开云体育

I have not used a 5V to 12V boost converter, but I have added a couple diodes to my QDX to pull 5V from the QDX USB data port and apply it to the +12V and VCC rails to power the rest of the radio. Since the QDX transmit power is relative to the input voltage, powering it will 5V results in about 100mW of transmit power. I have made contacts at 1000 miles using JS8Call with this modification. Powering the QDX with 5v has been discussed in other posts in the past.

BE AWARE! There is a known "issue" with the QDX switching regulator when rapidly transitioning from a lower voltage to a higher voltage (i.e. connecting 5V from the USB and then 12V) that will destroy components due to over voltage. Always connect power first before the USB cable after making this modification.

My original post title may be misleading. The symptom I’m seeing is the noise is present continuously when Digi mode is enabled, not just during the switching transitions.

Still investigating.

Cheers.

On Sat, Feb 24, 2024 at 11:52 PM, Burt Wizeman wrote:

Lost a Satruday on this Transformer!? Is there Continuity between A and B of T401 once it has been soldered in place?

Thank You,
Burt?
K4SRQ

Yes.? If you look at the circuit diagram, the primary and secondary of T401 are connected: the centre tap of the secondary is connected to the half-rail voltage derived by R401/R402.? The same voltage is used to bias the band selector switch IC to half rail.? Basically, all the terminals of T401 are connected together if you do a continuity check once it is soldered in place.
--
Peter Lee
G3SPL

Nice job Giovanni! ?You will have an easy time soldering in the new component if you clean all old solder from the pads with solder wick and flux,

?To test with a a VOM look for current with 12V on one lead and the other lead on the PPT tip or ring I would put a resistor in series with the 12V lead so that if/when the other lead shorts to the PPT ground ring the current is limited.
Note: some amplifiers such as the MX-50 require the PPT to sink more current (~39ma) than R205 will allow.? I built a transistor buffer into my MX50 to fix the issue.? On my QDXs I paralleled the R206 equivalent to allow it to sink more current.? For the QMX I decided I should fix the amplifier.?
I built a buffer circuit for transceiver with either grounded or high PPT control, Circuit below Note I added a diode across the amplifier's relay to suppress switching spike,? If you only plan to use it with the QMX you don't need both buffers:

roebi via groups.io <roebi@...> wrote:

I had the same problem with THIS KEY on other radios, so I suggest you
check the key with other radio/keyers, if it is a problem of the key or
the radio.

This is strange. I tested the key with a multimeter and it's fine, it
didn't make any unwanted dits when dah was pressed.

But I also tested QMX by shorting tip-sleeve and ring-sleeve, and it
worked fine as well.

Now the problem disappeared completely, so I'm puzzled. I'll make some
more tests to rule out the key if the problem returns.

Hi,

I think it might interest (some of) you. I made myself something like
this:



And now the whole setup (QMX, power supply, speaker, key) is compact and
even more portable. I'll be testing it more, but so far it seems to be
working fine.

Lost a Satruday on this Transformer!? Is there Continuity between A and B of T401 once it has been soldered in place?

Thank You,
Burt?
K4SRQ

Mine one week old QMX works great tip and sleeve.

Hello, I have a question.

From the QMX page:
"GPS interface for frequency calibration"

I've found no information how to calibrate the frequency by using a QLG2? Where should I look?

73, Ludwig

Folks - I have two different QMX rigs - one low band (rev 1), one high band (rev 2). In the configuration I have enabled TX ground on both on each band. I've soldered in a short jumper to correct the trace error on these early boards. Both rigs are at firmware version xxx.17. I've plugged in a 3.5mm cable into the PTT jack on the right side. The other end is bare wires (for testing). I've attached my VOM across the tip and ground, press the key, and.... nada. No ground happening. I've tested continuity with the cable unplugged and also verified that the wires I think are tip and ground are in fact tip and ground.

?So, is there some other magic stuff I have to do to get PTT ground working?
--
Jim / K7TXA
Eagle, ID

SKCC 10447T
BUG 301

Jeffery fixed two of my radios.? ?One day they both stopped working; I thought they were done for.? ?A few months later, I saw a group.io about Jeff fixing QCXs and emailed him.? He fixed both and they run better than before.?
He is on a mission from God.
Rick KF4CGP?

Thank's, i order AOD403 MOSFET,?We'll see you again, 73 de it9xjj

I must controller other components??

I Desoldered!? Thanks for the encouragement! It9xjj op. Giovanni?

The noise on an ESD event here was exactly that sound at full volume. Have not had the problem after I switched back to the plastic knobs.
Gary
W9TD