On 24/02/2024 10:34, Dan Hurd W5DMH wrote:

I am wondering if I tried powering directly from the USB 5v (no buck converter at all) could damage the QDX?

Dan,

There would not be enough voltage to run the QDX if you put 5 volts to the power socket. I see no reason that it would be damaged, just not work.

It is possible that with a slight mod to the QDX it could run at low power from 5 volts directly. Possible but probably not worth the effort.

73 Alan G4ZFQ

Low power on all high band about 1-2 watts, kit 12v, tks for answer, i will check what you tell me. Tks, i will inform you next. 73 de it9xjj

I am using it on a Panasonic Toughbook, USB 3.0 and probably higher current rating than a standard USB 3.0 port, but I have been unable to find a specification for the current on those ports.?
I see no noise in the waterfall at all and reception appears to be the same as on battery.?

I am wondering if I tried powering directly from the USB 5v (no buck converter at all) could damage the QDX??

FYI Allison most recent production of BNC's are mechanically compatible.? Makers could get a long way towards 75 ohms with different insulation materials? and adjusted internal dimensions at the solder /crimp end so the volume production is indistinguishable by fit.

?

Of course the two impedances still exist and old cables are still around with different part? numbers for the two types (except on ebay ?)

?

The OP's problem was a dimensional issue on the threaded part.

On Sat, Feb 24, 2024 at 01:27 AM, Eric W. Hansen wrote:

Despite the lack of a backlight, my computer recognized the QMX, so I installed the firmware and it worked (even got a backlit display).? Maybe the processor thought I was in firmware update mode rather than initial setup mode?

Setup and testing will continue tomorrow.

This is the expected behaviour.? When you very first power up a QMX it looks completely dead - no display or anything and is in a state expecting to be connected to a PC and have the firmware loaded in.? Once the firmware is in it then springs into life :)

Good luck with the rest of the testing - they are great radios.

Evan and team,
Very interesting observation I would not have seen if I did not replace R13 and C33.?
L13 was soldered on its one side only.? The other side is totally without solder meaning there was no blocking of AC signals to ground.? Don't know if this is perhaps just my board (v4) or if this is the same on other V4 boards.
Worthwhile to just check.
73 de ZR6TM
Timo

On Fri, Feb 23, 2024 at 11:52 PM, mike/w1mt wrote:

Remove the washer. Of all the QCX's I've built I've had to leave that washer off on all of them.

That's odd. On all three of my QCX minis, the BNC connector is fine, even with the lock washer in place. I wonder if the part has been changed.

Cheers,.
Ronan
MM0IVR?

My V1 QMX has since the same thing since day one, over several different firmware versions. It affects the left encoder on mine rather than the right. It seems the software debouncing of these could do with a bit of tweaking. It's mainly noticeable if I try and turn the encoder one step ccw to change menus when it often changes then bounces back... Not the end of the world, but a bit nippy.

Cheers,
Ronan
MM0IVR?

On 24/02/2024 07:27, Hans Summers wrote:

The official spec of USB 2 is 5V 500mA max. But probably many modern ports can exceed that.

I was surprised when Dan said it worked.
A QDX might take up to 700mA at 12 volts transmit.

From 5 volts a buck converter would take more than twice 700mA to produce 700mA at 12 volts.
It does seem that some USB outlets could provide that current.

73 Alan G4ZFQ

Took lock washer off and connector works as it should. Thanks for the help.

73, glenn/ac0m

Took lock washer off and connector works as it should. Thanks for the help.

73, glenn/ac0m

I'm aware of that.? Have done it as well.

Also it depends on bias setting and the winding of the transformer.
By that I mean how tight and careful both windings are done.

I look at it as interesting but, what use is it beyond diagnostic
if ian amp is not developing full power as then the transformer can
be ruled out or not.

I have done the reverse on a board without finals loaded and the
Drain to Source path with R/C to simulate active devices to test
if the transformation of the transformer is valid.? I use that more
at VHF and up amp designs.? Same for input transformer or
matching save for the simulated load will match the gate to source.

As to input impedance, its nice to know but it was never meant to
be 50 ohms.? Again it can check the transformer.? FYI the QSX design
the driver was power limited but not voltage swing limited so higher
input impedance was needed.? That was the design source (QSX).

The test fixture I use verifies the assembly is flat and has known?
(measured loss) as that is a full two port test then the DUT(amp or other)
is added.? Since it build it up and measure the rare case is I find a
bad attenuator or cable early in the process.

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

I yanked some bristles out of a wire brush but the steel stuck in the solder! I have some bamboo sticks that might be worth a try...
--
73
Karl
KI4ZUQ

Despite the lack of a backlight, my computer recognized the QMX, so I installed the firmware and it worked (even got a backlit display).? Maybe the processor thought I was in firmware update mode rather than initial setup mode?

Setup and testing will continue tomorrow.

Thanks again, Ludwig,
Eric

Thanks Gary. Unfortunately this issue appears with and without the knobs. I guess if I’m going to figure this out I’m going to need to become friends with the schematic and try to reason out what in changing to “Digi” mode could cause this “noise” to appear at the audio port.

It sounds almost like it would when you picked up the phone while your 14.4K modem was active on the line.

One possible problem is the cable has 75ohm connectors...? BNC connectors for the different
impedance due to dimensions of the plastic insert and the pin.? Both parts must match.

That and come cheap prefab cables are just crap.

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

开云体育

Same experience here - leave the nut, but the lock washer prevents any BNC from fully seating. This has been true for 6 out of 6 rigs built by me. Sandy KB3EOF