Re: QMX Band Pass Filter (and Band pass filters in general) question
Hi Jonathan
The analysis is too simplistic. The filters can be designed approximately using some theory (such as your calculation) but then in the real world the results differ considerably. There are interactions between the LPF and the BPF, and other components such as the load on the filter, termination impedances, and a lot of parasitic circuit elements such the capacitances of the BPF MUX switch pins, and of the PCB traces etc. Generally since these parasitic elements are ADDING to the desired circuit values, the resonant frequency?realized in practice is normally lower than the value given?by a simple calculation.?
In the QMX 80-20m version the lowest filter is used for 40/60/80, the mid filter for 30 and the highest filter is used for 20m. The use of few filters, and wide (single series resonant circuit) is a design compromise for the targeted small size and cost. The fact that the QSD intrinsically has such high performance mitigates the liberties taken with the BPF so the overall performance is still excellent. Other choices of receiver?architecture would differ. For example if using a much weaker mixer such as a <shudder>SA602</shudder> then you would probably like to use a much narrower and sharper filter to better protect the weak mixer.?
> I eventually want to have a 5 band circuit made of SMD? > components so I can shrink my design into a portable package? > so I am avoiding the QRP labs Band pass filters since they? > use transformers.
That's also a compromise, size vs performance. Trade-offs, trade-offs. Physically smaller inductors have lower Q and lower saturation levels.?We assume that in a receive application, flux density is not important as we aren't passing watts through the toroids however in reality flux isn't something that is zero until a certain level then suddenly kicks in. Smaller inductors can easily become the limiting factor to performance of the whole radio. That depends on the rest of the radio architecture. But it is worth bearing in mind if you are aiming for a high performance front end.?
Martein PA3AKE's pages? are an excellent read, and specifically in this instance, his discussion on IMD in toroids:?
But in the end it's all trade-offs, if very small size is critical then some sacrifice has to be made.?
On Thu, Feb 29, 2024 at 9:07?AM Jonathan Kayne, KM4CFT < jzkmath@...> wrote: Hi,
I am currently in the process of designing a band pass filter for a homebrew CW radio I want to build. I was looking at the bandpass filter design for the QMX and was confused because the passband of the filter doesn't seem to match up with anything on the appropriate bands.
If I am reading the schematics properly, there are 15 and 23 turns on a T50-2 Toroid, which would have inductances of 1.1uH and 2.59uH respectively. Connecting them to the listed caps we have the following combinations:
- 1.1uH, 30pF: 27.7MHz
- 2.59uH, 56pF: 13.21MHz
- 2.59uH, 220pF: 6.67MHz
What confuses is me is the first combination which is clearly not in the 80-20 meter bands. I am pretty sure I am missing something but not sure what. I am not even sure if a single resonant band pass filter is the best option for my use.
Honestly I have been at my wits end trying to design a functional band pass filter, because when I simulate a filter in Elsie or RF tools, the passband on the built filter is off by a few MHz. Whenever I try to use recommended values from Experimental Methods in RF Design or Solid State Design plugging it into LTspice or Elsie yields a completely different passband. I eventually want to have a 5 band circuit made of SMD components so I can shrink my design into a portable package so I am avoiding the QRP labs Band pass filters since they use transformers.
Can anyone point out to me what is probably a blatent mistake I have made?
Thanks,
-Jonathan KM4CFT
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QMX Band Pass Filter (and Band pass filters in general) question
Hi, I am currently in the process of designing a band pass filter for a homebrew CW radio I want to build. I was looking at the bandpass filter design for the QMX and was confused because the passband of the filter doesn't seem to match up with anything on the appropriate bands. If I am reading the schematics properly, there are 15 and 23 turns on a T50-2 Toroid, which would have inductances of 1.1uH and 2.59uH respectively. Connecting them to the listed caps we have the following combinations:
- 1.1uH, 30pF: 27.7MHz
- 2.59uH, 56pF: 13.21MHz
- 2.59uH, 220pF: 6.67MHz
What confuses is me is the first combination which is clearly not in the 80-20 meter bands. I am pretty sure I am missing something but not sure what. I am not even sure if a single resonant band pass filter is the best option for my use. Honestly I have been at my wits end trying to design a functional band pass filter, because when I simulate a filter in Elsie or RF tools, the passband on the built filter is off by a few MHz. Whenever I try to use recommended values from Experimental Methods in RF Design or Solid State Design plugging it into LTspice or Elsie yields a completely different passband. I eventually want to have a 5 band circuit made of SMD components so I can shrink my design into a portable package so I am avoiding the QRP labs Band pass filters since they use transformers. Can anyone point out to me what is probably a blatent mistake I have made? Thanks, -Jonathan KM4CFT
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Re: QMX Feature Request - field “tune” mode
Hi all
I do think?W6CSN's request is fulfilled by the SWR feature in the hardware menu. However, it does need operational convenience improvements as Garrett KC3UNP says. It was already requested and on my list that the frequency and band should default?to the current operating parameters; then the left knob should adjust band and the right knob, frequency.?
Regarding a graphical sweep display: it is my eventual plan (but after other higher priority items) that all the graphical tools in the terminal screens (Image sweep, BPF, LPF, SWR sweep) should also be available in miniature form on the LCD; remember?we only have 8 characters to use for custom graphics but it is nonetheless possible to make a quite usable display from this. Some readers may recall, dare I say it, this QSX video? that demonstrates some code I wrote for that. It just needs to be adapted?and incorporated into QMX.?
On Thu, Feb 29, 2024 at 8:53?AM Garrett kc3unp < kc3unp@...> wrote: I find that the SWR feature under the hardware tests menu works very well for tuning (and power level of that SWR test is configurable in the setup menu to boot!), though it’s a bit tedious to access for your frequency in question, even if you’ve been in the menu just a minute ago. It would be great to have a shortcut from the operating screen. For anybody doing band switching, I suspect it’s more used than the presets or the A<>B functions (the latter of which has tripped me up a few times)
. Moving the GPS menu item out of the way in the hardware menu would help a bit for starters, but the functionality also suffers from pulling only off of VFO A frequencies, defaulting to a band you’re not operating in, and sometimes resetting your VFO frequency (possibly the worst culprit is the 60m band) when you back out of it.
But it works great both for manual tuning needs as well as triggering an auto tuner, since it’s not a sweep by default. That function has been fantastic, just has some usability quirks at present.?
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Re: QMX Feature Request - field “tune” mode
I find that the SWR feature under the hardware tests menu works very well for tuning (and power level of that SWR test is configurable in the setup menu to boot!), though it’s a bit tedious to access for your frequency in question, even if you’ve been in the menu just a minute ago. It would be great to have a shortcut from the operating screen. For anybody doing band switching, I suspect it’s more used than the presets or the A<>B functions (the latter of which has tripped me up a few times)
. Moving the GPS menu item out of the way in the hardware menu would help a bit for starters, but the functionality also suffers from pulling only off of VFO A frequencies, defaulting to a band you’re not operating in, and sometimes resetting your VFO frequency (possibly the worst culprit is the 60m band) when you back out of it.
But it works great both for manual tuning needs as well as triggering an auto tuner, since it’s not a sweep by default. That function has been fantastic, just has some usability quirks at present.?
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Re: list of acceptable digital modes?
Thanks Cliff, I noted that in the manual that they did not work with PSK31, frequency or phase shift, or any multi-tone modes. Olivia was acceptable, I'm hoping that Thor is also OK, and I may wish to try IL2P on HF as an alternative to AX.25 Ron VE8RT On Wed, 28 Feb 2024 21:08:04 -0600 "Cliff" <ae5zaham@...> wrote: Ron,
All the digital modes in fldigi, HRD, Wsjtx all work with the QDX, but not with the QMX unless you turn off the Transmit ID function. FT8,4, etc all work with the QMX.
73,
Cliff, AE5ZA
On Feb 28, 2024, at 20:31, Ron VE8RT <ve8rt@...> wrote:
Rather than ask only about a particular mode of interest, in this case
Thor, has someone put online a list of digital modes that do work with
the QCX QDX QMX series?
Ron VE8RT
--
Ron VE8RT <ve8rt@...>
-- Ron VE8RT <ve8rt@...>
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RF preamp for power amp - HF and 6 mtrs. Magic silicon does all.
here's a? design which I believe to be be mature that will take 3mW or so up to? 270 mW or so to drive RD15HH or similar mosfets.
No originality? claimed but? it's potentially useful to many ? well not many Qmx users ,? but hell I'ms sure Joe Biden or even? the CIA could use one.
Or indeed as a building block for the QSX.?
This OP chip from Tx has been around for quite a while and has been yanked into a? number of other? ham radio designs - which makes me suggest it is the only
one about with the HF performance and power output that can do this duty . Second source ?? prolly none.
The transformers appear to be from? Mini circuits but peoples can wind their own on bihole ferrites (generally type 43 for the IP - output side could be type 61.
NB I have some questions on how this chap has come up with the Av for the? first? chip. I get similar but not the same.? However I have to rush out will lealve for some other time.? NB nbt two - he makes claims for? Av only ,not power gain.? His claim that a given transformer is? lossless looks like Drek to me.? Trust be Verify...
Now there's a UKR outfit that is selling something like this? but with the RHS? Video amp condensed out and a cut and shut done.? Their one? is for? HF only and they claim? 10 W out at the? mosfets with? 12V Vcc and? 2mW of drive at? 50R .? I have huge reservations about that claim.? THe UKRs give no circuit details on ebay. They do give photographs of the component layout? ?and some of them concern me. I'll drop them in a later post, if any interest shown (and if their wsite is not shut down).
It appears that the? 5 plus 5? R? power resistors in the OP circuit are required to protect the OP when it is run into a nominal open circuit . Something similar appears on the? standard design cct? from Tx instruments for the intended use as a high tech communications driver? (modem duty).
I purchased? two of these chips from an Ebay seller at about? 7USD each.? That's about the going rate for suppliers like? Mouser too last time I looked.
in order to use the chip you need a Frit? to hold it and convert it to DIP or you have to design up a SM PCB.? Frits are available from likes of? Futurlec.com which is an Aussie outfit that pretends to be US based.? That's a statement not a recommendation.
Is there any other? Video amp that offers the same performance in a single chip -? does anyone know ?
Ok need to jump aboard my broom and flit off into the night....call sign for the design originator is on the lower RHS of the drafting sheet .? Looks Americano.
TEF
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Re: list of acceptable digital modes?
Ron,
All the digital modes in fldigi, HRD, Wsjtx all work with the QDX, but not with the QMX unless you turn off the Transmit ID function. FT8,4, etc all work with the QMX.
toggle quoted message
Show quoted text
On Feb 28, 2024, at 20:31, Ron VE8RT < ve8rt@...> wrote:
Rather than ask only about a particular mode of interest, in this case Thor, has someone put online a list of digital modes that do work with the QCX QDX QMX series? ??Ron VE8RT -- Ron VE8RT < ve8rt@...>
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list of acceptable digital modes?
Rather than ask only about a particular mode of interest, in this case
Thor, has someone put online a list of digital modes that do work with
the QCX QDX QMX series?
Ron VE8RT
--
Ron VE8RT <ve8rt@...>
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Re: Low Band Rev1 QMX for sale
The QMX has been sold. Thank you
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To further clarify, in case of QCX i used with one BS170 and currently with my QDX-M a pair of BS170 one in each side. Both operating with 5Volts? -- ?
73, Barb
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Re: Faulty Progrock2 - no response to ticket
#progrock2
Hi
Can not reach ProgRock2?
Try turning down bluetooth first
sometimes it create conflicts on com ports
73 de muhsin TA1MHS
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Re: QMX Feature Request - field “tune” mode
Is the "Hardware Tests" -> "Tune SWR" menu item sufficient for your use case? (%voltage settable in "Protection" menu)
On Wed, Feb 28, 2024 at 12:43?PM < w6csn@...> wrote: The SWR metering and protection are features that really make the QMX a field capable radio. However, from several outings now I’m finding that I would like a front panel means to activate a reduced power transmit setting so that I could make adjustments to the antenna tuning while monitoring SWR on the QMX.
Often my antenna is a rather high Q base loaded vertical in which small adjustment to the coil position can result in big swings in feed point impedance. I’ve been using an external SWR/Power meter which presents a 50 ohm load to the QMX while measuring SWR, but this meter is twice as big as the QMX itself and means an extra piece of equipment and coax jumper to carry into the field.
If I could, from the front panel menu enable, a “tune” voltage setting and corresponding tune mode SWR protection threshold, I could leave the external meter at home and dial in the the antenna tuning using just the QMX.
Stretch goal request: an SWR sweep around the operating frequency shown “graphically” on the LCD.
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Re: #qmx high band harmonics
#qmx
Thanks, Hans.? The tinySA has been on my list for a while.? Now I have a good reason to get one!
Eric
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QMX Feature Request - field “tune” mode
The SWR metering and protection are features that really make the QMX a field capable radio. However, from several outings now I’m finding that I would like a front panel means to activate a reduced power transmit setting so that I could make adjustments to the antenna tuning while monitoring SWR on the QMX.
Often my antenna is a rather high Q base loaded vertical in which small adjustment to the coil position can result in big swings in feed point impedance. I’ve been using an external SWR/Power meter which presents a 50 ohm load to the QMX while measuring SWR, but this meter is twice as big as the QMX itself and means an extra piece of equipment and coax jumper to carry into the field.
If I could, from the front panel menu enable, a “tune” voltage setting and corresponding tune mode SWR protection threshold, I could leave the external meter at home and dial in the the antenna tuning using just the QMX.
Stretch goal request: an SWR sweep around the operating frequency shown “graphically” on the LCD.
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Re: Magical smoke out of QDX, two leftmost BS170 very hot
On 28/02/2024 17:54, Volker Kerkhoff wrote: Should changing the 4 BS170 (I have been so cautionary to stock some) fix the issue or should I look at something else before, lest I burn them again straight away? Volker, Remove the BS170s. Test for 5 volts at the gate pads when in transmit. 0 volts receive. If good replace BS170s. Maybe consider a diode across L14, could protect against one failure mode. 73 Alan G4ZFQ
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Re: #qmx high band harmonics
#qmx
Hi Eric
I don't think 'scope FFTs are anywhere near good enough for HF transmitter harmonic testing, and get worse as the frequency goes up. The job needs a real spectrum analyzer. The TinySA is very good value, some 70dB dynamic range if I recall, which is plenty for transmitter testing, and in comparisons I did with my professional SA it was always within a dB. All for somewhere in the $50 ballpark..
73 Hans G0UPL
On Wed, Feb 28, 2024, 9:34?PM Eric W. Hansen < kb1vun@...> wrote: High-band QMX rev2 (2024), 9V version, Firmware 017.? Having fun learning about this radio. LPF cutoffs are good, though LPFs 1 and 2 show stopbands a little high, about –30dB.? I get 4W out on 20m and 17m, less than 3W on 15m, 12m, and 10m.??
I thought I'd take a look at the output spectra, after reading several posts here about harmonics.? I don't have a tinySA, but I do have a 200MHz oscilloscope with good FFT capabilities.? I made the following setup:? QMX --> Dummy load --> 10X probe --> Scope.? The second harmonics on 15m, 12m, and 10m are higher than what I would expect, between 39dB and 42dB below the fundamental.? 20m and 17m are OK, 63dB and 52dB down, respectively.
My understanding is that the push-pull Class D amplifier is effective at suppressing even harmonics, prior to any filtering, so I'd like some ideas about where the high levels might be coming from and what I might be able to do to reduce them.
Thanks!
Eric
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#qmx high band harmonics
#qmx
High-band QMX rev2 (2024), 9V version, Firmware 017.? Having fun learning about this radio. LPF cutoffs are good, though LPFs 1 and 2 show stopbands a little high, about –30dB.? I get 4W out on 20m and 17m, less than 3W on 15m, 12m, and 10m.??
I thought I'd take a look at the output spectra, after reading several posts here about harmonics.? I don't have a tinySA, but I do have a 200MHz oscilloscope with good FFT capabilities.? I made the following setup:? QMX --> Dummy load --> 10X probe --> Scope.? The second harmonics on 15m, 12m, and 10m are higher than what I would expect, between 39dB and 42dB below the fundamental.? 20m and 17m are OK, 63dB and 52dB down, respectively.
My understanding is that the push-pull Class D amplifier is effective at suppressing even harmonics, prior to any filtering, so I'd like some ideas about where the high levels might be coming from and what I might be able to do to reduce them.
Thanks!
Eric
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Correct! In my case I smoked out two of the BS170 and ended up with one heathy BS170. QDX is ?still alive and kicking with that one!:)
3x BS170 is absolutely a better option to distribute output power.
So to summarize here is my QDX QRPp setup:
- removed IC2 - 78M05 from pcb.?
- USB socket 5V pin goes to IC2 - 78M05 5V output pin
- In my case one BS170 is active but 3xBS170 is better.
- No 12V connection.
- The whole rig is powered by PC USB. RF power output around 500 mw to 700 mw band dependent.
The advantage of this setup is I carry only my laptop, ebd fed half wave antenna and ?QDX to Park. No PSU. PC supplies at least two hours of continus fun. My laptop is a microsoft surface laptop.
--
?
73, Barb
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Re: Magical smoke out of QDX, two leftmost BS170 very hot
Ah, yes. more data. This happened on 40m, 7074 KHz. I was transmitting sucessfully right before, couple of POTA QSOs, tuned antenna to SWR 1,2:1 (with NanoVNA)?
73 de EA7KLK Volker
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Magical smoke out of QDX, two leftmost BS170 very hot
Hello,?
'fraid my QDX let out the magic smoke today.?
I had one of these rare moments when it would not transmit after changing band / frequency. I unplugged from both PC and power, plugged pwer back in and it started smoking and stinking immediately. Two leftmost BS17o get very hot and smoke.?
12V build, latest Firmware 1_10, being run at 11,3V - first thing I checked was if my downconvertar had gone nuts - no, it hasn't, it's outputting wonderful 11,3V, under load and without.?
Should changing the 4 BS170 (I have been so cautionary to stock some) fix the issue or should I look at something else before, lest I burn them again straight away??
73 de EA7KLK, Volker
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Jonathan Kayne, KM4CFT
Garrett kc3unp
Timothy Fidler
Barb WB2CBA