Hi Folks,?

really love my new toy - this tiny QDX TRX and it work excellent.
To prepare for longer FT8 sessions I tested and meassured a bit with the PA temp, as I it felt a bit high (first by fingertip measurements).

At the Hermes Lt2, to increase the cooling.
There the PCB to rail connection is used for primary heat transport and even the screw alone transports some temp to the case....

It could be an idea for a new hardware revision of the QDX to inlcude the PCB/Case connection into the PA cooling.


I modified my QDX and was able improve the PA temp by 5 °C (10 Minutes test cycle) and I assume the result will be even be more convincing after a longer test cycle.

How to do the simple mod (on your own risk ;-) ):

1. removed the nut, washer and screw at the PA.
2. while the QDX PCB is inserted in the case, use the existing whole in the PCB to mark the spot for the whole in the lower U profile of the case
3. drill a 3mm whole and countersink from outside (see picture)
4. replace original screw with a longer one with countersunk head
5. gently tighten the screw?
   Attention: do not tighten the connection to much, as there is a risk to crack the PCB.

I traced the following temperature curves at the surface of one of the BS170s (under the washer).
Condition in both cases where the same:

• f = 7074,5 MHz
• U in = 9V
• I in = 1,07 A
• P out = 5W
• Duration = 10 Minutes
• Duty Cycle 50% (WSJT-X/FT8)
• Room Temp 21°C
• Meassured with PeakTech Bench Type DMM 4090

With the original mounting method I meassured max 47,5°C after 10 Minutes:




After the mod, the temp was max on 42,3°C.




vy 73 de
Alex, DK4FT

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QDX - HW Rev 1.0 - U=9V - FW 1.01b - RPi4b with WSJT-x 2.5.1

Since the DC connector is the same the likelihood of that happening is a possibility.

Alas, there’s a confusing array of these connectors with little in the way of standards. I am only just now making some sense of them. Given that you probably have 12 volt devices that use the QRP Labs's standard 5.5x2.1 versions, you might want adopt something incompatible for your 9 volt build. Here’s are lists that might be helpful.





You’ll probably need to find one whose power jack has the right dimensions for the PC board.

This issue reminds me of when I first became interested in radio back when tubes were more common than transistors. At first I assumed that those who designed tubes had the “wisdom” to make sure that only the right tube would fit in a socket. I soon realized that wasn’t so. Every tube in my first radio had the same kind of socket.

—Mike Perry, WA4MP

Since FT8 is often operated using split frequencies within the customary spectrum, a designated QRP frequency does little, and it would grab even more scarce spectrum away. I can’t figure the dB reporting or -9 and higher dB that don’t come back to my 100w. Just call regardless of the level you are sensing.?

curt

I measured a lenght of? 223.75 cm of the 0.66mm wire, left over from winding L6, L4, and L7.? Therefore, I will have 5-lengths of 44.75cm wire to work with in making the bifilar and trifilar colls.? I am assuming that I will have enough wire to do the job.? From the photos in the manual, there appears to be plenty of extra wire when using 46cm per wire.?

Just wondering what others have found for this step

Thanks

Kent KC9LIF

As I wait for the next round of QDX kits become available I've glanced through the manual and am impressed (again) with the thoroughness Hans has put into the rig and the documentation.

When I get the chance to build a QDX I think I'll opt for the 9V version.

My question is if you build for 9V (3:3 winding) and mistakenly apply 12V volts will you let out the magic smoke?

Since the DC connector is the same the likelihood of that happening is a possibility.?

I think the gotchas at this point are transmitting without a suitable antenna and DC reverse polarity. Is this another one?

If this is a possible point of failure, putting a big "9V DC ONLY" sticker on the case is one solution. Maybe a different sized DC connector is available with the same form factor could be used?

Just a thought, thanks for clearing this up!

--Al
WD4AH

No shame in that, I use one too: they're invaluable. I just wish I could stop mine from slowly drooping down and sitting on my nose...

--
Julian, N4JO.

On Thu, Nov 11, 2021 at 03:24 PM, Bill Lamm wrote:

Several projects need to clear the bench (and maybe new glasses)

I got one of those head magnifiers (no they fit on the head rather than magnifying it). One of the best purchases in a while, make everything bigger and better.

I reckoned if they were good enough for Hans to use then they were good enough for me. Just been working on a new QCX+ build and the magnifier makes it much easier than the ones I built previously just using my glasses.

Reg?????????????????????? G4NFR

I'm very active on FT-8.? I can run 100W but very often it s more like 10-25W
as that seems more than enough.? Exceptions are DX where the pileup on them
will bury even 100W stations.

FYI station here runs on a 150AH battery and solar so running 100W FT-8 is
not a heating problem but it eats battery.? Economy of power is the game
and the mode helps weak signal operators.

I have found strong station running low power that cannot hear, alligators all
mouth no ears.? Most common reason for that is their local noise is terrible.
The other reason is their antenna is poor so they try to make it with power.

A good station can easily hear to -23db, most can't due to antenna or noise.
Also some receivers are very poor and suffer AGC pumping and desensitizing
due to other very strong signals.

In the end its funny I'll hear a station that is -12 and go back with 5W and
get a -5 received signal report.? Says a lot about their antenna or maybe mine.

FYI my best is JAs running 25W from Eastern Massachusettes on 20,
17, and 15M.? Key to that was not power but time of day!? We were both
grey line (about 5pm EDST) here.

Antenna for that was 160M inverted V (center at 10M) and the ends more
than 4M high.? Seems to work well on the mid bands with lobes that aim to
Europe.

Slways try but observe thewaterfall as the station seems to be in a
dense clump of signal likely not hearing well (their agc may be pumping).
I try to stay in the clear and that makes for better results.

As to QRP subband? it too late for that.? However 30M is ideal as it is
power limited (least here in the USA).

Allison
-------------------------------
Please reply on list so we can share.
No private email, it goes to a bit bucket due to address harvesting

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The QDX looks like a real game changer.? I would like to purchase one, but so does the rest of the world..
I realize that there is a backlog, and getting all the parts are difficult.?
Is there any way to get on
a list to purchase one as they become available.

By: wa9rvu@...

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A new chat has been created:

New

The QDX looks like a real game changer.? I would like to purchase one, but so does the rest of the world.. I realize that there is a backlog, and getting all the parts are difficult. Is there any way to get on a list ?

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开云体育

For a lot of you who aren't as old as I am I'd like to tell you something about Steve Weber. He used to be the designer and maker of QRP kits and was well known in the QRP community. I purchased and assembled several of his kits myself. He also took about half a year off and walked the Appalachian Trail from northern Georgia to Maine. That's about 2190 miles with lots of up and down along the ridges of the Appalachian mountains.

He's quite an interesting individual and I'd like to welcome him to the QRP-Labs group.

Jim - W4BQP since 1953

I first connect the QDX with WSJT-X, then exit the program
I start up windows (10) terminal (cmd)?
I type in /dev/ttyACM1 in the terminal and I get "can not find path specified" error message.?
I type in "mode" and get that I am connected to com4 at 9600 baud.?
Why does this refuse to work??
73, Steve KD1JV?

you shouldn't limit yourself to that. ?I have been running qrp all year, and most of my contacts are easily in the -20 to -15 range.


Anthony - N1IG

On Wed, Nov 10, 2021 at 01:10 PM, Curt - KC9CTP wrote:

Just got an email saying that my order #50260 status has changed to shipped as of today.

Not sure if it has shipped from MO or Turkey, but it doesn't matter. It is on the way here and it will get here when it gets here :D?

?The email will tell you where and how it was shipped.? USPS was from US Warehouse.

I was gifted a QDX to build and decide to add reverse polarity protection as accidents do happen. It is simple to do, especially if a fresh build.?
1. bend the +power tab on the back of the DC jack up.?
2. Solder in the DC jack, but don't push it too far back, just enough to line up the front with the edge of the board
3. Insert a 1N5817 diode into the rear pad (banded end), and attach the anode end to the DC power tab.
4, solder in the diode
5. Also insert the + lead of the 220 ufd cap into the board pad.?
Now you don't have to worry about connecting up your power cable to the supply wrong.?
73, Steve KD1JV?
?

No many/most is not all. As I'm here having my brekkie I just worked my best QDX to date:


--
John AE5X