBITx kit transceiver to be CAT controlled by WSJT-X.

10. Other minor bug fixes


A 3.5″ screen for digital modes/ rig control on the front panel

Vince, N2AIE,  worked Tom VE3THR and Bill NG1P tonight on 7.277 out of his QTH in Cedar Rapids IA.  These were his first uBitx contacts with other uBitx and bitx40 rigs.

Vince has loaded (after some angst) the KD8CEC firmware, and has the rig interfaced with Ham Radio Deluxe (in both directions).  His rig also has a 3.5in touchscreen Raspberry pi for digital modes built in on the right hand side of the front panel as illustrated above.

Take a look at the rear panel of his rather attractive build:

700Hz CW Audio filter board

Nik VK4PLN has yet another board design – this time for an audio CW filter similar to the QCX and HiPerMite.  Nik says “he is  loving the cheap and easy EasyEDA/JLPCB boards and simple web designer”.

He “takes no credit for the design, just copied it and added a switching relay.   He has ordered 10 boards at $10 posted”.

Details of the filter

Center Frequency: 700 Hz
Bandwidth: 200 Hz
DC Power: 5VDC
GAIN: Upto 20dB via R11 and R12 + trimpot.

Resistors 1206 SMD:
R1 33k
R2 33k
R3 1M
R4 47k
R5 47k
R6 36k
R7 36k
R8 10k
R9 750k
R10 10
R11 100K
R12 100K

Capacitors 1206 SMD:
C1 0.1u 104
C2 47n 473
C3 36n 363 (33n + 3n3 mount on side together)
C4 1n 102
C5 39n 393 (33n + 5n8 mount on side together)
C6 1n 102
C7 2n2 222
C8 2n2 222
C11 0.1u 104
C14 220u Electrolytic

Relay OMRON G6S-2-DC5
200K/100k trimpot

R11 and R12 are optional to parallel the 200k trimpot to make it a logarithmic 100k.   Or just use a linear 100k pot.

Use a switch connected to 5V to turn on the filter.

This powers the opamp and switches the relay feeding the audio into the circuit.  When off the relay just passes the audio straight through unfiltered.


Making a PCB? Find the cheapest PCB manufacturer

John, WA2FZW,  noted a suggestion from a friend that if you are designing your own PCB, the PCB Shopper website will help find the cheapest PCB manufacturer:



Kerr Smith confirms this recommendation saying,  “This site is definitely worth using when you are looking to get PCBs made. The last time I used it it suggested ALLPCB which had an offer on at the time so I got 5 boards for $5 with free courier shipping (my PCBs arrived in 5 days).

“I would highly recommend using the site to see which PCB fabricators are currently the cheapest. You can then do a bit of research and get some user reviews and decide if you want to get your boards made with them.

“There are so many different PCB manufacturers this site makes it really easy to get an initial price per PCB for lots of them with you only needing to enter in some basic data such as PCB size and number required etc.”

What sort of soldering iron/station should I use to wire up my uBITx?

Richard WB8YXF asks what sort of soldering iron or gun should be used to wire up his uBITx.   The answer is pretty much anything.

Doug Wilner responded as follows:

“Kind of like asking what car you should buy or shovel or rifle or whatever.  We can be much more helpful if you know your goals.  Are you on a limited budget and this is the only thing you plan to ever build and need the cheapest way to just get this done or do you have so much spare cash you light Cuban cigars with $100 bills and want the best tools that will last for generations?

“Personally my go to iron is a supposedly 60w adjustable pencil type iron that I keep planning to upgrade but I like it and it gets the job done.  I have this one  that was around $15.  It isn’t available anymore but there are tons of similar Chinese ones on Amazon.  While you’re at it I would suggest picking up one of the copper scrubby looking tip cleaners.”

Perhaps not a soldering gun (first seen in the 1950’s).   You have to press the trigger and wait for them to heat up.  A soldering iron with a thermostat and adjustable temperature is a much better option.

These soldering guns were a source of wonder to the editor in his youth, because his Elmer had one and swore by it.   Of course, said editor earned an income from mowing lawns around the neighbourhood and this meant he simply couldn’t afford it – it was around NZ$60 even then.   Joe KD2NFC said, “I used to watch my grandfather repair tube TV’s with this one.”

The Weller 853D shown at the top of this news item is a full rework station as well and on special can be around US$70.

Chris, KF4FTR, makes the observation, that “Having a hot air gun available for tighter pitch work is important.

“Spark fun has an old multi page tutorial on SMD work located at .

“Is it possible to use just an iron? Sureand again it depends on the work that will be done. However, if you look at the page for removing multi pin SMD ICs you can see the results of trying to this without hot air. You can try and physically force them out of place or use an xacto knife to try and cut the pins. Both are bad because just flexing the part can rip a pad out which means you will need forceps and wire to fix it, or you can cut traces with the knife.

“The best thing to do if any rework or SMD parts need to be placed is to get the right tool for the job which is a hot air rework station. I have seen people suggesting 100$ irons. Well, if you spend the 70$ on a rework station you wont have that problem… This again is all based on the assumption that this person will need to work on the UBitx or mods or possibly other kits. Sure its another 50 bucks or so, but it will save hours of frustration for a person who hasn’t even used an iron in a long time.”

Rich WB2GXM also points out, “There are two very good Youtube videos by Dave Cassler, KE0OG, on soldering irons, accessories and techniques”:


A very nice looking build in a metal case

Joel, N6ALT, has declared that he “is done with his µBITx”.   And we can see why!   This is  a very nice build in a very classy case.

After three attempts at different enclosures, he settled on this one from China.

The PTT switch is mounted in the pen housing on a small piece of perf board.

It is built very well and super light. Only 4 screws hold the whole thing together yet it is very strong and rigid. Very ingenious.

The radio weighs 2 pounds. Joel did not leave the display mounted to the main board as it would make the display not centred and too low on the front panel. He built a short flat extension cable out of a female and male header.