Date   

Re: Twist in a jiffy! Tip for transformers-Use an electric drill #50w

Karl Haas
 

Very tidy job!  I just hope the bird doesn’t want its feet back!

 
Tuesday, June 21, 2022 4:27 PM +02:00 from Brian N7BKV via groups.io <cl@...>:
 
On Tue, Jun 21, 2022 at 06:20 AM, Karl Haas wrote:
I tend to twist and shout.
Right, Karl!  Came out so good it made me twist and shout!

 
 
Karl 
 


Re: WTB: 30m QCX Mini #qcx #30m #qcxmini

Al Holt
 

Dan,
I have a 30m mini available. Can't figure out how to DM you, sorry.
--Al
WD4AH


Re: Twist in a jiffy! Tip for transformers-Use an electric drill #50w

Brian N7BKV
 

On Tue, Jun 21, 2022 at 06:20 AM, Karl Haas wrote:
I tend to twist and shout.
Right, Karl!  Came out so good it made me twist and shout!


cannot fix the vol. klob #qcx

Andreas Wulff
 

It is not possible to mount the Poti Knob of the QCXplus in the "7 o clock position" because the axis
is flat where the screw of the knob has to be.
Is there any chance to mount the Knob in the correct position?


WTB: 30m QCX Mini #qcx #30m #qcxmini

Daniel Baker
 

Looking to buy an assembled 30m QCX, QCX+, or QCX mini. If you have one gathering "dust", please drop me a line! I've got a home for it! ;)

Thanks & 73 -

Daniel Baker /K4DB
Taylors, SC


Re: Twist in a jiffy! Tip for transformers-Use an electric drill #50w

Karl Haas
 

I’ve used this method before, and if it goes wrong, I tend to twist and shout.

 
Tuesday, June 21, 2022 3:15 PM +02:00 from Brian N7BKV via groups.io <cl@...>:
 

Yes.  Over twisting was a concern.  But with adequate tension it all evened out in seconds.  As for twists per inch, yes, the manual says nothing.  So I just went by the picture with the finished wire next to the tape measure and made mine look about the same.

Brian N
N7BKV

 
 
Karl 
 


Re: Twist in a jiffy! Tip for transformers-Use an electric drill #50w

Brian N7BKV
 

Yes.  Over twisting was a concern.  But with adequate tension it all evened out in seconds.  As for twists per inch, yes, the manual says nothing.  So I just went by the picture with the finished wire next to the tape measure and made mine look about the same.

Brian N
N7BKV


Re: QCX+ mini 2W o/p

Hans Summers
 

Hi Curt

Yes, the low hFE thing (or I should say, less high than average but still well within spec) is rare but does happen; I'm just saying if all else fails, if the turns are correct, and squeezing and stretching didn't help - then it's another thing to check. 


On Tue, Jun 21, 2022 at 4:06 PM Curt wb8yyy via groups.io <wb8yyy=yahoo.com@groups.io> wrote:
Interesting disclosure from Hans that transistor in extreme case could be short on gain. Possible there could be some out there. Higher probability I cannot count turns or wind neat enough. 

Well on destruction either we know or won't admit. As Paul maybe hasn't removed a turn yet I am hopeful that's all that may be in play. Yes worth some time to get another 3 dB. 

Curt


Re: QCX+ mini 2W o/p

Curt wb8yyy
 

Interesting disclosure from Hans that transistor in extreme case could be short on gain. Possible there could be some out there. Higher probability I cannot count turns or wind neat enough. 

Well on destruction either we know or won't admit. As Paul maybe hasn't removed a turn yet I am hopeful that's all that may be in play. Yes worth some time to get another 3 dB. 

Curt


Re: Twist in a jiffy! Tip for transformers-Use an electric drill #50w

Peter Lascell
 

So for those of us who didn't keep their safety wire pliers from our military experience, we can use locking vise grips instead, and spin them from the adjustment knob as they hang on the wires.  Still waiting a few more days for my QDX to arrive and test the twist. 
Pete W4WWQ

On Tue, Jun 21, 2022 at 7:31 AM Donald S Brant Jr <dsbrantjr@...> wrote:
I used safety wire pliers to twist my wires also, but instead of using the twister feature I just clamped it to the wire ends, let it hang and spun the tool itself.  I was concerned that pullng the twister knob would put too much stress on the wires.
It came out great.
73, Don N2VGU



--
Pete Lascell
Forest, VA


Is Coherent CW possible on the QCX+ ? #clock #gps

Earl
 

Hi

I listened to the ARRL Eclectic Tech podcast (#62)   just as I was finishing up my clock kit with GPS.  The QLG2 GPS module impressed me with it's capabilities and connectivity ( I have it connected to the Rasp Pi 4's powered USB hub ) .   With a QLG2  and all the optional headers provided on the QCX+ I am hopeful that some brilliant forum member can figure out a way to implement coherent CW.   Even if you don't believe that this is practical I still recommend listening to the podcast.  Coherent CW would go a long way to removing the annoying city RFI we have at this QTH.  The cw decoder should make easy work of perfectly timed code...

The clock and the GPS went together without issue and of course, I had to make a few mods:
     1) micro USB socket for the GPS in place of USB-B [USB-C optional]
     2) clock powered through the GPS (photo)
     3) on the clock PCB I added a 10 uF 0805 between the +5V rail and ground at the point where the jumpers connect.
     4) used a 4 line display  (photo)
     5) determined current draw at 5V for the two boards + display to be 140 mA peak, so I connected it to the USB hub.
     6) used micro switches as programming buttons (see photo);  

The Raspberry Pi 4 (64 bit "Build a Pi") can read the GPS data concurrent with the clock module so that I can compare the number of satellites seen / used with the two systems.  

Looking forward to comments.

73

Earl, 4Z4TJ


Re: Trouble Oscillation qcx 40? #40m #alignment #problem #qcx40

Gianpaolo
 

Hello Jim... thanks.. it is exaclty what I was very afraid to hear... gosh.. it was very hard for me that winding... and I have made with a lot of carefully, but probably not enough... I well remember I hacve scracthed a lot the enamel, and the solder joint seems to be ok....

Ok will try to make it.... and will come back.

Thanks again.

Gianpi

Il 20/06/2022 15:41, James Daldry W4JED ha scritto:

Hi, Gianpi

If you have watched the past week or so we have had a number of people describing what they do to make sure all the connections on the toroids work. On your radio, the T1 winding between the bias network (R1, R2, C6) and IC4 pin 7 is "making the trip", but the winding connected to pin 9 isn't. Pins 7 and 9 are connected together with maybe 15 cm of copper wire. You might be able to read the resistance with my old Marconi RLC bridge , but I have my doubts. So get your tweezers out, determine which winding of T1 goes to pin 9, and pull the wires up, clean the enamel off, re-insert and solder. You could try applying lots of heat to the connections, but that may or may not work.

Once you get equal voltage and drive to the 2 pins, the I/Q stuff should work. While you're at it, check the resistance between the antenna connector center pin and C29. Check both ends of C29, since capacitors block DC from the ohmmeter. One end of C29 should be zero ohms to the antenna connector center pin. If you don't have the zero ohms, one of the low pass filter toroids, L1, L2, L3, isn't making connection. It's one common cause of no reception but working alignment signals.

73

Jim W4JED

On 6/19/22 16:19, info@... wrote:

Hello Jim, and Happy Father's day by way !

today we was here busy with a family party, and we start eating at 12.30 and we finished at 17.00... it was a long party, but nice... kids playing around and adult drinking wine and bier.. a typical sunday party day ! I see most of american HAM are related with somebody in Italy, and this is very nice... I was looking on QRZ.com after the ARRL Contest, and I found a lot of them... 

Anyway, I am just arrived at home and bring back my QCX.... I am thinking I could by already assembled and aligned hihi... probably would be quickly, but got a lot of fun building... now I am trying to let him working.... thanks' god there is "good boy" like you and other people that helps the "poor technician people" as I am .. hi hi.. and Happy Birthday !!!! But please get it slow with the 6 'er bier pack ! hihi..

Back to the measure here the result:

  • IC4 pin 7 and 9 ... 5.35  kohm ... how looks like ? Seem not really near zero... gosh...
  • IC4 ... pins 7 I see 2.21 volt ...  pin 9 I see 5.00 volt
  • IC5 ... pins 1 I see 2.03 volt and pins 7 I see 2.01 volt

Are we good or did I have to start thinking to buy one assembled .. ? hihi.. Of course I am jocking...

Back to you !

By the, tonite we have here in the close valley a big fire in the wood, and still few minutes ago I had 3 plane and one helicopter flying over my head trying to fight against the fire... hope will be fixed soon.. it's seems will be a long night for firemen !

--
IK1TTD "Gianpi"
DX-CONTEST-CHASE-DXPED
Logo
 
Via San Francesco 443
18018 Arma di Taggia (IM) ITALY
e: INFO@...
 
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Re: Twist in a jiffy! Tip for transformers-Use an electric drill #50w

Bryan Curl
 

I also used a drill motor. Slick, like trout.
Only question I had that manual didnt answer, how many turns per inch are best. The drill can quickly twist on more than is probably needed if not careful. 
--
regards,
Bryan, N0LUF


Re: QCX+ mini 2W o/p

howard winwood G4GPF
 

The  clue  is in what you wrote, WHY did the PA and switching transistors fail?????

On 20 Jun 2022, at 22:45, Paul Bigwood <paul@...> wrote:

My 20m kit built QCX+ mini only produces about 2W o/p after LPF alignment with DC supply of 13.8v.

I’ve adjusted the LPF turns spacing for max o/p. The amplitude of the spike waveform at the BS170 collectors is 30v pp as measured on my 200MHz scope with 10x probe adjusted as per Hans Power output measurement notes.

This is well below the indicated 48v that is mentioned as the amplitude of the PA waveform for a 5w output at the BNC socket.

The load is the QRP labs dummy load and the dummy load voltage on my DVM matches the 2.5w output as per the kit information.

What can cause the RF voltage at the collectors to be below expectations?

The PA and switching transistors failed during testing. I’m not sure why, but I had to replace the BS170 PA transistors and the MPS751 switching transistor. I matched the gain of the 4 transistors I used for the PA.

I am wondering if the transistor load inductor is not large enough.?

I’m baffled as to why it is only producing 2.5 W.

73 Paul G3WYW



Re: Twist in a jiffy! Tip for transformers-Use an electric drill #50w

Donald S Brant Jr
 

I used safety wire pliers to twist my wires also, but instead of using the twister feature I just clamped it to the wire ends, let it hang and spun the tool itself.  I was concerned that pullng the twister knob would put too much stress on the wires.
It came out great.
73, Don N2VGU


Re: Covid-19

Roelof Bakker
 

Hello all,

Some facts to ponder over.

All poor souls with Covid-19 (100%) in January / February at the Intensive Care Unit of a
nearby hospital were:

1. male
2. over 60
3. more or less obese
4. not vaccinated

The latter is likely due to a substantial part of the local population that refuses
vaccination on religious grounds.

Does this proof anything? Not at all, yet it is interesting.

73,
Roelof, pa0rdt


Re: Twist in a jiffy! Tip for transformers-Use an electric drill #50w

Roelof Bakker
 

Hello Brian,

- Where have you been?

I have been using the same method for decades, though instead of an electric drill, I am using
a small elbow steam driven manual drill.

Regarding the discussion of removing the enamel insulation, the 'solder blob' method is hard
to beat. I have yet to come across enameled wire it won't work, besides some pre-WWII stuff,
which has been binned.

73,
Roelof


Re: QCX+ mini 2W o/p

Hans Summers
 

Hi all

There's one more thing, not related to inductance. 

The MPS751 transistor (Q6) hFE varies wildly from one batch to another. The ON Semi datasheet specifies a minimum of 75, with no typical or maximum values. I have never measured one as low as 75, they usually measure several hundred. 

BUT - if you did get one that had a rather low hFE, then what would happen is that the base-emitter current, through the 1.2K resistor R42, would not be enough to saturate the transistor in the "ON" state. Collector-Emitter current is hFE multiplied by Base-Emitter current. So you can see that if hFE is low, and the base-emitter current is limited by the 1.2K resistor, R42, then the Collector-Emitter current maximum amount may be not as much as the PA wants to draw. In that case the voltage at the collector will be lower than it should be, and power output will be too low. 

How to check this: 

Measure the voltage at the emitter of Q6, and measure the collector voltage, during key-down. The difference between them should be about 0.7V. If it is more than that (for example collector 12V, emitter 10.5V, so a 1.5V difference), that is an indication that the transistor is not saturated, the collector-emitter current limit is being too low because the hFE is on the low side (but still within spec for the MPS751 according to its datasheet). 

The resolution to that is to decrease the value of R42. The easiest way to do this is to put another resistor in parallel. 
10K in parallel with 1.2K gives 1071 ohms
4.7K paralleled with 1.2K gives 956 ohms
3.3K paralleled with 1.2K gives 880 ohms
2.7K paralleled with 1.2K gives 830 ohms

You should find that the difference between the voltage at the emitter and the collector drops to around 0.7V. On the rare occasions we have seen this issue here, caused by a lower-than-average hFE of the MPS751 Q6 transistor, 10K or 4.7K in parallel fixes it always. 

It's perhaps not an ideal situation as the parameters of the rise/fall shape of the RF envelope are also affected; but this is an analog radio, you don't have the luxury of a real raised cosine key-shaping etc., so the answer is to live with it; and if you really want to investigate and attain perfection then be prepared to measure a bit and adjust a few component values. 


On Tue, Jun 21, 2022 at 1:20 AM Curt wb8yyy via groups.io <wb8yyy=yahoo.com@groups.io> wrote:
Paul

Sorry you had previous issues, but with 2.5 watt consistent output rig may be healthy. 

My 20m mini started out with similar output. I had to remove turns on the inductors. Try removing one or two turns on the PA side of the LPF to see if power goes up some. I reduced turns on both outside inductors to get its power up above 4.5 watts. 

Curt


Re: Help with QCX-Mini S-meter display #qcxmini

dl4sas@...
 

Ron, thank you very much for your helpful explanation and prompt reply.
I better understand now the S-Meter functionality.
Will keep this in mind when operating the QCX-mini.

Have a good day, 73 Eugen


FS 50 Watt Amplifier for 40 Meters

Dennis Rieger
 

I have a QRP-Labs 50-watt amplifier configured for 40 meters for sale. $65 plus shipping. (Shipping USPS Priority Mail $16.10), CONUS only. Power measured ~21 watts at 12 VDC and in excess of 50 watts at 20 VDC driven by QCX+.

Dennis
KK5DB

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