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#qmx One bug and one idea
#qmx
Hans,
One bug, and one idea. Bug:? When doing RF image sweep immediately after startup via console (doing nothing else), the graph shows no rejection on 80m.? When I switch bands and come back to 80m, I get -25dB rejection and it works.? Not sure exactly what's going on, but I'd suspect something isn't getting set in line right. Idea:? I've noticed that the BPF for 40m, 60m, and 80m are all the same BPF tap (Full inductor, 1200pF) using IC402 Y3 / Pin 13.? I feel like it wouldn't be too hard to put a another capacitor in C403? (DNP in 20-80m rigs) and have pin 10 selected for 60/80m (or just one of them, depending on what gets tried) and adding in a dozen turns or whatever onto L401 that cross over the incoming pin from RX_IN.? Discovered this while tuning my BPF, I think I left a turn off L401, all the BPF filters are up off center, but then I was wondering why 60m/80m was so far off center, finally realizing it's shared with 60m/80m.? Is there a way to manually set the BPF configuration for 60/80?? (Or is there a way to do a test build that I can load?)? Since I can't do it myself since the firmware isn't open, I have to ask.? (Not criticizing there, I get why you wouldn't want to release the source code). |
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Re: #qmx High Noise on all bands, screwy receive and bad diagnostics
#qmx
Alrighty, I got the replacement PCM1804's in, and the replacement went off without a hitch.? I cleaned up the pads, put down a touch of paste, hit each pin with the knife edge soldering iron, gave it a good IPA clean, and it worked.? The only victim of all my debugging was 20m, first initial try and it was getting no receive on that band, which I traced back to having left the BPF split toroid (L401) unsoldered at the mid tap.? Putting that back in and it RX's just fine.? I can't say I enjoy the user interface as much as my KX3, but hey.? Martin |
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Re: #qmx Base PCB washability
#qmx
Sounds good, I just cleaned the backside, I didn't really need to immerse the whole thing, but a good scrubbing with an ultra-soft toothbrush leftover from the dentist and 99% IPA did the trick.? The QMX of Theseus lives......!
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Re: #qmx Base PCB washability
#qmx
Hi Martin,? 73, |
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#qmx Base PCB washability
#qmx
Hi,
What is the washability of the main PCB?? Naturally, I wouldn't wash the display/encoder boards, but I might like to remove some of the flux I've added in the QMX of Theseus (as I'm now going to call it).? I normally wash my PCB's with technical grade IPA and/or hot water with a soft toothbrush for scrubbing before drying really well, but since I didn't design this PCB, my biggest concerns are the audio jacks.? Anything else I should be concerned with? [*taps foot waiting for Fedex to deliver new AD codecs*] |
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Re: QMX - Any progress on key clicks please?
On Thu, Mar 14, 2024 at 05:03 AM, Charles Johnson wrote: That's what I get for posting way too late at night! My overall point, though, remains: namely, that due to the different impedances, the performance of the output audio amplifiers will not be exactly the same, thus possibly explaining why clicking was being heard in ear buds, but not via a line-level input. Due to the comments on it going away at low volumes, however, I'd lean towards the impedance differences merely amplifying (no pun intended) the true source of the problem, rather than being the problem.
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Re: NEED TO KNOW STATUS OF QMX HI BANDS SHIPMENT... Order# 81173 - ORDERED IN DEC 2023
Hi Larry I did reply to your helpdesk ticket almost immediately the same day you wrote it. But it would appear that some email providers such as are further ratching up their spam filter aggressiveness. Previously it applied to shop emails only but now it appears helpdesk emails are also getting affected. I'll forward you by email what I wrote. But anyway others have already sent you the link.? 73 Hans G0UPL On Thu, Mar 14, 2024, 10:25?PM Larry, AH6AX <lpwandel@...> wrote: Hans:? I'm unable to get any info from your site re: my Dec 2023 order for HI-Bands QMX (factory built). Order No. 81173. When I go on site and request support, I'm told I need to give my 'ticket #); however, although I submitted a ticket last week, I did not know I was to keep the number.? I then went to site to request status and sent that I did not know number. I've been waiting for an email response with ticket number so I can ask the status of the order that I made in December.... My email is correct but for some reason I can't get the email from QRP Labs... (Yes, I checked spam & junk files...)Please help! Thank you! This forum seems to be the only way I can contact you at the moment!!! |
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Re: NEED TO KNOW STATUS OF QMX HI BANDS SHIPMENT... Order# 81173 - ORDERED IN DEC 2023
Hi Larry, You're in #465 73, Wei, AG6AQ On Thu, Mar 14, 2024 at 12:25?PM Larry, AH6AX <lpwandel@...> wrote: Hans:? I'm unable to get any info from your site re: my Dec 2023 order for HI-Bands QMX (factory built). Order No. 81173. When I go on site and request support, I'm told I need to give my 'ticket #); however, although I submitted a ticket last week, I did not know I was to keep the number.? I then went to site to request status and sent that I did not know number. I've been waiting for an email response with ticket number so I can ask the status of the order that I made in December.... My email is correct but for some reason I can't get the email from QRP Labs... (Yes, I checked spam & junk files...)Please help! Thank you! This forum seems to be the only way I can contact you at the moment!!! |
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Re: NEED TO KNOW STATUS OF QMX HI BANDS SHIPMENT... Order# 81173 - ORDERED IN DEC 2023
Hi Larry, ? You are 463rd in line as of March 14th. I don¡¯t know how many he is making a week right now but 30 a week was the number the last time I followed it.? |
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NEED TO KNOW STATUS OF QMX HI BANDS SHIPMENT... Order# 81173 - ORDERED IN DEC 2023
Hans:? I'm unable to get any info from your site re: my Dec 2023 order for HI-Bands QMX (factory built). Order No. 81173. When I go on site and request support, I'm told I need to give my 'ticket #); however, although I submitted a ticket last week, I did not know I was to keep the number.? I then went to site to request status and sent that I did not know number. I've been waiting for an email response with ticket number so I can ask the status of the order that I made in December.... My email is correct but for some reason I can't get the email from QRP Labs... (Yes, I checked spam & junk files...)Please help! Thank you! This forum seems to be the only way I can contact you at the moment!!!
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Re: power supply plug
¿ªÔÆÌåÓýwhat manual.? none was received and i have not been able to find one online dave On 3/14/2024 11:38 AM, geoff M0ORE via
groups.io wrote:
Does the manual not describe what it use is?? |
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Re: QMX Rev 3 USB connector
I've mentioned this before: before shipping, all boards have their bootloader programmed and verified, and that there are no shorts on the 3.3V rail, and that there is successful USB connectivity. The soldering of the USB connector looks rather bare but there IS a connection. My recommendation to touch up with some extra solder is only to strengthen the connection which looks a bit delicate for my liking.? 73 Hans G0UPL On Thu, Mar 14, 2024, 7:24?PM Greg McCain via <gamccain50=[email protected]> wrote: Yep. Mine looked the same. |
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Thx Adrian, Hans and Allison.
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Appreciate the feedback. Will proceed carefully. Greg
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15M? results say the amp has issues. Either low bias or LPF filter??
20M 10W for 2 in seems? a bit low as well (I'D expect 13-15W) At the same time the 40M results suggests maybe other things going on. For 40M at 3W in I'd expect about 17-25W at 13.8V.? Part of the reason is there was no intention to get flat gain from the amp.? No surprise with a class C amp.? Hoeever if the bias is set high you do get more power and possibly other things like spurs. The IRF510 is performs poorly at lower voltages that why at 20V it can easily do 50W but at 13.8 you may get around 20W. Oddly I have an amp that uses MRF141(dual) and at 28V its easily 330W, but at 13.8V it barely does 90W for the same drive.? THis is often seen with all Mosfets and Bipolar devices because whne you lower votlages characteristics change. -- Allison ------------------ Post online only,? direct email will go to a bit bucket. |
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Yes, 100% agreed with Allison.? MOSFETs don't have an intrinsic frequency limit like a bipolar. Which is also why good board layout and attention to parasitics is important because you can easily get VHF oscillations.? But as Allison said the gate capacitance is the issue. Which in other words means it gets harder and harder to match the ever lower impedance efficiently as you go up in frequency.? Even though the IRF510 is often accused of only being a car headlamp switching transistor... These capacitance and impedance issues affect even "real" RF MOSFETs as much or almost as much.? With careful feedback and layout as in the 10W Linear amp kit the gain can be made quite flat across HF 1.8-30MHz to within a dB or two.? The 50W PA kit was a much more basic design effort originally done for 40m where everything is easiest as Allison mentioned. Reasonable worthwhile performance obtained up to 20m made those acceptable options too. I'm not surprised 15m was even lower down.? 73 Hans G0UPL On Thu, Mar 14, 2024, 7:30?PM ajparent1/kb1gmx <kb1gmx@...> wrote: I have a linear amp that gets over 40W at 6M using IRF510s. |
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I have a linear amp that gets over 40W at 6M using IRF510s.
Wasn't hard to do that. The characteristics are not great but its not about capacitance as a sole factor.? Then again input Z is a factor even MRF and BLF series MOSFETs. The problem of wideband amps with MOSFETs is input and output matching. The gate is a capacitor and that makes input matching difficult.? Most designs using IRF510 or IRF530 40M is a sweet spot.? The problem being input impedance goes down with increasing frequency. Develop voltage at the gate effectively you get power out. -- Allison ------------------ Post online only,? direct email will go to a bit bucket. |
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Re: QMX Rev 3 USB connector
Yep. Mine looked the same.
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Took Han's advice and touched them up. Super pointy iron tip, turned down the heat a bit and easyyyyy on the solder. I have a bit of 0.015 inch solder. Goes fast. I do use a head lamp magnifier, board holder armature and anchor my little fingers somewhere on the edge of the pcb or armature when possible so my iron and solder feed motions are as steady as possible. Easy to create bridges here ... Yep did that also in two places though they were minor. Just reheating one pad side briefly with a clean tip that has no solder on it caused the bridge to whisk itself back into the heated pad. Whew ... In hind sight, might just leave them as is and see how it works on startup. Can always go back and touch them up.? Greg KI4NVX
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Colin Kaminski
Larry, AH6AX
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