Date   
Re: Very Hot Voltage Regulator, Blank Screen

Dean Smith
 

sounds like something is taking excess current from your regulator! if the atmega is socketed try removing from pcb first, then repower board and see if you still have same regulator over heating. if you then have 5volt line back and no overheating, then the atmega maybe your problem.
This goes for anything else that is socketed on the pcb. If it still overheats it must be something else. The display i think can also be tested same way...
good luck.

Re: Very Hot Voltage Regulator, Blank Screen

ajparent1/KB1GMX
 

IF the 7805 regulator is getting hot maybe a short on its output (its used for all the digital stuff)
is the cause.  

The first place i'd look is for a short from soldering as in a ball or spach of solder has
moved or maybe a loose wire touching something it should not.

Allison

Very Hot Voltage Regulator, Blank Screen

Nathan Long
 

I completed the assembly of my QCX last week and everything was going well.  I connected it to a cheap 12v switching supply and noticed a lot of hum, which wasn't surprising.  I then connected a 9v battery, which cleared up the noise and everything was going swimmingly.  I could hear cw signals, and the radio alignment went off without a hitch with expected values.  With all my newfound success I decided to go ahead and hook up my 12v SLA battery.  From that point forward, the screen stopped working and the 7805 got very hot.  It was reading under 3 volts on the 5v line.  I swapped it out for a good 7805 that I had lying around.  Now, the voltage reads as expected initially, and seems to creep down to 3v or so as it heats up.  The only thing I can figure is that there was a whisker that fell off the power cable and shorted something.  Has anyone seen a similar issue?  Any advice on where to start would be very much appreciated.  Unfortunately,  I have a cheap old multimeter, and limited troubleshooting skills when it comes to circuits like this.  It doesn't seem reasonable to spend too much time on a $50 board, but I do have a spare atmega328p sitting around that I could flash and install.

Thanks, 

Nate K9BFG

Re: TX clicking / woodpecker #qcx #mods

Stephen Farthing G0XAR JO92ON97
 

Hans, 

It was Guido Pe1nnz who gave you the hint.

Yours, sleepily enjoying a beer with Alan at Schipol prior to flying home, 

Steve G0XAR 

Re: Sidetone clicking

Gregg Myers
 

Hi Karlis, Hans,

Good idea. I implemented this and the sideline does indeed seem nicer. A 0.1uF axial cap (e.g. mouser 581-SA105E104MAR) is easily inserted in series with R59 and you wouldn't even notice it was there.

Keep up the good work and 73,
Gregg W7GRM



On Mon, Nov 4, 2019 at 7:23 AM Hans Summers <hans.summers@...> wrote:
Hi Karlis

I agree with your analysis of the sidetone clicks, and your solution. A 0.1uF capacitor in series with R59 makes a big improvement. 

As you suggested, at full sidetone volume there is no issue. But at low sidetone volume there is a DC level change which causes a click. The 0.1uF capacitor removes that. I have tried it at many sidetone volumes and it eliminates the click on all of them. 

I will add this to the QCX modifications page! Very nice! Thanks!

73 Hans G0UPL

On Sun, Nov 3, 2019 at 10:51 PM Kārlis Goba <karlis.goba@...> wrote:
Investigating the sidetone injection circuit (R59) and looking at scope traces, I found a remedy for the clicking in headphones at every dot and dah. It suffices to insert an extra 100n cap in series with R59. The reason is how the sidetone signal is formed in the microcontroller - the IO pin is normally in high-Z state, and during dit/dah emits 0/5V push-pull PWM square wave which gets filtered by the audio LPF chain to get a nice sinewave. The problem is that during high-Z the input at R29 is at ~2.5V DC, but at the start of PWM the voltage goes suddenly up or down depending on your sidetone volume setting. So there's a noticeable discontinuity which gives the clicking sound. Inserting a cap in series helps greatly.

While investigating the woodpecker sound (active if you have the S-meter enabled), I was looking for ways digital noise from the 5V rail could enter audio chain, and I noticed C6 is specced at only 100n. That's the bias feed point, and it should normally be low impedance. In other QSD implementations it's usually at several to ten microfarads. I soldered a 2.2u SMD cap in parallel to it, and my sensitivity went way up, and compared to that the woodpecker became way less prominent. Before I could rarely hear band noise with antenna attached, and now it's noticeably better.

--
Karlis YL3JG

Re: TX clicking / woodpecker #qcx #mods

Kārlis Goba
 

Regarding the C6 cap, I still think it should have significantly larger value than 0.1uF, since it is in essence in series with the C43-C46 caps, which are larger by capacitance. It just feels that way intuitively if you think about the AC path, but I will run simulations of equivalent circuits. I think it adds unnecessary loss at the mixer currently.

--
Karlis YL3JG

Re: TX clicking / woodpecker #qcx #mods

Kārlis Goba
 

Wow, brilliant! While I was aware that the woodpecker is not really a very important issue, since it gets drowned by noise and not all use S-meter or decoder, it still nagged me that there has to be a solution for the sake of good engineering. This morning I also traced the source of the woodpecker to the LCD_RS pin, but didn't go deeper to investigate. My idea was to try to insert a series resistor on the LCD_RS line. I also observed that the LCD VO supply has a very obnoxious ripple for some reason which might be related or unrelated to this.

Isn't it just wonderful that it all can be solved by firmware update.

--
Karlis YL3JG

#case #enclosure #clock #qlg1 #clock #qlg1 #case #enclosure

regzzz@...
 

Good day all,  I thought I would share the design and some pictures of the 3D printed enclosure for the Clock kit with a 20x4 LCD and with the QLG1 GPS.
The design can be found on Thingiverse:  https://www.thingiverse.com/thing:3955678






Cheers all.

--
73 de Reg  VA2VEC

Re: Sidetone clicking

Kārlis Goba
 

Sorry, AUDIO2, not AUDIO1.


On Mon, Nov 4, 2019 at 05:03 PM, Kārlis Goba wrote:
unnecessary for AUDIO1
--
Karlis YL3JG

Re: Sidetone clicking

Kārlis Goba
 

May I suggest also that R49/R50 and C39 might be unnecessary for AUDIO1, since you have 2.5V DC bias at the output of IC6/IC7 anyway and the ADC will be happy. Since you already have the C39 cap on the board, for the mod one might rewire and swap AUDIO1 and SIDETONE traces somewhere on the PCB, swap R53 and R59, and remove R49/R50. Sure you'd not get a perfect 2.5V DC bias that way since there is an offset error at the output of IC6/IC7, but it would be reasonably close and that could still be processed by firmware.

--
Karlis YL3JG

Re: Inductance meter

Alan G4ZFQ
 

with the accuracy of a Marconi LCR bridge (but only does L and C, but down to fractional pf and nf) Google VK3BHR.
Jim,

Also known as "A Surprisingly Accurate Digital LC Meter" https://sites.google.com/site/vk3bhr/home/lcm1
I see there are updates/mods to the firmware but the links are dead.. No problem but would be interesting.

It is surprisingly accurate. Also it shows negative readings, useful to indicate that the zero has drifted. Neither of the Chinese ones I tried had this feature.

73 Alan G4ZFQ

Re: Toroid Wire Size

_Dave_AD0B
 

Thanks for the links and ideas about winding cores.

The reason to not start in the middle of a wind is to conserve wire used. 

The only problem I had was I had to remove a few turns on t1 after tuning the trimming cap. 

I really like the wire that was specified.
--
73
Dave
k0mbt
Ham_Made_Keys

Re: QCX 40 has zero audio output

James Daldry W4JED
 

Hi, All

Most likely there was a thin spot in the 12 volt foil, which broke, possibly under the solder resist. Etched PC boards are individuals, and during 40+ years of electronic service I saw a fair number of foil breaks underneath the paint. Don't try to find it. It ain't worth the effort, and you may add to the damage. Just take a short piece of insulated jumper wire and connect a "live" pin 8 to one of the "dead" pin 8's.

Panasonic PV-4000 portable VCR's that were used in the days before camcorders came from the factory with varying patterns of jumpers on the bottom of the board. Seems their etchant was a little aggressive and would eat a little more copper than it should. Occasionally you would have to add another jumper or 2 to make your repair.

Unless you are using a heavy-duty, unfused power supply, the problem isn't a short. If a short caused power to some parts of the board and not to others, you would be able to find the no-power condition by the black spot where the foil melted. Then the repair is 2 steps - find and remove the short, then jumper across the open foil. Then add a fuse before powering up.

73

Jim W4JED

On 11/3/19 8:02 PM, Peter GM0EUL wrote:
So something must have happened to the 12 volt supply to those chips.  I'm not sure what they all have in common that wouldn't affect the transmitter and I don't have the schematic to hand.  If there's nothing on pin 8 then follow the 12v supply back till you find some voltage.  Are you grounding the probe to pin 4 or somewhere else?  

Peter



Sidetone clicking

Hans Summers
 

Hi Karlis

I agree with your analysis of the sidetone clicks, and your solution. A 0.1uF capacitor in series with R59 makes a big improvement. 

As you suggested, at full sidetone volume there is no issue. But at low sidetone volume there is a DC level change which causes a click. The 0.1uF capacitor removes that. I have tried it at many sidetone volumes and it eliminates the click on all of them. 

I will add this to the QCX modifications page! Very nice! Thanks!

73 Hans G0UPL


On Sun, Nov 3, 2019 at 10:51 PM Kārlis Goba <karlis.goba@...> wrote:
Investigating the sidetone injection circuit (R59) and looking at scope traces, I found a remedy for the clicking in headphones at every dot and dah. It suffices to insert an extra 100n cap in series with R59. The reason is how the sidetone signal is formed in the microcontroller - the IO pin is normally in high-Z state, and during dit/dah emits 0/5V push-pull PWM square wave which gets filtered by the audio LPF chain to get a nice sinewave. The problem is that during high-Z the input at R29 is at ~2.5V DC, but at the start of PWM the voltage goes suddenly up or down depending on your sidetone volume setting. So there's a noticeable discontinuity which gives the clicking sound. Inserting a cap in series helps greatly.

While investigating the woodpecker sound (active if you have the S-meter enabled), I was looking for ways digital noise from the 5V rail could enter audio chain, and I noticed C6 is specced at only 100n. That's the bias feed point, and it should normally be low impedance. In other QSD implementations it's usually at several to ten microfarads. I soldered a 2.2u SMD cap in parallel to it, and my sensitivity went way up, and compared to that the woodpecker became way less prominent. Before I could rarely hear band noise with antenna attached, and now it's noticeably better.

--
Karlis YL3JG

Re: Inductance meter

geoff M0ORE
 

At least ten years ago, I built a tester to measure inductance and capacitance to a design by Bill Carver, K6OLG,in the magazine Communications Quarterly, Winter 1993. It consisted of a LC oscillator at about 2MHz but not important. The method of use was to measure the frequency of the basic oscillator and then put the component under test in the circuit as well. Measure the frequency again and by simple maths which were given in the article, the value of the component under test could be calculated. I wrote a simple spreadsheet to do the maths for me to save time. It does require an accurately known capacitor for set up but a 1% silver mica or two would be good enough.

I must admit it hasn't been used for a few years as I now have an easier way of measuring L's and C's on a N2PK VNA.

On 04/11/2019 12:39, ND6P wrote:
I use the Peak Model LCR45, available from Sotabeams.  Works very well.

Jim/ND6P

Re: Inductance meter

James Daldry W4JED
 

Hi, Folks

If you would like the fun of building your own, that compares favorably with the accuracy of a Marconi LCR bridge (but only does L and C, but down to fractional pf and nf) Google VK3BHR. The first hit will be a project that uses maybe $10 worth of parts. I built mine using banana jacks for test jacks and soldered 2 alligator clips directly to 2 banana plugs. Hold the clips together for zeroing L, leave them apart to zero C. I built mine in the box my National Geographic "Atomic" watch came in. The box was better than the watch.

73

Jim W4JED

On 11/4/19 7:39 AM, ND6P wrote:
I use the Peak Model LCR45, available from Sotabeams.  Works very well.

Jim/ND6P

Re: New RF devices in low cost packages

N1BUG
 

On 11/4/19 8:31 AM, SkipF, NT1G wrote:
Nuvistors (6cw4) are good for 3/4 watt. About the same as a BS170.
Paint them BLACK, and they'll look like an electrolytic cap.
And nobody will know.
Cool! I've used them in receivers but not transmitters. As low noise
receive amplifiers they work well at VHF. Will they provide useful
power output at VHF? I have a few around here somewhere...

73,
Paul

Re: TX clicking / woodpecker #qcx #mods

Hans Summers
 

Hello Karlis, Allison, all

I have now SOLVED the woodpecker problem. Completely. Via a firmware change only. 

The start of the story is actually Saturday, while I was at my QRP Labs stand at Veron Day of the Radio Amateur, the annual Dutch amateur radio convention in Zwolle, Netherlands. I was having a conversation with someone. Regrettably, and this someone, please accept my very sincere apologies - I met a hundred and one very interesting people during the day, and as usual on these occasions by the end of the day it was all a blur... so I cannot remember which of the radio amateurs I met, was talking to me about this. So therefore please can you identify yourself for the MANY THANKS which need to be heaped upon you, if you are reading this!

This person had noticed that the I2C SDA bus signal is shared with the LCD RS signal. The woodpecker noise is caused by the LCD updating the S-meter at frequent regular intervals (which we all know). It had been assumed that digital noise from the flurry of communication with the LCD is what causes the "clicks", which in quick succession we call a "woodpecker" sound (with apologies to real woodpeckers, who know what they really sound like when pecking wood). 

This person provided a theory that perhaps, since the processor is unashamedly using 5V signal levels, and the Si5351A is running at 3.3V, when the signal is high, the signal might be shunted to the 3.3V Supply of the Si5351A by internal ESD protection diode circuity inside the Si5351A. This could get onto the supply line of the Si5351A and find its way to the Si5351A output and through the audio chain. The thinking then was, that if I could change the firmware so that it did not operate the Si5351A SDA pin at +5V, but instead left it "Open-Collector" style when "high", pulled to 3.3V by R3, this could solve the problem. 

To test this I used my QCX-20, with audio output connected to my shack audio amp so I could turn the volume up loud in the pair of shack speakers. A dummy load connected to the input so that it's quiet. I could very clearly hear the "Woodpecker" when the S-meter is switched on. There is also an identical click whenever anything is written to the display (for example by the CW decoder), and when the frequency is changed (which updates the display). Since these clicks tend to be irregular, they are even less noticeable than the "woodpecker". 

All of these clicks tend to get drowned out by band noise in actual use; but as 20m and 17m have lower band noise, then if you are in an RF-quiet location, they could be audible. 

Then I cut the track from the Si5351A's SDA pin to the processor and replaced it with a switch - the QCX will not start up unless it has successful communication with the Si5351A. So once the QCX had started up, I flicked the switch to disconnect SDA... and sure enough, the woodpecker stopped. Next, I experimented with the theory of the 5V from the RS signal during LCD communication overloading the SDA pin, by using a diode so that the Si5351A SDA pin could only be pulled down by the RS pin. +5V could not feed into the RS pin. Result: FAIL! Still a "woodpecker" sound. So the theory seems not correct.

However, this led me to investigate other things, in the firmware. The RS pin is used to tell the LCD whether a command or a data byte is being written to the module (1 = Data, 0 = Command). I discovered that each byte which is written to the module, sets the RS signal according to whether it is a data or command byte. But it then just leaves the signal there, until the next byte is written and if needed, changes the RS signal level. 

Then I thought - what if I set the RS signal to what it needs to be, then clock the two 4-bit nibbles of the byte into the LCD module, then set the RS signal high again immediately... all over in less than a microsecond. Any disruptions which find their way into the Si5351A and the receiver signal path, will be of such a short duration that they will be well outside the audible passband of the receiver. Result: SUCCESS! The woodpecker stopped!

I tried "parking" the RS signal high (5V), and low (0V), and in both cases the woodpecker sound is eliminated. However, for unknown reasons, if I park it low, the clicks on frequency changes and decoded CW screen updates disappear also. With high parking, there are still clicks on frequency changes and CW decoder updates. Since it in any case feels more wholesome to park on 0V (considering the Si5351A theoretically doesn't prefer 5V), and it also eliminates all other clicks, I have left the RS signal parking at 0V. 

Conclusion: a 1-line firmware changes has completely eliminated all known clicks associated with display update ("Woodpecker" when the S-meter is on, frequency changes during during, and decoded CW text). 

I don't personally use the CW decoder or the S-meter, but I feel the improvement to tuning is very significant. With the dummy load on, the QCX gain control on maximum, and the shack audio amp on maximum, there is now simply no click at all when turning the rotary encoder. Only the mechanical click of the rotary encoder's detent mechanism :-D   My QCX happened to be tuned to 14020 and there seemed to be some kind of DX pileup going on there... some of the stronger signals were audible even with just the dummy load (no antenna connection). 

Many thanks to whoever was discussing this with me on Saturday and has prompted this investigation and solution with their discovery that the path the woodpecker noise enters the receiver audio, is the Si5351A SDA bus signal! 

I shall prepare a firmware release containing this improvement. 

73 Hans G0UPL

On Mon, Nov 4, 2019 at 8:42 AM Kārlis Goba <karlis.goba@...> wrote:
I realised I should have mentioned I was using Semi QSK. So that excludes Q7 and related circuitry.

--
Karlis YL3JG

Re: Toroid Wire Size

Jim Kortge
 



On 11/3/2019 7:19 PM, Chris Herd wrote:
Hi All

Dave in the link below uses a crochet hook for toroids, I dont know exactly how he does it.


I do.  You use a #2 plastic crochet hook to reach through the center of the toroid and grab the wire and back it through, then you wrap it over the top of the core, and reach through again and pull the wire through the core again.  You always start in the middle of the piece of wire to minimize the amount of free wire; keeps things a bit neater and easier.  Winding this way keeps the wire on the toroid core nice and tight inside and outside, and helps place the wire neatly on the core.  How do I know all of this?  I've been doing it this way for probably 20 years, maybe more...

72 and happy building,

Jim, K8IQY


Re: New RF devices in low cost packages

SkipF, NT1G <skip.flem@...>
 

Nuvistors (6cw4) are good for 3/4 watt. About the same as a BS170.
Paint them BLACK, and they'll look like an electrolytic cap.
And nobody will know.

On Mon, Nov 4, 2019, 8:24 AM Bill Cromwell <wrcromwell@...> wrote:
Hi,

Tubes *are* viable for use in QRP radios including the final amps and
multiband operation. That holds for the most stringent definition of QRP
being incapable of more than 5 watts RF output. QRPp as well- incapbale
of one whole watt RF output. There are hams building them and reporting
results on QRP related mail lists. Of course, an amp capable of 25 or 50
watts can also be dialed down to QRP and QRPp levels. Even my 100 watt
amps get down there.

If we want to modify a QCX for example we  could couple into a tube
stage or two after removing the final amp stage in the QCX. I don't know
why we would want to do that but it's a hobby. Do what interests you.
And allow what the other hams are doing to *dazzle* you:) Me? FT-8 and
WSPR do not interest me at all. But I think it's great that others can
enjoy it.

73,

Bill  KU8H

On 11/4/19 5:31 AM, N1BUG wrote:
> On 10/31/19 9:23 AM, jmh6@... wrote:
>>      I suppose for single band use, tubes may still be viable as an
>> amplifier?
>
> Depends on what you want and your capabilities, I suppose. Most of
> my amplifiers use tubes... one covers 160-10m, one is 6m, one is 2m.
> They are all homebrew and with careful scrounging for parts cost was
> about 30 to 40 cents per watt. But we are not exactly talking QRP
> for those... ;-)
>
> 73,
> Paul

--
bark less - wag more