CW Practice / Rag Chew report for 1/10/25 / announcement
On 1/10/25 I had a CW practice / rag
chew session on 30 meters. I worked four stations:
| Date
/ Time |
Call |
Mode |
Bnd |
Name |
Power |
Rec |
Snt |
SPC# |
Comments |
| 1/10/2025
15:20 |
K4SVS |
CW |
30 |
Bill |
10 |
599 |
579 |
SC |
K3
at 10 watts 100 ft slopping doublet |
| 1/10/2025
15:19 |
W8TWF |
CW |
30 |
Tim |
10 |
559 |
339 |
FL |
K3
at 10 watts 100 ft slopping doublet |
| 1/10/2025
14:12 |
K9WA |
CW |
30 |
Jim |
10 |
579 |
579 |
IL |
K3
at 10 watts 100 ft sloppin doublet |
| 1/10/2025
14:04 |
K4CIH |
CW |
30 |
|
10 |
|
119 |
USA |
K3
at 10 watts 100 ft slopping doublet |
Conditions
were OK. SSN = 126, SFI = 162, A = 10, K = 3.
I will be doing another CW on the air practice session next
week after I recover from football bingeing . Anyone
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:
Time - TBD
Band - TBD
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
|
Guide to optimizing bandpass filters on QMX+
I ran the sweeps on the bandpass filters of my QMX+ and while some are excellent, some are quite far off.? Is there a guide to filter optimization a la QCX optimization, or a written guide to approach this systematically?? I think I might be able to figure it out using the utility and my scope, but why re-invent the wheel?
?
72
?
Charles - NK8O
|
You are probably just too close to your receiver. I have a number of U3S transmitters and found that to receive it locally I have to:
-Hook the QRP-Labs dummy load to the U3S
-Disconnect the antenna from my HF rig
-Move the U3S to the other side of my 1-acre property.
-And with my new FLEX radio I need to add receive attenuation.
?
Hope this helps.
73,
BrianB
N6CVO
|
If you are doing section hikes as day hikes then you have an infinite set of options.? If you are going to be staying out and having to carry a load, you really have to focus on what you can leave behind, and what you can carry that has multiple uses.
?
If it is the latter case then QMX is required.? simple plastic key, simple single band EFHW (I would recommend for 20 m) with a really small 49:1.? You would need to bring some light line for hauling up a bear bag anyway.? For tossing the line into a tree bring a small stuff sack that you can put pebbles in to make a throw weight.? You will need batteries for other things: headlamp, any other small electronics.? Find a battery that can be multi purpose across the QMX and your other battery needs.
--
Chris / W2BPL
|
Re: Best QMX AGC settings?
I have read over the descriptions of what they do, and
not knowing the architecture, I can't relate the settings
to the problem I am seeing.
I'm an engineer, whacking at problems randomly is rarely
productive.
I agree, but I would not say that trying settings which other users have found to be effective, would necessarily be exactly "whacking at problems randomly". It could be worth a try.?
Did you read from page 58 to 63 of the operating manual, these 6 pages contain a comprehensive description of how the AGC works and also how the whole receiver is architected, the stages the audio goes through etc. It also explains the meaning and effect of all the parameters of the AGC configuration.? ? When the AGC is exposed to nothing but strong signals,
like W1AW, it is by far the best I have ever used.?
OK at least this is good :-)?? ? When the AGC is exposed to high ambient noise outside of
the CW filter's bandwidth, the audio produces sounds that
simply cannot come out of a properly functioning CW filter.?
Sibilance and cracky sounds have high frequency components
out to the 9th harmonic and beyond.? They shouldn't be
coming out of a CW filter.
Yes and no. Firstly, I explained in the documentation that the AGC takes place AFTER the CW filter. In the steps I documented, the CW filter is at step 14 and the AGC takes place at step 19. Noise that is outside the CW filters bandwidth cannot effect the operation of the AGC.?
But if there is high ambient noise outside of the CW filter's?bandwidth, then there must also be noise inside the filter's bandwidth, there can't magically be a hole in the noise right at that point.?
However if the issue is that the action of the noise impulses causes a sudden action to be taken on the audio samples stream, an instant change in gain applied to the audio samples, then this instantaneous change (like any instantaneous thing) has high frequency components, which perhaps could explain the crackling you hear. Since the AGC processing occurs after the CW filtering, if anything happens too fast in the AGC and causes high frequency components, that would not be filtered out.?
I can test this here at my location also when I have a moment. I also have quite high noise. ? They audio levels seem too low to have driven any of the
audio hardware into clipping.? Much higher levels haven't.
I understand, I agree I don't think it is clipping.? ? I too am enthusiastic about this product, so I understand
the excitement it brings.
But, being reminded that I checked a box when I made my
purchase acknowledging this is a Beta release, as if that
makes my questions unreasonable, feels like something else.
Your questions are not unreasonable. Don't worry.?? ? I don't want to see your effort "knee-capped" by fixable
problems you don't know about.
I have heard this high frequency "crackling" too. With some settings of the AGC, and under high noise conditions. I suspect now that perhaps there is some immediate action being taken under impulse noise, which could be appearing as high frequency crackles because it is instantly applied; I could perhaps smooth it over the course of several samples to make it more gentle.?
I will look into this, I have put it on my list for investigation.?
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On Fri, Jan 10, 2025 at 04:04 AM, <demonbeavis@...> wrote:
I have looked for a setting in WSJT-X but can't see a 'don't decode my own' box.?
See attached.
?
?
-Nate
N8BTR
|
I assume it’s not uncommon to receive QRP labs bits in separate consignments? I received a box and some pots, etc. but no circuit board (VFO order)?
I ask because there was nothing in the package to say it was part of a consignment; or anything at all!
It's normal for Ultimate3S, Clock and VFO kits where the enclosures are shipped directly from China where they are custom-manufactured for QRP Labs. We always had them shipped directly. This is on the?QRP Labs website *somewhere* maybe
My apologies for the delay but we were?not able to ship VFO and U3S kits for several weeks because of running out of the Si5351A Synth modules; unfortunately manufacturing?was a bit slow this time (a "bit"?) due to the time of year; however the 500 new Si5351A PCBs are with FedEx and making their way here rapidly. I checked the tracking number?771251467363 and they are now in Istanbul. Next stop Izmir for import customs then a little road trip down south to QRP Labs' Towers. I should have them in hand mid next week I hope. Then we can start shipping the backlog.
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Re: QMX+ with ~1000 tone on 12M & 6M
Nevermind.? ( Thanks, Gilda )?
?
I see Jeff had one that was Version 2.??
?
Ill go back to my cave and ponder while the parts get here.
73
Dick
W4PID
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Re: QMX, one of op-amps self-oscillates at 25 MHz (or picks up the system clock?)
Hans Summers via groups.io <hans.summers@...> wrote: I think Stan has it correctly identified as a red herring, an artefact of
the measurement procedure (the 'scope). And also 833Hz doesn't match the
symptomatic 100Hz noise either.
I think I am inclined to suspect a partially damaged MS5351M chip. Not the
25MHz TCXO. Stan, Hans, You are both absolutely correct. I: 1. Connected an external, adjustable square wave generator to the oscilloscope, set it to around 25 MHz, and observed similar artefacts 2. Connected an LPF (4k7 + 10nF, so 3388 Hz) to the gate output, and saw no signal on the LPF output (just DC bias) Another lesson learned... I'll order 5351, hopefully I'll be able to solder it without damaging everything around. I hope it will fix the problem (or we'll be back at square one)...
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Just a thought, what frequency are you trying to receive on? Same as the u3s or +1500hz? double check.
I can see your spots so you are getting out OK. Can't be much wrong.
Andy
--
The universe is made up of Protons, Neutrons, Electrons but contains only one M0RON.
|
I assume it’s not uncommon to receive QRP labs bits in separate consignments? I received a box and some pots, etc. but no circuit board (VFO order)?
I ask because there was nothing in the package to say it was part of a consignment; or anything at all!
|
Thanks all: dummy load it is! And point taken about blowing Mosfets; I am paranoid about that!
|
Re: Ultimate 3S reciever question
Whilst it may be good practice to have a band pass filter for each band I have found that it is not strictly necessary with the receiver module although I am only using an indoor aerial and have no high power transmitters nearby.
As far as the relays are concerned somewhere in the U3S documentation is the comment that two relays can be switched directly because of their low current consumption. This may not of course apply to other relays.
?
Regards
Ian
G3VAJ
?
?
?
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Oddly now others can decode my 17m WSPR transmissions but I can't. I have looked for a setting in WSJT-X but can't see a 'don't decode my own' box.?
|
Hans,
Thank you for your most excellent explanation of the reasons the historic U4B antenna works the best.
?
Tom
K1FQY
?
|
Thanks for the replies, the screen shows WSPR on the second line of the screen and the call is GW4SYI, my callsign. The U3S uses a QLG1 GPS device for the timing. Is any other info required?
?
Lucien
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Re: QMX, one of op-amps self-oscillates at 25 MHz (or picks up the system clock?)
Hi Adam
I watched your new video, thanks.?
I don't think it is possible for the IC202 output to produce that kind of signal, which looks so perfectly like 25MHz at one timebase then 833 Hz at the other. Note that the frequency measurement in the bottom right of your screen indicates 25MHz also, which would probably not be the case if there was some kind of interruption going on.?
I think Stan has it correctly identified as a red herring, an artefact of the measurement procedure (the 'scope). And also 833Hz doesn't match the symptomatic 100Hz noise either.?
I think I am inclined to suspect a partially damaged MS5351M chip. Not the 25MHz TCXO.
Hans Summers via <hans.summers=[email protected]> wrote:
> Downstream of IC202 there isn't any "almost", this is the very reason why
> IC202 is there. You will have a 3.3Vpp output at IC202 output.
I do. The scope shows some overshoots, but probably the probe needs to be
calibrated.
> Can you take a similar video please for the signal at IC202 output?
Yes -- posted below.
> I'm still having trouble trying to convince myself that the 25 MHz TCXO is
> at fault here rather than - sorry to say it - some weird artefact
> introduced by the measurement itself (at the TCXO output / gate input).
Don't be sorry -- in the realm of high frequencies I'm not sure of
anything :) HF never fails to find ways to surprise me.
BTW, I find this frequency weird as well. It's very low, compared to the
nominal frequency of the TCXO. It's probably way too low to result from
some stray capacitances or inductances.
It might be some weird artefact. But the oscilloscope never had such
artefacts before (I have it for 14-15 years), and symptoms (intermittent
CLK0 and CLK1 at 100 Hz, precisely the frequency of the buzzing both
audible in the speaker and visible in WSJT-X's spectrum view) fit.
Here's a new video with:
1. Output of the IC202 gate at various time bases
2. Signal from the TCXO with C203 (capacitor coupling TCXO with the gate)
removed -- so it's a signal on unloaded TCXO
3. VDD after L201 (so the power line of the clocking subsystem: TCXO,
gate, synth chip), showing some very minor ripple of the same frequency (I
suspect it's the effect of the problem, not the cause of it, but at this
point I'm not sure of anything)
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Re: QMX, one of op-amps self-oscillates at 25 MHz (or picks up the system clock?)
Feedback from a CMOS gate output to its input will result in oscillation at some frequency unique to each chip. It’s impossible to predict the oscillation frequency but in general, yes, it will typically be a high frequency. This is not good practice but if you want to bias a logic gate, you should use a pull-up and pull-down resistor at the input to create a half-supply bias. How is this different than using the feedback resistor? Well, the gate won’t oscillate continuously without feedback. Rather, thermal and/or electrical noise present at the input will cause the output to randomly toggle (no fixed frequency) or it may just get stuck high or low.
Using a CMOS logic gate as a high-gain amp is a risky practice. Logic gates are designed to be switches, not amplifiers for low voltage input signals. Running a 1V p-p signal into a logic gate powered at 3.3V or 5V will probably work but the totem pole input stage will carry switch-through current and may spend too much time in the linear region. This can cause unwanted high-frequency oscillation during each state transition. This is why logic gates have a maximum rise-time and fall-time spec - to minimize time spent in the linear region so the gate won’t oscillate during transitions.
A better way to implement this would be to use a Schmitt trigger biased at half supply using its positive feedback to rapidly pass through the linear region. Still, I’ve never seen a CMOS gate wired with a feedback component in my 45 years of engineering. In fact, doing such a thing would absolutely prevent passing design reviews.
I see nothing wrong with the use of the circuit in this way in this application. Without any input signal, the circuit will indeed oscillate in the VHF region. However this is not the situation; the 25MHz TCXO signal is always present and the circuit is always locked onto it. Unwanted high-frequency oscillation during state transitions would require a many orders of magnitude lower input signal frequency with therefore very much slower rise/fall times than the 25MHz TCXO signal. No unwanted high frequency oscillation is possible during the state transitions at 25 Mhz which are much too short to cause any instability.
Every single microcontroller on the planet uses an inverter gate with a resistor across it to put it in linear mode, as the? amplifier of its clock oscillator circuit. It's called the Pierce oscillation configuration which is really a development of the Colpitts topology. Before we had microcontrollers and we had CPUs requiring an external clock, we used to do it with 74LS TTL. Before that, they even had resistor-feedback inverter gate oscillators clocking the CRAY 1 supercomputer.?
Many manufacturers have app notes on the topic; examples: - ? - note, most of the app note is about unbuffered inverters, it does mention buffered can be used too, but are less stable and more sensitive to parameter changes.?
- Plenty of interesting reads on Google search term "inverter gate feedback resistor"
This circuit works reliably in QMX and QDX transceivers. I don't think there's a problem here...
73 Hans G0UPL
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Hello Hans
?
I am a bit concerned as to whether my e-mails are getting to you? Sent 2 recently but not seen any replies?
?
73
?
Ian G4GIR
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Re: Ver 1 vs Ver4 QMX...going bonkers
Thanks again Stan...regardless of how I measure, with power applied, or after hitting the on push button, all I see is supply voltage of 11.94 where the red probe is pointing and maybe 11.83 for the black--nothing at all on the 6 pin plug--no voltage at all.
?
Scott
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BrianB
Chris / W2BPL
Richard Hattaway
M0RON
Chris G7LQX