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Re: QMX and sidetone
Hi Adam, I am typing this on my phone at a concert with my wife. If you need more info send back your questions and I will respond tomorrow. ?
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Re: QMX and SSB -- how?
It's still a trick, albeit a passable one.
Not much more than line scanning or TV PAL where you can send signals fast enough to appear to the human eye as a continuous sequence as to appear continuous. Do it fast enough and it scores a pass, nothing wrong with that. But it will always be just slightly behind a true anallog signal in the *academic* sense. Digital representation is exactly that, a representation. Digital will always second to analog. Done fast enough then the human ear can;t tell the difference, but that depends upon transmission resources. Shannon theory of? communication blah blah come into play too. Bottom line is that *if* transmission is done fast enough then it scores? a pass. Too slow then the transmitted audio is crap. Thankfully using the STM stuff in newer kits should produce some very acceptable stuff on the future, and fitting SSB into a basic CW/Data rig should be a nice bonus with acceptable quality, nice. But just remember, anything digital = quantization. It;s always a *representative* of the analog, an incontrovertibly obvious fact, Quantisation yada yada. -- - 73 de Andy - |
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Re: QMX and SSB -- how?
Stephan Ahonen KE0WVA <stephan.ahonen@...> wrote:
The real trick to understanding this will be to develop an understandingCan you (or anyone) recommend a book or article that would show and explain it? I'm curious and would be happy to finally understand the quadrature modulation in practice (and why, for example, we extract the USB from I/Q signal by multiplying I by 1 and Q by -j, I never really understood that). |
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QMX, messages, and prosigns
It would be nice to have some modifier character(s) to be able to enter
prosigns into predefined messages. QMX wouldn't (and probably shouldn't) even have a predefnied list of prosigns, but have special characters to enter and exit prosign mode (sending without inter-character delay), or even a single character to toggle it. Something like: AR .- .-. [AR] .-.-. Or even: AR .- .-. $AR$ .-.-. Not a high priority (there are things of higher priority of course). Just a thing that would be nice to have. |
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Very unlikely that missing C410, Loss of some VCC decoupling would be the problem.??
I would lift just one of the T401 secondary leads and run the plots.?? But first I would double check all solder joints under high magnification.? Should result in a gain reduction compared with normal operation and probably screw up the Diagnostic/Audio Freq Sweep. Another debug test would be to Lift the T401 Primary and connect it to the <RXIN> that can be accessed at the intersection of C402, C402, C494 ( this could also be found as one side of C403 which is not installed)? This would bypass the BFP filters and? the plots?should be higher gain without much filtering. I am pleaded to help. Chris |
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Re: QMX and SSB -- how?
One of the earlier instances where the "trick" of getting linear signals through an ostensibly non-linear signal path was brought to the attention of the amateur radio community back in the mid 1970s with the launch of the OSCAR-7 Satellite.
In that case, a method called "HELAPS" was used - and has since been used in one form or another on other amateur radio satellites equipped with linear transponders since then:? A bit of history may be found here:? ? (There's a scan of the HELAPS design document from the '70s out there, but I was unable to find it on a search just now.) In short, you do this: - Take the analog signal source - whatever it is, convert it to a lower frequency (I believe that they used 10.7 MHz) and band-pass filter it, then split it into two signal paths. - On one signal path you do a hard-limit (as is done for analog FM reception) of the signal to eliminate the amplitude component. - On the other signal path you do an envelope detection to eliminate the frequency component. - The 10.7 MHz signal from the limiter was frequency converted to the final frequency and applied to the drive of the final amplifier. - The supply voltage of the Class-C final amplifier was modulated - using PWM (switching supply) techniques with the envelope-detected voltage that we derived earlier. The result, if done perfectly, will be a faithful recreation of the original signal.? In this case, it was a transponder with many SSB and CW signals - but it could be combination of any type of signal, of any mode. In the case of the QMX we have the basis of the above: - A phase/frequency modulatable source of some sort. - A means of amplitude-modulating the final amplifier. When I spotted the comment about possible inclusion of non-linear modes (such as SSB) in the QMX manual two questions crossed my mind: - Is the bandwidth of the drain-voltage modulator of the PA sufficient to permit modulation at audio frequencies?? I thought this noting the presence of C506, the 1uF capacitor. - Is it possible to phase/frequency modulate the Si5351 at a rate sufficient to permit the production of the spectral components of speech?? I know that there are limitations related to PLL tracking in the '5351 but if one can work around those (e.g. phase adjustment, dividers) this might be doable. If both of the above are true, it's possible to do this, given sufficient processor power (and it probably doesn't take terribly much:? If Hans has pulled off doing Hilbert transforms of 80 taps or so in the receive path, he can do this!)? If if it turns out that speech isn't practical for whatever reason, other modes involving some sort of envelope modulation (certainly PSK31 - which I have done on a lowly PIC by modulating frequency/phase and amplitude separately) certainly are. 73, Clint, KA7OEI |
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QMX and sidetone
Maybe it's not a bug and I'm just not getting how it should work, but
operating manual states that sidetone frequency is only for operator's convenience. It looks like this frequency is added to the dial frequency when switching from digi to CW. I receive a signal with digi filter, switch to CW filter, and the signal is shifted by the frequency set in the sidetone frequency setting. Let's say I have the sidetone set to 400 Hz. I connect QMX to the fldigi on a PC to see the waterfall. I set digi filter, tune to a signal, I can see the CW line at 200 Hz. I switch the filter to CW without changing the frequency and the signal moves to 600 Hz (400 Hz + 200 Hz). Is it supposed to work this way or is it a bug? |
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I remade T401 again and checked for continuity. I measured resistance between IC402 pin 7 and ground it is about 6kohm. I re-soldered L401.
I noticed that C410 is missing 0.1uF VCC to ground. Could this have an effect? Should I solder it in. No change to BPF plots. I am lost at what it can be. --------------------------------- 73 de Marek SP9TKW |
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LightAPRS 2.0 APRS Tracker Info
I hadn't seen any recent posts about this tracker but had a few questions.
1. Is it in stock? 2. Is the BMP085 sensor on board or is it required to be externally connected? 3. Is there a manual of any sort?? [I found the github info useful but a manual would be nice :-) ] 4. More for the group: have y'all successfully connected other I2C Sensors to this tracker?? I'm planning on using this as a remote weather station. -- 73 ? Mitch N0DIM () |
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Re: QMX Shipped, panic stage
#qmx
Billy, |
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Re: FT8 for U3?
On Sat, Sep 2, 2023 at 08:22 PM, GIUSEPPE wrote:
Good evening everyone, I agree with what Jerry wrote, the WSPR propagation does not determine the openings in SSB,WSPR allows a typical signal of 30db below the noise to be confirmed depending upon the decode engine used. 1 watt of WSPR = 1000 watts of SSB for a typical S1 signal of SSB. If you get a decode of -30db on WSPR then you need 1000 watts of SSB to make the trip with an S1 signal. WSPR reveals a path, but it doesn't guarantee that some some one on SSB is listening, or has 1kw ERP to make the trip. Whence the disparity of WSPR reports vs actual SSB QSO's. -- - 73 de Andy - |
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Re: FT8 for U3?
On Sat, Sep 2, 2023 at 07:56 PM, Jerry Moyer wrote:
I wonder why WSPR is less effective at VHF?? Is it due to the more rapid fading as opposed to the almost 2 minute frame for WSPR?Doppler shift. That's is also why WSPR is crap when the path passes the polar zones. Haven't you noticed that the successful reported wspr paths tend to be only basic north and south or east to west or vice verce paths ? Shove an interesting path that *traverses* either the north or south auroral zones and it turns to complete crap. What's the bloody point of sending? 6Hz wide signal across a path that smudges the signal by 30Hz ? Hard facts dude. There's another more useful? mode built in to all the all the QCX/QMX/U3S kits. Seek and you will find. -- - 73 de Andy - |
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Re: FT8 for U3?
GIUSEPPE
Good evening everyone, I agree with what Jerry wrote, the WSPR propagation does not determine the openings in SSB, I have a beacon on 6m with a QCX MINI modified by me and I noticed that when in Northern Europe they receive the beacon signal the 6m band is closed, this also applies to all wspr hf frequencies, I also have 2 U3S for all hf frequencies and a QCX MINI for 20 and 30m.? Nigel you are right, WSPR is not suitable for vhf and above frequencies, no.? I've never seen a spot and then there would be a need for powers above 10W to get some listening.? In FT8 I don't know, I don't use digital modes, certainly in CW it would be the most ideal thing for a beacon.? 73 and good evening everyone Giuseppe iu8eun Il Sab 2 Set 2023, 20:56 Jerry Moyer via <ac5jm=[email protected]> ha scritto:
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Re: QMX and SSB -- how?
On Fri, Sep 1, 2023 at 10:08 PM, Colin Kaminski wrote:
If you look in the audio domain, you have a two (or multi) tone signal. ?However in the RF domain, you see close to an almost pure single frequency RF waveform with nearly invisible frequency changes (on the 20M band, SSB modulation only changes the RF frequency by 2.5kHz/14MHz or a max of 0.02% change). ?Those changes are very slow (audio rate) compared to the RF frequency, but can include an array of many microscopic sidebands, a lot more than just two. ?So you can change a narrow-band close--to-pure RF waveform in amplitude and phase by tiny amounts at a relatively slow rate, and end up with tons of audio frequencies when those tiny-at-RF sidebands are modulated back down to baseband, where they now become large differences relative to each other in terms of rich audio. -- 73, Ron, n6ywu |
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Re: QMX and SSB -- how?
On Sat, Sep 2, 2023 at 02:17 PM, Stephan Ahonen KE0WVA wrote:
The real trick to understanding this will be to develop an understanding of the IQ representation of RF signals. Seeing what an FM signal looks like on an IQ diagram, and seeing what an AM signal looks like, and understanding why those signals look the way they do, is really the key to understanding the fact that every arbitrary signal can be broken down into FM and AM components.Conversely, given sufficient bandwidth and precision of the IQ data stream it is possible to generate any arbitrary signal, or combination of signals, of any modulation types.?? 73, Don N2VGU |
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Re: QDX - protection of BS17O PA
Motorola used to use a neon lamp in their VHF base station receivers at the RF input to ground.? Neon lamps usually start to conduct and light up at about 60 volts.? I wonder if that would accomplish the same thing? -Jerry AC5JM
On Friday, September 1, 2023 at 04:20:22 PM CDT, <wb2cba@...> wrote:
QCX mini has a class E pa different than QDX which has class D PA with two sets of bs170s. In qcx mini one 1N4756 zener diode will do the job. In qdx we need two of them. 73 Barb WB2CBA |
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Re: FT8 for U3?
WSPR is great for determining propagation conditions for digital communications like FT8 but really isn't all that useful for determining if conditions are great for SSB voice, at least that's what I've experienced on HF.? WSPR can seem wide open and voice communications aren't possible.? In my opinion CW beacons are best for determining if voice communications are possible and that both beacon modes are useful. I wonder why WSPR is less effective at VHF?? Is it due to the more rapid fading as opposed to the almost 2 minute frame for WSPR? -Jerry AC5JM
On Saturday, September 2, 2023 at 10:29:56 AM CDT, Nigel ZS6RN <zs6rn@...> wrote:
Hi John, From research undertaken seems that WSPR on upper VHF bands for DX propagation is not very effective. Have found more than one study / paper that arrives at the same conclusion. 73 Nigel ZS6RN |
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Re: QMX and SSB -- how?
On Sat, Sep 2, 2023 at 10:24 AM, Da Amazin' man G0FTD wrote:
Surely this just amounts to creating? at any given point in time only one sampled frequencyIn the simple case of two simultaneous tones, you are not modulating frequency at all. You can produce two tones solely through amplitude modulation. Think about the spectrum of an AM signal - an AM signal produces two full sidebands without changing the frequency of the oscillator at all, simply by modulating amplitude. To produce an SSB signal, you add some frequency modulation to the above procedure. Not by tuning the oscillator to every frequency in the entire signal, but rather by tuning the oscillator to the "instantaneous frequency" of the signal at any particular moment, the same way you produce a full spectrum of sound by making a DAC produce the instantaneous voltage of the signal from moment to moment. The real trick to understanding this will be to develop an understanding of the IQ representation of RF signals. Seeing what an FM signal looks like on an IQ diagram, and seeing what an AM signal looks like, and understanding why those signals look the way they do, is really the key to understanding the fact that every arbitrary signal can be broken down into FM and AM components. |
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Re: QMX on Android?
Hello Chuck,
I just noticed your message. I am trying to get my QDX-M to work with andFLmsg on an android phone, so a different application from you. I might however be able to solve the first part of your problem of getting the phone to recognize your QMX. I obtained a terminal app from the Play Store, I used "Serial USB Terminal". Once the app was installed and I had connected by OTG cable to the QDX, I opened the app menu, selected USB devices and found there the QDX device. Selecting it caused the app and QDX to connect. I then selected the radio app I wanted to use (in my case andFLmsg) and I was able to communicate and send text to the QDX for transmission using Olivia (in VOX mode). I am still having problems receiving audio back from the QDX to the phone, but I figure I am more than half-way there! Let me know if this works to establish communication between your phone and QMX. |
Marek SP9TKW
Mitch Matteau N0DIM
Donald S Brant Jr
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