Next PCB rev for QCX-mini #qcxmini #usdx


Robb Bates
 

Hi Hans,

First, congratulations on the QCX-mini!

I'd like to make a few suggestions for the next rev of the QCX-mini PCB.  These are geared primarily to assist in the modification for the uSDX but also some general hacking.  I understand you don't officially support it, but these changes would help those of us insane enough to attempt the mod.  And these are assuming there's room and they won't break the circuit.

1) Replace the zero ohm resistors with cut trace jumper pads.  i.e. two closely spaced pads with a trace connecting them which you cut with a hobby knife to disconnect the op-amps.  That will eliminate the need to install the zero ohm jumpers (save a few pennies) but will allow one to revert back from the uSDX to the original QCX-mini by bridging the pads with solder.
2) Include some of these cut trace jumper pads before or after R53, R54, R59, the trace going to the DVM section before the node connecting R56, R57 and R58, and the trace going to D5/R60.
3) Add 0603 pads (with cut traces connecting them) in series with R7 and R10.  You can cut the traces and install a 72k resistor (or whatever is the closest standard value).  That will allow you to leave R4 and R7 and jumper the new pads if you wish to revert.
4) Include some surface mount pads connected to the T1 pads for the installation of the 2x1k resistors and 1nF cap required for the uSDX mod.
5) Add some cut trace jumper pads for T1 pins 3, 5, and 7.  That way you can install T1 but then cut the jumpers to install the mod.
6) Add a pair of through holes right before the BNC connector (with a cut jumper trace).  I'm going to try to install a SWR LED indicator (QRPguys) in the case.
7) Add some strategically place through holes for header pins to allow for swappable LPF daughter boards.
8) Add some other strategically place through holes in places that make sense for general hacking projects.

Some of these make more sense than others.  But they were just ideas I had to brain dump.

Thanks,
Robb K5RAB


Richard - N1RBD
 

ICYMI, it has been stated many times that the QCX Mini is not meant to be a development/hacker project, such as the QCX+ is.


Mike Besemer - WM4B
 

Amen!  Some of us still want a QSX!

 

Mike

WM4B

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Richard
Sent: Saturday, December 26, 2020 2:15 PM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] Next PCB rev for QCX-mini #qcxmini #usdx

 

ICYMI, it has been stated many times that the QCX Mini is not meant to be a development/hacker project, such as the QCX+ is.


Robb Bates
 

No, I get that Richard.  It's up to Hans if he wants to implement these or not.  If not, then no loss.  If he does, then bonus!

But these change won't cost anything other than a little bit of Hans' free time.  He has lots of that, doesn't he? ;P

Robb  K5RAB


Hans Summers
 

Hello Robb

Thanks for the suggestions... some questions inline below

1) Replace the zero ohm resistors with cut trace jumper pads.  i.e. two closely spaced pads with a trace connecting them which you cut with a hobby knife to disconnect the op-amps.  That will eliminate the need to install the zero ohm jumpers (save a few pennies) but will allow one to revert back from the uSDX to the original QCX-mini by bridging the pads with solder.

I understand but is it really easier? Can't the existing 0603 0-ohm resistors pads be bridged with solder to revert back? I've done it, it's easy. 

4) Include some surface mount pads connected to the T1 pads for the installation of the 2x1k resistors and 1nF cap required for the uSDX mod.

It isn't required to leave out T1 for the uSDX mod, if I'm not mistaken. Leaving out T1 reduces performance in both QCX and uSDX. The only reason to leave out T1 is that it makes it easier to go multi-band because the BPF is one less thing to switch. 

Regarding the other points... there aren't exactly acres of PCB area to add through-hole header pads... some might be possible. 

In any event the next batch is already being made now so it is too late to make any changes. I can consider it for the 3rd batch. 

73 Hans G0UPL