Date   

Re: Reverse Polarity Protection [Was: Experiences with 50 watt Amp]

K2DB Paul Mackanos
 

This is great, I just ordered three of them, for obvious reasons, I was just wondering if they will fit inside of the 50 W amp enclosure, or will we have to mount it on the exterior of the enclosure.
Paul K2DB
P.s. Maybe we can ask Hans, to add this as a kit 👍😉

On Sun, Jan 26, 2020 at 10:21 PM Bill <groups191227@...> wrote:

KC9ON has MOSFET reverse-polarity protection kits in his store.  Both through-hole and SMT.  Six bucks as a kit, nine if you want it assembled.  Good for 4.25 continuous, so should be enough for the 50W Amp.

 - Bill  KB3T




Re: QRP Monthly Challenge

Carel PA0CMU
 

I finally participated this challenge for the second time. Poor conditions here too but no QRM or interference today. 

DH7BWM/qrp
DK4YF
OK2PUX  QCX
SP1G  200W
DM4MM  4W - KX1 
OK2BQN  QCX (tnx Zdenek) 


Re: QRP Monthly Challenge

N3MNT
 

Fair conditions here.  One standard station and 2 QCX stations.
Try again at 1900hr.


Bias setting 50W. PA #qcx #pa

Don, ND6T
 

Another lesson learned! It seems to be most prudent to set the power supply to the highest anticipated voltage when setting the bias adjustment.
I set mine at 13.8 volts when I first set mine but, while doing initial testing, I increased it. When it reached 20 volts both output transistors suddenly and quietly expired. After I replaced them I found that, indeed, the bias adjustment was supply voltage dependent.
Since I was using a current limited supply nothing else was affected. In fact, I spent a couple of hours searching for some other (non-existent) fault since there was no visual evidence of a problem. The output merely dropped from 45 watts to a couple of milliwatts in an instant. 
Great kit! Highly recommend it. I probably won't use the amplifier much but It was too nifty to pass up. Thanks Hans! 73, Don


Re: QRP Monthly Challenge

Zdenek OK2BQN
 

Poor conditions and great local interference (QRM)
DK1WU     200W
LB6BG      7W
OK2BQR   50W
PA0CMU   QCX  TNX

Zdenek OK2BQN


Re: QRP Monthly Challenge

Martin DK3UW
 

seams no one heard me alltough I got RBN 0n 20 m even from the us. Worked HB9AFI/P which was SOTA and non QRP 4Z4DX and QRP LZ1XN
No QCX. There was a Pile up on 14.0617 but I could not hear the Stn. Will try to borrow a 7 mhz QRP rig for 19 UTC

DK3UW
Martin


Re: QRP Monthly Challenge

Hans Summers
 

Hi all

<ashamed />... In the various trials and tribulations of fighting the online applications process for my 3-year residents permit extension, I forgot all about it... I realized just a few minutes before the end of the session. I heard OK2BQN on 7030.5 and answered but he was weak with a lot of QSB, then RT3O came up CQing on frequency and very loud here, and I couldn't work OK2BQN. 

I heard some other QSO around 7030.0 but not for long enough to identify participants. 

So there was some activity, which was great! I shall try to do better at 1900Z :-) 

73 Hans G0UPL

On Mon, Jan 27, 2020 at 4:32 PM Luc ON7DQ <on7dq@...> wrote:
Don't forget to use the Chat page in the newsgroup, and post your activity.
I have been calling for half an hour on 20m , only 1 reply from a local ham, and no QCX ... 
Now moving to 40m ...

Luc ON7DQ


50W amplifier: power rating of TR switch

John Seboldt K0JD
 

Glad to see the 1N4007-based diode TR switching in the 50W amp kit. I also have a 120W linear amp kit, long ago completed but has been waiting for final packaging with TR switching and filtering. Do you think this switch will work at the 100W or so level? If not, who can guide me to a nice polished design for a switch at the 100-200W level?

John K0JD
Milwaukee, WI


Re: QRP Monthly Challenge

ON7DQ Luc
 

Don't forget to use the Chat page in the newsgroup, and post your activity.
I have been calling for half an hour on 20m , only 1 reply from a local ham, and no QCX ... 
Now moving to 40m ...

Luc ON7DQ


Re: si5351a issue spectral output above 90Mhz

Hans Summers
 

 

hi

i could confirm these results

SI5351 is very bad above 20mhz and very sensitive to frequency settings

it is worst if you use 2 outputs  !!

impossible to clean it !

it is due to fractionnal dividers.

All QRP Labs firmware uses even integer MultiSynth dividers (not fractional). 

I would not be surprised if spectral purity started to degrade as we get way up into VHF but I would expect it to be still very good at 20MHz. 

If using two outputs beware the crosstalk issues; these are reduced to a negligible level if you load the outputs lightly (i.e. use a buffer, not a low impedance load). 

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


Re: si5351a issue spectral output above 90Mhz

f1us
 

hi

i could confirm these results

SI5351 is very bad above 20mhz and very sensitive to frequency settings

it is worst if you use 2 outputs  !!

impossible to clean it !

it is due to fractionnal dividers.

73

F1US

 

 

 

 

> Message du 27/01/20 12:56
> De : "Phil Crockford" <pcc@...>
> A : QRPLabs@groups.io
> Copie à :
> Objet : [QRPLabs] si5351a issue spectral output above 90Mhz
>
> I have built a number of the Si5351a synthesizer boards for use in a prog-rock and sig-gen projects and they seem to work fine below 90Mhz and the use of a suitable Low Pass filter removes the products above the wanted frequency. I have a spectrum analyser capable of display to a 10hz depth up to 1.5Gig and all seems fine below approximately 90Mhz. I see that filters exist for 2 meters and above and ordered a 220Mhz LP Filter. I programmed a Prog-Rock for 212Mhz and found that there is frequency content below the wanted frequency  that are only -30db down above and below the wanted frequency of  212Mhz and would not be removed by the use of a LF Filter without removing the wanted frequency. I have looked online at the analyser picture of the 220Mhz filer and the picture of the o/p of the Si5351a DDS, prior to any filtering, at 220Mhz does show these products above and below the wanted frequency. To comply with the rules these should be at least -43db below the fundamental frequency. Can I ask if someone with suitable spectrum analyser could confirm these findings.
Phil G8IOA. 


Re: QCX Unreliable operation with GPS connected

Hans Summers
 

Hi all

It was never the intention that the GPS should be left connected all the time or while editing other menu items. It should only be connected:

1) When operating the QCX as a WSPR beacon

2) When using calibration menus 8.11, 8.12 or 8.13. 

The issue is that the GPS signals are the same processor pins as the paddle input. As far as the processor is concerned, when the GPS is connected, it appears as though someone is operating the paddle. The system is also active decoding data from the GPS such as the time and locator. 

The GPS also keys the transmitter, and recent firmware versions include automatic protection against this - if the system detects 9600 baud serial keying the paddle it recognizes this fact and switches the QCX "practice mode" on to prevent keying the transmitter. 

We have been assembling QCX here and calibrating them without any trouble, using the latest firmware 1.03. Normal procedure is to activate menu 8.13 "GPS Data", then plug in the GPS. Wait for "A 3D" which indicates successful satellite lock acquisition. Then turn the rotary encoder one click anticlockwise to 8.12 "Cal sys. osc" and wait a few seconds for the 20MHz system clock to calibrate. Then turn one more click anticlockwise to 8.11 "Cal ref. osc" and wait a few seconds for the 27MHz reference oscillator to calibrate. Then unplug the QLG1 GPS. This procedure does not appear to present any difficulties. 

The latest firmware 1.03 did include some changes to the way GPS information was parsed, and it is not impossible that some cosmetic alteration has occurred, which might make it behave differently when in menu items. But I haven't seen any evidence of that yet. If anyone has any more info to share on this please let me know. 

73 Hans G0UPL

On Fri, Jan 24, 2020 at 5:19 PM Dave Steinberg <daveandnitza@...> wrote:
Hi Chris,
I seem to have the same difficulty with my QCX and QLG1. 
I am not able to automatically calibrate the 27 MHz crystal at all. I know that it must be pretty close to 27,003380 because when I transmit on 7.000000 MHz the carrier
zero beats with my 100 KHz crystal calibrator. Editing the 27 MHz setting is very inconsistent and my Maidenhood location sometimes overwrites the the first digits of the displayed frequency.
I am also using a rev 4 PCB with ver 1.03 firmware and have the same problem with older versions. If I disconnect the QLG1, the QCX appears to operate normally.
When I go into menu 8.13, I  can see that there is no problem with the GPS signal - the message always appears OK. But when I  go back to 8.12  to "calibrate"  the 20 MHz crystal ( I think that measure is a more accurate term), the result is inconsistent and I usually get 20, 033,XXX or 20,033,XXX (the last 3 digits vary quite a bit). Surely, the 20 MHz crystal cannot be that far off. 
If you have solved the problem, your help would be much appreciated.
73,
Dave 4X1RS


si5351a issue spectral output above 90Mhz

Phil Crockford
 

I have built a number of the Si5351a synthesizer boards for use in a prog-rock and sig-gen projects and they seem to work fine below 90Mhz and the use of a suitable Low Pass filter removes the products above the wanted frequency. I have a spectrum analyser capable of display to a 10hz depth up to 1.5Gig and all seems fine below approximately 90Mhz. I see that filters exist for 2 meters and above and ordered a 220Mhz LP Filter. I programmed a Prog-Rock for 212Mhz and found that there is frequency content below the wanted frequency  that are only -30db down above and below the wanted frequency of  212Mhz and would not be removed by the use of a LF Filter without removing the wanted frequency. I have looked online at the analyser picture of the 220Mhz filer and the picture of the o/p of the Si5351a DDS, prior to any filtering, at 220Mhz does show these products above and below the wanted frequency. To comply with the rules these should be at least -43db below the fundamental frequency. Can I ask if someone with suitable spectrum analyser could confirm these findings.
Phil G8IOA. 


Re: how does the Noise Blanker work on the QCX

George Korper
 

Hey Dave, you have a really good website. I have family in NM. My XYL lived in Taos. I can't wait to share some of those stories on there.

Maybe I can get up to ABQ in the Spring. That is a fascinating branch of the hobby and powerful listening station. Well deserved awards. 73 from
here in  Old Mexico. K3GK


On Mon, Jan 27, 2020 at 4:45 AM Hans Summers <hans.summers@...> wrote:
Hi Dave

There is some description of this setting in the manual. Basically it causes the CW decoder to ignore short bursts of signal. The setting is in milliseconds. Any signal burst shorter than the noise blanking period would be ignored and not detected as a "dit". 

Setting it to a very short value would cause short bursts of noise to be interpreted as a dit. Short noise bursts are quite common for example, static crashes. A better way to detect these is to use two Goertzel windows either side of the wanted one, and subtract half the side lobe windows from the main window. The theory being that any noise burst will be wideband and occur approximately equally in all three windows, so will be cancelled out by this method, to a greater degree than the impact on the wanted signal or inflicting any signal in those side lobes as interference on the wanted signal. Whether this works well or not I don't know, but anyway there is neither sufficient CPU time nor sufficient code space to implement this kind of complexity in the limited resources of the ATmega328 in the QCX. 

Setting the noise blanker to a too long value will cause the decoder to ignore genuine dits of higher speed Morse. 

73 Hans G0UPL

On Mon, Jan 27, 2020 at 9:17 AM David R. Hassall WA5DJJ <dhassall@...> wrote:

Dear Members,

 

Does anyone have an explanation on how the QCX’s Noise Blanker work and how can it be setup to operate.    It is in the DECODER SECTION 5  option 5.1  Says period in milliseconds.   But I couldn’t find an explaination on how to set it up and

Use it.   How is it turned on and off? 

 

Any information gratefully appreciated.

 

Take care and have fun.

 

73 Dave Hassall WA5DJJ  Las Cruces, New Mexico

Website: http://www.zianet.com/dhassall/

QRSS SUPER GRABBER WEBSITE: http://www.qsl.net/wa5djj/

 


Re: Measuring output watts with an oscilloscope

Hans Summers
 

Hi Richard

Great article, but one nit-pick! You say " If we took an infinite series of voltage measurements along the sinewave, and squared them, and then took their average, we'd end up with Vrms. " You need to take the square root of the average to get Vrms. (That's the R in RMS).

Yes correct, and well-spotted. I was just checking to see who was paying attention :-/   I have fixed it now! http://www.qrp-labs.com/qcx/rfpower.html

73 Hans G0UPL


Re: T1 Installation problem

David Wilcox
 

I hope I don’t offend anyone with this but here goes.

I don’t know what the problem is.  When you insert the wires from the T1 through the  pc board you can see with some magnification or a photo on your smart phone that there is bright shiny copper wire with the varnish removed (shiny copper wires) on the underside (soldering side) of the board.  If you don’t see that remove T1 and scrape the wires a little closer to the toroid itself.  Again, my Knipex wire stripper works wonders.  Remove varnish until you see shiny copper right up to the toroid.   NO COPPER WIRE, NO SOLDER!

Dave K8WPE

David J. Wilcox K8WPE’s iPad

On Jan 26, 2020, at 8:38 AM, John Canfield <bucket@...> wrote:

I've been building kits starting about 1960 and have quite a bit of experience with a soldering iron. With a bit of finesse you can use side cutters to scrape the enamel off, sometimes I'll hold pull the wire against one blade of the side cutter. After you measure out the correct wire length there should be several inches (or cm) of extra wire - use the excess to practice different techniques.
--
John, WB5THT
EM00ig


Re: Measuring output watts with an oscilloscope

Richard G4TGJ
 

Hi Hans

Great article, but one nit-pick! You say " If we took an infinite series of voltage measurements along the sinewave, and squared them, and then took their average, we'd end up with Vrms. " You need to take the square root of the average to get Vrms. (That's the R in RMS).

--
73
Richard
G4TGJ


Re: how does the Noise Blanker work on the QCX

Hans Summers
 

Hi Dave

There is some description of this setting in the manual. Basically it causes the CW decoder to ignore short bursts of signal. The setting is in milliseconds. Any signal burst shorter than the noise blanking period would be ignored and not detected as a "dit". 

Setting it to a very short value would cause short bursts of noise to be interpreted as a dit. Short noise bursts are quite common for example, static crashes. A better way to detect these is to use two Goertzel windows either side of the wanted one, and subtract half the side lobe windows from the main window. The theory being that any noise burst will be wideband and occur approximately equally in all three windows, so will be cancelled out by this method, to a greater degree than the impact on the wanted signal or inflicting any signal in those side lobes as interference on the wanted signal. Whether this works well or not I don't know, but anyway there is neither sufficient CPU time nor sufficient code space to implement this kind of complexity in the limited resources of the ATmega328 in the QCX. 

Setting the noise blanker to a too long value will cause the decoder to ignore genuine dits of higher speed Morse. 

73 Hans G0UPL

On Mon, Jan 27, 2020 at 9:17 AM David R. Hassall WA5DJJ <dhassall@...> wrote:

Dear Members,

 

Does anyone have an explanation on how the QCX’s Noise Blanker work and how can it be setup to operate.    It is in the DECODER SECTION 5  option 5.1  Says period in milliseconds.   But I couldn’t find an explaination on how to set it up and

Use it.   How is it turned on and off? 

 

Any information gratefully appreciated.

 

Take care and have fun.

 

73 Dave Hassall WA5DJJ  Las Cruces, New Mexico

Website: http://www.zianet.com/dhassall/

QRSS SUPER GRABBER WEBSITE: http://www.qsl.net/wa5djj/

 


how does the Noise Blanker work on the QCX

David R. Hassall WA5DJJ
 

Dear Members,

 

Does anyone have an explanation on how the QCX’s Noise Blanker work and how can it be setup to operate.    It is in the DECODER SECTION 5  option 5.1  Says period in milliseconds.   But I couldn’t find an explaination on how to set it up and

Use it.   How is it turned on and off? 

 

Any information gratefully appreciated.

 

Take care and have fun.

 

73 Dave Hassall WA5DJJ  Las Cruces, New Mexico

Website: http://www.zianet.com/dhassall/

QRSS SUPER GRABBER WEBSITE: http://www.qsl.net/wa5djj/

 


Re: Experiences with 50 watt Amp

George Korper
 

And if there are others out there who like to have protection rather than smoke here is a neat explanation:

On Sun, Jan 26, 2020, 8:53 PM George Korper via Groups.Io <georgekorper=gmail.com@groups.io> wrote:
SOLUTIONS +  Thanks!