Re: 10W HF Linear Power Amplifier
#10W_PA
On 25/02/2024 09:07, timo.vandermerwe@... wrote: I measure the ohms between *Ground and In* as well as *Ground and Out*. To my surprize it is around 0.3 ohms - basically a dead short. To DC. If you look at the schematic you see input and output has transformers. DC resistance very low. But reactance to RF is not low. 73 Alan G4ZFQ
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Hi Jim.?
I had made the same assumption as you when I first tested my QMX PTT out after firmware 017 was released and I installed the jumper as you have done. But Hans explained that the circuit in the QMX sinks an external current, and a multi-meter can't be used to simply test tip to ground. It doesn't work that way.?
The device you want to trigger needs to supply some (low) voltage and current, and the QMX in the tip to ground configuration, will sink that current, looking like a short to the external device (but not to an ohm meter).?
In my case I need to trigger an external TX RX switch which allows my SDR Play receiver to share the same antenna that QMX uses. That device supplies 4v and a few mA of current (I forgot the amount) to that lead coming from the QMX, and the QMX effectively shorts that line (tip to barrel of PTT out) and triggers the device.
So, the QMX PTT out does in fact, work properly (once the board has the jumper installed, and the configuration settings are enabled for each band, as you've already done). It can't be tested with only an ohm meter, however.?
It can be tested using an external power source (3.2v for a typical LED) and an LED with current flowing through (in series with) PTT out tip and barrel. In QMX RX mode, the LED will be bright, when it goes to TX the LED will significantly dim or go off. (when configured as grounded on TX)?
So it does work as advertised, just not as both you and I assumed it would work.?
73
Roy - KI0ER?
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10W HF Linear Power Amplifier
#10W_PA
I measure the ohms between Ground and In as well as Ground and Out.? To my surprize it is around 0.3 ohms - basically a dead short.? What resistance would be expected here.? The amp seems to start-up fine and can be adjusted for bias.?
73 de ZR6TM
Timo??
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Re: GPS for frequency calibration?
#qmx
#gps
Hi Ludwig
Frequency calibration hasn't been implemented yet. It's not high priority because QMX has a high performance 25 MHz TCXO as standard, for it's frequency reference. Unlike QCX where it's an option. The 25 MHz TCXO is normally within a few Hz anyway.?
73 Hans G0UPL
On Sun, Feb 25, 2024, 12:59?AM < DH8WN@...> wrote: 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
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Re: QMX Audio Noise when switching to Digital mode
Or it might be no issue at all. The volume level on digital is just much higher than when on CW. Perhaps something I need to add an adjustment for. So this could be NO issue at all, just an expectations thing?
73 Hans G0UPL
On Sun, Feb 25, 2024, 3:59?AM < w6csn@...> wrote: 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.
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Re: Noise around 150Hz on digi mode with my
#qmx
Hi Quentin
This is a WSJT-X feature called "Flatten", which is intended to compensate for the imperfect passband of some crystal filters etc (with suitable calibration). On QMX the passband is already flat, it's a DSP filter and very flat. You need to switch off "Flatten". It's a checkbox at the bottom of the waterfall display screen of WSJT-X.
73 Hans G0UPL
On Sun, Feb 25, 2024, 9:14?AM Quentin VA4HSW/F4HSW via <qrp.le8b2= [email protected]> wrote: 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
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Hi Howard
> BE AWARE! There is a known > "issue" with the QDX switching > regulator when rapidly > transitioning from a lower > voltage to a higher voltage
You're mixing up with QMX. QDX doesn't have switching regulators. There isn't any such issue on QDX...
73 Hans G0UPL
On Sun, Feb 25, 2024, 4:11?AM Howard < howard@...> wrote: 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.
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Re: QDX SWR protection circuit?
#qdx
But unfortunately, there's no SWR sensing in the QDX...
73, Paul -- AI7JR
On 2/24/24 20:12, Mike KK7ER wrote:
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
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Noise around 150Hz on digi mode with my
#qmx
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
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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
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10 watt linear amp in the 50 watt case, can it be done?
Has anyone mounted the 10-watt linear amplifier in the case intended for the 50-watt amp??
Justin N2TOH?
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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."
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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."
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Re: QDX SWR protection circuit?
#qdx
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?
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Re: [QMX] Portable speaker, power bank, and key holder for the QMX
Nice work! Thanks for sharing your ideas!
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Re: #key #qmx QMX Straight Key Mode incorrect
#key
#qmx
It works correctly with a paddle but the ring/tip option for a straight key is wrong.
Gary
W9TD
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Re: QMX on a stick - a minimalistic SOTA activation
#qmx
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
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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.
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Re: QMX V2 - T401 Is there continuity between A and B ?
Thanks Pete, ?
Just looked at the schematic. ?Thanks for the answer!!
Burt
K4SRQ
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QDX SWR protection circuit?
#qdx
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.
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Paul - AI7JR
k6whp
Todd W2TEF
Gary W9TD
Rob VK5ZIK
Burt Wizeman