开云体育

Tnx Hans, will do the mod ASAP.
A quick question: would there be any reason for which a Schottky diode wouldn't work (even better) in this scenario? I honestly can't see one and I have a whole bunch of them, so I'm tempted :-))

73s
YO3GFH
op. Adrian

Minor edit to the description on the web page is needed:

Currently: "TRANSMIT:?During receive, the "RX: signal is at DC Ground potential, as is the Q508 source"

This needs to say "during transmit" (looks like a copy & paste error).

73,

Dav

On Thu, 4 Jan 2024, 09:27 Hans Summers, <hans.summers@...> wrote:

Hi all

I have written an article about the recommended PCB Rev 2 modification that prevents potential destruction of IC402 (74CBT3253 BPF MUX) due to large parasitic oscillations. See?

This modification involves adding a small signal diode (such as 1N4148 but it is non-critical) to the Tx/Rx switch transistor Q508. It is highly recommended for any QMX Rev 2 owner whose kit or assembled radio was shipped during 2023.?

Very important to note:

1. This modification is NOT required for any QMX Rev 1 PCB... though if you don't read this note and you do it anyway, there will be no harm done.?
2. This modification is NOT required for any QMX Rev 2 PCB shipped in 2024, the QRP Labs team are already modifying all PCBs (kit and assembled radios) before shipment.?

73 Hans G0UPL

Hi all

I have written an article about the recommended PCB Rev 2 modification that prevents potential destruction of IC402 (74CBT3253 BPF MUX) due to large parasitic oscillations. See?

This modification involves adding a small signal diode (such as 1N4148 but it is non-critical) to the Tx/Rx switch transistor Q508. It is highly recommended for any QMX Rev 2 owner whose kit or assembled radio was shipped during 2023.?

Very important to note:

1. This modification is NOT required for any QMX Rev 1 PCB... though if you don't read this note and you do it anyway, there will be no harm done.?
2. This modification is NOT required for any QMX Rev 2 PCB shipped in 2024, the QRP Labs team are already modifying all PCBs (kit and assembled radios) before shipment.?

73 Hans G0UPL

Giuseppe iu8eun

Il Gio 4 Gen 2024, 10:27 Hans Summers <hans.summers@...> ha scritto:

Hi all

I have written an article about the recommended PCB Rev 2 modification that prevents potential destruction of IC402 (74CBT3253 BPF MUX) due to large parasitic oscillations. See?

This modification involves adding a small signal diode (such as 1N4148 but it is non-critical) to the Tx/Rx switch transistor Q508. It is highly recommended for any QMX Rev 2 owner whose kit or assembled radio was shipped during 2023.?

Very important to note:

1. This modification is NOT required for any QMX Rev 1 PCB... though if you don't read this note and you do it anyway, there will be no harm done.?
2. This modification is NOT required for any QMX Rev 2 PCB shipped in 2024, the QRP Labs team are already modifying all PCBs (kit and assembled radios) before shipment.?

73 Hans G0UPL

Hi all

I have written an article about the recommended PCB Rev 2 modification that prevents potential destruction of IC402 (74CBT3253 BPF MUX) due to large parasitic oscillations. See?

This modification involves adding a small signal diode (such as 1N4148 but it is non-critical) to the Tx/Rx switch transistor Q508. It is highly recommended for any QMX Rev 2 owner whose kit or assembled radio was shipped during 2023.?

Very important to note:

1. This modification is NOT required for any QMX Rev 1 PCB... though if you don't read this note and you do it anyway, there will be no harm done.?
2. This modification is NOT required for any QMX Rev 2 PCB shipped in 2024, the QRP Labs team are already modifying all PCBs (kit and assembled radios) before shipment.?

73 Hans G0UPL