Wonderful. Thank you Bob.?

73 Jim
VE4BWG

High James,

Have you verified the LPF diode switches?? ?I would start there.

73
Evan
AC9TU

Hello all. I've completed a revision 3 12v low band QMX and running into some issues.?
I've searched all over the group for hints but just can't find the exact combination of what I'm experiencing.
After thoroughly inspecting everything with a loup, I found nothing unusual. I reflowed the pertinent inductors and transformers and don't seem to have any enamel interferrence.
All suggested continuity checks pass.

My sweeps all look strange, SWR sweep showed straight 10 on all bands, I'm seeing zero output at the BNC into a dummy load, and no RX with an antenna.
With a signal generator nearby I can hear the tone, but it doesn't change volume whether I have an antenna attached at the BNC or not.
The SWR protection was kicking in, so I bypassed T507 in case it was wound wrong. I also re-worked T501 (RWTST) to be sure I didn't mess it up.

Here are my latest test results:
19mA? ?- Powered off
120mA - RX
1.3A? ? ?- TX @ 80m
.55A? ? ?- TX @ 60m
.95A? ? ?- TX @ 40m
.5A? ? ? ?- TX @ 30M
1.2A? ? ?- TX @ 20m
I suspect the varying band results have to do with the LPF inductors, which I'll fine tune once things are somewhat normal.

I probed around with an antenna on 40m and can hear CW signals at pin 9 of IC403 and stronger yet at the 23 turn of L401.

I'd go ahead and rework L401 and T401, but they both look okay. I'm also trying to avoid excess desoldering since it's a gamble of breaking something every time.?

Any suggestions of test points or anything else I can verify?

Thanks very much in advance.

James Shrum - AB9LM

I’ll take it!

Mark N8MH

I have a QMX transceiver kit for sale. ?Shipped to me this last August. ?Has enclosure, dummy load and power cable. ?This is all new in the box. ?$129.00 includes shipping to 48 conus.

TU, Bob. ?Fixed the math.

开云体育

Hi Roger,

An alternative to changing the QMX is to mod the 50 watt PA.? The current requirement comes from the LED indication that a PTT signal has been triggered.? If you change the supply to D12 from the PTT line to the output of IC1, the load on the PTT line drops to almost nothing.? The potential disadvantage is that there is not enough load on the gate of Q6 to keep it turned off in a noisy environment.

The safest design change to the amp would be a MOSFET buffer on the PTT input.? That requires adding another 5-volt regulator as well as the FET.

Or, add a 100 ohm SMD resistor on top of the R210 SMD 220 ohm resistor in the QMX.? R210 is accessible on the bottom of the mainboard.? You can get at it by removing the bottom cover.? No other disassembly should be required ;-)

73
Evan
AC9TU

Thanks for the replies.? Yes Bojan, after looking at the circuits in both I came to the same conclusion that R210 must be a lower value..? I was hoping not to have to open the QMX to make mods but it seems to be necessary.

73, Roger KF9D

I have similar problems with FW 1_00_017 on 20-10m hardware.
When I enabled Japanese limits, it does transmit on 20m band but not for any other bands. It seems no RF signal on CLK2 but TX control is there resulting? large Id current on BS170 transistors but no RF output.

Ron JK1DVP

Have you tried reflashing the firmware to see if it is just a software glitch?

I mean use a little bit of glue to hold the diode to the point of the cocktail stick.

I’d use the soldering iron with small tip, you’re soldering across the pins of an existing transistor and that will move with hot air gun.

Firstly “refresh” the existing solder joints on the board with a tiny bit of fluxed solder.
Position the diode and tack it in place one side by just heating the joint, then solder the other side with tiny bit of new solder, then go back to the tacked side and solder that properly too.

I used a wood cocktail stick with a little bit of glue to place the diode. I’ve also used fine tweezers/forceps, but the components have a tendency to “ping”away. Covering the worktop with a decent size piece of white cloth offers a better chance of finding the component that’s flown away…

I need to do the add a diode mod to my QMX Rev 2.? I want to use an SMD diode but have little experience with SMD soldering. And this part is tiny!

What's the best way to do this??

I have a hot air soldering station.? Hold the diode in place with some tweezers and apply hot air and let the existing solder reflow?? Use flux? Use a tiny dab of solder paste?? Or use an iron with thin tip?

Thanks for any advice.? ?Chip -- KM4AF

Most hams eventually discover that a good, dead cheap, quiet, RF proof, fail safe, reliable power supply is only available as a gift from a generous friend ??

Hi Roger,
I had to add a 100R resistor parallel to the R210 in the PA +5V PTT line to get reliable PA switching.
--
73 Bojan S53DZ

REV 1 factory assembled ???

es vy 73 de "baab" w9ya

Four things that got this working for me OM:

1) Select the Kenwood TS570 at 9600 baud, 8 -n-1, usb plus cat in the Settings window of FT8CN.

2) Be sure to set to "Lockd TX=RX" immediately to the right of the "Audio freq" entry in the same Settings window.

3) Set the "Signal output strength" to "100%" using the slider control which appears when you hit/select the speaker symbol on the right side of the/any FT8CN screen.

4) On the QMX set the MENU -> DIGI INTERFACE -> VOX to "ON".

Finally go ahead and restart the FT8CN program with the QMX running in DIGI mode. FT8CN will ask you to select the serial port. DO THAT and you should be a happy camper.

es vy 73 de "baab" w9ya

I have a QMX transceiver kit for sale. ?Shipped to me this last August. ?Has enclosure, dummy load and power cable. ?This is all new in the box. ?$149.00 includes shipping to 48 conus.

I have clicks all the time to the point that the QMX is not usable for cw, I did role back to rev 10 as suggested in one of the treads and seemed to be better. works well FT8.

Ron VA3LM

Hello,

I am wondering what the current operability status is between FT8CN and QMX (1_00_017).

Mike KK7ER reported on FT8CN and QMX back in July 2023 (#105559) with regard to 1_00_005.

Jim?
VE4BWG