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But unfortunately, there's no SWR sensing in the QDX...

73, Paul -- AI7JR

Interesting thought. I have not seen it discussed before here. Hans could switch to a 2 color LED or add a second LED to indicate when SWR protection has tripped (or add yet another blink pattern). And perhaps he could add a custom CAT command to read the SWR so it could be displayed on the host computer. Just dreaming...?

73, Mike KK7ER?

-- 
Paul -- AI7JR

Hi,

I build my QMX 1 week ago. The process run well and I'm able to use it.

However, I got some weird noise around 150Hz on WSJTX, as you can see in my screenshot. I trying both magnetic loop antenna and dummy load. It don't know were to search to find the reason on the noise. I tried a 9V battery and a USB-C PD set on 9V as power source but I still have the noise. I try with both ACG/VOX enabled/disabled.

I ran the sweep hardware test using the terminal access and all curve sounds good, according to the operator manual. I also verify my band settings on the menu and all correctly setup too.

Do you have any clue what can be the cause of that RX noise?

Thanks,
VA2HSW/F4HSW

Hi Chris - thanks for the reply and the schematic.

?However, I'm not understanding why, if I want to verify that QMX is actually grounding the tip of the plug when I transmit, can't I simply put my VOM across the two wires at the end of the cable plugged into the PTT jack of QMX? It should go from an open circuit to a closed circuit, yes? Is there something strange about that jack / connection that I can't see?
--
Jim / K7TXA
Eagle, ID

SKCC 10447T
BUG 301

Has anyone mounted the 10-watt linear amplifier in the case intended for the 50-watt amp??

Justin N2TOH?

Please disregard above. Jim, AJ8S, has suggested a product that my resolve my quandary.

A very good way to reduce risk is to limit the current available to the rig, I use a buck converter set to 12 volts out and with current limiting set to 0.7 amps. I use this one: For those of you running on batteries this device will also keep the voltage going to the rig at 12 volts even when the battery droops lower than that.

..if I am all wet of this, advice appreciated.
--
William, k6whp
--------------------
"Cheer up, things could get worse. So I cheered up and things got worse."

Sorry to hijack this thread, but I built my high band QDX to run off off 12VDC but realize that my gel cells can carry an initial charge of as high as 13.93 VDC. After treading the admonitions, I am hesitant to? power up the QDX with these unless I use a 78L12 or similar. The only problem is that the regulators are inefficient and require 2,5VDC headroom to operate. Similarly, buck converters require 1 VDC of headroom.

How is this situation addressed?

TIA!
--
William, k6whp
--------------------
"Cheer up, things could get worse. So I cheered up and things got worse."

Interesting thought. I have not seen it discussed before here. Hans could switch to a 2 color LED or add a second LED to indicate when SWR protection has tripped (or add yet another blink pattern). And perhaps he could add a custom CAT command to read the SWR so it could be displayed on the host computer. Just dreaming...?

73, Mike KK7ER?

Nice work! Thanks for sharing your ideas!

It works correctly with a paddle but the ring/tip option for a straight key is wrong.
Gary
W9TD

G'Day Matt
USB Power - May be worth noting that if you wriggle the connector & there is the slightest bad connection, then the Voltage negotiation sequence will start again..!!
Rob
VK5ZIK

Forgot to mention that USB current draw on transmit is less than 500mA when running the QDX on 5V from the USB data connector as mentioned. This is a picture of a USB power meter while transmitting with a QDX powered solely by 5V from the USB port on a Raspberry Pi 4.

Thanks Pete, ?

Just looked at the schematic. ?Thanks for the answer!!

Burt
K4SRQ

Apologies if this has been discussed. I searched and did not find anything relevant.

Are there are any plans to implement the SWR protection circuit from the QMX in the QDX? The QDX is perfect for certain applications due to the absence of controls.

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.