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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Re: Brainstorm question: How to "view" QDX LED status remotely?
On Wed, Feb 28, 2024 at 07:51 AM, Colin Kaminski wrote:
What if you remove the LED and resistor and drive an Arduino pin directly?
That may be an option! On Wed, Feb 28, 2024 at 08:00 AM, Paul Jewell wrote:
Could you add a webcam to the remote PC, and point it at the devices, so you can view them remotely? You could also set up a Raspberry Pi and camera, and use that for viewing.
Paul, I have limited upload speed there, (600kbps), so remotely viewing video is rough. But fair point I could use the remote desktop to view on the screen of the remote PC at a reduced quality...but that seems to handle it better than it would directly trying to tap into a security cam that needs 1MBPS or more upload for video.? On Wed, Feb 28, 2024 at 08:17 AM, Alan G4ZFQ wrote:
On 28/02/2024 14:10, Alan G4ZFQ via groups.io wrote:
an easy way of checking operation is looking for spots on WSPRnet.
Or, presuming you are checking by VNC (?) click TX and be monitoring on a local RX.
I run WSP{R/FST4W on at least 3 RXTX QDXs and the situation you describe, no TX, is very rare.
Alan, I use PSKReporter frequently to confirm my TX is going out. Not easy to local RX sometimes.... depending on band/hops. But I'm more concerned about viewing the LED to diagnose a no-TX issue once I know I have it. Also guessing it's more common for me because I'm messing about in WJST-X with changing bands and modes...probably more often than you are with WSPR? On Wed, Feb 28, 2024 at 08:23 AM, Colin Kaminski wrote:
Thinking about this some more, a Trinket M0 could monitor the voltage of the LED with a GPIO and output it while emulating a USB keyboard.
Colin, that is an interesting one! I like this thinking/device! On Wed, Feb 28, 2024 at 08:14 AM, Steve wrote:
Hi Nate.? One quick solution is to purchase a cheap USB enabled DVM with software.?
Steve, that's an easy/quick solution, too. I had the same thought that Donald did about update rate, but fair point it may just work! Thanks for the input, all! Gives me plenty to mull over/think about my options here.? -Nate N8BTR
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Re: looking for non-US keyer chip
I made a no-frills keyer with only 3 standard CMOS ICs. See:??or?replaced?the BJT keying transistor and base resistor with a 2N7000 FET. Also used a 78L05 regulator since it behaved erratically at 12V.
Gary
W9TD
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Re: #qdxm QDX-M - new single-band version of QDX available
#qdxm
On Thu, Jan 12, 2023 at 10:13 AM, Hans Summers wrote:
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.? -Nate? N8BTR
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Re: looking for non-US keyer chip
Ron, I built this one a few years back. It works perfectly.
On Thu, 29 Feb 2024 at 16:27, Chris <chris.rowland@...> wrote: I've made an Iambic keyer using a Teensy, a sort of Arduino on steroids.
As for shipping costs, for small things I use eBay's free shipping or Amazon Prime and go with UK sources, even if they are more expensive than China.
Or wait until I have accumulated enough for a free shipping order from Digikey or Mouser.
Chris, G5CTH
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Re: QMX on Inovato Quadra
I had the same problem this morning, actually. I'm looking into increasing decoder speed any way that I can...I did find that I should not have had the AGC on (I did) and I should have had the audio gain lower than it was (I had to turn it UP for JS8Call). Apparently there are other decode speed options in WSJT-X, so I'm going to try those. Additionally, I had the Quadra running off my tenuous phone Hotspot to keep time, while waiting for my GPS dongle to come in...since Conky is running to keep the time accurate regardless of the input, I assume that some processing will be freed when it isn't relying on NTP but using direct input.?
What was your setup?
I may end up running a PI variation headless off my tablet eventually. The Quadra was cheaper and appealed to my wallet XD
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Re: looking for non-US keyer chip
I've made an Iambic keyer using a Teensy, a sort of Arduino on steroids.
As for shipping costs, for small things I use eBay's free shipping or Amazon Prime and go with UK sources, even if they are more expensive than China.
Or wait until I have accumulated enough for a free shipping order from Digikey or Mouser.
Chris, G5CTH
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Re: looking for non-US keyer chip
Tayda Electronics has Nano clones that are top notch and low cost.??
I've used several of their parts.
Jim, K8IQY
On 2/29/2024 10:59 AM, Brock VA7AV
wrote:
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Show quoted text
I've had good luck with the Elegoo Arduino clones. Both Uno and
Nano. I don't recall whether I used Amazon or AliExpress, but they
work fine. They go into enough projects that I think I bought
3-packs or 5-packs for better pricing.
Brock VA7AV?
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Re: QMX Feature Request - field “tune” mode
?
And for whom with out that dang ole toroid
Or not want to fiddle with winding one
Check out "THE"? GQRP Site
The Resistive SWR Bridge
Highly recommended for both beginners and experienced constructors
https://www.gqrp.com/technical15.htm
N3AAZ
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Donald S Brant Jr
Ronald Taylor
Gary W9TD
Rich Collins
Jim Kortge, K8IQY