Thanks Hans
I still have a QDX enclosure fulfilled with a burnt QDX?
now it has a future?
-- I2RWR Roberto Ranzani - JN45mn
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Re: QDX FDT86256 Mosfet PA Modification
Hi Robert,
QMX uses a similar Class D PA. I think same mod should work fine. The only issue is there isn’t much real estate to place pa mod daughter pcb unless we ditch the case.
73
Barb WB2CBA
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Re: Newbee Q: Are there 'designated builders' for QRPLabs kits?
A good portion of that assembly time will be spent winding toroids, checking the turns count, checking the tap is correctly located, double checking and triple checking, then correcting turns count errors.?
I have been amazed at the dearth of complaints about toroid cores breaking. I worked in a couple of shops were wound inductors using toroids and the new guys took a few days to learn to wind an inductor without breaking a core in half. You always knew who the new guy was by the expletive laden tirades following a couple of hours successive core breaks.
Chuck?
WD4HXG
On Sep 21, 2023, at 7:23 AM, EA3GNU <Sadelta@...> wrote:
Just a quick note. Please, consider that building the QMX kit takes time. Before receiving it, I thought it would take me a couple of hours of work. It ended up taking me about.. 6-8 hours. I'm not a kit builder expert but I'm also not bad a it. Just take that into account when you ask some builder for the price of putting the QMX together... it takes time!
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Re: Newbee Q: Are there 'designated builders' for QRPLabs kits?
Just a quick note. Please, consider that building the QMX kit takes time. Before receiving it, I thought it would take me a couple of hours of work. It ended up taking me about.. 6-8 hours. I'm not a kit builder expert but I'm also not bad a it. Just take that into account when you ask some builder for the price of putting the QMX together... it takes time!
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Re: QDX FDT86256 Mosfet PA Modification
Hi Barb,
Nice work!? I have not looked in detail yet, wondering if you have assessed if your mod would also work in the QMX?
73,
Robert, WA2T
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Re: How to get output to tracking page
#u4b
Hi Dave,
I have it working.
I renamed the flight and changed the call sign to ZS6STN (my ARC).
I think it was related to using the same call sign and maidenheads.
73 Stewart
ZR6WT
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Re: QMX assembly successful but no receive or transmit
Thanks for the info Evan!
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Re: QDX FDT86256 Mosfet PA Modification
Sverre,
I did test on high bands. For 17m,15m and 12m no power reduction with standard binocular transformer windings but on 10m there is a reduction in power. If RTWST binocular transformer winding scheme is used all high bands power scheme improves significantly including 10m.?
73
Barb WB2CBA
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Re: QMX LPF for [40m/30m] - Version 1 measured results
Nick,
I only have a TinySA to test my LPFs with and the rejection but I did get some good plots from this. Usually, Hand builds my designs after send him the info and he checks on his up-market spectrometer. He hasn’t tested this yet.? If I can find you my TinySA screenshot amongst the plethora of pics I’ll post.?
Mind you, the LPF was tested on a 12V RWTST in the QMX.?
73
Ross
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On 21 Sep 2023, at 09:43, Nick G4IKZ via groups.io <nds12321@...> wrote:
?Hi Ross
I'm guessing you've done as much work on this topic as anybody. Do you have any idea of the inherent even-harmonic rejection of the QMX PA. If we knew that then we'd have a better idea of what filtering is actually required. I'd measure my own but my entire QMX is now toast.
- Nick.
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Re: QMX LPF for [40m/30m] - Version 1 measured results
Hi Ross
I'm guessing you've done as much work on this topic as anybody. Do you have any idea of the inherent even-harmonic rejection of the QMX PA. If we knew that then we'd have a better idea of what filtering is actually required. I'd measure my own but my entire QMX is now toast.
- Nick.
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I do have a 20/17/15 design as well.?
73 Ross?
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On 21 Sep 2023, at 09:38, Nick G4IKZ via groups.io <nds12321@...> wrote:
?Multi-band filters involve an interesting design issues when using the existing QMX filter topology. So it's good to see people looking at the alternatives and posting their results. I'm not sure if you know about 'NanoVNA saver' but it's an easy way of controlling your NanoVNA from a PC and downloading the sweeps from it.
The issue with the existing topology is this.
At first glance it might seem that tri-band filters such as for [20m/17m/15m] would be just as easy to implement as dual-band filters for [80m/60m] or [40m/30m]. After all the fractional bandwidth is very similar for all of them. But there's an important difference. In the dual-band designs the frequencies of the upper and lower bands are in a ratio that fits nicely on to the second and third insertion loss ripples of a fifth-order Chebyshev response. And for the same reason they also fit nicely with the regions of good return loss. So with a little patience the filter responses can be optimised to 'fit' nicely on the two bands. That's basically what I did in my designs for [80m/60m] and [40m/30m]. And it would also be possible when designing a dual-band filter for [20m/15m].
But in such a dual-band filter the 17m band is then at a frequency where the opposite situation is true. 17m is then in the region where insertion loss of a fifth-order Chebyshev is greatest and return loss is worst. The [20m/15m] filter can of course be modified to improve the performance in the 17m band. But that then limits the second harmonic rejection. So the performance of multi-band filters with the existing topology will involve more design compromise - and that will have an impact on the VSWR seen by the PA.
I guess another option is to have three single-band LPFs and accept that it's then just a three-band radio. That would allow excellent harmonic suppression with very good filter match. But I doubt if many builders would want to do that.
Please keep posting your results!
- Nick.
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Multi-band filters involve an interesting design issues when using the existing QMX filter topology. So it's good to see people looking at the alternatives and posting their results. I'm not sure if you know about 'NanoVNA saver' but it's an easy way of controlling your NanoVNA from a PC and downloading the sweeps from it.
The issue with the existing topology is this.
At first glance it might seem that tri-band filters such as for [20m/17m/15m] would be just as easy to implement as dual-band filters for [80m/60m] or [40m/30m]. After all the fractional bandwidth is very similar for all of them. But there's an important difference. In the dual-band designs the frequencies of the upper and lower bands are in a ratio that fits nicely on to the second and third insertion loss ripples of a fifth-order Chebyshev response. And for the same reason they also fit nicely with the regions of good return loss. So with a little patience the filter responses can be optimised to 'fit' nicely on the two bands. That's basically what I did in my designs for [80m/60m] and [40m/30m]. And it would also be possible when designing a dual-band filter for [20m/15m].
But in such a dual-band filter the 17m band is then at a frequency where the opposite situation is true. 17m is then in the region where insertion loss of a fifth-order Chebyshev is greatest and return loss is worst. The [20m/15m] filter can of course be modified to improve the performance in the 17m band. But that then limits the second harmonic rejection. So the performance of multi-band filters with the existing topology will involve more design compromise - and that will have an impact on the VSWR seen by the PA.
I guess another option is to have three single-band LPFs and accept that it's then just a three-band radio. That would allow excellent harmonic suppression with very good filter match. But I doubt if many builders would want to do that.
Please keep posting your results!
- Nick.
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Re: QMX LPF for [40m/30m] - Version 1 measured results
?
?
Nick and Ryuji,
Here’s my SOTA 30/40 LPF design it measures quite well after building
73
Ross
Sent from my iPhone 6
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Re: replaced SMPS cards and the QMX is not detected by win 10 to load the firmware.
Old fashioned fault finding. ?
ignore the windows detection for now. ?and Look at the circuit. See if a resistance measurement across +to- ?(caution. your meter may not be +ve on the red lead. Testing a diode is an easy check)) can see a problem and so avoid testing in ‘smoke mode’ with power on.?
Print out board layout
Remove components or cut tracks (to isolate the part of the circuit drawing too much current) marking what you did on the print for later restoration . ?
Check component placement and polarity?
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Re: replaced SMPS cards and the QMX is not detected by win 10 to load the firmware.
By increasing the current to 1 A the Qmx turned on for about 10 seconds, it was connected to the PC with win 8 and it was detected, then I smelled a burning smell and I immediately disconnected the voltage, I noticed that the card underneath the SMPTs was a little hot and it didn't turn on anymore.? I hope it can be repaired.? 73 Giuseppe iu8eun
Good evening everyone, today the SMPS cards arrived after almost a month of waiting, the post offices here in Italy work badly, well, this evening I replaced them, no shorts on them, I carefully checked all the soldering and I have no found no problem, I connected the QMX to the PC and it is not detected by win 10 whether powered with 7V or with 8, 9 and 12 V at 500 mA. Would anyone have any suggestions for me to do further tests.? Thank you very much 73 IU8EUN Giuseppe iu8eun
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Hello Roberto
Ross EX0AA has had success using QDX-M built directly for 6m.?
Hi all QRPers
I'm a QDX builder/user and want to try 50MHz activity. Any suggestion about transverter or rtx kit?? Any future project from our Guru?
73
Roberto
--
I2RWR
Roberto Ranzani - JN45mn
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Re: Bench power supply for QDX, QMX etc
Use what you have and filter it with a Drok buck boost device for $16 USD.?
Boost Buck Converter, DROK DC 5.5-30V to 0.5-30V 5V 12V 24V Output Adjustable Power Supply Regulator Module, 4A 35W High Power Voltage Step Up Down Converter Board with Case LCD Display https://a.co/d/e07r1CU
I use batteries, SLA or Lithium, or shack supply but run it though the Drok first.
Remember that each time you turn it on you need to check and possibly readjust the Drok to 12 volts. It doesn’t have a memory. At least that is my take on it. I’ve only been using it for a week. I have a bunch of 7 A SLAs and after a few uses are down to 12 volts. Be careful of the Lithiums or the 13.8 v shack supply.?
It works for me.
Dave K8WPE since 1960 and haven’t smelled or seen the magic smoke in quite a while. ?The QMX is quite a radio. I was gifted one from a friend and so far have been very ?impressed. Thank you Hans. ?But then again, what QRP Labs kit isn’t a beautiful thing in the kit and/or assembled. I have assembled many of Hans kits since he began production.?
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On Sep 20, 2023, at 11:31 PM, Tom Henderson - N6QDI <n6qdi@...> wrote:
? I'm a bit of a newb.
What bench power supply would you recommend for building kits like the QDX and QMX?
I would prefer to buy a new product (vs used) and if possible like to keep the price to $150US or less.
There are MANY power supplies in this range;? it is hard for me to compare.
If anybody has a suggestion please reply!
Thanks in advance!
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Re: QMX assembly successful but no receive or transmit
"On the pcb there is a footprint for an sma
connector. Make sure there is not too much solder and making a connection."
I think this short to a SMA pad can easily hapen if installing BNC too low on PCB. I would suggest Hans to include a word of caution about this in the Assembly Manual.
73 Bojan S53DZ
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Hi all QRPers
I'm a QDX builder/user and want to try 50MHz activity. Any suggestion about transverter or rtx kit?? Any future project from our Guru?
73
Roberto
--
I2RWR
Roberto Ranzani - JN45mn
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Re: QMX LPF for [40m/30m] - Version 1 measured results
Ryuji,
The response and values that I posted to Tony are OK but better filters are possible. For [40m/30m] this is better:
390pF, T30-6 16 turns, 620pF, (T30-6 13 turns//150pF), 330pF.
The attached simulation sweeps show 17dB R.L> and 24dB second harmonic rejection.
This still isn't quite right but it's closer. The real problem isn't in deriving the ideal values for the best filter, but in going from those to a filter that can be made with the available inductor and capacitor values.
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Barb WB2CBA
Stewart ZR1WT
Bruce Akhurst
David Wilcox K8WPE