I just ordered a midband QMX and I'm not disappointed because I will have the QMX unbuilt, I'm disapointed that I'll have to pay shipment a 2nd time. I will build both.
I know that the QMX+ is intended for experimenting, but a different housing without all the empty space would be nice for /p (I'll probably lay the LCD board flat and 3d print or modify the housing), and as it is alredy bigger, a larger (graphical!) screen would be nice. With a better form factor and a bigger display it would be an Elecraft killer. ;)
As I just ordered the midband QMX, I'll wait some time for the QMX+ to develop and evolve, but I guess the better display won't happen.
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Re: Old Timer Soldering Question
Like in the old days, soldering is all about the flux! ?Many inexpensive 60-40 solders and the newer (and not nearly as easy to use) lead free solders don¡¯t have enough flux in them. ?This is why the Multicore solders work so well. Lots of flux. ?I like to use a liquid flux, usually in a pen that looks a lot like a fat tip perminant marker, to wet the area I¡¯m working in with adequate flux. ?Then it¡¯s the old heat apply solder, the flux encourages the solder to wick through the hole quickly.
If you can see a little solder dome wetted around the component lead on the top side of the board, you know you have a perfect joint.
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On May 16, 2024, at 23:40, Jim Bennett / K7TXA via groups.io <w6jhb@...> wrote:
?Hi Foks,
?I've been soldering electronic kits together from as far back as the 60's with Heathkits. Started out as point-to-point connections, then circuit boards came along. Most of 'em were single layer boards: you heated up the board pad and the wire for a few seconds then touched the solder to it and bada-bing, bada-boom - connection done.
?Well, what about these six layer boards? I've simply been doing the same thing with them: heat 'em up, apply solder. But, I've made three QMX units over the past year and all three have had some sort of issue, the first two needed help from Jeff Moore to get going. I'm working on my third one and hopefully will have this one on the air soon w/o needing it shipped out to Jeff's "E.R.". Seems that possibly I hosed something with that RWTST transformer and it is being re-done.
?So, am I doing something wrong? With these QMX six layer boards do they need to be heated up and a ton of solder jammed into the joint, basically forcing solder through the layers, or is the "old fashioned way" sufficient to get a good connection?
--
Jim / K7TXA
Eagle, ID
SKCC 10447T
BUG 301
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Hello,
I did also sent a QMX for repair and alignment to Jeffrey.
He did a wonderful job and the QMX is now up to specs.
Bought the QMX used and was very unhappy with the performance.
Now the QMX is a beautiful QRP-Radio(low band version).
Thanks again Jeffrey.
My advice for foreign OM form Europe.
Send two paypal transaction to Jeffrey, one for the parts and shipping and a second for the donation.
I had to pay sales tax for the parts+shipping and the donation because I did one transaction.
Below 150 Euro there is no custom duty to pay, but always the sales tax(19% in Germany) for the whole value.
73 de Harry, DK2GZ
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Re: SWR disagreement and 50-watt amplifier
For anyone wondering what the suggestion re revised bias was about, schematic given above. I? have used a known good schematic? and marked it up.? so there are no doubts it has been proven , at least with? and RD16HH? 20 W amp.
Changes required.? R5 and R6 become 100 - 120R , to match the? 1:4 transformation provided by the trifilar transformer.? Mosfets? of course? become IRF 510.? The return path for gate current in? Q2 would? be to GND and across the gnd plane, back through R6 and to the opposite? secondary leg of the trifilar transformer .??
If the? IRF 510 Mosfets? are represented by about? 20 - 200 j as a? gate impedance at frequency? then the 100R? ?Resistor plus gate pair? as a parallel unit represent about? ?80 < -40 or? 61.3 -51.4 j and? as a series set Q2//R and Q3//R? then 160 <40 ohms which is a lot better SWR match and much lower reactance? than will be given by the mosfet gates alone in the? std? CW 50 W amp cct.? The? original bias potentiometer still applies of course.?
=====
Correction-?
From previous post - for the? calc of SWR corresponding to an RD16HH with no loading resistor .
ZL - Zo /? ZL+Zo?
or? ((20- 50)Re? ?- 90j) /( 70 MINUS? 90j)?
which? simplifies to about? 0.832? <-56? ?( angle? - 56 deg)
The bold shows the change made.? The mag? and angle were calculated correctly.? The error was transcribing from paper
to the? typed version??
?
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I would suspect that there are quite a few people disappointed after just having bought a QMX. I wonder how many unbuilt QMX kits will appear on Ebay?
--
Phill EA5JHA
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At 106 x 55 x 146mm it is a fair bit smaller than a K2 and not that much larger than a KX3 so still eminently portable. In volume it is a good deal smaller than an Icom IC-705.
Sure not the deck of cards size the QMX is but I'd certainly put it in the true /p category. I'll certainly be hiking out into the moors with it.?
And yes, having a bit more board space to work with will be very nice indeed. I enjoy the challenge of building the OG QMX however I'm looking forward to having a bit of room and to be able to do a really nice build :).?
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Re: Old Timer Soldering Question
I find a really hot iron (3-400c) means you don't need to apply hest for long and the solder gets wicked through the layers nicely. So you need a decent iron that gets plenty hot.?
I use a fine chisel tip as well rather than a fine point - better for heat transfer.
You need to make sure that the solder has made its way through to the top layer - this is usually be pretty easy to check visually.?
Finally a good quality multicore solder is a must. I used quality solder on my LB build which works beautifully. I used cheap Ebay special stuff on my HB which doesn't work. Not saying its definitely the solder but given I'd had a successful build first time I'm suspicious of the solder.?
For the QMX+ I've bought some Loctite Multicore lead solder. Quite expensive but I know that if there are issues, it's not the solder!
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AGC bug in QMX fw 1.0.0.18?
Hello, while writing my reply in a conversation in Winfldigi forum, I realized there might probably be a bug in AGC implementation (not very sure, but see below). Maybe it is not exactly as what I wrote in my reply below, but I rely on more experienced technicians to figure out what is happening.
Repost from Winfldigi below:
----
Mike, in case of QMX there is no "analog gain" except the path between DAC and the headphones. All signal processing starting after the mixer (I and Q channels fed into CPU ADC pins) is purely digital. I just wonder why, when I set the AGC chain to "let S9 signal through AGC sound like S9" I get a very weak output to fldigi. I would expect just the opposite. If the AGC threshold is, let's say,? at S4 (-30 dB vs S9), AGC compression is very flat (let's say 30 dB signal increase before AGC should cause 1 dB signal volume increase after AGC) then logically, S4 signal should be as loud as S8 (am I wrong). Subjectively, this is what I can hear in the headphones - louder band noise. Yet, in the other signal path, the USB audio, it seems to do just the opposite - as if S9 signal were pushed down (attenuated) effectively to S5 level and then fldigi cannot "hear" sufficiently strong signal to detect.
BTW I think this might be a bug in AGC implementation in the newest QMX and therefore off-topic here. I will repost this thread into QRP Labs forum.
73! Jindra
On Thu, May 16, 2024 at 05:43 PM, Mike Black wrote:
All audio over USB is digital....that doesn't change what I said is you want all your "gain" done in the analog space which means in the radio in your case (sound cards in some other rigs).
?
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?
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On Thursday, May 16, 2024 at 09:58:56 AM CDT, ok4rm <radio.miskovice@...> wrote:
?
?
Well, two points... 1. AFAIK the "audio" output from QMX to USB is "purely digital" or "purely virtual". The audio signal is the result of DSP processing, it is (somehow?) transferred into soundcard chip and is provided via USB as digital data. The audio signal for headphones output is generated by a DAC and fed to some op amp amplifier. I don't recall if the soundcard chip gets audio signal for RX from the DAC output or if it is passed somehow directly to form USB data, maybe in form of I2S stream directly from the processor. However, what I can see in fldigi input signal indicator (at the bottom of fldigi main window) is -100 dB noise floor and if there is a moderately strong signal, the level reaches some -80 maybe -75 dB.? With AGC off, I have to reduce the headphones audio by many dB by turning the volume knob at least one full revolution, maybe two (headphone output gain it is controlled by rotary encoder and the step in dB is configurable, so this depends strongly on my particular setup); but the headphones volume control has no effect on the USB output for RX. It's an additional amplifier/attenuator only for the headphones output. And, well without AGC the noise floor in fldigi seems to be around -50 dB and signals then may peak near -30 dB or higher (I am referring to fldigi indicator without knowing what numbers or levels actually appear at the connected audio device). I agree that at full volume and loud signal it should rather be near -10 to -3 dB, but I can't explain what is the problem. The input volume control in Windows Sound Control Panel can only be set between 0 and 100%, while other sound devices (using a different Windows driver) usually offer additional 10 or 20 dB "amplification". With AGC off, both the JS8call and fldigi waterfalls show something reasonable at first glanceeven when the level setting for input from QMX is set to 10% (which is -10 dB, I suppose; or should it be -20 dB?). 2. What I don't know is why with the level of signal produced by QMX with AGC on JS8Call seems to adapt and decode at least something. It might look weaker in the waterfall but the signal is visible and its "optical" strength more or less corresponds with the subjective strength as heard in the headphones. And the waterfall background in JS8Call is the same dark blue color as when the AGC is off. This leads me to a conclusion that JS8Call probably might perform some digital conditioning of the input signal (virtual amplification or attenuation prior to FFT processing). Whereas fldigi simply does not show anything if the same level of signal (same band, of course not the same JS8 signals) is below those mentioned -80 dB. I actually have some problem with RTTY in fldigi in general - it does not seem to decode incoming signal correctly. Yesterday it was not able to decode strong and clear signal of CQ from II3GM on 7045, nor could I get any reasonable text from listening to German DDH weather service at 10100 kHz. Regardless of switching FSK/FSK-R mode (effectively it switches QMX demodulator between USB and LSB) anything received did not comprise a readable text. This was true for both the II3GM signal (classic 45,45 Bd @170 Hz shift) and the DDH signal (50 Bd TTY @ 425 Hz shift). I suspect something might be wrong with my fldigi installation. I will keep on investigating, without proper reception there cannot be a proper RTTY QSO anyway... 73 Jindra OK4RM P.S. maybe it's a Windows problem?? On Thu, May 16, 2024 at 01:29 PM, Mike Black wrote:
You don't want "digital amplification" as it serves no purpose at all for decoding signals....computer sound should show 0dB on both record and playback.
Multiplying a digital signal will give exactly the same answer as with no amplification...all scaled exactly by the amplification.
So things like SNR or FFT frequency resolution do not change at all.
?
Does the AF Gain on the QMX control the USB audio level?? For JS8Call, WSJT-X set the audio level to give you a bit less then 60dB on the WSJT-X level meter.? That will work well with all digital programs including FLDigi.? The documentation does says "30dB minimum" but notice the "minimum" wording.? That level maximizes dynamic range and overcomes quantization effects....but is not the best level to use for inter-program operation.
?
You want all amplification to be in the rig and/or the audio device analog space to retain the resolution of the signal.
?
Other programs like WSJT-X do automatic flattening of the visual space to remove the DC offset which is why JSCall and such still show a waterfall at low levels.
?
?
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Mike W9MDB
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On Thursday, May 16, 2024 at 02:37:42 AM CDT, ok4rm <radio.miskovice@...> wrote:
?
?
Issue #1: QMX is in TX mode, but there is no output despite fldigi generating signalSOLUTION:? "The only right channel is the right channel" (not mentioned in QMX Operation manual, though). BTW I had the same problem with TS-480 & Digirig mobile, in general this applies to any interface (USB or other) which uses only the right channel for AFSK input into the transceiver. Unlike other programs which show options like "Mono" or "L+R" when setting up soundcard (JTDX, JS8Call, VARA etc.), fldigi is not so straightforward. Issue #2: QMX receives signal (and it can be heard in headphones), but there is no waterfall in fldigi no matter what threshold settings for the waterfall you choose. Signal level indicator in fldigi shows noise level at about -100 dB and incoming signal in peaks does not exceed minimum level needed for detection, for instance does not exceed -80 dB. This issue is very confusing due to the fact that other digi programs (such as JS8Call, which I used to test this) seem to find this signal level satisfactory, detect signals and show usual waterfall picture.IMMEDIATE SOLUTION: on QMX open menu, Audio/AGC settings/AGC = OFF. Or, you can tweak your AGC settings until you achieve at least -50 dB audio level supplied to fldigi input.LONG TERM SOLUTION:?Variant 1: modify fldigi to automatically adjust for the level needed for detection (a kind of digital AGC or digital amplification, to amplify the signal to move the peak level e.g. to -20 dB for weak audio signal)?Variant 2: modify QMX firmware to adjust output level presented to the audio interface just in the USB path (such as? shift left a couple of bits) so that the peak level is never less than, let's say, -60 dB.(both variants would be welcome, but either one should suffice).Yes, I know it is not good manner to tell software developers how they should do their work, I apologize! Just wanted to decrease level of frustration among the users of both fldigi and QMX :)--73 de Jindra OK4RM, OM0RM
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The developer blank slate leaves open many intriguing possibilities that were not possible on the QMX due to the tight confines of the case. Imagine putting something like a Pi-Zero in there!
--
Tisha, AA4HA
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I just packed up two more of them and put the 6x9 envelope in the mail box for the morning pickup.
--
Jim / K7TXA
Eagle, ID
SKCC 10447T
BUG 301
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Karl - are you telling me that it has not arrived????? Should been 2-3 days unless they¡¯ve employed snails.
Jim Bennett / K7TXA
Eagle, ID
SKCC #10447C
B.U.G. #301
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On May 16, 2024, at 5:55?PM, Karl via groups.io <karlshumaker@...> wrote:
You have any idea how long it SHOULD take Idaho to Tennessee via usps?
--
73
Karl
KI4ZUQ
--
Jim / K7TXA
Eagle, ID
SKCC 10447T
BUG 301
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As soon as I saw the announcement, I jumped in and ordered one with all the trappings! I have build numerous QRP lab kits and every one has worked at first powerup. Hope they ship soon!
73
-Mike
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Old Timer Soldering Question
Hi Foks,
?I've been soldering electronic kits together from as far back as the 60's with Heathkits. Started out as point-to-point connections, then circuit boards came along. Most of 'em were single layer boards: you heated up the board pad and the wire for a few seconds then touched the solder to it and bada-bing, bada-boom - connection done.
?Well, what about these six layer boards? I've simply been doing the same thing with them: heat 'em up, apply solder. But, I've made three QMX units over the past year and all three have had some sort of issue, the first two needed help from Jeff Moore to get going. I'm working on my third one and hopefully will have this one on the air soon w/o needing it shipped out to Jeff's "E.R.". Seems that possibly I hosed something with that RWTST transformer and it is being re-done.
?So, am I doing something wrong? With these QMX six layer boards do they need to be heated up and a ton of solder jammed into the joint, basically forcing solder through the layers, or is the "old fashioned way" sufficient to get a good connection?
--
Jim / K7TXA
Eagle, ID
SKCC 10447T
BUG 301
|
Re: New LB QMX RF Sweep Analysis
OK my friend - the new transformer has been wound (the old way) and will be soldered in on Friday. Wish me luck with power-up! :-)
--
Jim / K7TXA
Eagle, ID
SKCC 10447T
BUG 301
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Possibly never. It is a goal that hopefully will be obtained but has never been promised.
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Any reason not to replace the QLG1 battery with a supercap?
--
Brent DeWitt, AB1LF
Milford, MA
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On Thu, May 16, 2024 at 06:02 PM, Shirley Dulcey KE1L wrote:
the QMX+ already has an output of about 5 watts. The 10 watt linear amplifier would not be a huge increase in power, barely worth the trouble.
My rule of thumb is that 10dB power gain is the minimum amplifier gain worth bothering with.?? 73, Don N2VGU
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Re: New LB QMX RF Sweep Analysis
No, only some Ohm would be wron73 Ludwig
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Hans. I just placed an order and it has wrong billing address.? ?The shipping address is correct.? ?Here is the correct billing address?
Doug Hendricks?
3247 N. Dee Ann Ave
Fresno, CA 93727
Please correct.? ?Thanks Doug?
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You have any idea how long it SHOULD take Idaho to Tennessee via usps?
--
73
Karl
KI4ZUQ
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Timothy Fidler
Phill
Tisha Hayes, AA4HA
Brent DeWitt
Donald S Brant Jr
Karl