Date   

Re: QRP-Labs 50 W Amplifier - low power output

George Korper
 

The toroids are very good.  I use them in making 49:1 antenna transformers for Half Wave End Fed Antenna systems
where they also work well. Never had a bad one in 10 amps. 
That being said I have found that stripping and pre-tinning the enamel wire is essential. 
Checking the continuity of the transformer before soldering on the board, allows for easy soldering with less heat. 

On Sat, Aug 22, 2020 at 12:56 AM Hans Summers <hans.summers@...> wrote:
Hi TIm

Your point 5 isn't just from left field it's off the field all together. There is nothing wrong with the supplied ferrites. I spent a vast amount of time on suppliers and material testing in order to choose the best ferrite for the job. I would not be supplying ferrites which are not up to the job. Many constructors have built this amplifier successfully and to spec. As with all QRP Labs kits, if it does not work there is a probability of at least 99% that it is due to an assembly error or fault, not a defective component. 

Regarding transistors, yes, replace them together. I wouldn't agree that the biasing scheme is crude, it is designed for a particular task and it accomplishes this perfectly. Separate bias for the two MOSFETs This is a Class C amp. The answer may be different if it was a Class AB amp where we were aiming for highest possible linearity. Nevertheless I would always recommend replacing both together, and would recommend that for any PA including the Class E finals in the QCX/QCX+. For the pennies these transistors cost it isn't worth taking chances. 

Sourcing the transistors does need care. A lot of cheap IRF510s are just some generic MOSFET onto which is printed various labels purely for selling them - such as IRF510, IRF520, IRF530... they don't necessarily have the correct characteristics of our beloved IRF510. The transistors used in the kit are Vishay brand and are reliable and correct. If you want to replace them then buy IRF510s from a reputable supplier. For example if you buy in US, Digikey IRF510s are also the same Vishay type and are known to be good. It doesn't have to be Vishay, just buy from a reputable place so you know it is is what it says it is. 

Regarding point 4... somewhat just off the Left Field boundary... do NOT add a capacitor and 100-ohm resistor at the wiper of the pot! You really will reduce the power output of the amp then, I guarantee it! I don't see what is confusing. The pot sets a DC bias that is applied to both gates. It works...

Good luck!

73 Hans G0UPL
http://qrp-labs.com

On Sat, Aug 22, 2020 at 12:29 AM Timothy Fidler <engstr@...> wrote:
Point 5 . of the last  Troll post is from Left Field  (at least in terms of the OPTrafo only ) because all the indications are that the problem may be ahead of the gates of the Mosfets.

regards, TEF


Re: GPS and Message Tags. #u3s

Phil Crockford
 

Thanks for pointing that out Alan.

Phil G8IOA

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Alan de G1FXB
Sent: 22 August 2020 09:09
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] GPS and Message Tags. #u3s

 

Bob,
not calling just you out, but to all replies in this thread.
To advert Chinese *whispers* the original poster has the issue with the CW mode and Message setting = #CS #M6 #LT #LN
specifically #LT and #LN tag formatting

 WSPR mode cannot encode any of the U3S custom #message tags.......


Alan

On 21/08/2020 23:04, N3MNT wrote:

Recently built U3S ver 3.12a and OLG1.  No issues with WSPR.  Longest report 8950 mi on 20M.

 


Re: 0.03w RF output, 1w at transistor drains, Help? #qcx

Alan G4ZFQ
 

I'm not quite sure, how should i probe them? what am i looking for?
We have already established that you get no RF output. It is not due to IC3.

Going back to your Q1-3 measurements does your supply hold up at 14 volts on TX? What current is taken in RX and TX?

73 Alan G4ZFQ


Re: QCX+ 20 No Transmit

Alan G4ZFQ
 

Gary,

Q6 switches 12 volts to Q1-3. Check that first.

The only other component you mention that is connected with TX is IC3. Q5 switches the RX antenna input.

73 Alan G4ZFQ

 The problem is that I have no transmit.  As a matter of fact it appears that the rx/tx switch is not functioning.  I assume that is related to Q5.


Re: GPS and Message Tags. #u3s

Alan de G1FXB
 

Bob,
not calling just you out, but to all replies in this thread.
To advert Chinese *whispers* the original poster has the issue with the CW mode and Message setting = #CS #M6 #LT #LN
specifically #LT and #LN tag formatting

 WSPR mode cannot encode any of the U3S custom #message tags.......


Alan

On 21/08/2020 23:04, N3MNT wrote:
Recently built U3S ver 3.12a and OLG1.  No issues with WSPR.  Longest report 8950 mi on 20M.


Re: 0.03w RF output, 1w at transistor drains, Help? #qcx

 

I'm not quite sure, how should i probe them? what am i looking for?


Re: 0.03w RF output, 1w at transistor drains, Help? #qcx

Alan G4ZFQ
 

It seems there 's some unreliability with my external DVM, the internal DVM seems to measure the same voltages perfectly fine
_._,_._,_
Yes, most DVMs read OK on these points but some do get affected by the RF. Yours does.

So it seems IC3 is OK.
Q1-3 are suspect.
And Q6?

73 Alan G4ZFQ


Re: QCX firmware updating #firmware

Alan G4ZFQ
 

I was surprised my user settings weren't over written when I went from 1.05 to 1.04 and back again to 1.05...is this normal?
Steve,

The fuses are set to retain EEPROM data so settings are saved when updating flash

73 Alan G4ZFQ


Re: QRP-Labs 50 W Amplifier - low power output

Hans Summers
 

Hi TIm

Your point 5 isn't just from left field it's off the field all together. There is nothing wrong with the supplied ferrites. I spent a vast amount of time on suppliers and material testing in order to choose the best ferrite for the job. I would not be supplying ferrites which are not up to the job. Many constructors have built this amplifier successfully and to spec. As with all QRP Labs kits, if it does not work there is a probability of at least 99% that it is due to an assembly error or fault, not a defective component. 

Regarding transistors, yes, replace them together. I wouldn't agree that the biasing scheme is crude, it is designed for a particular task and it accomplishes this perfectly. Separate bias for the two MOSFETs This is a Class C amp. The answer may be different if it was a Class AB amp where we were aiming for highest possible linearity. Nevertheless I would always recommend replacing both together, and would recommend that for any PA including the Class E finals in the QCX/QCX+. For the pennies these transistors cost it isn't worth taking chances. 

Sourcing the transistors does need care. A lot of cheap IRF510s are just some generic MOSFET onto which is printed various labels purely for selling them - such as IRF510, IRF520, IRF530... they don't necessarily have the correct characteristics of our beloved IRF510. The transistors used in the kit are Vishay brand and are reliable and correct. If you want to replace them then buy IRF510s from a reputable supplier. For example if you buy in US, Digikey IRF510s are also the same Vishay type and are known to be good. It doesn't have to be Vishay, just buy from a reputable place so you know it is is what it says it is. 

Regarding point 4... somewhat just off the Left Field boundary... do NOT add a capacitor and 100-ohm resistor at the wiper of the pot! You really will reduce the power output of the amp then, I guarantee it! I don't see what is confusing. The pot sets a DC bias that is applied to both gates. It works...

Good luck!

73 Hans G0UPL
http://qrp-labs.com

On Sat, Aug 22, 2020 at 12:29 AM Timothy Fidler <engstr@...> wrote:
Point 5 . of the last  Troll post is from Left Field  (at least in terms of the OPTrafo only ) because all the indications are that the problem may be ahead of the gates of the Mosfets.

regards, TEF


Re: 0.03w RF output, 1w at transistor drains, Help? #qcx

jim
 

IC3 is a TTL ic ...NO negative voltages a(nywhere on that chip ...
Pin 4 and 10 are fed with a CLK2 (mostly) square wave signal corresponding to the Transmit frequency ...
Pin 5 will be at 5 volts dc on Transmit
this means that

PIN 6 will have square wave ( 0 volts to 5 volts) at transmit frequency

and

Pins 1 and 2 will have square wave (0 volts to 5 volts) at transmit frequency and
Pin 3 will have square wave (0 volts to 5 volts) at transmit frequency ....as will the Gates of Q1,2,3 ....


attempting to measure RF with a DC meter results in (mostly) meaningless results


SUGGESTION:  beg/borrow/steal/buy/build RF PROBE ...Hook to external DVM ...Measure results

Jim

Keydown:
-3 -2.5 -3 0.5 5 -2.5 0
5 0 0 5 0.5 0 5

On Friday, August 21, 2020, 5:57:08 PM PDT, spam via groups.io <spam@...> wrote:


Ic3 as read from the internal DVM:
 
Normal:
5 5 0 0 0 5 0
5 5 5 0 0 0 5
 
Keydown:
2.5 2.5 2.5 1.7 5.0 2.5 0.0
5.0 0.0 0.0 5.0 1.7 0.0 5.0
 
ic3 as read from external DVM:
 
Normal:
5 5 0 0 0 5 0
5 5 5 0 0 0 5
 
Keydown:
-3 -2.5 -3 0.5 5 -2.5 0
5 0 0 5 0.5 0 5
 
It seems there 's some unreliability with my external DVM, the internal DVM seems to measure the same voltages perfectly fine


Re: 0.03w RF output, 1w at transistor drains, Help? #qcx

 

Ic3 as read from the internal DVM:
 
Normal:
5 5 0 0 0 5 0
5 5 5 0 0 0 5
 
Keydown:
2.5 2.5 2.5 1.7 5.0 2.5 0.0
5.0 0.0 0.0 5.0 1.7 0.0 5.0
 
ic3 as read from external DVM:
 
Normal:
5 5 0 0 0 5 0
5 5 5 0 0 0 5
 
Keydown:
-3 -2.5 -3 0.5 5 -2.5 0
5 0 0 5 0.5 0 5
 
It seems there 's some unreliability with my external DVM, the internal DVM seems to measure the same voltages perfectly fine


QCX+ 20 No Transmit

hamhog1
 

I just completed building the QCX+ for 20 meters.  Construction went well and the receiver works beautifully.  The Alignment was per the manual and the only variance was that the I-Q Balance, low and high audio shifts had very little dip to get to minimum.  When connected to my outside antenna, I was able to copy several signals.

 The problem is that I have no transmit.  As a matter of fact it appears that the rx/tx switch is not functioning.  I assume that is related to Q5.  I have no rf output at L1, the rf connector, or the BS170’s.  All the voltages for T1 are correct.  All voltages at IC-3 are normal.  The following are within range Clk0, Clk1, D2, IC5, IC6, IC-7, IC-8 with the exception of pin 3 and pin 5 which are at 1.8 v instead of .65 v. IC-9 with the exception of pin 3 and pin 5 which are 2.0 v instead of .67 v. IC-10 with the exception of pin 6 which is at 6 v. instead of 3.94 v.

 

 Any help is greatly appreciated.

 

 Gary K4VIG

 


Re: Atmel problem

Ronald Taylor
 

Either way works. But you have to email Hans directly to get the .eep file ... Ron


On Fri, Aug 21, 2020 at 2:48 PM Tech Guy <tech48055@...> wrote:
I had an accident measuring rf. I accidentally touched the internal probe to dc. Since then I think the chip has problems. I tried updating it from 1.00b to the latest version. Trouble booting unless connected to the UNO I used to update it. Sidetone has static too. Do I just need to order a new chip or is there a eprom file to use to burn a blank with the hex file?
73’s John N4HNO


Re: GPS and Message Tags. #u3s

N3MNT
 

Recently built U3S ver 3.12a and OLG1.  No issues with WSPR.  Longest report 8950 mi on 20M.


Atmel problem

Tech Guy
 

I had an accident measuring rf. I accidentally touched the internal probe to dc. Since then I think the chip has problems. I tried updating it from 1.00b to the latest version. Trouble booting unless connected to the UNO I used to update it. Sidetone has static too. Do I just need to order a new chip or is there a eprom file to use to burn a blank with the hex file?
73’s John N4HNO


Re: GPS and Message Tags. #u3s

Dean Smith
 

The current version of firmware is 3.12a.To my knowledge, all the previous versions of the firmware are in the files section.
There has not been in my mind a revision to the lat/long tags since creation by Hans, maybe somebody else knows different (chime in).
But one is puzzled why you would send position data in raw format? Due to position ambiguity (GPS wandering) the last digits are changing all the time! USA military spec for outsider unpaid use!  A QRA locator of four and 6 digit is usually more than adequate for most use.


Re: QRP-Labs 50 W Amplifier - low power output

Timothy Fidler
 

Point 5 . of the last  Troll post is from Left Field  (at least in terms of the OPTrafo only ) because all the indications are that the problem may be ahead of the gates of the Mosfets.

regards, TEF


Re: QRP-Labs 50 W Amplifier - low power output

Timothy Fidler
 

1. check the phasing of the phasing choke / transformer.

2.  Get some sort of temperature probe , borrowed or one you have . work out some consistent thermal insul system and see if you can find a difference between the two  power mosfets under bias conditions. If one is notably cooler given the identical bias  then you prolly have your issue pointed at. But in that case check all solder joints in the current path very carefully before you point  the gun at the silicon.

3.  If Power Mosfets need a change out , buy them as  a pair  from Hans or some  known source. There are a lot of white spot and repackaged IRF510s around. You need a pair that come from the same production batch as the bias scheme on this amp is so crude. 

4. Examine the Pot. R5. Is it Exactly the same in the build photos ? I have a theory that this very unusual common bias scheme works because there is some capacitive bypassing from GND to the wiper of the bias potentiometer.  If the potentiometer checks out physically then there is the kludge available of using a 0.1uF multilayer cap (ie RF rated) and a 100R resistor mounted from the wiper to GND to ensure that the drive signal can get from the source of the respective IRF to the cold side of the driving transformer 's Ct.

5. Hans gets his ferrites pounded together by Dwarfs  mit Feuer und Eisen from some Trollish undeground factory.  They have no brand but are very cheap which gets you this kit for USD 25 or so.  Consequently it is possible that the ones in the OPT or even the IP single toroid are not as per the golden test board.  the OPT ones are nominally type 43 but do not have a mafr certification I believe. It is possible that his supplier has mixed cores of different  material types. The colour and dimensions are a good go by.

From a dwarfish troll in the Sth Pacific.


Re: 0.03w RF output, 1w at transistor drains, Help? #qcx

jim
 

I agree with Dave...Still recommend buy/build/obtain RF probe (if you cannot beg/borrow/steal a 'scope)

Jim

On Wednesday, August 19, 2020, 6:50:36 PM PDT, Dave <ve3gso@...> wrote:


So the sources are connected to ground, so of course the potential there is zero. The other voltages are reasonable, considering you are using a DC voltmeter to measure circuits which have DC and RF signals combined.

Dave


On Aug 19, 2020, at 20:20, spam via groups.io <spam@...> wrote:



Measuring the voltages on the pins of q1-3  at 14.1v supply voltage are as follows:

unkeyed:

source: 0.00v (?)

gate: 0.00v

drain: 13.66v (?)

keyed: 

source: 0.00v (?)

gate: 2.5v

drain: 9v

I dont quite understand why i couldnt get a reading on the source leads, but are these numbers correct?

 


Re: GPS and Message Tags. #u3s

Phil Crockford
 

Thanks for replying to my request. I had already scanned the documents you indicated and have examined them all but cannot find any mention of the chance made to the Lat Long display as indicated by the forum comments.
As I do not know when the mod was done I can't attempt to order firmware that may provide a fix for the problem I have.

Unless I can find someone who has a U3s that has good GPS validation and or an un modified on screen display of the LAT and Long I will have to reluctantly abandon my plans for the use of the U3s.

Thanks AGAIN FOR YOUR HELP.

Phil G8IOA.

-----Original Message-----
From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Alan G4ZFQ
Sent: 21 August 2020 13:51
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] GPS and Message Tags. #u3s

I think is the latest version V3.12a, It is hard to tell as the
revision history not mention this version?
? http://www.qrp-labs.com/ultimate3/u3firmware.html Maybe you'll find the mod you mention, I do not see it.

2/ Is it possible to still obtain a previous version of firmware?
https://groups.io/g/QRPLabs/files/Firmware%20for%20U3%20and%20U3S%20kits?p=dirname,,,20,1,20,0&jump=1

73 Alan G4ZFQ