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#qmx #mod Modification for correct grounded PTT output #qmx #mod

 

Hi all

Many thanks to Yuji JJ1GPM who found my PCB and schematic layout error. The modification will be performed by us on all Assembled QMX shipped from 10-Feb-2024 onward. We will NOT do the modification on kit boards - because by doing so we would fill up the holes used for the 3.5mm jack connector with solder. The modification needs to be done AFTER the connector installation.?

I have documented this modification on this new page:?

Without this modification, the grounded PTT output will not work. However there will be no other functional impairment and no risk of damage to your QMX. Note also that of course if you want PTT to work (grounded or?+5V) then you need to enable this for one or more bands in the Band Configuration screen.?

I also updated the PCB Rev 2 assembly manual with a link to this modification page and added a bold red note on the main QMX page.?

73 Hans G0UPL
 

Thank you Yuji JJ1GPM for surfacing this error!? I can now trigger my SDR TX/RX Switch via PTT Out Grounded on TX so I can share my TX antenna with my SDRPlay receiver.
Note that for this to work, you must be running firmware 1_00_016 or later plus perform the modification suggested here??

Here's a pic of my QMX fixed (QMX Rev 1 low band) per the recommended modification:
 

A low ohm resistor makes a good jumper, doesn't need an insulation? ?I have a bunch of 1 ohm that I'll never need.
 

Hi Chris, all

Yes that works too.

We started adding the wire to all assembled QMXs here, and we're just using a capacitor lead offcut. There's space for it to easily fit between the resistor and capacitor on the board, on a direct route from pins 2 to 4, and enough clearance that there isn't any risk of shorts, so even with a bare wire there is no problem.?

73 Hans G0UPL


On Mon, Feb 12, 2024, 11:29?PM Chris KB1NLW via <chrisrey1=[email protected]> wrote:
A low ohm resistor makes a good jumper, doesn't need an insulation? ?I have a bunch of 1 ohm that I'll never need.

 

Photo was removed during Group.IO cleanup, so reposting a photo via an external link. Jumper is the black insulated wire. Also shown (to right of the US dime) is the resistor mod required for Rev 1 pcb QMXs only. These are size 0805 5.1K ohm surface mount resistors so that USB-C to USB-C QMX PC connections work correctly.



--
73
de Roy - KI0ER
Littleton, Colorado USA

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