Re: QRP Labs postage stamps
Hi Jim
We post 600-800 packages per month. A lot of money!?
73 Hans G0UPL? ?
How did you pull that one off, Hans?
The word about QRP Labs is definitely getting out!
73 de Jim KM5M
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I think TLC272 should also do the job, except perhaps for the final headphone stage. It's a similarly specced part, and is available in DIP.
Regarding the supply voltage, look at the lowermost right corner. There you see (ok, it's an educated guess) all of opamps being supplied straight from 12V rail. Common sense tells that too, since the common mode voltage used in the circuit is 5V.
Karlis
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You are correct: the TS922 is now only available in SMD packages. You would either have to find some NOS DIPs or use an SOIC to DIP adapter. The other alternative is to find another suitable part. So far as I can tell, the QCX schematic doesn't show what the power supply voltage supplied to those ICs is, so I can't tell whether they are attached to the nominally 12V input or to the 5V regulated output. If it's the latter (which is suggested by the bias circuit seen on IC9) you could use a lower voltage op amp such as the TLV2462, which is the op amp that Adafruit sells to replace the TS922. It's a 2.7-6V op amp that otherwise has similar specifications and the same pinout. IC10 (the output amplifier) appears to be biased to run from the 12V rail so it definitely should NOT be replaced by a lower voltage part. On Sun, Sep 2, 2018 at 5:33 PM, John VA7JBE via Groups.Io <va7jbe@...> wrote: There's some great advice in this thread and replacing IC6-9 sounds like a
worthwhile mod, but I'm having a bit of trouble sourcing the TS922 in a DIP8
package. They seem to have been discontinued in favor of SMD packaging.
Does anyone know of a source for these or a substitute that's still in
production?
Cheers,
John VA7JBE
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To get the best power output from QCX.
---
This email has been checked for viruses by AVG.
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Re: My first time QCX build - fail.
I've made progress but it still isn't working right. I rewired T1 and reinstalled it. That fixed the loud tone but I caused more problems. I lifted a trace off the board from pin 4 of T1. It appears to me to go to the source of Q5 so I hooked it directly to it. It now seems to work but I can't hear anything but noise and clicking when on an antenna. Also, now when I key the transmitter I can barely hear it in another receiver where before it was a strong signal. I'm close to giving up. I no longer have test equipment except a DMM.
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There's some great advice in this thread and replacing IC6-9 sounds like a worthwhile mod, but I'm having a bit of trouble sourcing the TS922 in a DIP8 package.? They seem to have been discontinued in favor of SMD packaging.? Does anyone know of a source for these or a substitute that's still in production?
Cheers,
John VA7JBE
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Re: QCX Enclosure Modification Video (detailed) by Juddie WD8WV
#case
#qcx
#encl
Great job on this video again Juddie with that CW switch plunger.? I did the same with mine, but I made my own plunger mod similar to yours.? I am interested now, in your "tilt up" stand that I can see in your video shots.? Can you describe how you did that?? Thanking you in advance and 73, de Karl, KO8S
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Re: U3S on 630M "crashes" the system.
#u3s
#630m
??? I do not know if it helps, but I have encountered all sorts of resets ,frequency shift?and blocking LCD?with VFO signal generator transformed into TX WSPR in 28 and 14 Mhz. Now I'm feeding the three BS170 with two LM7805 in parallel and the rest with a single LM7805. I chose?two LM7805 with the same voltage (4.98V) at 0.5A for parallel mounting without equalizing resistors. The secret I think is in the multilayer 0,47microfarad capacitors connected briefly between the input and the?GND at each LM as recommended by the manufacturers. The LM7805 is better than any other 7805. Everything goes right now for days ?with these? three?LM sources powered by an?single ?ordinary SMPS?9V / 1.5A? wall type.?? Obviously there are also 2 pieces short-mounted of 1000micro / 10V for each LM and a heater . Best wishes! ?Daniel , 73? YO8SAK
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Hi Alan,
Academic??
ALL failures are an opportunity to learn and make a product more robust.
I am surprised no one has talked about bringing up the power in steps? Measuring things as we go up to full power.
From where I look, this would give up real data to look at in the event of failure.
Lots of fun :).
John Concord, NH
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On Sun, 2 Sep 2018, Alan de G1FXB via Groups.Io wrote: Hi Glenn,
I'm in defence of all Hans views as well.?
/g/QRPLabs/message/26421
(I keep pointing out his statement that he has never experienced a failure
of any prototypes and beyond to production testing.
Last was my Post /g/QRPLabs/message/26498)
What I'm trying to understand is the conditions that lead upto what appears
to be a one or two a week report of PA failure,
Is it always user abuse, and / or is there any easy solutions ?.
My posts:-
/g/QRPLabs/message/26420
?/g/QRPLabs/message/25533
/g/QRPLabs/message/25822
Putting it into perspective the QCX has celebrated it's first birthday
Best case, its perhaps 52 out of 5500 units built, equates to just over 1%
failure(?)
of the most heavily stressed and abused components of any transmitter.
(it's probably fair to assume that failure is likely to be under rather than
over reported,
many would just replace the components rather than post a question about it
here?)
It's academic, we will move on and soon have a new unit to talk about.? :-)
Alan
On 02/09/2018 16:44, Glen Leinweber wrote:
In defense of Hans,
I don't recall seeing a brag about QCX able to handle
infinite-SWR conditions. (ie: antenna short or open-circuit).
?I can see a dangerous scenario....
if you're using an open-circuit type outdoor antenna - one that
measures open-circuit resistance between driven
element and ground. An extreme example might be a kite-elevated
long wire. This type of antenna can attain
a considerable charge, and rise to very large DC voltage levels.
Then you attach this antenna to your radio. Could even be an
un-powered radio....
Ka-blooy!
The QCX has an output filter that nearly floats as far as DC is
concerned. It has a path through R43, a 120k resistor
to one of the four 74ACT00 logic gates - most likely in a logic
"high" state. If you measure the DC voltage at the
antenna connection terminals with a high-Z DC voltmeter, you'll
measure close to +5V.
I would ensure that any antenna has a DC path to ground, either
through a RF choke, or a resistor, to bleed off any
static charge. The QCX's 120k resistor path is too feeble to
serve as a reliable discharge. A charged antenna can
blow the finals nearly instantly when connected. There is no
over-voltage antenna protection in the QCX.
A loop-type antenna is safer from this scenario, but I'd still
include a discharge path from the loop to earth.
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Hi Glenn,
I'm in defence of all Hans views as well.?
/g/QRPLabs/message/26421
(I keep pointing out his statement that he has never experienced a
failure of any prototypes and beyond to production testing.
Last was my Post /g/QRPLabs/message/26498)
What I'm trying to understand is the conditions that lead upto what
appears to be a one or two a week report of PA failure,
Is it always user abuse, and / or is there any easy solutions ?.
My posts:-
/g/QRPLabs/message/26420
? /g/QRPLabs/message/25533
/g/QRPLabs/message/25822
Putting it into perspective the QCX has celebrated it's first
birthday
Best case, its perhaps 52 out of 5500 units built, equates to just
over 1% failure(?)
of the most heavily stressed and abused components of any
transmitter.
(it's probably fair to assume that failure is likely to be under
rather than over reported,
many would just replace the components rather than post a question
about it here?)
It's academic, we will move on and soon have a new unit to talk
about.? :-)
Alan
On 02/09/2018 16:44, Glen Leinweber
wrote:
toggle quoted message
Show quoted text
In defense of Hans,
I don't recall seeing a brag about QCX able to handle infinite-SWR
conditions. (ie: antenna short or open-circuit).
?I can see a dangerous scenario....
if you're using an open-circuit type outdoor antenna - one that
measures open-circuit resistance between driven
element and ground. An extreme example might be a kite-elevated
long wire. This type of antenna can attain
a considerable charge, and rise to very large DC voltage levels.
Then you attach this antenna to your radio. Could even be an
un-powered radio....
Ka-blooy!
The QCX has an output filter that nearly floats as far as DC is
concerned. It has a path through R43, a 120k resistor
to one of the four 74ACT00 logic gates - most likely in a logic
"high" state. If you measure the DC voltage at the
antenna connection terminals with a high-Z DC voltmeter, you'll
measure close to +5V.
I would ensure that any antenna has a DC path to ground, either
through a RF choke, or a resistor, to bleed off any
static charge. The QCX's 120k resistor path is too feeble to serve
as a reliable discharge. A charged antenna can
blow the finals nearly instantly when connected. There is
no over-voltage antenna protection in the QCX.
A loop-type antenna is safer from this scenario, but I'd still
include a discharge path from the loop to earth.
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Re: My first time QCX build - fail.
Oops, sorry.? I meant Jim, not Ted? :-)
72 de Gary W0ITT
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Re: My first time QCX build - fail.
Ted - I had a similar experience.? Be sure you are using a stereo plug in the key jack.? The QCX requires one.? If you put in a mono plug it just keys the transmitter, and the tone you hear may be the side tone.?
After my build I heard a tone, so I took my time to carefully do the alignment steps.? That ruined my finals because they were on transmit for so long,? To make sure, when you're doing alignment just unplug the key from the jack and use the little onboard key.
I had to replace several transistors.
That may not be your problem, but it is one to avoid.
72 and good luck
Gary W0ITT
?
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In defense of Hans,
I don't recall seeing a brag about QCX able to handle infinite-SWR conditions. (ie: antenna short or open-circuit).
?I can see a dangerous scenario....
if you're using an open-circuit type outdoor antenna - one that measures open-circuit resistance between driven
element and ground. An extreme example might be a kite-elevated long wire. This type of antenna can attain
a considerable charge, and rise to very large DC voltage levels.
Then you attach this antenna to your radio. Could even be an un-powered radio....
Ka-blooy!
The QCX has an output filter that nearly floats as far as DC is concerned. It has a path through R43, a 120k resistor
to one of the four 74ACT00 logic gates - most likely in a logic "high" state. If you measure the DC voltage at the
antenna connection terminals with a high-Z DC voltmeter, you'll measure close to +5V.
I would ensure that any antenna has a DC path to ground, either through a RF choke, or a resistor, to bleed off any
static charge. The QCX's 120k resistor path is too feeble to serve as a reliable discharge. A charged antenna can
blow the finals nearly instantly when connected. There is no over-voltage antenna protection in the QCX.
A loop-type antenna is safer from this scenario, but I'd still include a discharge path from the loop to earth.
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Re: QSX radio feature requests
Hello Allison and Hans
Many thanks for the detailed reply, I will take on board both yours
and Hans' advice, much appreciated!
Friday, August 24, 2018
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On Fri, Aug 24, 2018 at 02:54 AM, Chris Wilson wrote:
I would value Allison's opinion on how important FET lead lengths and
trace routing and widths, and those of FET driver IC's remain at LF
and MF as I am fond of experimenting "down there", particularly with
Class D amps. I suspect it is still important as gate and drain
traces seem to respond to careful minimisation of lead lengths and
usage of wide traces.
Its very simple, IF you want long leads stay near DC. Look leads for high current
fast rise time pulses are essentially no different hat upper HF to VHF CW signals. Think of this way would you intentionally put a choke in series with the three legs?
Of course not but yet many don't consider a 40nh lead as important. I've used those driver ICs to 13.56mhz. More of same for wide traces and ground planes. Or from a different view point Hans did it right and it works to VHF. Allison _._,_._,_ -- 2E0ILY Best regards, Chris mailto:chris@...
--
Best regards, Chris Wilson (2E0ILY)
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Re: #QCX 4174 Ready for practice test
#qcx
The practice test was negative. My mistake: My tuner tunes to antenna voltage, no control of adaptation to the PA. This caused the PA to overload, causing the MPS2907 to burn. Repair ok. Change tuner is in progress.
I use follow regulator https://www.ebay.de/itm/Mini-DC-DC-4V-12-24V-To-5V-3A-Adjustable-Step-Down-Power-Module-Buck-Converter/272694825804
In my overvoltage-protection the 0,47? - C is reduced to 10nF
There is a unknown problem on my QCX: Full QSK works fine, Semi QSK not - no intermission between the characters (version 1.00e)
73 DL8LRZ
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It would be good to get to the bottom of
what brings on the perfect storm while Hans testing didn't highlight anything. Alan, I don't know how Hans had no trouble although it could be that most QCX do survive abuse. Maybe only a few actually have problems? The design here was mentioned by someone, it shows how to protect 3 little BS170s from some class E hazards. Difficult to spot the actual PA components! 73 Alan G4ZFQ
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The LDG Z-100Plus requires only 0.1 watt to tune according to LDG and is rated for 125 watts which leads me to think that it has lower losses than some of the "QRP" tuners with much lower ratings.? Dunno for sure about that.? It uses latching relays so power consumption is almost zero once tuned.?
?
No relation to the company...just a satisfied user.
?
73,
?
-Lee-??? WA3FIY
?
------ Original Message ------
From: "Richard Harris via Groups.Io" < g3otk@...> Sent: 9/1/2018 2:07:18 PM
Subject: Re: [QRPLabs] QCX tuning
?
Hi Matthias,
When tuning, the T1 auto-ATU may present an impedance to the QCX that causes excessive current to flow through the PA FETs or causes an excessive voltage across them? One solution is to connect an attenuator between your QCX and T1 auto-ATU when it is tuning and disconnect it when a match has been found.? ?This will limit the range of impedance "seen" by the PA FETs.? A 3dB attenuator will ensure the QCX "sees" a load between about 17 and 150 Ohms.? A 6dB attenuator will ensure that the load is always between about 40 and 85 Ohms.??
When I built an auto-ATU for my 20m QCX, I thought that damage to the PA FETs was possible and so while the ATU is tuning an attenuator is switched into circuit by means of a relay.??
Richard G3OTK
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Never a truer word said in jest,
transistors being the fastest fuses on three legs.....
Q1-3 & Q6 blown while protected by a F1A fuse,
It does put things in perspective what a task it appears to be?
It would be good to get to the bottom of
what brings on the perfect storm while Hans testing didn't highlight anything.
Alan
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On 01/09/2018 19:54, Alan G4ZFQ wrote: It was a 1A fuse fast type. Supply voltage was at 15V via stepup converter fed from a 12V Pb akku. That might confirm the saying that semiconductors blow fast in order to protect fuses from blowing...
73 Alan G4ZFQ
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>>>So, in the midst of this discussion, if my finals blow is there a ¡°drop in¡± replacement with similar characteristics but that will withstand considerably more abuse?<<<
No, a more robust device will reequire a stronger driver device and likely a?
revised DC feed.? ?The class E has fairly narrow bounds before it gets to
a bad state.??
To protect it use a switchable attenuator before the tuner 3 or 6DB is
not all that much but?easily leaves enough power for a T1 to auto tune.
The T1 tunes well even at 1W.?
Or use a manual tuner?with a resistive bridge SWR detector (tayloe).??
Better suggestion, tune the antenna to not need the tuner.? IF a tuner is
needed you not going from total mis-match to 1:1
All tuners will go through a state of high SWR to the radio, its unavoidable.
Try it by hand and see.
.
Allison
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So, in the midst of this discussion, if my finals blow is there a ¡°drop in¡± replacement with similar characteristics but that will withstand considerably more abuse?
72,
Charles - NK8O
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On Sep 1, 2018, at 2:56 PM, Matthias Zwoch <zwoch@...> wrote:
Am 01.09.2018 um 20:07 schrieb Richard Harris via Groups.Io:
Hi Matthias,
When tuning, the T1 auto-ATU may present an impedance to the QCX that causes excessive current to flow through the PA FETs or causes an excessive voltage across them One solution is to connect an attenuator between your QCX and T1 auto-ATU when it is tuning and disconnect it when a match has been found. This will limit the range of impedance "seen" by the PA FETs. A 3dB attenuator will ensure the QCX "sees" a load between about 17 and 150 Ohms. A 6dB attenuator will ensure that the load is always between about 40 and 85 Ohms.
When I built an auto-ATU for my 20m QCX, I thought that damage to the PA FETs was possible and so while the ATU is tuning an attenuator is switched into circuit by means of a relay.
Richard G3OTK
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Shirley Dulcey KE1L
Alan de G1FXB
Gary Freeman