Re: QMX Display Brightness
Hey Cal -?
Tried to look you up via QRZ to ask you a question about the AT-100M.
Here it is:
For Function #10 "Calibration" what setting do you use for 20W radios such as the Xeigu G90 or FX-4CR?
It's not 10w but it's not 100W either?
Thanks
Gregory
AC1NY
Boston
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Re: QMX enclosure question
Ok great.? Thanks for the quick answer.
The USB-C jack may create an issue and there will be no mic hole.
Nothin a dremel can't solve.
-mike/w1mt
On Wed, Sep 27, 2023 at 12:03?PM Brent Kaser <wb9uxn@...> wrote:
>
> I happen to have an extra QCX mini enclosure.? If I order a QMX will it physically fit in the mini enclosure, understanding that the silkscreening probably differs?
>
> Thanks,
> Brent WB9UXN
>
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Re: QMX RX BPF troubleshooting, a new clue
ALL:
If I have any question regarding the Zin(fRX - fLO) characteristics, it is more on how we can take advantage of it. If that function is a steep concave, particularly at lower fLO like 3 to 10MHz range, the BPF bank can be made with a single inductor optimized for higher bands and let the mixer reject the unwanted frequency. That would be very nice. It sounds a bit too good to be true to us but it would also be a big strike against someone trying to build a high sample rate wideband receiver.
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I have considered removing them as a last try. I've used them in my QDXs, but there was room to build a much beefier heat sink there. Also, as I've said before, with the number of dying BS170s I've had the sockets save the board. We'll just have to take it one thing at a time.
Thanks for the hint on using low temp solder. Good idea.
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Thanks, Cliff, your pictures are perfect. I still suspect poor heat removal from the BS170s.? Can't prove it from here in Michigan though. If you decide to eliminate the sockets in the future, I suggest using low-temperature desoldering alloy to remove them.? Less chance of damaging your board. /g/QRPLabs/topic/92402784/g/QRPLabs/topic/97094943/g/QRPLabs/topic/98831808Before you install new BS170s, clean all of the weird alloy off with desoldering braid and flux.
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Re: QMX enclosure question
The USB-C jack may create an issue and there will be no mic hole.
Nothin a dremel can't solve.
-mike/w1mt
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Show quoted text
On Wed, Sep 27, 2023 at 12:03?PM Brent Kaser <wb9uxn@...> wrote:
I happen to have an extra QCX mini enclosure. If I order a QMX will it physically fit in the mini enclosure, understanding that the silkscreening probably differs?
Thanks,
Brent WB9UXN
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I happen to have an extra QCX mini enclosure.? If I order a QMX will it physically fit in the mini enclosure, understanding that the silkscreening probably differs?
Thanks, Brent WB9UXN
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All,
Well now there's a thing.
Rx is now fine - original fault ????
Tx, is FUBAR!
I know why but not why.
In Rx there is a nice signal on the Clk0 & Clk1 lines at the Rx frequency and they are 90 Degrees apart.
On Tx then the frequency on those lines doubles! i.e. if 40M set then 15-ish MHz is seen. They are correctly phased on the gates of the FETs (removed but looks like I didn't need to).
If I run a sweep the Clk0 & Clk1 sweep across the frequency band set but Clk2 is ~2F
That's not right!
A reload of the firmware & factory reset results in the same result!
That explains the sweeps - all well out of range as Clk2 is also 2F not F.
Ideas - Hans?
Regards & thanks for the help
Nick
M0HGU
--
What your soldier wants - really, really wants - is no-one shooting
back at him. (alt.fan.pratchett)
Wed 10984 Sep 16:40:02 BST 1993
16:40:02 up 3 days, 23:37, 8 users, load average: 0.74, 0.38, 0.39
--
73 Nick M0HGU
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Re: QMX RX BPF troubleshooting, a new clue
JZ, I totally understand your concern, but as far as I'm concerned, that is a non-issue until it is proven to be a problem. It is probably a minor factor in the mess, but it is not the dominant factor as far as I see. You can't get distracted by minor factors and lose sight of the dominant factors... that's probably why a lot of people believe RF is too much voodoo and little theory.
The BPFs are low Q because (1) they are designed that way, and (2) the interaction with the TX LPF's reactance curve makes the BPF even wider passband by partially undoing the series resonance. I thought I explained above. My posts were chronological and they might have taken people to a mini tour to my experimental journey, which I know can be mentally tiring a bit. I can rewrite more clearly after the whole job is done.
As you see in my traces with (1) my finger on the LPF, dampening/detuning the filter operation, and (2) shunt resistor, dampening the LPF impedance swing both show the BPF response close to theoretical one. If you saw a significant deviation there, you would next look into the next suspicious element down on the list, but I'm totally satisfied with those filter responses for a practical transceiver. I only wish we could easily decouple the LPF and BPF on this very tight board space. Without doing something about this LPF-BPF interaction, doing something about the detector impedance will not improve the BPF operation to any appreciable level.
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QRP Labs ordering web page still shows?
QDX boards ran out and we are waiting on a new batch; your order will not be shipped until around 11-Sep-2023 (estimated).
I have not been following the recently and a quick search of postings did not provide and answer.
Are QDX kits shipping again or is there still a wait for QDX boards?
cheers, Graham ve3gtc
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Re: QMX RX BPF troubleshooting, a new clue
Hi Evan,
The BPF plots do a fine job of assessing receiver sensitivity at any given frequency. That is exactly how they work, and that is very helpful in providing feedback to the builder that he has done his job correctly.
The filter plots do not provide a correct view of the susceptibility of the receiver to unwanted signals distant to the receive frequency, as these plots know nothing about the intrinsic BPF property of the Tayloe circuit.
Further, the plots know nothing of possible interaction between the highly varying Tayloe input impedance and the LPF/BPF chain response. This, precisely because each data point is taken basically right at the clock frequency. The impedance presented by the Tayloe circuit is then the same at each data point.
The plots I have been seeing appear to show receiver BPF responses that are very low Q. Their broad width suggests that they feed into a resistance of several hundred ohms. At the detector side of the input balun it would be 4X higher.?
In reality, at various distances from the clock frequency, the series LC circuit BPF may see anything in the range of a few tens of ohms to a few thousand ohms. But we don't look there. We only look 12 KHz away from the clock, at each and every data point.
Complex stuff...JZ
On Tue, Sep 26, 2023, 9:07 PM Evan Hand < elhandjr@...> wrote: Hi John,
I have to disagree with the invalidity of the BPF sweep.? Granted that it might measure total response as the receiver's sensitivity could change, the receiver is being adjusted to the desired reception frequency each time.? This means the clocks to the Tayloe detector are changed so any impedance would follow.? The one point I agree with is that the measured results would not be the same as if the BPF were scanned with a VNA out of the circuit; in this case, that would not matter as the only adjustments available to tweak the response are the L and C values of the BPF.
For the purposes of tweaking the BPF, the included sweeps make total sense to me.? As for modeling the response, that might be a different topic altogether.
73
Evan
AC9TU
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On 27/09/2023 14:10, Evan Hand wrote: Hi Nick, Evan - thanks - replies interleaved - it is a Rev 2 board The T button in the terminal transmitter test is a push button.? You need to hold it in to keep the transmitter on. Just seen that in the trouble shooting guide DOH! :-) When doing the transmitter test, what output do you get?? This would help determine whether it is in the common RF path for both receiver and transmitter or only a receiver problem. 0.08 - 0.12 W i.e. 80 - 120 mW If power levels on transmit are OK, then as Cliff points out, T2 could be the issue. Very not OK, the 'new one' is ~ 5 W each band (sl. less on 20M obv.) The sweeps point to the signal getting lost between C2 and IC10. That's my feeling but ... where there is continuity & R19 measures at 101K I would verify that you do not have a connection issue with the dummy load and the QDX BNC. Yes, checks good on three different ones! By chance, do you have a signal generator or a TinySA or NanoVNA that could act as one?? From what I have read, you do have an oscilloscope.? Verify that you can see the signal at a low level on your Oscope, then attach it to the BNC and trace it through the receiver parts of the radio.? You want to verify it is getting to the opamps IC7 and IC9 input.? They are 90 degrees out of phase between IC7 and IC9 at the output of the opamps.? An alternative to the signal generator is to add a temporary resistor parallel to R19 to boost the Sweeps generator so that the oscilloscope can measure the signal.? Here is the section of the QCX troubleshooting guide that explains the resistor bypassing: Yes: As far as I can see (schematic etc.) there is only one OpAmp chip on the QDX IC7 <snip> TinySA signal easily visible on the waterfall of wsjtx at -76dBm I suspect that Rx actually now works - off to try ... Yes, all good! Which rev of the QDX has the problem? Rev 2 and 2V5 is present on the 'mixer' The sweeps must be performed with a 50-ohm dummy load attached to the BNC. Indeed! So TX debugging it is. Thanks for the help Off to check on the 5351 /et al/ Then LPFs out and ... Regards Nick M0HGU -- In the Beginning It was a nice day. (Terry Pratchett & Neil Gaiman, (Good Omens) Wed 10984 Sep 15:05:01 BST 1993 15:05:01 up 3 days, 22:02, 8 users, load average: 0.69, 0.75, 0.69 -- 73 Nick M0HGU
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Re: Fault during transmitting
Thanks for the tips. According to the diagnostics, the BIAS SMPS is fine, even though the output signal then becomes poor. I need to get some cold spray or something for further tests.
Apart from that, the behaviour of my QMX is getting more and more mysterious.
I used an oscilloscope to look at the signals at the gate and drain of the Q503-Q506. At the gate everything was fine, even though the RF output became dirty after a while. At the drain, the signals also appeared normal at first. From the moment the RF output became unclean, a twitching could be seen. I can hardly describe this with my limited knowledge of English. I suspect that the output signal is temporarily interrupted.
For further troubleshooting I removed L502 and retinned the wire ends. I don't know that that matters. Anyway, the signals at Q503 - Q506 are now about twice as high as the set frequency. I have no explanation of that. What could be the cause?
73 - J?rg, DG0JDE
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Re: #u3s FST4W on the U3S?
#u3s
On 27/09/2023 12:40, VA3NCA Wayde via groups.io wrote: Hi Everyone,
Is there any possibility that a future fw for the u3s could support FST4W beacons? Perhaps with the GSPDO it would have the clock stability to be a pretty nice little FST4W beacon, perhaps even up into some of the HF bands, no? The minimum requirements for FST4W to be useful is a nice clean signal, the Si5351 is capable of this. As you realise frequency stability is also required, FST4W decoders do not allow for much drift. (Another thing that can help is absolute frequency accuracy but stability is more important.) With the U3 the GPS will not make it more stable, it is set once per calibration cycle, the crystal can drift in between. The QDX can transmit a signal suitable for spectral width measurement, so therefore the U3S could. It has to have the TCXO or other reference remote so heat does not affect it. The U3S may have a TCXO fitted, it may be good enough if the TCXO is insulated, it is not so likely to be affected by PA heat. FST4W is just like WSPR but with extra measurements of the signal. It shows on WSPRnet and could replace WSPR in the U3S. 73 Alan G4ZFQ
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I sent my QMX to Jeff W1NC for repair but unfortunately I managed to blow the CPU because of lousy soldering.? He is very professional and quick so if you need any QRP Labs gear repaired give him a shout - I highly recommend him.
And because I am apparently a glutton for punishment I ordered another QMX kit hoping I learned enough lessons the first time.
73, Bill NZ0T?
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Re: QMX - Looking for troubleshooting advice
I noticed that L509 is a 47uH inductor. Depending on the particular inductor model, the winding capacitance is usually on the order of a few picofarads, and the self resonance frequency can be as low as single digit MHz range. Above the self resonance frequency, the "inductor" appears as if it were a capacitor to the circuit. That may cause the LPF cutoff frequency to move lower. I think 47uH on 20m is probably ok in the majority of cases but I can imagine individual variability may bring it to an iffy zone in some cases. A smaller inductance may avoid this altogether. (Good to keep 47uH for the lower bands though.)
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Re: QMX - waiting for Qcx part..
FWIW, my QMX volume encoder was faulty and had to be replaced.? The best way to confirm the functioning of the encoders is thru the terminal program and go to the hardware tab.? There you can confirm the proper functioning of all the buttons/encoders/keys.? My volume encoder on the left had a working push button but faulty rotator dial and had to be replaced.
AB4BA
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Re: QMX - waiting for Qcx part..
Hi Matthias,
Mike stated that the left encoder should work, although the volume operation could be improved (Hans - maybe implement a log taper in software like most audio resistors use).? I had your issue with my first QMX that ultimately failed (be careful when testing when out of the enclosure - Pressing the encodes in can flex the boards and cause problems).? There have been updates to the assembly manual and posts on this server that point out possible shorts to the power connector (I have since taped that off for my 2nd kit).
Verify that all 5 pins of the encoder are connected.? It is easy to think you have them connected when they are open or shorted.? In my case, it was the center pin of the side with 3 pins.? It was not soldered in correctly.? For my second build, I installed the encoder with the washer and nut before I soldered the leads.? I ensured the leads were as far in the holes as possible (Hans - maybe a suggestion for the assembly manual?).
Do you get any sound out of connected headphones?
73
Evan
AC9TU
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Thanks, Cliff, your pictures are perfect. I still suspect poor heat removal from the BS170s.? Can't prove it from here in Michigan though. If you decide to eliminate the sockets in the future, I suggest using low-temperature desoldering alloy to remove them.? Less chance of damaging your board. /g/QRPLabs/topic/92402784/g/QRPLabs/topic/97094943/g/QRPLabs/topic/98831808Before you install new BS170s, clean all of the weird alloy off with desoldering braid and flux.
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On Tue, Sep 26, 2023 at 11:10 PM, Evan Hand wrote:
Alex,
175 ma seems high. ?I would remove the 5BS270d and see if the current drops. ?An alternative would be to disconnect one of the two leads of L14. ?Also check if IC2 is hot. ?That is a potential IC5 failure again.?
73
Evan
AC9TU
Wow, I need NOT to use my iPhone to respond to this list server.? Sorry for all of the typos. The message should have been: 175 ma seems high. ?I would remove the 4 BS170s and see if the current drops. ?An alternative would be to disconnect one of the two leads of L14. ?Also, check if IC2 is hot. ?This is a potential IC5 failure again.?Good luck, and have fun hunting the issue. 73 Evan AC9TU PS: Hopefully, this does not come across as bossy.? If anyone, Hans Summers is the Boss.? I am just a volunteer responder not directly affiliated with QRP-Labs other than I have built many of their kits.
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Re: QMX - waiting for Qcx part..
Push button should work fine. If you're having problems with double
clicks then change the double click number to 500 in the menu (the
default is 300). If you're having other problems with the push button
you may have an issue with the control board.
Make sure you are using the latest firmware. Volume control sorta
works - what doesn't work yet if AGC.
-mike/w1mt
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On Wed, Sep 27, 2023 at 9:07?AM Matthias Rauhut <matthias@...> wrote:
Just built a QMX successfully. The Qdx part of the tcvr works, ie. FT8. But for CW its still useless. The Volume Control is unusable.
As well as the push button function. Its not working reliable. Hope the future FW will solve it, whenever it will be ready.
So for now the nice Trcvr rests in the drawer... ?
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Gregory Kenley
Ryuji Suzuki AB1WX