Re: BITX40 Pop Fix

BevTed Stanier

Thanks for the reply Evan.

I seem to be having trouble matching the right BITX board to the right schematic to the right version of the Pop Fix mod etc.

I have a BIXT40 V3 old board that was passed on to me with no documentation. It is now working okay but wanted to do the PopFix mod.

You are right the BITX 40 that I have does not have a Q47 Mosfet. The schematic and parts list that I found on the net for this mod uses a Mosfet designated Q74 as well as a diode, resistor and a couple of caps. The drain of Q74 goes to flag M2 or the Vol H of the volume control and the source to Gnd. It shows the gate being fed by “TX/RX” but my Arduino wiring diagram does not show a signal called this “TX/RX”. Is this signal only on the uBITX  and this mod cannot be used on a BITX 40. The signal that controls the K1 relay is a 12v supply from the PTT sw. and not a 5v signal. I seem to be confused between BITX40 and uBITX 40 and trying to find the right mod for Popfix.

Any thoughts are welome.




Sent from Mail for Windows 10


From: Evan Hand
Sent: Saturday, July 25, 2020 12:36 PM
Subject: Re: [BITX20] BITX40 Pop Fix


Not sure that I understand what you are asking for the BITX40, as there is not a Q74 in that rig.  If your question is for the uBITX (any version), the T/R signal that controls the gate of Q74 is a 5 volt signal direct from the Raduino board.  It is labeled T/R, not TX/RX.  It is also connected to Q15 that then drives the K1 relay.



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