Date   

Ideal Power Voltage

Tom Gundlach <ks5x@...>
 

To get the best power output from QCX.


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Re: My first time QCX build - fail.

Jim - K9DD
 

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.


Re: LM7805 Replacement #qcx #parts

John VA7JBE
 

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


Re: QCX Enclosure Modification Video (detailed) by Juddie WD8WV #case #qcx #encl

Karl Schwab
 

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


Re: U3S on 630M "crashes" the system. #u3s #630m

danielu@upcnet.ro danielu@upcnet.ro
 

    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


Re: QCX tuning

jmh6@...
 

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

On Sun, 2 Sep 2018, Alan de G1FXB via Groups.Io wrote:

Hi Glenn,
I'm in defence of all Hans views as well. 
https://groups.io/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 https://groups.io/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:-
https://groups.io/g/QRPLabs/message/26420
 https://groups.io/g/QRPLabs/message/25533
https://groups.io/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.


Re: QCX tuning

Alan de G1FXB
 

Hi Glenn,

I'm in defence of all Hans views as well.  https://groups.io/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 https://groups.io/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:-
https://groups.io/g/QRPLabs/message/26420
 https://groups.io/g/QRPLabs/message/25533
https://groups.io/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.


Re: My first time QCX build - fail.

Gary Freeman
 

Oops, sorry.  I meant Jim, not Ted  :-)

72 de Gary W0ITT


Re: My first time QCX build - fail.

Gary Freeman
 

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

 


Re: QCX tuning

Glen Leinweber
 

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.


Re: QSX radio feature requests

Chris Wilson
 

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

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 _._,_._,_




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2E0ILY
Best regards,
Chris mailto:chris@chriswilson.tv
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Best regards, Chris Wilson (2E0ILY)


Re: #QCX 4174 Ready for practice test #qcx

DL8LRZ
 

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 0,47µ - 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


Re: QCX tuning

Alan G4ZFQ
 

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 http://www.norcalqrp.org/files/NC2030/NC2030_v5.pdf 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


Re: QCX tuning

Lee
 

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


Re: QCX tuning

Alan de G1FXB
 

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

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


Re: QCX tuning

ajparent1/KB1GMX
 

>>>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


Re: QCX tuning

Charles W. Powell
 

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

On Sep 1, 2018, at 2:56 PM, Matthias Zwoch <zwoch@gmx.de> 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


Re: QCX tuning

Matthias Zwoch <zwoch@...>
 

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
Hi Richard,

Thats a good idea. T1 should do it too with 3dB att - 2,5W. Using a 6db attenuator may cause the problem, that the tuner stops at a level what later is not good for the finals. I have a homemade Z-Match which does the same in the tune mode. But dont like the fiddling with the Z-Match.
At my 40m QRP trx (Mrs. Mosquita) I had blown a driver transistor years ago also using the autotuner. The autotuner brought the driver stage to oscillate, the output got at abt 30W for a sceond (made for 5w) and the fuse was blown out. However the RD16HHF1 survived and only one transistor had to be changed. Made a modification in the driver stage and now I can tune Mrs. Mosquita even with a long tuning sequence with the T1.

73 Matthias, DD7NT


Re: QCX tuning

Alan G4ZFQ
 

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


Re: Loading the Ultimate3s Firmware

Alan G4ZFQ
 

Did my first one this afternoon using an Arduino to program it on the board.  The information for the settings including the fuses are here https://groups.io/g/QRPLabs/files/AVR%20Programming and reading the aVRDundess1.pdf file.
Len,

I don't know why but the fuse settings do not seem to agree with Hans https://groups.io/g/QRPLabs/message/24845

73 alan G4ZFQ