Re: #QMX #Finals...did I kill it?
#qmx
Receive looks okay. Waterfall was showing incoming FT8 signals. I'll check anyway, thanks!
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Re: #qdxm QDX-M - new single-band version of QDX available
#qdxm
Hi,
I made my mono a dual band QMX-M: 12m and 10m. I have set my QMX-M for High bands instead for Mono band so I got settings for all 5 bands from 20m to 10m in the setup menu.?
I suppose you could do the same also for the low band version and than adjust the parameters to your needs.
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73 Bojan S53DZ
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Re: #QMX #Finals...did I kill it?
#qmx
Mordan42,
Hans sells BS170s in his component area:
Those would be the same as the ones supplied with the kit.??
73
Evan
AC9TU
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High insertion loss / early rolloff 6m LPF
I've assembled and tested the LPF kit from 160m to 6m. All the filters work as expected without adjustment except 6m.
The 6m filter starts to roll off very early and has a high loss in the 6m band (over 4db at 52Hz).?
I've checked for solder bridges and cold joints, continuity is good through the inductors and all the pads that should be connected. I can't find any shorts anywhere.
Any thoughts?
- Justin, AI6YM
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Re: #qdxm QDX-M - new single-band version of QDX available
#qdxm
Hello Nate? The QDX-M firmware displays only a single entry in the Band Configuration screen. The single entry is configured automatically by the firmware for the band you choose to build the kit for, controlled by your choice of jumper wires (install following the instructions in the assembly manual).?
If one is to build a QDX-M for a band lower than 20m how should they set up the jumpers? Or does it not matter, as you can change it all in the band configuration in the Terminal program?
(I'm thinking 160M, which I know the band name needs to be 160 to get the receiving set up properly.?
The firmware doesn't have defaults set up yet for all those other bands. So you would need to set up the band you want, manually, in the terminal.?
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Re: QMX Band Pass Filter (and Band pass filters in general) question
Hans ,? Jonathan says? -? "I am not even sure if a single resonant band pass filter is the best option for my use.."
This has some ambiguity? - does it mean a single resonant cct, one per band. ? That's marginal . SW Labs used that type of cct as the input to a mixer in many of their? ccts? (Dave Benson) years ago. It worked ok but was not state of the art. It only worked because it was backed by a Ladder filter further down the Rx chain. This sort of design only works with? a transformer input LC coil? ie it needs impedance transformation from the antenna? and it also needs to be decoupled from the forcing function as per all SHM resonators.
OR?
Does it mean a single filter with multiple resonant? band pass elements which sounds like a technical contradiction but is similar to your two band? LPF designs.?
FYI I sent him an old Arrl? design with three off? diode switched dual tuned? BPFs and a? bipolar? wideband booster at the far end.? THere is in fact a fault with the schematic x 3? which I pointed out to Jonathon.? If you want? Simple, buildable with no prototypes and decent performance, this is hard to beat.
TE. Fidler?
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Re: #QMX #Finals...did I kill it?
#qmx
Mordan42,
How is it doing on receive?
Check C510 and C526 to see if they are damaged. If either have cracked or have been overstressed by high RF current, output power will be very low.
JZ KJ4A?
Digikey has BS17s in stock ?for 0.59 each.? Buy 10 and you will have spares …
--
73, Bernie, VE3FWF
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Re: #QMX #Finals...did I kill it?
#qmx
Digikey has BS170s in stock for 0.59 each. ? By 10 and then you will have spares.
--
73, Bernie, VE3FWF
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Re: Low Band QMX Spectrum analyzer measurments
On Thu, Feb 29, 2024 at 06:52 PM, Chris wrote:
I reckoned that if the manufacturer wrote the maximum limit on the front of the analyser that was what it would cope with.
"Cope with" and "make accurate measurements with" are different things.?? 73, Don N2VGU
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Re: Magical smoke out of QDX, two leftmost BS170 very hot
Congrats on successful surgery! I second the suggestion to add an L14 diode to protect against a possible failure mode that sounds consistent with what you described. Other than the L14 voltage, I have also observed low efficiency and resulting thermal dissipation issues for my hi-band QDX only on 10m; 20-12m are fine. So you could also check whether the efficiency looks okay across all bands for you.
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#QMX #Finals...did I kill it?
#qmx
Hello all! I have a QMX rev. 1 low band that has faithfully served me on 19 POTA activations, almost 1,000 QSOs and, recently, I was successfully using for my first 4 JS8Call contacts. After using it at new ham's house this morning to show him how to adjust for a resonant antenna length (using the QMX's SWR sweep function), it now puts out 0.2 watts...and ONLY 0.2 watts...on all bands. Everything else is in the green on the diagnostics. This is my first kit rodeo and I assembled it 7 months ago. That's my first though (Factory reset did not change the issue).
Secondarily, does anyone have the link to the latest and greatest source for the proper transistors? (If that is the issue)
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Re: Low Band QMX Spectrum analyzer measurments
Thanks Ron,
I reckoned that if the manufacturer wrote the maximum limit on the front of the analyser that was what it would cope with. I'm running about half that power.
I've got a home made attenuator attached to my home made 8W dummy load which is about 38.7 dB attenuation, I'll give that a go.
Well you may have a point, using my home made attenuator puts the second harmonic at about -52 dB.That's relative to the primary that's about -2.5dBm
My home made dummy load consists of 4x 2W 50R thick film SMD resistors, then a 2k2 through hole resistor with the output across 2x100R SMD resistors.? My NanoVNA suggests that it's quite linear. I wouldn't trust it for absolute power measurements but maybe it's better for relative power.
dBc? Ah, relative to carrier.
Must look for more attenuators at the next radio boot sale...
Thanks,
Chris, G5CTH
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Re: QMX Feature Request - field “tune” mode
The aggressiveness with which the QMX swr protection kicks in gives me the confidence that I can present some pretty horrendous mismatches at the RF port and finals will be fine.
G0UPL demonstrates in?around the 5 minute mark.
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Re: QMX Feature Request - field “tune” mode
Chris G5CTH,
The N7VE is an absorptive bridge, so it is not the same thing. ?Power is intentionally dissapated while never allowing the transmitter to see greater than a 2:1 SWR no matter whether a dead short or open at the antenna end of things (while in circuit, I.e. tune mode).?
The op said he wanted to protect the rig while adjusting his loading coil. If the connection to the antenna goes open while adjusting, what will the QMX finals see? Personally I wouldn’t chance it.?
73 Steve W6WU?
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Re: looking for non-US keyer chip
To that I'd look at?
its a Arduino based keyer that's feature loaded and open source.
--
Allison
------------------
Post online only,?
direct email will go to a bit bucket.
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Re: Low Band QMX Spectrum analyzer measurments
Chris, you technically don't meet the -43 dBc requirement for harmonics on your 80 meter reading. However, I would suggest you add some more attenuation in the path to the SA. At?+15 dBm currently, you are getting very close to the maximum CW level of?+20 specified for your SA. Even though you probably aren't damaging the instrument you are possibly over-driving it and causing it to generate excessive harmonic energy internally. If you have another 10-20 dB attenuator available, put it in line with the 20 dB one and see if the fundamental and all the harmonics come down by that much, or if the harmonics drop even more than that, which would indicate it was overloaded at only 20 dB of attenuation.
Good luck ... 73 ... Ron
The High band spectrum analyser topic prompted me to post similar measurements I made with a low band QMX using an apparently good spectrum analyser.
I've attached the data and my analysis. It should describe what I did.
What strikes me is that the first harmonic may be a bit high, -40 dB on 80m.? The power also seems to be a bit low.
What do people think, do I have anything to worry about?
I did get the feeling that something changed after using it with a vertical antenna, the power seemed to decrease.? I've some spectrum analyser traces before that where the harmonics were lower but they were running at a lower supply voltage.
I know that power levels isn't an exact science but are the harmonics OK?
Chris, G5CTH
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Re: Magical smoke out of QDX, two leftmost BS170 very hot
Measured, all good, replaced BS170s and back in business, 5 quick QSOs over Europe from my balcony on the 1st floor are proof
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Low Band QMX Spectrum analyzer measurments
The High band spectrum analyser topic prompted me to post similar measurements I made with a low band QMX using an apparently good spectrum analyser.
I've attached the data and my analysis. It should describe what I did.
What strikes me is that the first harmonic may be a bit high, -40 dB on 80m.? The power also seems to be a bit low.
What do people think, do I have anything to worry about?
I did get the feeling that something changed after using it with a vertical antenna, the power seemed to decrease.? I've some spectrum analyser traces before that where the harmonics were lower but they were running at a lower supply voltage.
I know that power levels isn't an exact science but are the harmonics OK?
Chris, G5CTH
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Re: looking for non-US keyer chip
Kanga Products (UK company) do official K1EL winkeyer chips for not a lot at all....
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Re: looking for non-US keyer chip
Hi Ron,
You could get an ATTINY chip from Digikey and program it.? Digikey seems to have a way of getting orders into USA without their customers incurring $35 customs brokerage gouges.? Also, see the free shipping statement in Digkey's T&C in part 6.?
You could mail them a paper cheque with your order that includes whatever sales taxes apply to your location and they'll ship it for free.? I think that's because the owner of Digikey is a ham who started the business in part because he wanted to offer a keyer kit and found it difficult to purchase parts in small quantities.
Cheers
Halden VE7UTS
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Timothy Fidler
Donald S Brant Jr
Ronald Taylor