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Re: Waterfall / Panadapter on QMX+ : Add a freq-out for a second receiver?
Thank you all, for your valuable replies! I did, indeed, only read the QMX docs - even though it is mentioned on various locations that one design is based on another so now I have to ask myself why I did not use that obvious sources of information...
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On my superhets, I do use that buffer-board on the IF with great success, using the not-so-cheap Airspy-HF, I have great signal quality to work with, be it in GQRX, SDRangel, GnuRadio or even feeding it to flgigi / wsjtx after converting it to audio. Most of the time, working on SSB, I just use the panadapter do have the signals on the band in view - and checking out some new signals while working a pileup...
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I do now have a lot of information to work with - and a lot more manuals to read. I even found the longed-for block diagram. That, besides all the real-life necessities, should keep me busy some weeks.
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If someone has anything to add to: Please feel free, I absolutely appreciate it! I might come up with more questions down the road... and hopefully with a nice solution at a later stage! |
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Re: Waterfall / Panadapter on QMX+ : Add a freq-out for a second receiver?
The receiver gets RX_IN from Q508 in the upper middle of the final page of the schematics (page 5).
Q508 is where the transmitter is blocked from the receiver, though there will still be
a very strong signal on RX_IN when transmitting.??
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The receiver is on page 4, RX_IN goes into IC408 which steers the signal into the appropriate band pass filter,
IC402 selects the output from the appropriate band pass filter and has the received signal coming out on pin 9.
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So your SDR receiver could grab RX_IN, or it could try grabbing IC408 pin 9 and get it after all the local
AM broadcast band stations and (most of) the other amateur bands have been filtered out.?
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A buffer is a good idea, driving coax to your SDR receiver.
Mostly because you don't want a bare wire picking up other crud from the SMPS's and such.
No buffer would probably work fine, an extra 50 ohm coax load on RX_IN would drop the received signal
for the QMX by maybe 3dB, or half an S unit.
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You might want to use the "RX" signal on page 5 to desense your SDR receiver somehow,
perhaps by clamping the output of your new buffer when "RX" is logic low (0v).
"RX" goes low when transmitting, logic high (3v) when receiving.
Seeing some of the transmitted signal on the SDR could be a good thing,
it will tell you exactly what the receiver is tuned to.
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Your SDR receiver will inevitably see a very strong signal from CLK1 and CLK2 going into IC403
a few KHz away (12 KHz?) from the received signal.? Since they are at the same frequency?
but 90 degrees out of phase, they will be seen as a single signal.
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Using a cheap RTL-SDR type receiver for your panadapter might be sufficient.
If it works well, I'd expect such a solution to be very popular with QMX users.
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Jerry, KE7ER
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On Fri, Feb 21, 2025 at 07:15 AM, <410733@...> wrote:
Let's summarize my requirement: I'd like to have a second independent SDR-Receiver while QMX is in RX. I am very used to that feature and I don't want to miss that when working with the QMX. I will share my experience (solution?) here, I thing that might be interesting for other users, too. |
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Re: Waterfall / Panadapter on QMX+ : Add a freq-out for a second receiver?
On 21/02/2025 15:15, 410733 via groups.io wrote:
there's no IF at all?This is SDR, the IF is 12KHz. Thinking about it the IQ appears at IC407 input in normal mode. The RX antenna is switched at Q508. I am reluctant to suggest anything, I have not tried it myself. I wonder how capable you are:-) The questions you ask make me think you need more than suggestions. The manual provides much information on how it works. You may need to start by looking at the QDX manual, that is where Hans started. I am not sure where all the information is. Alan |
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Re: Waterfall / Panadapter on QMX+ : Add a freq-out for a second receiver?
This tread has hit a nerve.? I plan on doing something like this with my QMX+.? Proposal is to use a hi-z input buffer board at the receive frequency inside the QMX+ and send it to an AirSpy Discovery Plus mounted internally in the QMX+.? I can then use either HDSDR or SDRSharp as a pan adapter *and* a second receiver on my laptop.? This would require two USB cable to the laptop - and I presume the QMX+ and the SDR program can control each other (OmniRig?)? I do this with my TS-590.? If I want to use the QMX+ portable without the pan adapter, I can.? The AirSpy unit is tiny and light and gets power from the USB port.? So it doesn't draw power if it isn't plugged into a USB port.
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Many variations possible here....? SDR dongles, programs, etc.? I like the AirSpy with SDRSharp - the DNR in SDRSharp is the best I've used.
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73 Dave kx3dx |
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Re: Waterfall / Panadapter on QMX+ : Add a freq-out for a second receiver?
You can read more about the QMX receiver design in the QDX assembly manual - Hans did not repeat the design description for QMX.
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As others have said, there is no real IF.? If you really want to pursue your idea with the RF, you may be able to tap it after the tx/rx switch at the output of the band selector mux, but it may decrease the receiver performance, since it is an unbuffered signal.? Then as Allison notes, you will be limited to the relatively narrow bandwidth of your SDR receiver for your panadapter display.?
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For me it works to just use the IQ output directly through the USB port into SDR software, which provides a 12kHz panadapter display for CW, which is adequate.
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Stan |
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Matti,
please read QMX QMX_plus Startup to find the switch on process. There you will find also some testpoints and values to check.
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How much supply current when pressing the left encoder? How much before and how much after?
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73 Ludwig |
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Re: Handheld QMX?
Its been mentioned and can be done...save for that pesky antenna.
At 10M a moderately decent antenna is 8ft long.? However at 40M
anything that's under about 16ft long is about as efficient as a
dummy load due to the loading coils needed to shorten it.
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So if you mean hand held its nearly there as is (QMX+) but it needs
power, antenna, Key (for CW), MIC for SSB (future), or computer
for digital modes.? Antenna for QRP is not small unless highly
inefficient.
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Obviously you have missed all of the QMX ABS (antenna tuner, battery, speaker).
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--
Allison ------------------ Post online only,? direct email will go to a bit bucket. |
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Re: Why twist wire
For some of us, the priority here is operating.
For others, it is learning and understanding how this fascinating radio works.
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Personally, I have never had much interest in operating.
I do most of my communicating via email and web forums.
Occassionally get up out of my chair to talk to the neighbors.
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Jerry, KE7ER
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On Fri, Feb 21, 2025 at 07:32 AM, Bruce Akhurst wrote:
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Re: Waterfall / Panadapter on QMX+ : Add a freq-out for a second receiver?
Okay, but what about using the signal from the antenna-input directly? I can't use an RF splitter / power divider to the non-amplified signal, I might get away with that buffer board? Not sure about the usable bandwidth, though. Might be worth a try. In that case, I still need some sort of? RX/TX signaling, in order to tell the buffer board when to disconnect.
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If that approach is not viable at all, I might have to dig deeper on how to get the I/Q data directly. Although, I'm assuming that's better done in software. I'm aware, that the QMX firmware is under active development and at some point in time we might get an API, which would, if capable be a fist-class solution. I'm unsure, though what priority that feature has, and we can't expect Hans to do all at once. Therefore, I'm looking for alternatives. Also, I like the idea of processing the analog signal with a second, independent device. |
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Re: Waterfall / Panadapter on QMX+ : Add a freq-out for a second receiver?
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--QMX+ has an I/Q mode, that uses the soundcard as interface, allowing for a panadapter.
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You need bandwidth in the data or baseband that is not there outside of the design bandwidth.
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>A perfect solution for CW operation: Everything you need. Not-so-perfect for digimodes or future SSB, though: Those modes do need the soundcard for the audio data, so the current implementation does not allow for the use of the I/Q mode in the same way you can do in CW (this sentence may contain wrong assumptions as I do not have QMX at hand, yet). Also, the manual states, that the I/Q data delivered over the soundcard is not suitable for decoding digimodes. I remember having read thoughts about a? possible future implementation of a different type, maybe QMX+ will have that feature out-of-the-box some day, but while Hans is busy on ticking the SSB-To-Do-List, maybe it's not the right time to propose even more features... <
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Also the sound card interfaces are audio band width for all digimodes typically 3-4khz wide.
ITs limited to that as most radios have IF filters that are of at most FM bandwidth (15khz)
and for SSB modes (including Digital) typically less than 3.2khz.? ?For most radios that's all
the bandwidth possible.? They all do SSB well.
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What you thinking of is typical of the later generation of SDR (hybrid or direct RF to digital)
that have wide bandwidth digital conversion for later processing.? Example is IC7300, IC7610 (dual RX).
The digital stream bandwidth is megahertz in band width width.
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Your understanding of the QMX and QDX receiver is not complete.? It does digimodes as is (same as QDX)
as well as SSB RX.? I find the RX well suited (QDX and QMX) for digi-modes (all for RX) and depending on
the specific modes many for TX but not all (PSK31 RX is fine but not TX).? The reason is the RX is a fully
developed SDR receiver but not transmitter SSB will be done using SDR techniques but in a different way.
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You ned to read the white papers for both QDX and QMX... maybe even QCX as the down converter to
baseband is similar in all of them and they differ from QCX to later QDX/QMX in the post processing
of that baseband.?
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For Digital modes you only need audio bandwidth I run FT8/FT4 with 3KHZ wide and WSJT-X
takes that and gives me a very fine grained RX waterfall on the computer.
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Older multiple conversion transceivers often have SDR (built in, often hidden) with 22 or
25khz IF and most can easily be tapped before the first filter (usually a VHF frequency 45
to 65mhz) before its converted to some lower IF (for electivity) and converted again for
the internal analog to digital conversion.? They are all fundamental Superhet technique
and differ only in the last stage (detector).? The techniques you write about are suitable
for them.
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Allison ------------------ Post online only,? direct email will go to a bit bucket. |
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Handheld QMX?
Has anyone considered or even actually built an integrated handheld QMX rig? I am thinking something like the KH1. I can envision a 3D printed case that includes the QMX, small battery pack, and a manual Z-match or even automatic tuner that could be used with a whip or random wire antenna. Could include integrated touch paddles or paddles jack…
Seems like something like this could be in high demand. Steve AK0M |
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Re: QCX-mini... smoke
On Fri, Feb 21, 2025 at 03:03 AM, David Wilcox K8WPE wrote:
Get some low temp ChipQuick Dave's right.? That stuff works like magic!
A little clean up with isopropyl alcohol and the board is like new.
Using flux with the solder wick is also key.
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I don't think having crossed turns matters much (if at all).
There are many possible reasons for what happened (solder splatter, using a metal tool to spread the turns and inadvertently shorting something, etc.).
Hang in there.? Take it slow.? Inspect and clean before applying power.
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73, Mike KK7ER
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Re: QMX Warm Chassis?
Sorry for the delay.
toggle quoted message
Show quoted text
Life got busy . And I actually haven't tried the fins yet. I did some test runs on my fan modified QMX HB and my fan modified QDX HB. I found that I could safely push 50% duty cycle WSPR cycles, at 4w and 5W outputs respectively, for over an hour on both if I elevated the units about 1 inch above my worktable. ( Sitting just a bit of the short edges on? two stacks of small Post-It notes. ) Saw worst cases of an extra 4-5 or so degrees of exhaust heat rise. I also found that the exhaust air would return to the normal after idling in RX within about 4 to 6 minutes.? My fans are just small 25x25 mm units. Don't move a lot of air, but are super quiet, only use about 28ma, and do make a difference compared to being fully closed up and sitting flat on the worktable.? If just in RX,? The QMX appears to run about 3 degrees C above the surrounding ambient air ( ambient being around 24 to 27 C) while the QDX runs about 2 degrees above. This is in the fan on configurations.? I want to repeat those tests with an LM35 sensor attached with some tiny drops of super glue to the hold down washer for the PA xstrs with both fan on and fan off conditions. This may give a better indication of what's happening temperature wise closer to the little heat buggers.? Then I may try the fins on the bottom of the case idea I originally envisioned. Especially with some JS8 scenarios. Fun, fun, fun .... GREG
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Re: Waterfall / Panadapter on QMX+ : Add a freq-out for a second receiver?
There is a fundamental lack of understanding of the SDR receiver.
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First there is essentially no IF, its direct to base band which is the
IQ outputs.? All the work is done in the digital realm by the
ST32M4xxx mpu.
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For second receiver the bandwidth of that down conversion is
Relatively narrow band so the panoramic view (waterfall) would
be narrow as would the frequency of the "2nd" receiver.? Doing
a close in waterfall is taking what data there is (IQ outputs)
and translating that to a display format.
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Generally the idea of upstream tap is limited to radios that
are multiple conversion superhet transceivers.? That is typical
of many radios like ft817, FT450, IC756 and a large number?
of others.?
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Allison ------------------ Post online only,? direct email will go to a bit bucket. |
Peter HB9EBE
Bruce Akhurst
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