I have a version 1 QDX board I built up for 160 meters to drive a 630 meter transverter.? I left out switching diodes and jumpered low pass filter section.? Retuned receiver filter for 160.? Works well so far.? Transverter has enough filtering.? I can supply more details if needed.??

When I built my radio, I created my own check/cheat sheet while trying all the operations in the manual I felt most relevant to me.
It stuck. I think I only have ever referred to it twice.

73s Ted
2E0THH??

QMX Rev 3, built for 12 volts, 017 Firmware, shipped 21 Feb 2024, kit #319 with Mid-band field modification incorporated during assembly

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Immediately after the initial 017 firmware load this QMX exhibited a high noise level heard in the headphones with or without a dummy load fitted. Levels in excess of S9 in both CW and Digi modes were displayed when the S meter feature was selected ON.

Summary of initial observations:

Continuous S9+ noise

Only very strong received signals could be heard

Blasting loud noise in headphones when in Digi mode and FT8 displayed an overdriven audio level of RED at 82 dB

FT8 signals could not be heard on any band

Audio Filter and RF Filter diagnostic sweeps displayed erratically peaked traces of 0 to +20 dB

No LSB suppression

LPF sweeps appeared normal

CW Transmit function on all bands (60 meters not tested) was normal

Factory RESET resulted in no change

Reloading 017 Firmware resulted in no change

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Other similar reports on this forum led to the Audio A/D Converter IC 407 p/n PCM 1804 as being suspect. This IC was replaced and normal CW/ Digi noise levels were restored along with new diagnostic traces consistent with those provided in the Operation Manual.

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Photos and screen shots of the diagnostic traces in both pre and post IC 407 conditions are contained in the attached file.

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It is recognized that some additional “tweaking” of windings and menu settings may be required to achieve best operation of this field modified Mid-band unit. However, it is felt that the modification had no involvement with the high noise condition encountered during initial power up of this QMX Rev 3.

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Roy- KD1RT

Are you able to compare the device to another good, known receiver, same antenna? My QMX is as sensitive as my IC-7300. Also, be aware that HF conditions have been quite poor as of late and there are not that many signals on 20m the past few days.

Well, after doing a factory reset the graphs looked ok (except the RF filter plot for 20m showed it at -34dB at 14 MHz) so I decided to try my QMX on the air again.? In CW mode the 20m band was practically empty.? Changing to Digi mode I heard many more signals, but lost them when I switched to CW.? I also had S9+20 key sidetone clicks.
I really want to like this rig but this isn't helping.? I know the sidetone issue is being worked.? Any ideas on how to improve its ears?

Alan, I should have added some zeros. :) Also, I have the TCXO on mine now too, so I was trying to remember what I did before that.

--
73, Dan - W2DLC

On 20/03/2024 16:22, Karl via groups.io wrote:

"Birdies" on receive,

Someday this will be fixed in firmware..

Hello Karl,

The purpose of the diode mod is solely to protect the IC402 (MUX chip) from some unwanted parasitic ringing which may occur on some bands while transmitting (QMX in TX mode). While in RX mode, the diode has no effect, being reverse-biased. As far as I can tell, It won't eliminate any birdies, nor will it alleviate any low-power output issues.

The tones that you describe, that go up and down the band, I can hear them as well, on both the QMX and IC7300 - they're not caused by the kit. However, the fixed, very narrow birdies may be caused by the SMPS modules. Hans knows about them and will fix that in some future firmware update.

Regards,
YO3GFH
op. Adrian

On a roll with getting T507 actually connected to the radio, getting fw .017 loaded into radio and all by myself getting into PuttY repeatedly and seeing positive results!?

Then I see here someone putting in "the dreaded diode mod" and wondering what mod!?

There on QRPLabs.com site are TWO mods! The diode mod MAY SOLVE LOW POWER OUT PROBLEMS! Fancy that! "Birdies" on receive, unwanted oscillations...you mean those tones up and down the band like someone tuning up on CW and left his tool box sitting on the key ?? I got em! And I don't hear them on the IC-7300 nor the RS-918 mcHF clone.

Will report the results...
--
73
Karl
KI4ZUQ

On 20/03/2024 12:55, Daniel Conklin wrote:

It's normally not much. I think I set mine to 27.004

Dan,

With the current QRPLabs TCXO we think in terms of a few Hz. So the old crystals somewhere around 4000Hz off nominal might be considered a long way off:-)

73 Alan G4ZFQ

开云体育

I forgot to mention that from firmware 007 onward it didn't work at all until I think it was 017 when it began working without TxID on so progress is being made. At least that is what I recall and see here. Be sure you are using firmware 017.

Ok, thanks, I was not even sure if the display could be removed while the rest of the radio was in use.? I'll give it a try!

开云体育

You may have it on in your macros?

QMX and RTTY….




Chuck
NZ8I

One immediate solution is you can put the PDF of the manual on your smart phone or iPad.
The beauty of the PDF is you can search for whatever you need to address.
I hope this is helpful until a cheat sheet becomes available.

Thanks for the reply!? I thought I had TXID off, but I must have left it on, I will try again tonight.

Glad to hear I can still use the most popular digital modes!

It turns out that a factory reset fixed the plots.? I'm still not happy with the RF filter (-34db at 14 MHz) but I think it's ready to go!

SOLVED - I doubled checked the?SMPS supplies on the power board and found 1 pin on each one that did not have enough solder and was not making full contact.

On my QMX, I observed that the "garbage graphs" happened if I tried to step through the bands too rapidly, i.e., if I was on 20m and stepped up to 10m slowly, one graph at a time, all was well, but if I tried to go straight to 10m by stepping rapidly, interrupting a graph before it was done, I'd get junk.? As I recall, the solution was to power cycle the QMX and be more patient :-).