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Re: 12VDC for my new QMX+

 

Probably fine, assuming your antenna system is well behaved.
Safer if you add a voltage drop using a diode such as a 1n4007.
Safer still if you are a volt or two down from 12v, at reduced power out.
?
With moderate deviations in antenna SWR the drain voltages in the final
can exceed the BS170's Vdss spec of 60 Volts max, even when running at 12.0 volts.
This is especially true on 160 and 80 meters, where Vdss max is exceeded even with a 50 ohm load.
?
When the transmitter is operating continuously in digital modes
the BS170's can overheat with a supply of 12.0 volts and above.
?
The only part of the QMX at risk when operating with a 13 or 14 volt supply is the transmitter final amp.
That is relatively easy to repair, just clip the BS170's out and solder new ones to the pads without
bothering to clean the holes in the board.
The 74ACT08 used as a driver to the BS170's can also get taken out when the BS170's fail as a short,
that repair is best done with the aid of a low temp solder alloy such as ChipQuik
?
Jerry, KE7ER
?
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On Fri, Jan 24, 2025 at 10:32 PM, <steamguy261@...> wrote:

I've read a bit about the hazards of overvoltage for the QMX+. The supply I have produces 12.25 VDC dropping to 12.14 VDC under load. Will the QMX+ be safe at these voltages? I swear I wanted to find the answer without having to ask, but failed. I've only tried the little guy on receive, thus far but its performance was superb.
Re: Book recommendation

 

On Sat, Jan 25, 2025 at 07:02 AM, Jerry Gaffke wrote:
Experimental Methods in RF Design (EMRFD).
It was written over 20 years ago and is now out of print, getting difficult to find used.
?

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This book looks readily available as a pdf online.?
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I must confess I'm one of those that limp by though. I'd love to understand more of the technical aspect but sadly my spare time is limited and I have other hobbies to squeeze in as well as getting on air and operating.?
?
I have successfully built the QMX and QMX+ though so am happy enough with that success :)
Re: Book recommendation

 

Fernando,
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The QMX includes techniques first developed for the QCX and QDX.
There sections in each assembly and/or operations manual that delve into how it works.
They are not always terse.
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The Wiki of this forum has lots of good information too.
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Do a web search for "hans summers fdim" to find presentations Hans has given.
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The above is all QRP-Labs specific
?
?
For basic knowledge on how radios work, I can think of nothing better than Experimental Methods in RF Design (EMRFD).
It was written over 20 years ago and is now out of print, getting difficult to find used.
Personally, I think it is a major sin for the ARRL to not keep it available, at least as an ebook.
A thorough search of the web might find ways to obtain it.
?
The Radio Amateur's Handbook by the ARRL has lots of good theory and practical design, well worth owning.
?
RF Design Basics by the RSGB looks promising though I have never read it.
?
Many amateurs limp by without a thorough understanding of complex impedance.
As the name implies, this involves values of the form? ?a+jb? ?in the complex plane.
In electronics we use j for sqrt(-1) since I so so often used for current.
I can't think of a book I'd recommend though I'm sure they are out there.
What I can recommend is obtaining a nanoVNA, it is a very useful tool for the radio amateur
and is all about measuring complex impedances.
?
Digital Signal Processing is where you will find a good deal of math to puzzle over,
it is the foundation to how the software in the QMX works (and the hardware of the QCX).
An excellent introduction to this is this free book on the web offered by analog.com:
?
Also free from analog.com is the excellent LTSpice simulator, it allows you to model working circuits on your computer.
?
Perhaps others could recommend other sources of information.
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Jerry, KE7ER
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On Fri, Jan 24, 2025 at 01:25 PM, Fernando TUSELL wrote:

Please excuse this if somewhat off-topic here.? I would like to learn about the operation of the QMX
?family of kits over and above the terse explanations given in the manuals. I would be grateful for
advice on what to read, either in book or paper form. My background in electronics is rather poor,
but would not be intimidated by? maths. Thank you for any pointers.
Re: 12VDC for my new QMX+

 

I run my QMX and QMX+ on 3s lipos so 12.6 fully charged and never had an issue.?
?
I've also run them on a 12v lifepo4 so 13.6v fully charged and not had an issue.?
?
CW only into good antennae.? I doubt get much that you'll have an issue at the voltage you're suggesting unless there's underlying issues.
12VDC for my new QMX+

 

I've read a bit about the hazards of overvoltage for the QMX+. The supply I have produces 12.25 VDC dropping to 12.14 VDC under load. Will the QMX+ be safe at these voltages? I swear I wanted to find the answer without having to ask, but failed. I've only tried the little guy on receive, thus far but its performance was superb.
Re: the next time someone asks when SSB firmware will be ready

 

Bill,
?
What will the QSX do that the QMX could not?
The new approach to SSB transmission may well prove superior to what was planned for the QSX.
There are a few enhancements to the QMX that I might like to see
but the first few versions of the QSX would have things to change as well.
?
Jerry, KE7ER
?
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On Fri, Jan 24, 2025 at 05:20 PM, Bill Cromwell wrote:

The QRPLabs radio I want to see is the QSX. I am already past my expiration date like the oldest carton of milk in the dairy cooler. I hope Hans does not wait too long.
?
Re: QMX mini input voltage tolerance

 

Paul,

Welcome to the forum! This is a very regular topic of conversation. I thought the following recent thread was particularly on point:

/g/QRPLabs/message/137125

Scroll down to take special note of comments by:

Stan: /g/QRPLabs/message/137479
Chuck: /g/QRPLabs/message/137567
Hans: /g/QRPLabs/message/137569


Basically, 12v means 12v, not 12.1. Ditto for 9v. Could you get away with more? Yes, probably, if your antenna is well matched (low SWR). Will the extra .1 or .4 V make a difference in your power output? Not enough to mean anything on the air.

A number of people on the forums run their QMX below its rated value in order to leave more margin for flaky antennas.

I have had great success a 12V TalentCell battery which is the same size as my QMX mini. It has plenty of power even for a rove of 5-6 parks in a single day.

I'll try to attach a photo of my field setup (at the Statue of Liberty!). See if you can spot the battery under the radio.

73 de Todd W2TEF
Re: the next time someone asks when SSB firmware will be ready

 

Hi,
?
I have worked SSBat about 2 watts and astonished the other hams I was talking to while they were running hundreds of watts (evil grin). It is about picking the right band at the right time of day and that changes according the whims of the propagation faeries. And maybe they are influenced a little by sunspots.
?
The QRPLabs radio I want to see is the QSX. I am already past my expiration date like the oldest carton of milk in the dairy cooler. I hope Hans does not wait too long.
?
73,
?
Bill ?KU8H
QMX mini input voltage tolerance

 

Anybody know the tolerance for input power voltage?? i.e. is the upper limit 12.35v for a 12 volt build and let's say 9.27v for a 9 volt build?? Or is it so sensitive that i need to have 12.0 ish or 9.0 ish?
TU es 73
KM4JHK?
Re: Q

 

That's a possibility.? I suppose I could pop off the front panel and use a jumper in the appropriate pin socket.? That could eliminate both button pressure and vibrations.? But all roads lead to cold solder joints, and I just got a nice new chisel tip yesterday.

-- 73 -- rec -- ad5dz --

On Fri, Jan 24, 2025 at 3:24?PM <DH8WN@...> wrote:
I wonder if it's from the pressure at the encoder. Every time you press the PCB is bend a little bit. Could it be a colder solder joint is changing the parameters. Or could it be an unwanted solder connection does the same?
?
73 Ludwig
Re: Jeff Moore W1NC to the Repair Rescue

 

Bill,
I totally agree.? Jeff rescued me and I was completely hopeless about my QMX build.? First transceiver kit I've ever attempted, but Jeff got it!? He's amazing with constructive feedback about what he found with mine.? But best of all, I just made my first contacts with that QMX that wouldn't even power up before Jeff worked on it.? So thankful that he's willing to help us!
73
Paul - KM4JHK
Re: Q

 

I wonder if it's from the pressure at the encoder. Every time you press the PCB is bend a little bit. Could it be a colder solder joint is changing the parameters. Or could it be an unwanted solder connection does the same?
?
73 Ludwig
Re: My second QMX+

 

As a mag loop user myself (also awaiting delivery on a QMX+), I would like to hear more about what and how your SWR+ box works.
Re: order status

 

But not right now when I'm away due to family winter vacation. Next update will be something like Feb 2nd

73 Hans G0UPL


On Fri, Jan 24, 2025, 19:07 Udo Die?elberg DF4BJ via <udodiesselberg=gmail.com@groups.io> wrote:
mostly every day from monday to friday?
vy 73 de Udo DF4BJ?
Book recommendation

 

Please excuse this if somewhat off-topic here.? I would like to learn about the operation of the QMX
?family of kits over and above the terse explanations given in the manuals. I would be grateful for
advice on what to read, either in book or paper form. My background in electronics is rather poor,
but would not be intimidated by? maths. Thank you for any pointers.
Re: I have a craving...

 

Thank you.


On Fri, Jan 24, 2025 at 11:34 AM, Wolfgang, OE3WFA via groups.io
<wolfgang.franta@...> wrote:
no, there is no kit until now If there would be enough interest, I can think about it.
Wolfgang OE3WFA
?
QDX WTST vs RWTST

 

Hi, i initially built my QDX for 9v using WTST and .6mm wire, i took a couple power measurements into dummy load with a good power meter vs supply voltage. attached here. It was running a bit hot at 40m & 9v.
Then I decided i wanted to be able to run at lower power output for WSPR so i decided to rewire T1 for 12v using RWTST (& 26 AWG). After that I took a complete set of power measurements into dummy load. also attached.
I regret that I didn't take more measurements in the first configuration but i'm pretty happy with the plots for 12v/RWTST. I don't know if my results are typical and/or why 60m is attenuated, but I don't think its an issue for me.
in case this is of interest or helpful to anyone.
regards
Lars KN5UTE
Re: QMX+ display color?

 

That's great Randy, thanks for the reply, I like blue displays so well that I have at least 6 new ones in stock and will be using one on my QMX+.
?
Joel
N6ALT
Re: QMX+ display color?

 

Works great! I've done it on both QMX and QMX+, other 16x2 QRP Labs kits like QLG2.
Got them here: ?
--
Randy, N4OPI
Re: the next time someone asks when SSB firmware will be ready

 

On Fri, Jan 24, 2025 at 02:07 PM, Giuseppe Marullo[iw2jww] wrote:
Hi Todd, are you saying that we will have to wait until mid May?
LOL, see below:
Yup, I knew he was speaking at FDIM, so that's why I suggested that. It would have a certain poetic resonance with last year's release, and May is NOT FAR OFF. And there is the title of that talk, which could be given before the firmware's release, but would have a bit more relevance afterward.

I offered that speculation purely in jest. I know absolutely nothing.

Except that Hans has strong (and hard-learned) boundaries on offering release dates. Boundaries are good for mental health. I very much commend Hans for practicing this important component of self-care.
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