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Re: QCX-mini Blown IC?

 

Hi Scott. That usually happens when you install a blank IC2 without the EEPROM file loaded. I suspect something happened to IC2 when it was shorted. The easiest fix is to order a new firmware chip from Hans. Maybe your?Dad could add that to the order for the new rig. Doesn't hurt to have another one. If not too late he could change the order for the new one to be on a different band.

I see you said QCX Mini in the title and QMX Mini in the note but fortunately the picture is of a QCX Mini. Good luck

73 ... Ron

On Sun, Apr 20, 2025 at 10:04?AM waters.scott via <waters.scott=[email protected]> wrote:
Hi all,?
My Dad just finished his QMX-mini build and after adjustments,(before casing) accidentally laid it on a spiral notebook and shorted something out. Now he gets the message ¡°Use original IC¡±.?

The only reference to this in the groups is from 2017 where someone tripped a protection fuse in an IC and needed to update firmware I think. Any idea if this is a simple fix? Is it a hardware, software or both issue? This is the 20M version that uses IC2 AT mega328. Is the IC2 likely the culprit? Dad ordered another kit thinking it¡¯s all fried but I suspect it can be a somewhat easy fix if we can trace down the issue.?

thanks all,
Scott
KF0OUH QMX builder (and SSB user :) )
?
Re: QMX #12v

 

The other factor in all of this is the plastic package design. The heat sink practice for those other styles won't necessarily work here. The qmx design takes all this into account. Many cw qrp transmitters use 2 or 3 bs170 devices. Running digital waveforms provides a bit greater stress. Keeping the voltage at 12 volts or lower helps.?
?
Curt
?
Re: QMX #12v

 

On 20/04/2025 18:54, Wiggle Pig via groups.io wrote:
Given that the usual failure in the finals is through overheating, as a number of examples have shown,
A number of examples have shown BS170s blown apart.
But is that due to overheating in service or a result of a high voltage causing one to short THEN blow?

73 Alan G4ZFQ
Re: QMX #12v

 

So, as a bit more information (not all of it, obviously as you need to be security cleared for that!) I was thinking more of mainly increasing the thermal mass a little and perhaps trying to couple it to the case with a thermal pad or similar.
I have no real intention of using this unit for high duty cycle modes at the moment.
?
I¡¯m aware of the intention that the tinned pad on the board is the majority of the heatsinking but having done a fair bit of design and dev work on small RF units myself I¡¯m all too aware that the mounting washer here provides the majority of the sink mass, with the pad and board structure also providing a good chunk. Given that the usual failure in the finals is through overheating, as a number of examples have shown, I intend to try to reduce that heat by sinking it a little better; replacing the washer with a better heatsinking arrangement will likely improve things.
?
tra
Piggly
Re: QMX+ with WA3TFS amplifier

 

Very interesting, Jim ! I believe you meant Q4 and not T1, that is the base of the ¡®3904.
?
And so removing C1 is also advised (or lifting one leg). I believe there are 1/8¡± jacks that can be wired to do this when plugged in - that is disable a connection. I may have these in stock.
?
I¡¯ll be out of commission for ¡®a bit¡¯ - having lumbar spine surgery in the AM. But once I am cogent again, I¡¯ll anxiously read what you¡¯ve come up with. :)
?
73, Jamie
WB4YDL
QCX-mini Blown IC?

 

Hi all,?
My Dad just finished his QMX-mini build and after adjustments,(before casing) accidentally laid it on a spiral notebook and shorted something out. Now he gets the message ¡°Use original IC¡±.?

The only reference to this in the groups is from 2017 where someone tripped a protection fuse in an IC and needed to update firmware I think. Any idea if this is a simple fix? Is it a hardware, software or both issue? This is the 20M version that uses IC2 AT mega328. Is the IC2 likely the culprit? Dad ordered another kit thinking it¡¯s all fried but I suspect it can be a somewhat easy fix if we can trace down the issue.?

thanks all,
Scott
KF0OUH QMX builder (and SSB user :) )
?
Re: QMX+: Hearing a tone only when LSB is selected

 

And that's with the QMX+. I don't hear it at all with my QMX HB.
--
73, Dan - W2DLC
Re: QMX+: Hearing a tone only when LSB is selected

 

Don,
I've gone back to 027, but when I was experimenting with the 003 beta, I could hear a tone on 12 meters the strongest, then 11 meters, 10 meters not as strong because the noise level is higher, and on 6 meters. I could hear it weakly in digital mode, not at all in CW, very loudly in LSB and there was some time or greater noise in USB as well. This is all with a dummy load attached. It doesn't seem to be injected in the RF stages, but somewhere in the digital to audio conversion - maybe. I can still hear it in those bands with firmware 027 as well, but much weaker and only in digital mode.
--
73, Dan - W2DLC
QMX: After installing Beta, processing in LCD and nothing else

 

¿ªÔÆÌåÓý

Hi,


After the installation of the latest Beta, the LCD shows only processing. Is this normal?

Few minutes later i un/replugged the powersupply and it works as expected, ok, a little bit better than expected.


A big Thanks to Hans for this awesome peace of hamgadget.

73, Jens
Re: CW Filters

 

Hello Hans,

I would like to respond to your concerns one at a time

On Fri, 2025-04-11 at 18:00:46 +0300, Hans Summers via groups.io wrote:
I don't think your proposal would work well, though I find myself
lacking a deep enough understanding to explain why clearly. Perhaps
someone else could contribute here also. But I'll try. ... Weaver
demodulation is used in some SDRs. A disadvantage is that there is a
hole in the response at the sub-carrier frequency (the CW sidetone
frequency, in your nomenclature). In the analog world it is hard to
make the hole small but in DSP it could be made a lot smaller, such
that it is unobtrusive on an SSB receiver. However for CW, I wonder
how that would work... the "hole" would be exactly at the center of
the passband, and the CW transmission could well have energy either
side of it, and given that the actual bandwidth of a CW transmission
could be only 10 or 20 Hz, even a small "hole" would have a marked
effect.
There is no "hole" in the Weaver modulation if we make it digital. All
the information of the received signal is present in the I and Q
channels.

Suppose we want to listen to a CW signal transmitted at 7020 kHz. We set
the VFO to 7020-12 = 7008 kHz. The mixed signals contain the sum and
difference of these frequencies: 14028 and 12 kHz. Only the 12 kHz
components pass through the lowpass filters in front of the ADC, and
appear digitally as cosine and sine of a 12 kHz signal.

We are now in the digital world. We mix the 12 kHz IQ signals with the
-12 kHz IF frequency. The mixer outputs two DC components, which are the
cosine and sine of the phase difference between the mixed signals.

These DC components pass almost unaffectected through the lowpass
filters, say ¡À50 Hz. The outputs are then mixed with the sidetone
frequency (700 Hz) before being fed to the speaker's DAC. We will here a
700 Hz sine tone.

Suppose we want to move the passband 20 Hz up. Then we adjust the IF
mixer to 12020 Hz and the sidetone frequency to 720 Hz. The received
signal will now appear as -20 Hz signals in the LP filter (the frequency
needs a sign in the IQ domain). We will still hear a 700 Hz tone in the
speaker, while the passband will be from -20 to +80 Hz around 7020 kHz.
We shouldn't adjust the VFO because that would change the USB output.

An additional problem is that you lose the advantage of doing the SDR
at a 12 kHz IF. The 12 kHz IF gives immunity to hum and noise which
can often be found on a direct conversion receiver near to (or within
a few kHz of) 0 Hz. Operating at a 12 kHz IF produces significant
advantages. The conversion to 12 kHz IF is quite trivial digitally and
computationally inexpensive because the sampling is at 4x this (48
ksps).
I still use the 12 kHz IF, as described above. The bias, low-frequency
noise, and hum are avoided.

Finally another problem. To obtain a 50 Hz bandwidth CW filter, you
would need to have a 25 Hz LPF. To do such a low pass filter in DSP
will require a very long (large number of taps) DSP filter. To avoid
this, it will be necessary to decimate down to a much lower sample
rate. Which is fine. But you cannot avoid the fact that there will be
a large delay through the filter. Intuitively and/or approximately
speaking the filter must be 40 ms long for a 25 Hz LPF.
There is essentially no (extra) delay caused by the implementation of
the filters. They run as a series of first or second order filters, not
as finite-impulse filters. The realizations of the filters are on
so-called balanced form, which makes them numerically robust. It is
possible to run them using 16-bit arithmetics. (I have been running it
on a 48MHz SAMD21 M0+ at 16-kHz.). The response of the filter will have
a delay, but this is determined by the bandwidth and type of filter.

The proposed filter works both for CW and SSB (Rx and Tx), without using
Hilbert transforms.


Best regards

Anders
Re: QMX issues

 

Lundi = French for Monday??

Jack, W8TEE

On Sunday, April 20, 2025 at 09:59:45 AM EDT, Jerry Lunday <hpceng@...> wrote:


Intersting name. I don't see many "day's".
?
73.
Jerry/k5sop
QCX Classic Case WANTED

 

I post a message like this every 6months or so in hope...

I'm looking for someone who has an original QCX Classic case they no longer want. This is the BaMa Tech case that was sold by QRP Labs for sometime. The case is not available new any more.

If you have such a case or maybe a cased QCX Classic that is fried and dead and you want to sell, please contact me andy.mm0fmf AT gmail.com.

I'm in the UK and Brexit etc. has made shipping to and from the UK much more "fun and challenging" now. But if you are in the EU or in the US I have friends/relatives in either that will handle shipping to me making it simple for you :-)

Here's hoping.

Thanks
Andy, MM0FMF
Power out on 60 mtr QCX+

 

Hi
I recently built a QCX+ for 60 mtrs. Everything works ok except that I only get about 1.5watts out into a dummy. load.? Just wondering whether any one has built a QCX+ for 60mtrs and what power? out? that is expected for this band .
look forward to any replies.
Keith G4TJE
?
CW Practice / Rag Chew Session

 

¿ªÔÆÌåÓý


On 4/12/25 I had a CW practice / rag chew session on 30 meters. I worked one station on 30 then switched to 17 and worked one station there:

Conditions started out OK on 30 but after an hour it went dead. I switched to 17 which seemed better but still not much action. SSN = 114, SFI = 157, A = 20, K = 2.

My next CW practice session will be April 21 at 09:00 EDT / 13:00 UTC on 20 meters. Anyone and everyone is welcome. This practice is intended for operators who are new to CW or they need some practice. IT DOES NOT MATTER HOW POOR YOUR CW IS. Mistakes are OK. Poor fists are OK. Slow speed is OK. Really slow speed is OK. This practice is meant for you to improve your CW. I will do my best to adjust to your skill level. Operate at any power level. If several stations show up, I will operate as a round-table control station. I will do it as a round-table so everyone gets a chance to transmit. Please listen to my directions.


Details:

Date - April 20 2025

Time - 09:00 EDT? 13:00 UTC

Band - 20 Meters

How to find me - I will find a clear frequency and call CQ. Go to the Reverse Beacon Network and search for my call sign AB8DF.

That will tell you what frequency I am on. Tune your station to that frequency and if you hear me give me a call. If there is a QSO in progress, please wait for a break in the action. Then send your callsign. If I hear you, I will invite you to join the QSO and start a round-table QSO.


Reply to this email if you have questions.


IT DOES NOT MATTER HOW POOR CW IS


Ed

AB8DF

Re: QMX with POTA Yesterday

 

Nice description Jason.
?
Can you detail or link the diode fix please?
?
Thanks
Re: QMX+ with WA3TFS amplifier

 

Allison, thank you, I will do that.? I had removing C17 on my list to test, but didn't try it.? I mistakenly thought that once PTT triggered the relay, it was a non-issue.? I see now that leaving C17 is a problem.
?
Early on I tested +5V to R6 without RF in and the current was stable at 1mA.? With RF in, the current was much larger and unstable, I guess due to the rectified RF!?
--
73,
Jim - AE5JE
Re: QMX issues

 

Intersting name. I don't see many "day's".
?
73.
Jerry/k5sop
Re: What do I check when QMX transmit stops working?

 

Have you Enabled TX PTT in PuTTy? If not here are the steps to do so.
?
  1. Navigate to the QMX Menu:?Access the QMX putty menu using the appropriate method for your QMX device (e.g., using the on-board keys or a connected computer).
  2. Locate the "Transmit" Setting:?Within the menu, find the setting labeled "Transmit".
  3. Enable Transmit:?Press the "E" key to enable transmission for the selected band.?This allows you to transmit on the chosen band.
  4. Locate the "TX PTT +5V" Setting:?In the same menu, find the option labeled "TX PTT +5V".
  5. Enable PTT +5V:?Press the "E" key to enable the +5V signal on the PTT connector during transmission.?This provides the necessary signal to activate the transmitter.
  6. Verify Settings:?Double-check that both "Transmit" and "TX PTT +5V" are enabled for your desired band to ensure proper operation.?.
Re: QMX only hearing static

 

Kai, please don't apologise. No duty for a fast reaction, it's our hobby.
?
Your result points more to a broken PCM1804. It's the highest probability. But to exclude something more you may test this:
  1. Check voltage at IC403 pin 2 and pin 14 to GND. Both should show around 1.6V (pulses with 3.3V high and 50% duty cycle.) But take care not to connect these pins to others. You may destroy IC204. And it's hard to have access to IC403. If you don't want to check these voltages, no problem. If the TX is working there is a high probability the two signals are ok.
  2. Check voltages at IC405 and IC406 pins 1, 2, 3, 5, 6 and 7 to GND. For all you should see something around 2.5V.
If you don't want to replace the PCM1804 by yourselves you may contact Jeff Moore (please check th forum for his name).
?
I wish you success. 73 Ludwig
Newly assembled QMX, SWR=1.5 with dummy load

 

Hey,
?
I just assembled this a few days ago, made a couple of contacts with an end-fed. What I found odd is that when I attached a 50 ohm dummy load to the output and measured SWR, it was around 1.5 on 20m and <2 on other bands. Surely it shouldn't be that? What may have I done wrong? Should I worry?
?
73 de HF2J
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