Re: Reduced power on 40 meters. #ubitx #v5


Mark, interesting...I really know nothing about the legacy as this v5 is my first ubitx, but not my first home built rig.
I can't imagine a corrrectly designed filter would have a 3db or greater insertion loss, perhaps using wrong values by experimenters on earlier version could cause this. I suspect Allison is correct with just a wrong part in my filter.
In-circuit measurement isn't easy, I may try to use my vna on it to check it's transfer function, or just unsolder a few and measure..
Thanks all!

Re: power supply


Yes a low amperage fuse for now. There are many linear power supplies well under 10 amps on the planet, likely you can find one at what you in the UK refer to as a rally.

I have a little mfj switching supply, and I imagine some have homebrewed one similar.

Enjoy your build.


Re: homebrew ubitx roofing filter #bitx20 #bitx20help #bitx40 #bitx40help #filters

Ashhar Farhan

You could just make LC filters as well. A triple tuned filter should do the trick. While you are at it, change the 1st IF from 45 Mhz to 60 MHz or beyond.

- f

On Tue, Aug 20, 2019 at 1:54 AM <circular.simetry@...> wrote:
hello i have finished building the ubitx CM2KMK version and i have problems with the 45mhz crystal filter. the only filters i have in my inventory are the following--
22M03       45,1mhz     from a motorola GM300
49S10B     49,95 mhz   from a kenwood TK760
FL-210       21,8 mhz       from Icom M59
I have tested all of them by changing the frequency acording to each crystal in the source code.The best results so far i get with the 21.8mhz filter FL-210.
iI think the problem is matching the impedance with the two coils L5 and L7 i used 12 turns on T37-6 .
Please if someone have any documentation about the filters or knows what impedance they have i wil be very thankfull.
Thanks in advance ! 73de yo4huj

Re: homebrew ubitx roofing filter #bitx20 #bitx20help #bitx40 #bitx40help #filters


thank you but if i change the frequency to 60 mhz or more i have to change the value of the capacitors and the number of turns?

Re: homebrew ubitx roofing filter #bitx20 #bitx20help #bitx40 #bitx40help #filters


You could use one of these inexpensive ($5 ebay) Texscan LC filters for a 70 MHz IF and it might go well. These are 25 kHz wide at the 1 dB points and I have not seen a curve but the data sheet says "sharp skirts".

Re: homebrew ubitx roofing filter #bitx20 #bitx20help #bitx40 #bitx40help #filters



Re: homebrew ubitx roofing filter #bitx20 #bitx20help #bitx40 #bitx40help #filters

Lawrence Galea

Those filters are 25 MHz wide NOT 25kHz

On Tue, Aug 20, 2019 at 9:42 AM kh6sky <kh6sky@...> wrote:
You could use one of these inexpensive ($5 ebay) Texscan LC filters for a 70 MHz IF and it might go well. These are 25 kHz wide at the 1 dB points and I have not seen a curve but the data sheet says "sharp skirts".

Using CW to Tune #ubitx

Ivan Matías Leitner

Hi Friends !

My name is Ivan and i'm a happy owner of a V4 microbitx. I'm not using CW mode in my Microbitx but i would like to add a switch in the front panel to send the cw tone in order to tune. 

If someone can give me a hand i will appreciate 


Re: Using CW to Tune #ubitx



cool stuff.  remember that 4.7 k resistor you installed?  find the 'outside' of the resistor - and arrange a push button connection to ground.  the Raduino reads the voltage created at the 'inside' of this resistor (you can see it then with a DVM) to command the rig to transmit a CW signal.  the outside of course goes to where a key jack is located (whether you installed one or not -- this push button can exist simultaneous with a key jack). 


Bitx40 very loud, high-pitched, low frequency noise


Hi! I've just finished assembling my Bitx40, and when I turn on the radio, I hear a terribly loud noise (link to listen below). The radio works fine, because I can hear some operators behind that noise, but I cannot tune the radio loud enough to hear them properly, as the noise is extremely loud even on the smallest volume. I don't really know what's happening gere. Any help?

The noise:

Eyesight prohibits finishing uBitc ver 4

Michael Mitchell <mitchellmichaelh@...>

Cant see well enough to finish
Ubitc ver 4 mounted in chassis along with auto tuner and power supply. Switches and jacks installed. Includes pc oscilloscope and RF tap for use with oscilloscope.

 search uBitx on ebay

Re: Bitx40 very loud, high-pitched, low frequency noise


Fun fact, when I start to touch and move around the brown wire from volume control knob, I can hear local FM radio station.

Re: Using CW to Tune #ubitx


Curt, I do that very thing for a "tune" button for an outboard antenna tuner. Simple and effective.


Re: Help #arduino


Here in cuba not is possible buy component, i an take the aviable components .

Re: bitx and ubitx encoder replace ment

Sascha Bohnet | DL5SMB

As this is still relevant to this topic I refrain from opening another thread and write here again.

I can confirm Mark's problems with the speed of the 100ppr encoder:
If the encoder is span slowly it works acceptable, but if the speed is increased, problems arise (See my reference video )

Has anyone found a way around this for KD8CECs software?

There are of course different ways which can be tried:

The following methods I thought of, but they are also burdening up some other problems (at least for me)

1.) My first idea was to simply change to a Arduino Nano Every to keep investements low and to gain something from the change. It's a bit faster, pin compatible and has interrupts everywhere but the eeprom is smaller and it will probably not work with the uBITX Manager. And it also does not compile as the softserial_tiny.cpp is incompatible and would require a rewrite (or a write out of the libray)

2.) Just changing the pins to interrupt capable ones and use another libray for the encoder.
This might be a solution as  Pin 2 and 3  are at the moment used for the CW key and TX-C (I think) which seems to control the low pass filters. I would need cut some connections and rewire here to make the software experiments possible with an unknown result.  Therefore I would rather just try a  software approach.

3.)Try to use portmapping to be able to read out the encoder faster. I found the FastDigitalWrite-Libray but I am not sure if it can be used with analog inputs.
KD8CEC uses the following code to check the encoders status:
byte enc_state (void) {
    return (analogRead(ENC_A) > 500 ? 1 : 0) + (analogRead(ENC_B) > 500 ? 2: 0);
The libray above only supplies
  • digitalWriteFast(pinNum, state) (sets or clears pin/port faster)
  • pinModeFast(pinNum, mode) (sets pin/port as input or output faster)
  • digitalReadFast(pinNum)(reads the state of pin/port faster)

So no support for analogRead. And I guess if it was possible to read out the analog ports digitally,
this would have been done by KD8CEC before using this workaround.

Does anybody have an idea, what could be done?


Re: Help #arduino


Senior CO8PAP

Sorry we got off your topic, and not everyone appreciates your challenges there.

Please visit my club's website for many simple modifications you can consider. Also okay to email me.

The basic display does work nicely.


Re: Help #arduino

Jerry Gaffke

I'm guessing your "GLCD 32160" display is like the G32160x02 from Crystal Clear Technologies:
That datasheet says it uses the SBN1661 controller:
It appears the SBN1661 is supported under Arduino by u8glib

Datasheet says the SBN1661 always has an 8 bit parallel data bus plus Read, Write, ChipSelect.
The uBitx currently uses a 4 bit parallel bus, so you won't have enough pins
unless you go to a bigger processor than the Nano that is used on the Raduino.

I've made a number of assumptions above.
Check your display over, see if any chips are labeled "SBN1661"

This might not be easy to get working.
But could be a fun project if you have an extra Arduino processor to play with.

Good to know you have your uBitx up and working.
I am quite happy sticking with the original 1602 display.

Jerry, KE7ER

Tapping audio out to DSP filter from VOL-H or VOL-M #ubitx

Rob French (KC4UPR)

I'm looking to potentially add an audio DSP filter to my uBITX... I've got a Teensy 3.2 lying around that hasn't been used for anything, and I figured that 'd be the perfect toy to try out for this application.  Some thoughts and questions in no good order...

(1) I'm thinking I'd like to tap off the VOL-H location... so the DSP filter would come before the volume pot.  What are the pitfalls to this, if any?

(2) I would also use the Teensy as the interface to the computer for digimodes.  So by having the Teensy prior to the volume pot, I would be able to have separate control over the level into the computer, and the level through the speaker/headphones.  I could adjust audio output with the volume control for my ears, but meanwhile have a separate, independent control over the level seen by the computer (more so for e.g. CW w/ fldigi rather than PSK or FT8).

(3) Buffer?  Transformer?  Both?  I see that the JackAl has a similar arrangement, though it taps the audio off of VOL-M.  Why is the 1:1 isolation transformer prior to the preamp?  Would it be viable to have a high-impedance buffer first (to decouple the two outputs), and then the 1:1 transformer prior to the Teensy?  

(4) Is there a spec or expected audio voltage level at the output of the uBITX audio preamp? (prior to the volume pot and LM386)  The Teensy audio adaptor has adjustable sensitivity, so I would think that I would want to set the input sensitivity (which goes up to ~3V, I believe) based on the design output peak voltage of the preamp, plus a small pad.


Re: homebrew ubitx roofing filter #bitx20 #bitx20help #bitx40 #bitx40help #filters


Well that makes more sense.  How do you make a 25 kHz wide LC filter at VHF? You don't.  I optimistically misread. Thanks Lawrence.

As Roseanne Rosannadanna used to say..."nevermind."

Where many of the ICs we still use today were born.

Tom, wb6b


This interesting article shows prototypes like I see in projects in this group, are like the test and development prototypes for many analog ICs. A look into the days before SPICE simulations became the standard.

Tom, wb6b