Date   

Re: QDX Build Videos Thread

Ryan Flowers
 

Very nice, John! And don't you hate it when that happens? I can never seem to get the inductors to line up either, and that drives me crazy. Short drive, mind you ;-) 

More videos published:

QDX Build Part 11: Little Red LED: https://youtu.be/u2EZdIcA8nM

QDX Build Part 12: USB, Power, BNC Connectors!:     https://youtu.be/AZ8emza9dOE

QDX Build Part 13: Electrolytic Capacitor: https://youtu.be/ZDBLlC2kE3A


I've also made a playlist that is exclusively build videos from start to finish, although I haven't got the video series finished just yet. I'm hoping to have all the editing done and the videos published tomorrow. Here's the QDX Build Playlist:

https://www.youtube.com/playlist?list=PLDP9oGiu60jJdiQOQx6-5DRn3l5GrfQQM


--
Ryan Flowers - W7RLF
MiscDotGeek - QRP and More (Website)

QDX News, Tips, Build Series (YouTube)
QCX Mini "Mini Tip" Series (YouTube)
QCX Mini Troubleshooting and Repair (Website)


Re: Classic QCX C1 fully meshed

 

But....
if you're getting two peaks, that means it is peaking with capacitance to spare, right? So if that is so, what exactly is the issue? Or am I misinterpreting what you're saying?
--
Julian, N4JO.


Re: Classic QCX C1 fully meshed

 

Hi Dave,
Yes, adding capacitance should, within limits, have the same effect as adding turns (inductance).
The resonant frequency is 1/ (2* PI ( sqrt(LxC))). In simple terms, the resonant frequency goes down if the product of L and C goes up, so that making either one bigger makes the product bigger.
Now here's the problem: you just said that you started with 2.2pFd, and ended up adding 39pFd in parallel with the 30pFd trimmer, and got no change. That should be doubling the capacitance, so it sounds like there's a problem.
My suspicion is that the capacitors you are adding might be bad: if they are leaky, they will pull down the Q factor of the tuned circuit, possibly to the point that it won't peak noticeably, Are they from the early kit?

Also, to pick at your words here - just to be clear - you said "yes, there were two peaks, but at opposite ends of the plates". I presume you mean at opposite sides of the fully meshed position, right??
Theoretically, if you added just the right value - say 22pFd, you would move the resonant points down to either side of the full unmeshed position. You didn't achieve that inadvertently, did you?

--
Julian, N4JO.


Re: QDX next batch

richlim11
 

Hans, just got home…long day. Yes you are correct, that is what I read early this am. Maybe I need to have my morning coffee before answering emails! Thank you and sorry about any confusion/stress I caused.

Rich KQ9L

On Monday, November 1, 2021, 12:00 PM, Hans Summers <hans.summers@...> wrote:

Hi Rich

I believe you are referring to a thread which mentioned occasional problems with 20m Low Pass Filter capacitors in early model QCX Classic kits. 

It does not apply to any later QCX-classic, or any model at all of QCX+, QCX-mini or QDX, all of which are already supplied with Vishay (occasionally TDK) NP0/C0G capacitors sourced from Digikey US and are always of known good quality. 

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


-------- Original message --------
From: "richlim11 via groups.io" <richlim11@...>
Date: Mon, Nov 1, 2021, 7:35 PM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] QDX next batch
Hans, I’m at work now and can’t access my email program at home. The thread was from earlier this am (about 5a CST) and pertained to several caps which need to be replaced in order to get appropriate output. You did reply to the thread as well. Forgive me if I misread the thread title but I think it was something like “Low output” or something to that effect. I can check later when I get home but it will not be till  much later.

R
KQ9L




On Monday, November 1, 2021, 9:55 AM, Hans Summers <hans.summers@...> wrote:

Hi Rich

Can you direct me to that thread or post please? 

Thanks, Hans

On Mon, Nov 1, 2021 at 5:53 PM richlim11 via groups.io <richlim11=yahoo.com@groups.io> wrote:
Cool! Are you modifying the caps in band pass filter as noted in a previous thread?

Rich
KQ9L




On Monday, November 1, 2021, 7:22 AM, Hans Summers <hans.summers@...> wrote:

Hi all

I have managed to obtain sufficient parts to manufacture 375 more QDX kits which is less than I would like, but it is something to quench the thirst of the masses... at least for a little while to let me search for more components. 

It might take about 5-6 weeks to prepare these kits. I will update you when I have more news about the estimated availability date. 

I am not going to take pre-orders except for a few special cases and requests related to the first batch, who I will communicate directly with. 

73 Hans G0UPL


Re: Classic QCX C1 fully meshed

Curt wb8yyy
 

If the receiver works to your satisfaction I am so tempted to say don't change anything. If you got a great calibration with good nulls, and your qcx is receiving lots of signals, time to enjoy it. 

Curt


Classic QCX C1 fully meshed

David Wilcox K8WPE
 

Hans, Julian,

I just built a Classic QCX I bought from Hans at Dayton years ago.  C1 only peaks at fully meshed position (or close, maybe 95% full mesh).  Another advisor suggested adding some capacitance to C1 ( In the 30 meter version you don't use both caps at positions C5 and C8 so there was a spot to add capacitance).  So I started with 2.2 pf, and went up 10 pf, 15 pf, 33 pf and finally 39 pf but it didn't change the meshing of the plates. They stayed 95% meshed no matter what cap I put in place.  Yes, there were two peaks but at the opposite ends of the plates.  

The rest of the alignment went as the manual describes.

I know the instructions say to add 5 turns to T1 and I can do that but adding a cap sounded so much  easier.  Or maybe go smaller.  Take the 22 pf cap out of C5 and go smaller???  I am old and am getting confused which way to go (other than follow the directions and add 5 turns.....ha!)

Can you two gentleman shine light on this idea...... 

Thanks.

Dave K8WPE

Virus-free. www.avg.com


Re: QDX - how to best check the filter performance

Shirley Dulcey KE1L
 

There are two possible concerns with the filter alignment on transmit; maximizing transmitter output and checking for harmonics and spurs. You should be able to get plenty of output with no adjustment at all, and the filter design is not identical to the QCX (where adjustment of the filters has been beneficial), but you still might be able to squeeze out a bit more output by adjusting the wire spacing on the toroids. Hans has posted on adjusting the QCX for maximum output.

As for checking spectral purity, you don't need to. If you build your QDX properly you will be just fine. Again, YOU DO NOT NEED TO DO THIS. (Emphasis added to keep Hans from getting lots of unnecessary requests.) If you don't have the gear to test it, just build and operate the thing and be happy; Hans has you covered in the design.

But you asked. If you DO want to have a look you will need two or three tools: a spectrum analyzer, a wide range SDR, and an attenuator or RF tap. The last of those is used to reduce the output of the QDX to a safe level for the other two. The full output of the QDX will range between +33 dBm and +36 dBm (in other words, 3 to 6 watts), depending on operating voltage and how you wound the binocular transformer. Depending on your test gear, you probably need to get that down to somewhere between 0 dBm and -20 dBm (in other words, one milliwatt to 0.01 milliwatts), so you'll need anywhere from 33 to 56 dB of attenuation. A good test setup for testing QRP rigs that isn't too costly is a good fixed attenuator or RF tap in the 30-40 dB range, plus a step attenuator to switch in the exact amount you want. (The fixed attenuator goes FIRST; the step attenuator can't handle the full output of your rig.) For these tests you are connecting the test gear directly to the output of the QDX through the attenuators; no antenna is involved. If you use an RF tap rather than an attenuator you also need a dummy load that can handle the full output of the QDX.

The spectrum analyzer is the tool for checking for harmonics and out of band spurs. Use the attenuator to get the signal down to a level your analyzer can measure and then have a look. The inexpensive TinySA is sufficiently capable for this test; something fancier like a Rigol, a Siglent, or a surplus Hewlett-Packard is nice to have but more than you need. If you are patient, there is also software that will turn some SDRs into a rather slow spectrum analyzer; that is adequate for looking for major problems, but the SDR's gain over a wide bandwidth may not be flat enough for accurate measurements. (The software does hundreds or thousands of tune-measure steps, captures the data on your PC, and plots it as a spectrum.)

If you have a spectrum analyzer with a nice narrow minimum setting for analyzer bandwidth (RBW), which means the minimum width of signal it can display, you can do all the tests with it. If you are using one with a wider RBW such as the TinySA, an SDR is a useful tool for checking for near-in spurs and the width of your transmitted signal. Once again, use the attenuator to reduce the output to a safe level for your SDR, tune the receiver to your output frequency, and have a look at the spectrum display. You can use a dedicated SDR that tunes the appropriate range such as an Airspy or SDRPlay, an inexpensive Softrock, or the spectrum display offered by some fancy transceivers. An RTL-SDR dongle paired with a transverter will also work though its dynamic range is more limited. In addition to looking at the output frequency, you can also tune near the harmonics and spurs to see if anything unusual is going on there.

You can use the same procedure to look at the spectral purity of any rig, not just the QDX. You'll need an attenuator that can handle more power (and more attenuation in front of the step attenuator) if you want to test non-QRP radios. If you want to start building your own transmitter designs, this kind of test setup is important to make sure that your transmitters are compliant with the rules where you live. You can duplicate most of the tests that the ARRL Lab does with a couple of hundred dollars worth of gear, something that was not true a decade ago; that is a huge step forward for homebrewers.

On Mon, Nov 1, 2021 at 8:06 PM Bob Benedict, KD8CGH <rkayakr@...> wrote:
Please see the QDX manual section on terminal apps starting on page 82. Section 6.6 on page 89 describes the built in Rx RF filter sweep.
--
  73
    KD8CGH


Re: QDX on 60 meters?

Shirley Dulcey KE1L
 

In an earlier post that is, where I noted that the US and Canadian rules allow only one CW or digital signal on each channel, which must be at the center frequency of the channel. Therefore, transmitting FT8 at any offset other than 1500 Hz is not allowed.


On Mon, Nov 1, 2021 at 8:15 PM Shirley Márquez Dúlcey <mark@...> wrote:
I'm aware that there is plenty of US activity on 60 meters. By my reading nearly all of it is a violation of the rules, as I explained in my post, and therefore I can't recommend that US hams (nor Canadians, because they have rules identical to the ones in the US) buy a QDX to transmit FT8 on that band. There are still plenty of other reasons to buy one, which is why I am eagerly awaiting mine.

On Mon, Nov 1, 2021 at 8:06 PM August Treubig <atreubig@...> wrote:
Shirley,
FT8 on 60m in the US is very busy and allowed.

Aug
AG5AT


Re: QDX on 60 meters?

Shirley Dulcey KE1L
 

I'm aware that there is plenty of US activity on 60 meters. By my reading nearly all of it is a violation of the rules, as I explained in my post, and therefore I can't recommend that US hams (nor Canadians, because they have rules identical to the ones in the US) buy a QDX to transmit FT8 on that band. There are still plenty of other reasons to buy one, which is why I am eagerly awaiting mine.


On Mon, Nov 1, 2021 at 8:06 PM August Treubig <atreubig@...> wrote:
Shirley,
FT8 on 60m in the US is very busy and allowed.

Aug
AG5AT


Re: QDX on 60 meters?

 

Shirley,
FT8 on 60m in the US is very busy and allowed.

Aug
AG5AT


Re: QDX - how to best check the filter performance

Bob Benedict, KD8CGH
 

Please see the QDX manual section on terminal apps starting on page 82. Section 6.6 on page 89 describes the built in Rx RF filter sweep.
--
  73
    KD8CGH


Re: QDX on 60 meters?

Shirley Dulcey KE1L
 

Not everybody lives in the US. There are many parts of the world where FT8 activity is fully legal on 60m.


On Mon, Nov 1, 2021 at 7:34 PM Lee <Lee@...> wrote:
Why?  What would you use it for?
 
-Lee-  WA3FIY
 
------ Original Message ------
From: "John AE5X" <ae5x@...>
Sent: 11/1/2021 7:25:00 PM
Subject: [QRPLabs] QDX on 60 meters?
 
With a firmware change & using the 40m LPF? Es posible?
--
John AE5X
https://ae5x.blogspot.com


Re: QDX on 60 meters?

Lee
 

Why?  What would you use it for?
 
-Lee-  WA3FIY
 

------ Original Message ------
From: "John AE5X" <ae5x@...>
Sent: 11/1/2021 7:25:00 PM
Subject: [QRPLabs] QDX on 60 meters?
 
With a firmware change & using the 40m LPF? Es posible?
--
John AE5X
https://ae5x.blogspot.com


QDX on 60 meters?

John AE5X <ae5x@...>
 

With a firmware change & using the 40m LPF? Es posible?
--
John AE5X
https://ae5x.blogspot.com


Re: QDX Build Videos Thread

John AE5X <ae5x@...>
 

I didn't notice that out-of-alignment cap until I posted the photo - now it's bugging me big time. Now I gotta make like an orthodontist and snap that little baby into place.
--
John AE5X
https://ae5x.blogspot.com


Re: QDX Surface Mount inductors

Curt wb8yyy
 

It would be interesting to know the context of how and where part is used to determine if it's a problem. Presumably the qdx works already is what I am thinking. In a few apps designers I observed in the past wanted to operate near self resonance, but that may not be intended here. Don't readily jump to conclusion there is a problem yet, in particular if part isn't a sole bias choke. 

Curt


Re: QDX Build Videos Thread

John AE5X <ae5x@...>
 

About 1h15m into the build. So far, so good:


--
John AE5X
https://ae5x.blogspot.com


Re: QDX BPF/LPF Switching Frequencies and tuning range.

Lee
 

So ... it appears the QDX is not useful on 60 meters. It will not do pactor or PSK31 which are the only modes allowed on 60 meters. That ARRL posting is quite enlightening. Oh, the QDX does not even cover 60 meters so that settles that question! :-)

Been thinking about getting an QDX for my traffic work here when they become available but have not yet learned enough about it to know if it would serve. Now that they are coming on line, I hope to learn a lot more about the finer points of that thing as new users comment on various features.

BTW my 40M QCX is useful for traffic. Enough selectivity, power and frequency stability. Nice break-in keying and, with an audio clipper, nice smooth operation. But, since I often need to switch between 80, 40 and 30m in a given session, I currently use an Argonaut VI. Now there is a wonderful traffic radio! :-) I suspect the QSX will be likewise! Maybe I will just wait for that one! :-)

73 de WA3FIY Lee

------ Original Message ------
From: "Mike Perry, WA4MP" <editor@...>
To: QRPLabs@groups.io
Sent: 11/1/2021 12:18:23 PM
Subject: Re: [QRPLabs] QDX BPF/LPF Switching Frequencies and tuning range.

The ARRL has a lengthy statement about amateur operation in the U.S. on 60 meters that includes this:

Digital Operation
Our expanded privileges on 60 meters were the result of collaboration between the FCC and the NTIA – the National Telecommunications and Information Administration, the agency that manages and coordinates telecommunications activities among US government departments, the primary users of the band. The NTIA expressed concern about possible interference and requested that amateurs limit digital operating to PSK31 and PACTOR III only.

It is certainly possible to interpret the FCC Report and Order somewhat broadly as it concerns digital operating on the band, but be careful not to read too much into the text.Therefore, as a practical matter it appears that any J2D data emission is to be permitted up to a bandwidth of 2.8 kHz, provided that care is exercised to limit the length of transmissions

With an eye to the potential for expanded 60 meter privileges in the future, the ARRL believes it is critical to cooperate fully with the NTIA. Therefore, the ARRL asks all amateurs to restrict 60-meter digital operations to PSK31 or PACTOR III.
http://www.arrl.org/60m-channel-allocation
Read the entire posting for other details. Keep in mind that we share this band with services that have a higher priority, so we need to play well.

—Mike Perry, WA4MP






Re: QDX BPF/LPF Switching Frequencies and tuning range.

Shirley Dulcey KE1L
 

The US rules for operation on 60 meters require that CW and digital signals be at the center of the channel. That would appear to allow only one FT8 signal in each channel at an offset of 1500 Hz. That is almost totally incompatible with how FT8 is used, and devoting an entire channel to a single low bandwidth FT8 signal would be a waste of a channel. Therefore it is not practical for US hams to transmit on the band at this time. Receiving FT8 on 60m can still be a useful way of gauging whether the band is open to non-US locations.

Allowing only one CW signal on a channel that is nearly 3 kHz wide is bad enough. I hope that the US regulations on 60m are eased in the future, but for now we have to live with what we have.

On Mon, Nov 1, 2021 at 12:51 PM Evan Hand <elhandjr@...> wrote:
Allison,

Thank you for the explanation!
73
Evan
AC9TU


Re: QDX Surface Mount inductors

Fred Spinner
 

I was thinking that it might be more trouble than it is worth when you mentioned digging for new inductors.  If you are worried about the leaded ones physical security to the board, once you get it working, simply epoxy them down.   That's an industry fix on prototypes and for many "white wire" changes. 

Fred W0FMS 

On Mon, Nov 1, 2021, 10:12 AM Gregg Myers <gregg.w7grm@...> wrote:
The self resonant frequency is often on the datasheet for these inductors. However, but as Hans mentions, you have to also consider the harmonics as well. Anyway, If I were to experiment I would start with the datasheet (example attached) and then really prove it by testing the actual result.

Good Luck & 73,
Gregg W7GRM

On Mon, Nov 1, 2021 at 11:06 AM Hans Summers <hans.summers@...> wrote:
I don't know the answer either. 

I think the only answer actually is trial and error... If you want to substitute components other than those supplied, be sure to carefully check the harmonic output on all four bands using a good spectrum analyzer.

73 Hans G0UPL


-------- Original message --------
From: Ryan Flowers <geocrasher@...>
Date: Mon, Nov 1, 2021, 7:43 PM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] QDX Surface Mount inductors
I don't know the direct answer, but if you're wanting to fit SMD parts rather than the leaded parts because it looks hard- it's not. Not at all. I'll be posting a video about it today or tomorrow. I documented my complete build. 

--
Ryan Flowers - W7RLF
MiscDotGeek - QRP and More (Website)

QDX News, Tips, Build Series (YouTube)
QCX Mini "Mini Tip" Series (YouTube)
QCX Mini Troubleshooting and Repair (Website)