Re: LCD Display error on new assembled QMX?
No luck with pressing on that area.?
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A friend of mine, an OM, had an LCD unit. I have now replaced this and the defective one is going back to Hans via the OM on the Ham Radio.
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Re: Input voltage for QDX Digital Receiver
On 27/12/2024 15:59, Nick Garrod via groups.io wrote: section 4.3, Hans has provided a graph of output power against voltage Looking at the charts I'm not sure Hans has said how to get it to work at 5 Volts when the regulator must have an output a fair bit less than that. I guess maybe the QDX will still work? I run mine at 7.5 Volts and have series diodes to feed the PA dropping that to around 5 Volts, I Watt output. I do not think I ever ran them at 12 volts, 8 Watts output seems scary! 73 Alan G4ZFQ
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Re: Enhance QMX+ To 10W SSB QRP
Dale,
The SSB Peak Envelope Power (PEP) of a 5 watt radio is 10 watts, but Hans is working on having the QMXs use Controlled Envelope Single Side Band (CESSB) which sort of levels up the peaks of the side-band envelope. Here's his explanation, or at least part of it: /g/QRPLabs/message/130882?
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73, Dan - W2DLC
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Thanks.? I just wanted to be sure that it wasn't just me.? I don't have any deadlines to meet for this kit.
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Have a happy New Year!
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Chris / W2BPL
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Re: Input voltage for QDX Digital Receiver
Hi Robert, all the information you require is in the QDX manual.
If you look at section 4.3, Hans has provided a graph of output power against voltage for both the 9 and 12V versions. From the graph 9V would give roughly 2W output from a transformer wound for 12V. The critical factor is not exceeding 6W output on TX. ?Receive isn’t an issue as the linear 5V regulator is quite robust and it’s absolute maximum rated input is 35V, however it would probably have shutdown due to thermal overheating before you reached that figure, plus if you activated transmit, your output transistors would have turned into three legged fuses.
The recommended minimum input voltage for the 78M05 to maintain regulation is V out plus 1.8, so 6.8V. So 9V is not too low. 73 Nick G0OQK.?
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Re: Input voltage for QDX Digital Receiver
It will work just fine. Your output power will be less, but hey lots of contacts to be made.
Happy New Year.
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Show quoted text
On Dec 27, 2024, at 10:16, Robert Rabin via groups.io <r.rabin@...> wrote:
? When ordering an assembled QDX Digital Receiver, the default configuration appears to be for using a 12V power supply. (There is a 9V option when ordering. What is the acceptable input voltage range with the default 12V configuration? Would 9V be too low?
Thank you!
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Re: Enhance QMX+ To 10W SSB QRP
Dan, are you saying the SSB enhancement will be equivalent to adding a 10w linear amp?? Could you give more details?
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Dale Hardin
KS4NS
Elberta, AL
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I eventually replaced the IRF510s. I also learned that lowering the QCX voltage in down to 11vdc or so greatly improved the amp output up to nearly 40w. not bad for 20m. I sat it on the shelf, well satisfied with myself.?
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Pulled it out the other day and found that it was acting weird again.? Now after a warm up and brief tx it quickly drops from 40 to 20 watts. then after it will drop almost immediately after key up.? like something is warming up and changing. Maybe a cap?
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So have been working through that issue and its been very evasive to me since I have the tools but limited circuit tracing skills. I have an Extech LCR meter which has a secondary ESR function that may help me find a bad cap if I can figure out how to go at it.
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regards,
Bryan, N0LUF
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Input voltage for QDX Digital Receiver
When ordering an assembled QDX Digital Receiver, the default configuration appears to be for using a 12V power supply. (There is a 9V option when ordering. What is the acceptable input voltage range with the default 12V configuration? Would 9V be too low?
Thank you!
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Re: Should I be disappointed?
I find the 10w amp works well on 20m with the 0.5W ?U3S connected via a 5dB attenuator?
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i have an alternative attenuator that has different values and a capacitor bypass that keeps the 10W on 20m and boosts the rather low 10m output to 3W - a series capacitor is a possible addition for the lower bands (which I currently don’t use)?
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Don’t bother with attenuator calculators much. ?Neither the TX output impedance or the 10w amp input is 50ohm resistive so beyond a first ( safe) high attenuation starting point it’s successive experimentation and spectrum analyser sweep as the radio steps through the bands?
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Re: QMX+ Receiver MDS measurements. (noise bandwidth of a FSK signal) (coherent CW)
Hello all, Note that FT8 vs CW cs SSB bandwidth MDS is a matter of specification.?
Converting from one noise bandwidth to another is a matter of adding 10 log (noise bandwidth ratio).
Similarly for FT8. Here the relevant noise bandwidth is 6.25 Hz (bandwidth of one tone). So you can calculate that for 2500 Hz noise bandwidth, the addition would be 26dB because 10 log (2500 / 6.25) = 26 dB. In other words FT8 has about a 26dB SNR advantage over SSB. All SNR reports in WSJT-X and JS8Call are normalized ro 2500 Hz noise bandwidths.
I would like to confirm that the noise bandwidth in a FSK signal is referred to a single tone. From my understanding, If we have 8 tones, to detect the symbol, we compare 8 magnitudes each other, polluted with 8 sources of noise.... So I was expecting an sensibility improvement of 10*log10(2500/(6.25*8))=17dB But I never found a clear explanation in textbooks about the topic. == A nice idea for these transceivers is to implement coherent CW, as explained some years ago in QST. With 6WPM, the BW is as low as 10Hz, and it does not need a computer to operate. But the lack of interest in these mode against QRSS3..30..60 make me think twice. Probably CCW benefits are less than the complexity of sharing a clock source between TX and RX. 73 dx and happy 25 eduardo ea3ghs
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Re: Input impedance of the Tayloe Mixer on the QDX-M for 630M?
The input impedance of the Tayloe circuit varies widely with frequency. For signals at the clock frequency it goes very high, infinite in the ideal.
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As the input signal deviates from the clock frequency the QSD input impedance falls rapidly, ultimately reaching a low value limited by the MUX channel resistance. It follows the bandwidth curve that the QSD develops?
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This behavior is not intuitively obvious. Far from it! It was confirmed in my simulations and also via Steve Dick's correspondence with Dan Tayloe himself.
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IMO a resistive pad could be used to limit the impedance excursions and make the performance of a preceding filter more predictable.
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Good question, OM ..JZ KJ4A?
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Hello Roland,
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D3 and D5 are switching correctly.? I thought of only D1 and D7 when I wrote the last post.? D1 and D7 are not switching correctly.? There may be an open connection.
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The resistance readings of the inductors are strange.? I would expect all four to be about the same.? Does L10 look different from the other three?? Was it replaced?
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Please take the R7/R13 junction voltage readings (Qdrain) for transmit and receive in practice mode, as the D1/D7 readings show a problem.? The voltages at the gate of Q4 indicate that Q6 is working correctly.
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Also, measure the voltage on both sides of L9 in both transmit and receive in practice mode.
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73
Evan
AC9TU
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Dears,
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I wish to all of you Happy Holidays and healthy year 2025!
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73 - Petr, OK1RP
QMX Midband #5278 | fw: 1_00_019
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Manufacturing is a challenge!!?
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Re: QMX and SDR++ on GNU/Linux
Yes, I tried that and different orders as well. dmesg shows [ ? ?8.418077] usbcore: registered new interface driver snd-usb-audio
... [ ? 45.132326] usb 1-4: USB disconnect, device number 4
[ ? 46.522527] usb 1-4: new full-speed USB device number 10 using xhci_hcd
[ ? 46.665037] usb 1-4: New USB device found, idVendor=0483, idProduct=a34c, bcdDevice= 1.00
[ ? 46.665040] usb 1-4: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[ ? 46.665041] usb 1-4: Product: QMX Transceiver
[ ? 46.665042] usb 1-4: Manufacturer: QRP Labs
[ ? 46.667477] cdc_acm 1-4:1.0: ttyACM0: USB ACM device lsusb shows Bus 001 Device 010: ID 0483:a34c STMicroelectronics QMX Transceiver
More over?gnome sound settings shows internal microphone, analog input QMX Transceiver?and Digital Input (S/PDIF) QMX Transceiver?options. Changing in QMX->Digi Interface->IQ from Enabled to Disabled or other way around does not change anything when it comes to devices in dmesg or lsusb.
I think it's seen as an Audio device and not a digital audio interface and this is a problem. This video shows? that it should show up as Digital Audio Interface, which is not the case for me. Am I correct about this ? My audio quality or waterfall is nowhere near the look on that Youtube video.
Did you power-cycle the qmx after you connected the USB cable to the computer?? QMX does not initialize its internal USB support unless the connection is present at startup.
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Hello Chris
We used up the 1,000 sticky feet I ordered from Amazon Turkey. There was actually a little drama because the seller only sent 500 (10 packs of 50) which was different to the description on Amazon. Of course I complained and they told me that the item description was in error and I should send back the 500 sticky feet and they would give me a refund. I told them no way, we already started using the sticky feet. Send the other 500 or refund half my money. They insisted I should send them back. So I explained again, look, we already started using them. You either refund half?my money, or you send me the other 500... or if you prefer, I dispute it through Amazon or my credit card company and they will refund my ENTIRE purchase... they replied, they're sending the missing 500. Consumer rights occasionally works.?
Anyway that took time but for sure I can't order from that seller on Amazon again... so meanwhile I had ordered one packet of 50 from a different domestic source, and they arrived, we tested them, they are good. So I ordered another 15 packets (750 feet) and now we are waiting for those to arrive. Allegedly they should only take a day or two but...
So I'm sorry - there is still a bit of a delay :-/?
On Fri, Dec 27, 2024 at 6:40?AM Chris / W2BPL via <kwaj.speedo= [email protected]> wrote: Is there still a hold up on QMX+ kits?? I have not progressed from Complete to shipped on 10 days.
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Chris / W2BPL
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Hello Evan,
Here the results:
L1:? 1.7 ohms
L2:? 1.7 ohms
L10:? 0.5 ohms
L9:? 1.6 ohms
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Diode test: voltages on cathode (qcx in practice mode)
D3:? 0.07 v? (tx 5.05 v)
D5:? 0.07 v? (tx 5.06 v)
? ? ? ? ? ?It is low in rx and high in tx!?
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I also tested
D1:? 0.26 v? (tx equal)
D7:? 0.25 v? (tx equal)
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Mni tnx es 73, Roland
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Re: QDX Died shortly after arrival
#qdx
I have not heard of a burnt BS170 shorting out and causing high current draw and the radio not booting up. This one no longer has a USB interface - no sound card, no terminal access, nothing.
What really gets me is that I haven't found the source of the smoke. It looks pristine but has a short in the power circuit somewhere.
I bought a pair of used QDX's shortly after I placed the order for this factory built one (LB & HB) and they are both still working great. I don't think it's my station that's killing them.
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Input impedance of the Tayloe Mixer on the QDX-M for 630M?
Just going to mess with the RX filtering on the QDX-M for 630M.
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Does anyone know the measured input impedance there?? It has lots of variables if you calculate and I don't want to re-invent the wheel.
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I have an assortment of MCL RF Transformers and will probably use something like the 8:1 ADT8-1T+ or lesser step-up.
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Thanks,? N0UU
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Daniel Conklin
Chris / W2BPL
Dale Hardin KS4NS
Bruce Akhurst
Roland OE5ARN