Many 40mm DIA 32 ohm speakers available on Amazon:? Search on?

Weird.? Have you tried adjusting the blue pot to the left of the screen, regardless?

Jason / K1LOL

Hans took the time to created a great QMX schematic on the QRP Labs website including component numbering which corresponds to the page number of the schematic. For those of us trying to help and to follow the posted information flow, it would help if everyone please double checks the component numbers they use to describe the problem/fix.

73 Kees K5BCQ

Hi Hans,

> It's 6dB per bit. So 45dB would be 7.5 bits. Not 15.

You're right, of course, about the 6dB per bit.
But I think Audacity may be confusing things a bit (seems to me that Audacity is off by a factor of 2).
Let's look at it a different way.
The maximum absolute value of the samples in the 24-bit PCM wave file recorded on the QMX is 389.
Therefore the entire wave file has a 10 bit dynamic range (all values fall within [-512,511] so are representable using 10 bit signed integers).
That leaves us with 14 bits to spare.
So there really is a lot of headroom here.
Whether or not we are missing FT8 decodes due to quantization error depends on the RF noise floor as well as quantization noise floor.
But it sure seems possible to me that we could be missing decoding some of the weaker signals.

I'd love to know the dynamic range you and others are seeing on the QMX with default gain of 54.

My Windows audio device gain is set to 100% for the QMX audio device.
I'll play around with the gain value in the QMX configuration screen and report back.

73, Mike KK7ER

Mystery Solved:?
Bad Q505 (BS170) was conducting when off.? During startup, before the first transmit,? the PA voltage control provides full voltage to the PA transistors even though the QMX is in receive? (this is a firmware anomaly).? This was the cause of the extra current.??
Replacing the bad BS170 corrected both the startup current and low transmit power.

Also, I did check the transition from the 3.3V linear and the buck regulators which was correct.

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Me too ! (Serial number 100)

es vy 73 de "Baab" w9ya

Sad to report that my QMX kit is missing the BN43-1502 (T507) binocular core. Hans - please do your magic and see if one of your staff can get one to me.

In the mean time I can continue at step 2.15 and revisit? T507 when the part arrives.
--
Jim / K7TXA
Eagle, ID

SKCC 10447
BUG 301

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Maybe a flakey solder joint on the display board?

Hi All,

I'am still unable to get good RF sweep in my QMX, 9V version 55mA RX 3-4W output into dummy load, but receive is very quiet. I presume this is due to BPF.

All continuity checks are OK. Here are my sweeps as well as picture of L401, link between 28t and last is on another side of the board. Any pointers or suggestions will be greatly appreciated.



---------------------------------
73 de Marek SP9TKW

Hans,
Unless I am missing something the diode D101 has not failed even though I had a short between the two drains. I powered it up after I moved Q103 and it has been working just fine.

Dennis
KK5DB

Oddly this seems to have worked itself out. Backlight contrast was horrible the first day or two of use. I just turned backlight back on and it seems to be good now. Not sure what changed.

With the backlight on, I can barely read the screen of my QMX. That's with the trim pot turned full counter-clockwise Increasing that trim pot at all, and I can't see anything but the backlight. With the backlight off, screen contrast is quite good, but that's not so helpful in a dark room. Is there any way to fix this?

That's great Chris, thank you.?

Steve

As an update, as I look further into this it would appear the paddle also doesn't work. If I set practice mode and just key nothing happens. Doesn't appear to be a common element between the key and the audio but something is a miss. Might have to set this aside for a while then come back. Something might jump out then.?

? Don..?

James, I experienced the same. Here's a link to get a pack of them overnight on Amazon:?
Works fine once installed. I'll send a couple by snail mail if you want to save $7. LMK
73, Mitch NK3H

Hans,

Thanks for all of the updates. Wonderful radio. Incredible engineering/design. I'm so happy!

I'm not sure if this is the right place for reporting bugs or if what I'm experiencing is a bug!

Unlike the QCX, where beacon mode starts when you back out of the beacon menu (presuming it's set up), QMX doesn't start it up. The only time I can get into beacon mode is on power start up. Not sure if I'm alone in experiencing this or if I'm doing something wrong. I've set beacon mode for WSPR and set all of the parameters for WSPR just like in the QCXs. Firmware 009 (I've also tried 007 & 008). Thanks. 73, Mitch NK3H

Thanks guys - I'll ignore that "loop" on page 33 - it sure is confusing!
--
Jim / K7TXA
Eagle, ID

SKCC 10447
BUG 301