Parks On The Air (POTA) with my QMX (#133) has found a 100% activation success rate using a simple wire antenna that tunes 40M and 20M with the aid of the 4 State Tuner. 18 gauge speaker wire with one side 15 meters and the other side 7 meters is tied in an electricians knot at the center and then 10 meters is left together zip cord style terminating with banana plugs. This plugs directly into the 4 State Tuner without the need of a balun. I throw the ends into trees and support the center with a Jackite telescoping pole up 32 feet that just conveniently leans into the overhead tree foliage. I have now activated over 20 parks with this setup using a QMX and full voltage 13.8v LiFePO4 battery. Everything fits into a small box and when carrying my pole it looks like I'm going fishing!

Interestingly, the AGC issue caused me to briefly switch to using the QCX-Mini, but the non-resonant antenna has a buzzy side tone with the QCX-mini that the beautifully shaped CW envelope in the SDR QMX totally eliminates! So I just very quickly turn down the volume when a loud station follows a faint one. Signals from all across the USA come in loud and clear. Thank You Hans for the perfect POTA machine. 72, Sandy KB3EOF

My QMX is getting close to the head of the queue.? Will it be built for a 12V supply or a 9V supply?

Regards
Bev
COAA
Portugal

Hey, all! I moved my radio over to a PI and it works!!

First rule out solder bridges and stray pieces of wire on your board. ?My experience in this kind of short on a QMX main board is that it’s from a failed chip. ?5V is supplied to the chips in the receive path (mostly), a few capacitors and the display. ?Remove the display first to rule that out. ?Then it’s a matter of elimination. ?Once you find the fault, then you have to ask why. Chips don’t fail without a reason.

Good morning, Evan. I tried that and it didn't solve my problem. Thanks, though. I'm still trying some things. I'm also in the process of getting a PI together to give a try.

I just did exactly the same thing, but I think the jump in the power supply voltage from going in and out of current limiting toasted something in my unit

开云体育

If it were me I'd redo T401 (the trifilar). If that is not wound
properly then the Rx will not work at all.

-mike/w1mt

On Fri, Aug 25, 2023 at 4:08?AM Paul Harrison via groups.io
<dj0cu@...> wrote:

Tried that, no change. Below couple of screen shot, maybe they tell you something? I have no idea?
Thanks Paul DJ0CU

OK Folks,

So, today I reverted to 1.06 Firmware on the QMX and can confirm FT8CN works perfectly with that firmware but fails to work properly (as described in my original thread) with later versions. Out of interest, I also tried a USB C to C cable with 1.06, but still no luck there. So the FLDigi issue described by others seems to be releated as suggested by Mike KK7ER

HANS - CAN YOU PLEASE CONFIRM YOU ARE AWARE OF THIS ISSUE FOR FUTURE UPDATES WHEN TIME PERMITS?

Thanks.

Daimon. G4USI

Paul,

QMX has no spike voltage issue at end of transmission because of the built-in wave shaping system.

Regarding Zeners for QDX, they may provide some protection against the hi-Z SWR case, but they are not a good solution to the inductive spike problem. At the moment the BS170 transistors turn off, there is approximately an amp +/- of current flowing through L14. That current will now go to the Zeners, where it most likely will be shared unequally as they are not identical. The datasheet for 1N4756A shows a maximum current of 95 mA.

The voltage at the BS170 drains will be well above the Zener voltage of 47 volts, as that high current and the Zener diode resistance conspire to elevate it well above the BS170 breakdown spec. The diode instantaneous power will be very high, perhaps as much as 75 watts each for a very brief time.?

These are not healthy conditions, either for the Zener diodes or the transistors. A commutating diode across L14 which is capable of handling the coil's current avoids all these problems.

JZ KJ4A

Yesterday I have successfully energized the QMX for the first time. As recommended, voltage to 7 volts, current to 250 milliamps. So far everything is fine.
Today I wanted to send for the first time. However, every time I pressed the paddle, a crackle and the QMX shuts down. Well, a loose contact? Are my soldering skills not good after all?
So I unscrew the case and start to examine the PCB and the paddle socket, but all is well.

But no, silly me, the QMX needs much more than 250 milliamperes to send. I just forgot to turn off the current limiter.
"If one has no work, one makes oneself some. :)
To the web SDR Heppen to Belgium, 220 km, with 3.8 watts to hear perfectly. What a dear little magic box!

I'm going to order the basic 5351 synthesiser board, I have 3 mcu chips here, tried all but no change so I'll change the 5351 as they are cheap. In the meantime I'll play with sdrconnect for wspr receiving.
Andy
--
The universe is made up of Protons, Neutrons, Electrons but contains only one M0RON.

Hi Don,
Yes, I remember your original posts and did try the diode method on a couple of QCX's until the little AGC module was developed. As I said, I'm sure Hans will include AGC limiting in a future firmware update so I'll not bodge this radio for the time being.

An external adaptor is an option, as you say, but it's yet another thing to pack/forget/lose.... besides, it's just limiting the level of an already badly distorted signal. Much better to have the levels controlled gracefully at an earlier stage in firmware and avoid those nasty square waves in the first place.

Cheers,
Ronan

Maybe this is what you are dreaming of?

That is indeed a dream come true. Thanks for the pointer.

And Barb, I like the idea, but do need the CAT option. But I have it bookmarked for later.
--

73 Lex PH2LB?

Tried that, no change. Below couple of screen shot, maybe they tell you something? I have no idea?
Thanks Paul DJ0CU?

?
Probably not a lot of people needing this feature but if you would like to use a QRP Labs product on a chromebook then click the link and "star" the issue. This helps them prioritize appropriately.?

I use NetTime 3.14 from www.timesynctools.com on all my windows machines, no
problem. Just install it and forget its there. Seems to work, flawlessly for
me, over wired networks, Wi-Fi,networks 3G and 4G networks using mobile
routers and pocketable 'hotspots', Cannot speak for 5G, there are no 5G masts
anywhere near, nearest I believe is 75 miles away.

Linux, the sensible OS, just does it without any user intervention..