Evan, Ludwig,

problem solved, thank you so much!!!!

The culprit was indeed our L502 friend. I re-soldered and measured again, but still no luck. Therefore, I stepped up the game, disassembled it completely, rewound, and re-soldered it in place: that did the trick!!?

I¡¯m happy to confirm 3 FT8 QSOs already on 20m :)

Thank you both, really appreciated, I hope to meet you on air too!

73, Ettore

Hot off the assembly line and I haven't even put my MB QMX in the case yet. Built for 9V operation, measurements made when powered by a 7.5V NiMH AA battery pack (6 cells), which sags to 7.1V when transmitting, fed into a 52ohm dummy load with a diode so measuring DC Vpeak with a Fluke voltmeter. Inductors wound per the manual.

60M 2.9W
40M 2.9W
30M 2.9W
20M 2.7W
17M 2.3W
15M 2.6W

If I use an 8 AA cell pack, the output exceeds 6 watts on most bands except 17 metres, so I plan on running it in the field with 7 NiMH cells. I would like to try 2x18650 cells sometime...

vy 72 de va3rr

¿ªÔÆÌåÓý

Just received the june 2024 edition of

K9YA Telegraph
A Free, Monthly, Ham Radio eZine

There is a fine article about High Altitude Baloon Tracking and APRS network congestion problems due to wide line-of-sight.
The eZine is sent as a link emailed to registered users. Each link of the monthly magazine is only valid during the pertinent month.

I thought that this might be of interest to owners of the U4B Balloon Tracker.

73 de Eike

--

Eike Lantzsch KY4PZ / ZP5CGE

Non dominant hand keying is simplified greatly? using a paddle as a side swiper or cootie since dits and dahs are not assigned to one side or the other and are interchangeable unlike an elect keyer or worse yet a bug. I can use mine in either hand without retraining at all.
;-)

A tip for articulate code formation with a side swipers and cooties? is to learn not to grab the paddle. Rather, set a space between the thumb and forefinger of about 1 inch. This gives solid contact where otherwise the code may sound somewhat slurred. It may also help mitigate a shaky hand where incidental contact may send? an errant? dit now and then.

Good luck finding a solution so we can continue to hear you on the air however you do it.
--
regards,
Bryan, N0LUF

Using torch or other high heat source is problem as it oxidizes the copper then
you have to clean that.

Tools that scrape the wire can nick it if one is not very careful.

The wire supplied wants a HOT soldering iron to melt it and tin.
I turn my PES51 up to 9(max heat, way hotter than normal soldering temp)
and go to it.

For a large number of wire I have a mini solder pot based on a
Ungar 47W element and a copper pipe cap mounted in a protective cup.
makes short work of lots of enamled wire.

For high temp poly or formvar, torch is a way or since often its thick wire?
in the #16 AWG or thicker Dremel tool with abrasive drum.??

--
Allison
------------------
Post online only,?
direct email will go to a bit bucket.

Even,

No need to specify input limits.? You have a lot of gain and 10W design power.

The only way to give an input limit would be no damage input limit which
would be well over (more than 10db) the 1db compression point.

--
Allison
------------------
Post online only,?
direct email will go to a bit bucket.

The answer is at the bottom of the amplifier's home page. The tests, eg sig gen attenuated to 10dBm.

73 Alan G4ZFQ

Evan,

The power output is in the title and the gain is well described.
Just read the manual.

FYI if I knew nothing about the amp but had only the schematic
it should be easy to guess that two push pull stages using a lowball
wild guess would be at least 11db per stage for a total of
22db plus or minus.??


Bruce:
I have 5 of them and lowest of the bunch at 10M is 25db.? ?The
other four are above that to 30mhz.? ?At the high end the
transformers get fussy and added leads and other possible
variations can lower upper frequency gain.? The amp was
tested to 50mhz where the gain was measured?21DB.
Anotehr factor is what the bias is set at, higher than
125ma/Device is more linear but more heat.? Lower than
125mA device results in reduced gain.? I've run up to 250ma
and 160ma seems a fairly broad point where gain and heat
are balanced.

Note if the driving stage is unhappy due to the input to the
amp you will see power/gain variation.? The input was never
designed to be a 50 ohm load. it is possible to optimize that.
As is at the low end its about 200 ohms and at the high end?
decreasing to nearly 50 with a reactive component.

Rather than countersink the heat sink, trim the shoulder washer,
its easier.

For all applications LPF must be used as 3rd harmonic is high
as push-pull stages do that.? Also 13V is that ithe ower supply
or actual votlage to the amps input?? ?Generally amps at
low voltages exhibit power supply sensitivity to max power.
FYI at 20V and a bit more drive over 20W is easily had.

--
Allison
------------------
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direct email will go to a bit bucket.

Hi Ettore,

nice information from the Diagnostics screen shots in the right bottom (Transmitter section).

1.) no key:
PA Voltage 0.8 V - nearly no supply voltage to the PA, that's ok. 0.8 V seems a little bit much.

2.) key P:
PA voltage remains 0.8 V; I'm not sure about the value and couldn't test yet

3.) key T:
PA voltage remains 0.8 V - wrong. The voltage should be much higher, around 9 V or more.

Let's have a look at the schematics page 5. "+12V" goes via Q507 and L502 to the PA-Transformer T501. From the connection Q507 to L502 via the voltage divider R525 and R526 the voltage is measured. From this value the value in the Diagnostics screen is calculated (as far as I know). Regarding to the wrong value for 3.) it looks like Q507 don't open the path for the voltage. So could you measure please the voltage at all three connections of Q507 for each situation 1.) to 3.)? And check please if all three connections are soldered properly.

And let us know the current for each of the three situations.

73, Ludwig

Both Hans and Wayne provide good magnet wire that works well with the solder blob method. I have a roll of .45mm magnet wire that Superman couldn't burn off the insulation. I have to scrape, then use the solder blob method, and sometime sandpaper afterwards. No worries about nicks in the insulation, I guess...

73 de va3rr

Allison,

Thank you for the reply.? I asked Hans to point out that I could not find the input limits in the documentation.? That could be why this thread was started on the power input question.? None of the Q_X series of transceivers would work with this amp without significant attenuation or modification.? ?It was designed to take an SDr output like the Softrock or the QSX it was intended for.??

From the order page:

Features:

• 10W output from 2 to 30MHz, using 12V Supply
• Suitable for 10W PEP, CW or Digital modes
• Generously-sized heatsink, will not overheat even on continuous 100% duty-cycle modes
• 2-stage amplifier provides 26dB of gain
• Push-pull driver and push-pull finals, for high linearity and low harmonic content
• +/- 1dB gain flatness from 1.8 to 30MHz
• 4dB down at 6m (50MHz) and 8dB down on 4m (70MHz)
• Standard 50-ohm output
• Through-hole plated PCB, several SMD components already pre-mounted
• PCB size 69.69mm x 33.97mm (2.744 x 1.338 inches)
• Standard inexpensive components throughout
• Tested for 1 hour at full-power 10W, 100% continuous duty-cycle with no forced air cooling
• Tested for 15 minutes at 20W, 100% continuous duty-cycle with no forced air cooling
• Tested at 20V supply
• Tested into open load, shorted load and various mismatches without instability (oscillation)

So, unless I missed it, the documentation needs to be updated.? It would be best to put it on the order page.

73
Evan
AC9TU

Hans,

I will look again, but I could not find it.

73
Evan
AC9TU

For the 10W linear PA, mmax input power will be less than .05W 50mmilliwatts
for saturated power out.

IF that is not clear take the 10W output (its 40dbm) and subtract 26DB of gain
and you get 14dbm (25 milliwatts) of drive.

So how that applies to your question is...? Increasing p input power to the amp
since its well over what is needed to saturate the amp by not less than 22times
mans the output never changes.?

IT also mans the input stage of the amp will likely be fried!

So D, which should be "none of the above".

As 1.2W (31dbm) increased by? 26db is 57dbm (assumes the amp can do it)
or ~250W and the amp is designed for 10w is classic extreme overdrive.
OK you might get 13W, and blown BS170s in the driver stage of the amp.

Hint linear means the output will be some fixed amount of gain above the input?
IF the input does not exceed some maximum.


--
Allison
------------------
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direct email will go to a bit bucket.

Hans,

The power input range for the 10-watt linear amp is not specified anywhere in the documentation. Based on the 26db gain, my calculations show it is around 30 milliwatts. Can you please confirm the power input limits?

Thank you
73
Evan
AC9TU

The Canadian FedEx must be more efficient than back in Blighty. I received my QMX last friday, and got my invoice yesterday. I don't mind though, as I don't think those 330uH inductors could survive shipping by postal service - lol

My QMX is up and running FB, despite having a senior's moment when installing a pin header socket. Nothing a little solder wick couldn't fix...

Thanks Hans!
de va3rr

Tony,

that sounds like a bargain to me, lol.

DHL charged me a total of 23€ for VAT + service fee.

VAT was roughly 8€, so guess how much the service fee was.

73, Andreas, DM7AK

Welcome to the world of FedEx shipping. The charges are nothing to do with QRP Labs. The kits are shipped from Turkey so VAT and FedEx handling? charges will apply.?

Pick DHL in future. A little more expensive but they seem to take care of the VAT aspect for you (at least that's my experience).