Assembly instructions for the ubitx v4

Mario Koppensteiner

Hello Evan,

Am 16.08.2020 12:59, schrieb Evan Hand:
The Mini manual that Rick Price provided contains the following
information from HF Signals:
I saw this page already. I does not explain how to connect the AGC and the AMP to the board.

Both can be used to wire-up the uBITX v3, v4, or v5 manual with the
stock configuration. I would highly recommend that you verify stock
operation before you add the Nextion display. You might want to do
that before you mount it in the case.
I'll have a try when I have connected all the wires.



Mario Koppensteiner

Evan Hand


Before working on the AGC wiring, I would make sure the audio amp and the rest of the rig is working.  

I assume that you will be using the Front Panel PCB supplied and that you have solder onto it all of the parts.  I will also assume that you have wired the tuning encoder and the optional 4 pin mic connector if you will be using it.

There are then 2 connectors left on the front PCB:
1 - A three-pin connector for the volume control
2 - A two-pin connector for the "speaker" if the audio amp is not used.

The speaker connector on the audio amp (2 pin polarized) is the same as the speaker connector on the front PCB.  This allows you to first make sure the mainboard and controls are working before you add the audio amp.  Just be sure to make the speaker wire and plug long enough to reach the audio amp speaker (LS) connection.  You still need to make a 3 wire plug to 3 wire plug jumper to connect the volume control that you mounted on the audio amp board.  I would also connect one of the 2 wire plugs to the inside and outside of the volume control line.  There are extra holes that allow you to solder in the red and black (black should be ground) to allow connection to the AGC after you have the audio amp working.  When you are ready to add the audio amp, you lift the speaker plug from the front PCB and move it to the speaker output of the audio amp and wire a 2 wire jumper from the front PCB speaker jack to the Audio In jack on the audio amp.  You will need to adjust the blue variable resistor to limit the maximum volume and prevent feedback.

Once you have everything working, including the audio amp, THEN start on the AGC.

I found getting the AGC to work the hardest part of the assembly.  The pictures of where to tie in the IF lines do not match the schematics given.  I followed the schematics and wired the IF to go across R10.  I was also confused by the AGC socket on the audio amp board.  That can be used, however, the S meter will fluctuate up and down, as well as the AGC limiting change with volume control setting.  The original design lists the connection of the AGC input to the High and Ground of the main volume control, and that is where I connected it (the 2 wire jumper you soldered into the extra holes on the audio amp that parallel the large volume control).  Seems to work properly after adjustment. 

One caution is to ensure that you soldered in the 2 and 3 pin connectors in the correct facing, otherwise, you can short out the signal as normally the black wire is ground and the red the signal or positive connection.  I got that wrong on the audio amp AGC out connector.  To compensate I changed the AGC In connector on the AGC board (it was easier to rework that board) to work with the AGC out from the audio amp until I found that that connection did not work as I wanted.  Now I have two 2 pin connectors that are in "backward." Only the one on the AGC board is in use.

I apologize if the above is not clear.  I do understand your confusion, and even with very good schematic skills I still had to rework most of the wiring in the kit because there is conflicting documentation provided for a number of areas, not just the Audio Amp and AGC.

As curt suggested in one of the earlier emails, for the uBITX it is always better to test the rig as close to stock as you can.  Usually, that means temporarily wiring up the rig outside of the case and verifying that all is working, including the stock display.  Then you know that the problem is not with the basic board and is aligned at least close to good.  There have been enough issues without adding more with kit wiring mistakes.

Above is my understanding of the rig at this point.  Others may have better information or different experiences.

Good Luck!

robert pohorence


Based on my short time in the Ubitx group, all your posts have been most interesting and on point.

I for one realize that you have spend alot of your time analyzing each issue and then taking  time to write up recommendations of assistance .

Your technical support is a contributing factor to ubitx owners satisfaction.

Rob N8RT

Evan Hand

Thank you!  
I am retired, so I have quite a bit of time to do the research, and learn in the process.  I have also built and rebuilt 3 different uBITX as well as a number of other radios recently and used them in most modes EXCEPT CW for anything other than testing.  I am still too rusty in that mode to be willing to fumble through a QSO.

Again, Thank you for the compliment.