Re: New assembled High Bands QDX went into smoke
I'm relaxed again. Really a good, very good trx.
After replacement I could work DX on 17m?. 10 V and 3 Watts. That's enough at the moment. I hope not to kill it again.? I think, the high Band qdx is more sensitiv? against high voltage and bad swr??
I built up 3 QDX low, 2 for other Hams. They still work.?
I got a routine in fixing blown away P A s I think.???
The zener diodes will be a good idea anyway. Maybe Hans you can add some zener diodes to the kit. I know you told me, that it's hard to get the good ones who really work. ?.
But I think it's no placebo. And a kind of protection.?
73 de Matt.?
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Re: 50W amplifier - 13.8V power supply
Yup, been there, done that, got the t-shirt, now have a spare unit for my trouble. I’m so used to autoranging power supplies that I never even saw the yellow sticker advising me that it was set to 240V, so when it didn’t work I bought another one and got an RMA for the first one. “Fortunately” I noticed the sticker before i actually sent the first one back.
73, Willie N1JBJ
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On Jul 16, 2023, at 3:13 PM, Charles Johnson <cjohnson@...> wrote:
To all,
I use 2 Mean Well LRS-150-12 PSUs to power my gear and haven't had any problems except one of them produces a high-pitch WHINE when there isn't enough of a load on it. I have them set to 13.8V output and then just use a buck converter for my QDX. One FYI - I bought both of mine through Amazon and while they shipped from a US location to a US location, the AC supply switches were set to 230V, so check that the switch is in the correct position for your AC supply voltage before use. It didn't damage the units when I connected them to 115V, having not checked the switch (didn't know to on the first, didn't remember to on the second), but the required troubleshooting from the start was a bit annoying.
Regards,
Charles Johnson
KF4AYT
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Bill, ( The Butcher ) N4QA
Another 30m Q for my sweet li'l QDX. Tnx N0AAS.
72 !
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I have a QDX-M and after the final PA transistors and IC5 blew, I replaced them. Anyway, I also amended the configuration in firmware and put the 10m QDX-M on to the 20m band (no other changes made so far), just to try it out. I measured the power output on the 'scope and I get 202mW. As it turns out, PSK Reporter shows that I've been heard in the US on several occasions (as far as Ohio), up into Finland and over into Russia; best actual contact is just over 1,500km.
Turns out, I am quite enjoying the mW'ing :)
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Re: 50W amplifier - 13.8V power supply
To all,
I use 2 Mean Well LRS-150-12 PSUs to power my gear and haven't had any problems except one of them produces a high-pitch WHINE when there isn't enough of a load on it. I have them set to 13.8V output and then just use a buck converter for my QDX. One FYI - I bought both of mine through Amazon and while they shipped from a US location to a US location, the AC supply switches were set to 230V, so check that the switch is in the correct position for your AC supply voltage before use. It didn't damage the units when I connected them to 115V, having not checked the switch (didn't know to on the first, didn't remember to on the second), but the required troubleshooting from the start was a bit annoying.
Regards,
Charles Johnson
KF4AYT
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0.1 mm space is a bit tight for the via opening. The pins have part of a mm tolerance on diameter and solder is cheap... Maybe a quarter mm larger diameter to make fitting the part easier...
Have fun!
Bob
--
Bob WO6W
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Doh!... Yes, I am... duh sorry for the brain freeze...? I'm feeling better now (grin)
Thank you Evan
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I’m now contemplating a 50 watt amp for 20 CW
Mel,
Just as an FYI, with my QDX outputting between 2W-3W (I don't have my test records handy, but I know that it's between those power levels) and a 50W PA built for 20m supplied with 13.8V, I get ~13W (IIRC) output into a QRP Labs 20W dummy load. That's definitely a step up from the QDX's output?and the PA acts as an SWR buffer (if that makes sense), but the PA manual's chart is correct wrt power output at low supply voltages (I haven't tested high supply voltages, so I can't comment on those results).
I'm not saying to not build the PA, but on 20m, unless you're giving the PA 20+V for supply, it may or may not be worth it (think 'battery life'). YMMV ?
Regards,
Charles Johnson
KF4AYT
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Glenn,
Are you confusing the QDX or QMX with the QCX+?? The QCX+ is a CW rig that can do CW WSPR.? WSPR does not need a computer nor a PTT signal to operate.? It is configured in the QCX+ memory and triggered by a menu selection.
73
Evan
AC9TU
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Great! thanks Mike...
That makes me wonder how the rig is switched from xmit to rcv when using one of the digital modes?
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On the QCX rigs the PTT is an output. See the QCX+ assembly manual
page for your particular rev board as it changed and you need to use
the proper wiring for your revision.
-mike/w1mt
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On Sun, Jul 16, 2023 at 2:03?PM Glenn W2BX <fintronicsusa@...> wrote:
I'll make an assumption.. the "PTT" jack on the rear of the QCX+ is an input for when you're using a CAT device or some sort of PC software.
What I need is a contact closure on transmit, like most modern transceivers have a PTT out to key an amplifier or in my case to bypass a BCB band stop filter on transmit. Perhaps I can take a signal somewhere on the board and drive a external transistor to key a relay.
Thoughts?
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I'll make an assumption.. the "PTT" jack on the rear of the QCX+ is an input for when you're using a CAT device or some sort of PC software.
What I need is a contact closure on transmit, like most modern transceivers have a PTT out to key an amplifier or in my case to bypass a BCB band stop filter on transmit. Perhaps I can take a signal somewhere on the board and drive a external transistor to key a relay.
Thoughts?
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I just read on another thread that T1 rarely needs adjusting on the 20m version.
... continuing my build... just finished installing that boat load of caps!?The assembly manual is absolutely fantastic, and that's coming from someone who's done quite a bit of technical writing. I've built quite a few kits, homebrew devices over the years and I learned a long time ago to take it s-l-o-w one step at a time, no rushing in a quite, well lit place....?
Can't wait to get this baby on the air!!
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Next version,
hopefully pin spacing corrected and also the holes have a 0.9mm
size now.
I am having an hard time creating the 3D model in FreeCAD,
chamfer is not working and the 3d model is ugly:
Giuseppe? Marullo
IW2JWW - JN45RQ
On 7/16/2023 6:31 PM, Giuseppe
Marullo[iw2jww] wrote:
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Thanks Bob,
I will correct it, always willing to learn. I found somewhere
else it was a 0.7" spacing, then 0.75" and I probably didn't
correct it.
For the hole, where did you find it? I guessed 0.5mm for the
pins, but again...a guess. Ah, Now? I see there is? 0.8mm +/-
0.1, so maybe? 0.9/1mm is a better choice.
The pin orientation was the biggest issue for me, glad I did it
right.
Giuseppe Marullo
IW2JWW - JN45RQ
Back to the tool...
On 7/16/2023 5:02 PM, Bob, WO6W
wrote:
It looks like your pin spacing and via dimensions are wrong...
I found the OSC5A2B02 on ebay showing pin 1-3 and 1-5 with
19.05mm spacing.. pins 0.8mm.
Your spacing is? 17.78mm with via hole size 0,762 mm.
You need to correct both pin positions and via dimensions...
Pin orientation looks correct.
I can do a brief Zoom with you later today and show you how to
adjust these on your footprint... I can also show yo how to make
the part construction a bit easier!
73
Bob
wo6w at a r r l dot net
--
Bob WO6W
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Thanks Bob,
I will correct it, always willing to learn. I found somewhere
else it was a 0.7" spacing, then 0.75" and I probably didn't
correct it.
For the hole, where did you find it? I guessed 0.5mm for the
pins, but again...a guess. Ah, Now? I see there is? 0.8mm +/- 0.1,
so maybe? 0.9/1mm is a better choice.
The pin orientation was the biggest issue for me, glad I did it
right.
Giuseppe Marullo
IW2JWW - JN45RQ
Back to the tool...
On 7/16/2023 5:02 PM, Bob, WO6W wrote:
toggle quoted message
Show quoted text
It looks like your pin spacing and via dimensions are wrong...
I found the OSC5A2B02 on ebay showing pin 1-3 and 1-5 with 19.05mm
spacing.. pins 0.8mm.
Your spacing is? 17.78mm with via hole size 0,762 mm.
You need to correct both pin positions and via dimensions...
Pin orientation looks correct.
I can do a brief Zoom with you later today and show you how to
adjust these on your footprint... I can also show yo how to make
the part construction a bit easier!
73
Bob
wo6w at a r r l dot net
--
Bob WO6W
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Re: New assembled High Bands QDX went into smoke
Just a point of clarification, the BS170 is not driving 50 ohms. There is a transformer in between that reduces the impedance by the square of the turns ratio. And the turns ratio is the ratio of the 50 ohm side of the transformer to the half winding seen by
the BS170. The BS170s will see roughly???of 50 ohms.
Tony
AD0VC
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From: QRPLabs@groups.io <QRPLabs@groups.io> on behalf of Lee via groups.io <kx4tt@...>
Sent: Sunday, July 16, 2023 10:13 AM
To: qrplabs@groups.io <qrplabs@groups.io>; QRPLabs@groups.io <QRPLabs@groups.io>
Subject: Re: [QRPLabs] New assembled High Bands QDX went into smoke
?
Dave and I have discussed this at length; there are a large quantity of chewed-up textiles from our discussions. To add to his comments,? his calculation below is based on 50 + 0i? ohms, which is a PURELY RESISTIVE load with
a SWR of 1:1. Even if Z = 50 ohms, you can have V >> 47 V p-p if the load is reactive. If you want to play with the math, try calculating the impedance a 30 ohm resistive with first a 40 ohm inductive reactance then a 40 ohm capacitive reactance........................
Lee KX4TT
On Sunday, July 16, 2023 at 04:02:24 AM EDT, David Birnbaum <dbirnbau@...> wrote:
The relevant voltage is NOT 12V.? The RF voltage is over 40V.? For 5W into 50 ohms the voltage is roughly 47 V p-p.? If the SWR is greater than 1:1 the voltage goes up.? The BS170 has a max voltage of 60V, so it's running near breakdown
dave
k2lyv
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Re: New assembled High Bands QDX went into smoke
The difference between 3 and 5 watts is rather miniscule (for instance, you are copied at -14 or -15 dB instead of -13 dB); why not simply run the QDX at 10 volts?? K2LYV's calculation would then be ~38V (no actual calculation done; I just eyeballed it), which provides a bit more headroom. Of course, all bets are off if the antenna has a highly reactive element (see my last comment). Allison, KB1GMX and others have pointed this out as a reasonable solution; a little bit of applied math (or maths as the folks across the pond would say) bears her and the others out. The zeners may be a perfectly good backup dependant upon the internal capacitance across the diodes, but lowering the voltage a bit is easier.?
Lee KX4TT
On Sunday, July 16, 2023 at 12:10:27 PM EDT, mweidle@... via groups.io <mweidle@...> wrote:
I could fix the fault. Got 4 new BS170 and changed the 74ACT now only using 10V supply .I got 3 Watts Output. Until I get my zener Diodes I will not use a higher Power
73 de Matt
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Re: New assembled High Bands QDX went into smoke
Dave and I have discussed this at length; there are a large quantity of chewed-up textiles from our discussions. To add to his comments,? his calculation below is based on 50 + 0i? ohms, which is a PURELY RESISTIVE load with a SWR of 1:1. Even if Z = 50 ohms, you can have V >> 47 V p-p if the load is reactive. If you want to play with the math, try calculating the impedance a 30 ohm resistive with first a 40 ohm inductive reactance then a 40 ohm capacitive reactance........................
Lee KX4TT
On Sunday, July 16, 2023 at 04:02:24 AM EDT, David Birnbaum <dbirnbau@...> wrote:
The relevant voltage is NOT 12V.? The RF voltage is over 40V.? For 5W into 50 ohms the voltage is roughly 47 V p-p.? If the SWR is greater than 1:1 the voltage goes up.? The BS170 has a max voltage of 60V, so it's running near breakdown
dave k2lyv
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Re: New assembled High Bands QDX went into smoke
Matt,
AliExpress has the Zeners, 1N4756, 1W 47v. I'm not in the US/EU, but they are very cheap here, about a dollar for 50 and a dollar for shipping.
73,
Casey, NA7U
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Re: New assembled High Bands QDX went into smoke
I could fix the fault. Got 4 new BS170 and changed the 74ACT now only using 10V supply .I got 3 Watts Output. Until I get my zener Diodes I will not use a higher Power
73 de Matt
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Lee