Date   

Re: QRP DX #qcx

tk5ep
 

HI !

What kind of key is this ?
I never saw it before.

73 Patrick


Cardbord Box #qcx #case #enclosure

DG2FDD
 

Hi all,

after having started the new-case-with-space-for-the-optical-encoder project some months ago (and leaving the half-finished aluminum case in the shelf for several weeks), I decided to use a simple 3€ cardbord box. It's much easier to cut out the openings. Yet I assume longevity will not be the best. Well, for now, it works and I will hopefully be on air for the AGCW QRP contest next week.

An observation: I had not been using my QCX during these weeks. Instead, I was operating my Icom IC-735 and my mcHF. Hearing the great audio of the QCX this evening reminded me how good this jewel is! The IC-735 has good audio and great QSK, but the QCX still performs better. Maybe I'll present myself with a 20m version later this year.

73 de Jens, DG2FDD


Re: QRP DX #qcx

Andy V. Borisenko
 

hi all!
this is my QCX-20.
first QSO Dec 23, 2017.
last today.
made 1237 QSO, 82 countries, all continents.
antennas windom, dipol, GP.
great radio!


Re: QCX-SSB Help what do I do now? #qcx

Guido PE1NNZ
 

Hi Hans,
 
No need to change anything. QCX-SSB is implementing quadrature generation from the start and has an exact 0 and 90 degree phase shift, like QCX firmware does. There was however at some point a bug [1] that broke it for the lower bands, but it was also fixed loooong time ago. I am quite sure that this is what Allison has seen and keeps talking about.
 
Fully agree on the si5351 quadrature is easy to implement. I was too impressed with the superior phase performance compared to 74AC74 quadrature when I implemented this idea in 2015 in a ESP8266-FST3253-AK5720 based SDR design. The si5351 phase also remains very constant while changing the frequency, which is a nice property for a multiband rig. Unfortunatly I had to abandon the Wifi SDR transceiver idea because it was impossible to fix the 100mW 2.4GHz Wifi TX EMI issues on the codec+opamps that I had to deal with.

73, Guido

[1] https://groups.io/g/QRPLabs/message/41194


Re: QCX-SSB Help what do I do now? #qcx

ajparent1/KB1GMX
 

Hans,

That would be a good thing for the QCX main frame users.  His 20db
opposing sideband is rather poor and needs to be better on a busy band.
Even 30Db would be more usable.

I did it for a breadboard system and not the ultimate RX.   By doing the
7474 it makes the RX stable and code independent.  I know its less than
ideal but that was never the intent.  Its good enough so I've been doing
TX stuff.   I just wanted a decent RX for on air testing and that did it.

The breadboard has evolved to more than QCX so I'm doing something I'd
call a parallel project.  Namely an EER TX.

A breadboard or more correctly dead bug on ground plane (G10 copper)
Makes it easier to play and mod rather than hacking up the QCX.
So far TX testing is good for highly linear AM.  The am is mic to amp
and amp doing bootstrap modulator.  Basically Amp DC at about half Vcc 
and rthat is the DC to the class E amp. That's with basic VFO code in
the 328 for si5351 and lcd.  Next step is extracting the EER code to
drive the opamp and also the phase info to the 5351.   With a linear
system and better ability to drive it I expect much better result.

That was done as the system in place (Q4 and Q6) tends to heat
and shift operating point of just die.  That added a lot of distortion
non-linear control and set point drift.  Fair is fair it was designed
only to do CW keying with envelope control.  So cleaning that up
with a 358 opamp driving a PNP/NPN pair for power out boost
was cleaner.  I used (TO220 compliments laying around).

Allison
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Re: QRP DX #qcx

Simone Lugaresi (IW6CAE)
 

Great...!!! I'd like to see some photos of the change made, it's complicated


Re: QCX 40 NO POWER OUTPUT #40m #qcx40 #problem

_Dave_AD0B
 

Is the radio in practice mode?

--
73
Dave
AD0B
Ham_Made_Keys


Re: outsource QCX build

John Daly
 

Brian K9WIS - could you contact me off-line about the cost to assemble a K1-2 kit? I have one that I might be interested in having built.

John - w4usf@... (Lutz, FL)


Re: QCX Mechanical CAD files #qcx

Ted 2E0THH
 

Hi Jim

Yes, they come from China so a liitle patience is required.
I found a current link for the US 
https://www.ebay.com/c/1084367468

Else just search for:
Enclosure Case Black Aluminum Box Circuit Board Project Electronic 150*105*55MM
You might find one locally sourced but the Chinese ones are super cheap.

Hans flattered me by posting all the details of my build in the QCX builders galley:
https://www.qrp-labs.com/qcx/qcxgallery.html 
It's there somewhere towards the bottom of the page.

If you need any of my templates, I am very happy to share them.

73s Ted

2E0THH


Re: Question about BPF #filter

Hans Summers
 

Hi

In my opinion, the FFT function in digital oscilloscopes (DSO) is just a bad joke inflicted on us by the first DSO engineer as his contribution to humanity's artistic body in the study of dark humour. Subsequent DSO designers had to keep up with the Jones'es and implement the horrible thing otherwise their new creation would not look good enough. 

Doubtless the FFT is good for some purpose, like, er, um, he... (suggestions, anyone?)... well anyway, moving swiftly on... I think it probably causes 10x more confused people than those who actually use it for something useful. 

One of the most interesting aspects of digital technology such as digital signal processing, is understanding the limitations. When is what you see on screen a product of the digital approximations involved, and when is it real? Actually analogue has limitations too... of a different type but somehow they are less stark than in the digital world. 

Yes I know yours is a Rigol and Rigol is one of the best manufacturers; and it looks like a very nice 'scope at that; but, nonetheless the FFT is still a joke... 

Most oscilloscopes have an 8-bit ADC. On the basis of 6dB per bit, the maximum available dynamic range is 48dB (8 x 6dB = 48dB). Practically, the least significant bits are subject to some noise. And your input signal is unlikely to be at the right amplitude to make maximum use of the available range and so you can knock off another bit or two for that also. Then you have to add on to all this, all the artifacts inflicted by the DSP. In the end these FFT have no practical use for us in RF because the dynamic range of what they can show is nowhere near adequate for the kind of range we use in RF. A comparison between the results on a real spectrum analyzer and an oscilloscope FFT are quite revealing. Maybe I will do some measurements someday when I have time, just for making it clear. I mean... do you really think all those little spikes only 15dB down from the carrier, and the deep nulls on the harmonics, are real? 

My first experience with a DSO was a Hantek USB 'scope which I hated with an enormous passion, so much so that when it failed within a month or two of using it, I didn't even want to send it back under warranty. I retain some marginal interest in one day opening it up to look inside (as is my normal habit) but after more than 7 years have passed it is still sitting there on the shelf, very much unloved. That was my first experience of the FFT function and was educational enough by itself. After that I had a 100MHz old analogue 'scope. 

My next DSO was my 100MHz Owon XDS3102A which I purchased on leaving Tokyo Japan, simply because our 20-foot shipping container was going to take 10 weeks to sail around the world to Turkey and, the thought of being without an oscilloscope for 10 weeks was only marginally less horrific than hanging upside-down having my toenails pulled out one by one while being forced to read the Hantek DSO manual repeatedly. The Owon 'scope solved that by weighing only 2kg, which was small enough that, along with my soldering iron and a selected mini-junk-box and one of each kind of all QRP Labs kits, could negotiate (with the XYL) a safe passage in our suitcases and come with us on the plane. 

This Owon XDS3102A distinguishes itself by having a 12-bit ADC; which is unusual in its class (reasonably low cost desktop standalone DSOs); this was not an accident, I purposefully wanted the higher ADC resolution, rightly or unnecessarily, it felt important to me and worth the extra $150 for the increase in dynamic range. Before long, I hooked it up to my QRP Labs VFO/signal generator kit and played around a bit; the FFT function is one screen I had a look at ONE time, just for the entertainment value... just for several seconds, just long enough for me to be marginally less unimpressed than I had been with the Hantek FFT... the additional 4-bits of ADC resolution make some small difference but not a lot. That wasn't why I bought the extra 4-bits anyway :-)    I have never visited the FFT function again... 

Finally in the line-up I now have a 200MHz Siglent SDS 1202X-E DSO which was a gift from Siglent, as one of the sponsors of the homebrew heroes award 2019 https://homebrewheroes.org/ of which I am the proud inaugural recipient... and I don't like to say anything bad about it because one shouldn't look a gift horse in the mouth, should one. Anyway it has an 8-bit ADC and I did not look at its FFT joke, because I don't care about FFT jokes anyway, and my expectation in this regard is precisely 0.0000. The chain of causation since the engineer who first inflicted the joke on us and all the other following 'scopes had to follow it is so long now, we could hardly blame Siglent anyway could we. The rest of the 'scope is very nice and useful in the lab. 

I am lucky to own a rather old n'th hand Advantest R3361C Spectrum Analyzer which though not very modern, is accurate and performant, and I love it. But what I am saying here is. if I did not have that... then I would look to find some other way to look at harmonic levels, not the FFT of a DSO. These days there are a lot of very low cost pieces of test equipment available which maybe not professional grade but certainly come a long way to get close to it. 

Now I have that rant off my chest - back to the original question: 50MHz is VHF. Board layout becomes more and more important, the higher up in frequency you go. The relay-switched filter board was originally designed for low-mid HF. If you want to do well at VHF you use lots of shielding, short traces, coaxial connectors, etc. If you don't, then signal will leak past filters. What happens in the VFO/SigGen and Relay-switched LPF combination there is anyone's guess, but it really would not surprise me at all, if the results are different depending on which order you plug the LPFs in. I think this is normal and expected. Just choose the configuration which works best :-) 

73 Hans G0UPL

On Thu, Mar 5, 2020 at 1:55 AM danielu@... danielu@... <danielu@...> wrote:
Adrian,
Obviously we are talking about LPF, but it is my mistake that I wrote BPF. In fact it is not in the shop BPF filter on 6m.
Andrew,
Even if I lower the level the situation remains. The oscilloscope accepts 5Vpp (18dBm) in the 50Ohm setting and the measurement is done on the penultimate domain. The 20dBm indication is just the scale. I attach FFT with 30m LPF in position 1 and 6m LPF in position 4. It looks harmonic on 30Mhz and nothing in 50Mhz.
Maybe I had to choose the Blackman window for higher resolution on the vertical.
First of all I think this is a rectangular signal at the exit of SI5351 with one of the fronts incorrect . It remains to investigate with a very good oscilloscope in the next day


Re: QCX-SSB Help what do I do now? #qcx

Hans Summers
 

Hi Allison
 
Yes, it works very well if its implemented.  Using your code.
The Experimental SSB code tried up to 101d did not accurately do
that.  What I describes was a workaround for that failing as I was
more interested in the TX side.

That why I wanted to keep the QCX as it was because it does work 
so well.

Ah yes I see... in this case, I think Guido should consider changing the experimental SSB code to fix the Si5351A quadrature generation. It's easy! I described everything in this document: 

73 Hans G0UPL


Re: #qcx 50 watt amp, SWR tolerance? #qcx

George Korper
 

30 watts, 19.35 volts. 2.2 amps. 


On Wed, Mar 4, 2020, 10:18 PM Larry via Groups.Io <lradio1=yahoo.com@groups.io> wrote:
On Wed, Mar 4, 2020 at 01:19 PM, ajparent1/KB1GMX wrote:
Allison,
Many thanks for sharing your wisdom and skills.
Your posting will be a shortcut to successful  building, operation and Learning.
Wonderful fundamentals for building  and a reliable base  for further experimenting/building. Fun fun.

Dirt cheap semiconductors  from off shore are not  bargain  typically.  A waste of time and $.

Thanks to all who contribute  to the list.

Wonderful resource building and experimenting.

73,

Larry ns4q..


Re: Si5351 error

John Morris
 

Thanks for the encouragement, Bill.

John


Re: #qcx 50 watt amp, SWR tolerance? #qcx

Larry
 

On Wed, Mar 4, 2020 at 01:19 PM, ajparent1/KB1GMX wrote:
Allison,
Many thanks for sharing your wisdom and skills.
Your posting will be a shortcut to successful  building, operation and Learning.
Wonderful fundamentals for building  and a reliable base  for further experimenting/building. Fun fun.

Dirt cheap semiconductors  from off shore are not  bargain  typically.  A waste of time and $.

Thanks to all who contribute  to the list.

Wonderful resource building and experimenting.

73,

Larry ns4q..


Re: QCX-SSB Help what do I do now? #qcx

ajparent1/KB1GMX
 

Ah don't get what?  Been building SSB from scratch for decades
both commercial and ham.   I consider myself a life long
experimenter and no plans to give that up.  

I get that cheap SSB is some magic voodoo that many hope for.
Is it a realistic hope, I'm not so sure.  

QCX modified for SSB if it worked  would be cheap way in.  Seems
I'm still trying to make it work after a year though I was forced to take
a break in the middle.  Early code was terrible, and current wants a
lot of experimental setup and tweaking.  More MPU would be a step
in the direction of easier and better.  Its right now,  interesting, hence
an experiment, but not a drop in.   Goal to have a local op recognize my
voice and not hear, wow, that radio sounds broken.

Right now its still harder to do SSB EER that all analog.  I've been
doing analog SSB since the 70s in commercial space. So doing it
that way is trivial and many out there doing it.  The problem is the
typical kit cost is not representative of the hardware to do it.

The general reason the only other (singular) is the PolarExplorer
is it takes a lot of stuff (hardware) to get it right and right is at least
a reasonable sounding signal as ICKENYAE standard offerings. 
However it does do very high quality AM.  Heard the guy during
the AM Rally.  It too is limited to the lower bands.
 
The only place I see Class E is AM, both commercial MW broadcast,
and on the lower HF bands.  There are a few around me on 160, 75,
and 40m and they sound very good. But class E AM is much easier
than SSB.  Doing that at 28mhz is very hard and required exotic RF
parts (EGAN mosfets) I can say I know from trying before I got out
of that biz..   Lots of people working on it but very few products.

Allison
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Re: #qcx 50 watt amp, SWR tolerance? #qcx

George Korper
 

Will measure early tomorrow morning
It is closer to 30 watts. Too much for my accurate QRP meter. The MFJ is pegged at 0-30 and reads a little low on 0-300. 
The voltage and current I can do with accuracy.

On Wed, Mar 4, 2020, 8:51 PM ajparent1/KB1GMX <kb1gmx@...> wrote:
For 20W out what is the power in?  Voltage and current when transmitting?

Allison
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Re: QCX-SSB Help what do I do now? #qcx

ajparent1/KB1GMX
 

Hans ,

Yes, it works very well if its implemented.  Using your code.
The Experimental SSB code tried up to 101d did not accurately do
that.  What I describes was a workaround for that failing as I was
more interested in the TX side.

That why I wanted to keep the QCX as it was because it does work 
so well.

Allison
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Re: #qcx 50 watt amp, SWR tolerance? #qcx

ajparent1/KB1GMX
 

For 20W out what is the power in?  Voltage and current when transmitting?

Allison
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Re: #qcx 50 watt amp, SWR tolerance? #qcx

George Korper
 

Spreading the windings added 5 watts. The case makes no difference. So far no smoke!


On Wed, Mar 4, 2020, 4:16 PM George Korper via Groups.Io <georgekorper=gmail.com@groups.io> wrote:
Report on the Vishay Siliconix !R 510PBF from Digikey.
So far so good. 
Output 20 watts on 20 meters. 19 volts input. Bias just cracked.
No difference between dummy Load and antenna. 
I do notice a slight reduction in output when the bottom of the case
is on, but that could be just moving the unit. I do wonder if the low pass filter
might be lowering output. The case is very close to the toroids. 

Bottom line 20 watts is fine. Anymore and I get the feeling i'm not in the QRP zone and the finals
may be stressed.

On Wed, Mar 4, 2020 at 2:20 PM ajparent1/KB1GMX <kb1gmx@...> wrote:
OK a lot of things all interacting, many poorly understood.

Often I hear "I did all the right things and it doesn't work." and because its local
I get to see for myself.  That I did all the right things and it doesn't work usually
turns out to be far from true.  Most common is not measuring or worse no understanding
of what the measurement means other than a number.   SWR is not as stated at
the frequency in use is easy to fail, antennas do not have the same SWR across
the bands.  Bad cables and connections are common.  Or they put it up  according
to instructions except the instructions suggest at least 40FT high and they are barely
20ft or tuning will be needed,  however it was never done because hurry or lack of
equipment or someone else didn't do that and it was fine for him/her.

First doe the PS used tolerate RFI?  Some do strange things if RF gets into them.
One I had before modding it (bypasses and filters)  would go UP in Voltage, very bad!
Yes, it does happen and often even catches me unexpected.   I have a led lamp in
the room that a 2M HT makes it go off when transmitting and comes back on for RX.
Surprise!

The other is OCF has features and liabilities.  Features is it can be made to work
well on many bands. Liability is depending on the quality of the feed point
transformer (BALUN) it may (more likely will) have RF on the shield  and not all
parts of your system (QCX, AMP, Power supply) may be happy with that and
behave well.  The fix for RF on the shield is choking the COAX (10 turns of
coax on a 5-6 (15cm) inch form).  Grounds help too.

My 160M antenna with an 80m matching network gives a good SWR at 10W,
at 100W it fails.  Reason a cap in the matching system arcs over.  Unlikely
for your case but unlikely is not impossible.  Note: mine is a case of testing
a scheme so low voltage variable cap was used until the high power one
arrives.

Most meters if the SWR is good at 1W it will be good at 100 watts unless
something odd is happening.

An example, user of a 5W QRP had no SWR issues.  Bought a Ebay 70W amp
and SWR is 3:1 with same TX...  Two things the amp was over driven 2W was
max and dirty (spurs and harmonics) and no low pass filter so the SWR meter
was seeing all of the trash coming out all out of the antennas nominal tuning.
He couldn't understand why his RX sounded like the antenna was missing 
seems the TR switching was not working either (always in TX mode).
So for him and his first amp a lot of learning going on.

SWR is reflected power not a statement of impedance.  For all you know
at some frequency it will likely look like 30 ohms resistive and 35 ohms
reactive and that will present an OK (under 2:1) SWR but its not a nice
load.  Solution is to use and antenna matcher (its a matching network
not a tuner) to get a nice looking match for the amp. By setting the
Antenna Matcher for a perfect SWR presented that will help keep the
amp happy(working longer).

Do not reuse the not blown transistor, save if to something easier to open and repair.
It may have suffered Thermal, RF, or ESD distress without failing or has some.
Many issues that can occur will not be found with a ohmeter.  Things like gate
leakage and the like are not easy to measure. Using gate capacitance is not a
reliable indicator of device quality.   Use two known good ones from the same
batch.  that last item alone is sufficient, SAME BATCH is very unlikely with 
reusing an old by maybe good member of the existing pair.

REMINDER MOSFETS are ESD sensitive.  That includes BS170s and even
the MPU.

Also turning down the power 40W will be nearly impossible for the other guy
to tell from 50W but it reduces the eating and helps with SWR tolerance.
IF your using a power supply back it off one volt or two.
 
Lastly did you set the bias as specified, at the working voltage?  Is the Pi network
(low pass filter)  correct?   Were you putting in more power that you should to
get 50W?  Hint if you are running an efficiency under 70% (72DC watts or 3.5A
at 20V input to the amp) your doing it wrong and inviting failure.  Its worth
measuring the input voltage and current to be certain. Why?  At low efficiency
to get 50W your making a lot more heat.

One last thing the Vishay IRF510 is not a magic part.  Known real IRF510s 
from Vishay, TI, Fairchild, IR, ON semi, have all been used with normal results.  
There is no magic manufacturer that I know of,  only reliable sources.

This weekend I got a few from a friend who was getting bad results, marked 
IR and very real looking at that but the gate capacitance measured 680pF
A IRF510 to would be around 150pF, so its most likely a IRF530 as that's
closest,  remarked to pass as IRF510.  A lot of Non-RF applications that
part will work fine, some RF might even work.  For a lot of others RF projects
it would not work.


Allison
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Re: QCX-SSB Help what do I do now? #qcx

David Wilcox K8WPE
 

You guys just don’t get it.  There are some in this hobby who like to make things, and make things do more than they were intended to.  Congrats to them. I wish I had their knowledge and understanding, and especially their courage to do the “impossible”.  Anyone can buy a box radio but how many can build one from scratch or modify a simple one to do the complicated? 

David J. Wilcox K8WPE’s iPad

On Mar 4, 2020, at 6:58 AM, Andy V. Borisenko via Groups.Io <rw9rn@...> wrote:


gentlemen, maybe I don’t understand something ... but why buy a CW transceiver (when they bought everything they knew about it) in order to make it SSB?
is it such an idea to do the impossible?
could it be easier (and cheaper) to buy an SSB radio, or collect something more suitable?
I just don’t understand why buy, and then remodel?