Tayloe's article talks about using a higher current CMOS gate to drive
the class E amplifier. But many designs get more drive capability
another way: using multiple CMOS gates in parallel. 74x00 NAND gates
come four to a package, so it's often simple to use two or three of
the gates to get more current.

Never mind I had my path statement as D;\? instead of D:\? ..... How simple mistakes can make a difference.

Thanks,

Jim Ford N6JF

I encountered a very similar message when I flashed my QCX. If I'm following you correctly you just need to select the 328P in the drop-down box. The instructions point to selecting the Atmel 328, but as you found out you have a 328P. It's in the list of processors.

Does that help?

--Al
WD4AH

This has some discussions on protection circuits for Class-E PAs:

www.norcalqrp.org/files/Class_E_Amplifiers.pdf

PeterO
G0DZB





--
Please don't email me "off list" about "QCX low output" or my filter experiments.

I was trying to follow the directions to upload the latest firmware T1.00e.hex using the Arduino Uno ISP and DUDESS and managed to erase the T1.00b.hex file but I get this error code.? I am using COM4 for both the DUDESS and Arduino ISP program..

Reading | ################################################## | 100% -0.00s

avrdude.exe: Device signature = 0xffffff
avrdude.exe: Yikes!? Invalid device signature.
???????????? Double check connections and try again, or use -F to override
???????????? this check.


avrdude.exe done.? Thank you.

I took the label off the processor and I have a 328P.? A blue line shows up over the Flash Box sometimes which I guess means the path to the hex file is OK but not sure.

Any ideas what might be wrong?

Thank you,

Jim Ford N6JF

Greetings all;
? Well I got to play a little radio this afternoon with my QCX-20.? Well I worked EA5GX from NY.... That is a little over 1000miles/watt.? This is a first for me.??

Best 72;
Kurt - W2MW

YAHOOO!!!? It can now get into setup.? Swapped out L5 ONLY to be 47uH.? It seems to be able to get into the long-press menu.? Now to do the full alignment...

Yep best wishes to Hans and his team for Christmas and the New Year. My QCX 40m worked first time full 5watts what a fantastic little rig.
Richard G0ILN Fist? 398.

Rig has been working great for since I completed it last month. Now all of a sudden there is a loud tone when I plug the headphones in, have tried a couple. Tone sounds like the feedback you get when you put a microphone in front of a speaker. Rig was working fine, making contacts. Then yesterday I turn it on and there it is. Have also been running WSPR with it. Have been heard as far as Costa Rica and Germany. Anyway anybody have an idea where the feedback sound could be coming from?

I would suggest that you reset the idle current on the PA's as that point has changed because of the 0 point has changed. Because of the 2 added PA's? Also it sounds like you are getting RF back into the U3S so you would? possibly? need to add a Unun some distance from the U3S. I would start there...I run my U3S in this configuration. Ferrite beads etc may help you out too. Bill KN8DMK

Hans,if you have time to add any suggestion it would be appreciated.

I have interfaced to a new 5351 Adafruit breakout board and have left CLK2 disconnected. There is still no waveform for CLK2. CLK0 and CLK1 are present and in quadrature. I wondered if IC2 is faully and SCL or SDA not working but since CLK0 and CLK1 appear correctly it seems that the processor is OK.? Again any suggestions ?

73, Dave NE5DL

Hello Andy,

Saturday, December 23, 2017

With my high power Class D amps used with a U3S I have looked into
protection quite a lot. Whilst this VHF circuit initially probably
looks irrelevant it, when adapted to our needs, shows a pretty unique
trait. Using an SWR bridge means monitoring the voltage level of the
return side, Above X volts something happens to protect things (PA or
drive to it is shut down). All well and good. But a high SWR at one
Watt produces a far lower return voltage than a high SWR at say 50
Watts. This circuit used with a rotary switch allows you to preselect
at what return voltage level from the bridge a fault should be
assumed. Possibly a bit OTT for QRP but it's a useful circuit that
fixes an inherent issue with fixed return volts tripping the fault
circuit and affords tunability.

--
Best regards, Chris Wilson (2E0ILY)

I have a U3S which has started to act strangely. When I feed my beam it behaves well transmitting every 10 minutes as programmed. I also have an end-fed long-wire that is resonant on the Ham frequencies. The U3S used to feed that antenna with no problem. However, now when connected to the long-wire it will go through a single transmit sequence (WSPR) just fine. I get reasonable reports. However, when the second transmit sequence starts the U3S displays the opening "splash" screen and then just starts reading the GPS. HOWEVER, it thinks that the splash screen is still on because in you press the right (Edit) button it asks "do you want to reboot". Cycling the power gets it back to normal.

This behavior is consistent. Works on all bands the beam will tune. On any band with the long-wire (including bands that the beam will tune)? it transmits once and gives good reports. It will not transmit again, until it is rebooted. I tried inserting a QRP antenna tuner between the long-wire and the U3S hoping that a bit of isolation would help. No change in behavior. Transmits only once then locks up.

Please note that I've been using this for months on both antennas with excellent results. This trouble started only after I added two additional BS170 PAs. However, I am still operating with only 5 volts.?

Any ideas.? Sorry to trouble you all, but I really want to work the higher bands that are not accessible to the beam.

Thanks and 73. Dick W7DAX

On Sat, Dec 23, 2017 at 08:26 am, Alan G4ZFQ wrote:

The way I see it is low output impedance could be high PA current.
High output impedance could be high PA voltage.

I think you may well be right, so I guess one has think of both monitoring and reacting to high voltage or current.

Options.

(1) Use a current limiting PSU

(2) Use a voltage sensing device to provide a foldback arrangement.

(3) Use a zener diode for across the antenna terminals feeding a power dumping resistor in series to dampen high VSWR effects. Old CB's used this trick
and called it an Antenna Warning Indicator, when an LED was included in the mix.

(4) Better heatsinking of output devices to cope with temporary SWR faults. BS170's aren't easy to heatsink, but that's the price you pay for using them ;-)

(5) Use a better device that you can heatsink, and is over rated for the job (IRF510's or RD06HHF1 again).

73 de Andy

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Can be either but each if from different causes. ?I read about all of the failed PA devices in the emails and it makes me wonder why design and calibrate the output for perfect conditions (perfect SWR, limited voltage and current)? ?Its much more reliable to design the PA with a device and associated supporting circuitry with enough power dissipation, voltage excursion, and maximum current so that it works no matter what happens (eg no antenna connected). ?This has me curious enough to start a project in the new year for exactly that... simple, cheap, fool-proof, and plugs into an existing BS170 holes on the U3. ? ?

And also 80m WSPR The default frequency in WSJT-X v1.8.0 is now Dial
3.568600 (TX 3.5600-3.5800) to be within the Japanese allocation.
Why does everyone have to move to accomodate ONE country ?

Andy,

I do not think moving up is an option for JA?
I'm just the messenger.
But if I operated 80m WSPR perhaps I'd be pleased.
Or if I operated 80m CW I might not.
But as it's a WSPR default I guess everyone will get there eventually.

73 Alan G4ZFQ

Aren't both symptomatic of each other ?

Andy,

The way I see it is low output impedance could be high PA current.
High output impedance could be high PA voltage.
But what I do not know is how much antenna impedance affects the PA devices seen through the LPF.

73 Alan G4ZFQ

This very good Class E tutorial and design information by?Dan Tayloe, N7VE circuits both for over-voltage protection and over-current protection.

Jan,

Thanks, interesting that a bigger device is not really suitable for class E QRP.
But protection needs many more components. I'm not sure whether I would bother provided just the BS170s blew.

73 Alan G4ZFQ

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