I used the 47-volt version from this Amazon assortment (I always buy assortments to build my parts bin).


73
Evan
AC9TU

Probably T507 has one unmade connection (on the thin wire).
I would believe the scope reading, assuming a good 50 Ohm dummy load.?
Most of my other power readings disagree!?

Hi Stefan,

" lower IR" should be no problem, lower IR is better for reverse operation.
Look . The worst value for 1N4148 is 50 ?A @ 20 V 150 °C but only 0.025 ?A @ 40 °C.

"lower URRM" should also no probleme, see posts above.

73, Ludwig

My QMX hi-band build is great so far. Am currently measuring power output. However, I have two concerns:

1. The terminal emulator Diagnostics power output indicator always reads 0 watts out, even though I know there is close to 4-6W out depending on band. Any ideas why?

2. Measuring power output inconsistencies: because the terminal diagnostics power is not working, I am fortunate to have other methods: a) QRPGuys power/swr/dummy load, b) MFJ-941E tuner analog power/swr meter and c) DSO Siglent 1202X-E.?

The scope is giving me power out on 20m using 12.5VDC of 5.8W (from 48.4 Vp-p), whereas both the other meters say about 3.8W out. My scope is calibrated and I believe quite accurate, so I am going with what it tells me, but it is disconcerting that two other meters register similar and lower values.

Any ideas on both concerns above appreciated.

73 Larry VE7EA?

Evan
What zener do you recommend?

Hi Giuseppe,
Thanks for the information about the T37-6 yellow toroid. I seem to remember reading something about that while researching toroids. I'm only getting about 1/2 watt RF power out using the T37-2 so your discovery to use the yellow toroid must be reason for your results. I thought it was odd that the C30 cap was missing and now I understand the mystery. Hi Hi NIce images of the results of the beacon signals. I also subscribed to your YouTube Channel and enjoyed watching your videos.

Did you use the GPS from QRP-Labs for your beacon or is it not needed for a CW beacon? Once I get my 6-meter beacon working, I'll give you a full report.

Hello Stefan,

In all honesty, I don't think there's any noticeable improvement... or my ears don't hear it, at least. I did the mod because the pacient was already on the table for the recommended diode addition, otherwise I wouldn't bother.

Regards,
YO3GFH
op. Adrian?

开云体育

Hi Adrian, Lun, Jim & Paul,

I'm fascinated by your efforts to optimize the sweeps, however, I wonder, whether this will really have a recognizable effect in day-to-day operation.

From what I got now - after having looked at quite some messages with the sweeps - my QMX seems to me more or less an unoptimised average. -? I'm pretty much there, where Adrian was before adding the cap. Here we go:

I'll recheck again after the diode Mod from Hans ... But If nothing worsens, I'm not so sure, whether it will be really worth trying to tweak this to the end.

Do you have any practical tests apart from the sweep, that suggest a significant improved performance?

Vy73

Stefan.

Hello Paul,

Those are after adding 470pf to C402; the OP (Lun Yang BD8BTE) and I had the same issue with the 80m sweep, which was a bit low. In particular, my 60m was also a tad off.
Lun added 330pF, I couldn't find anything except 470pF :-)

Please see below the "before and after" sweeps:

80m BEFORE



80m AFTER



60m BEFORE



60m AFTER




40m BEFORE



40m AFTER



So, by the looks of it, 470pF shifted the center down by some 1.5 - 2 MHz for 80, 60 and 40. Right now, I'm listening to the 80m band and it doesn't seem like any great improvement, but this isn't of course very scientific :-)
One thing that I forgot to mention, after adding the 470pF cap to C402, all sweeps looked totally crazy so my heart sunked into my pants, thinking that I've managed to fry something... turned the thing on and off, but no change. But after a full factory reset, all seem to be ok now.

73,
YO3GFH
op. Adrian
?

-- 
Stefan U. Hegner    <db4st@...>
              * * *
DB4ST --- German Ham Radio Station
D-32584 L?hne ----- Locator JO42IE 
              * * *
GPG-Key | C3CC 23A4 FBA8 622B 48AE
F-Print | 4F19 D0EE E39E ABDC 2BCE

Hi folks,
now that I got my filter sweeps fine after replacing Q508, I want to do the Diode mod.

However, I have no 1N4148 lying around.

What I got at hand that comes closest is a BAW76, specs (and the 1N4148 specs in brackets):

• Size: DO-35 (same)

• URRM: 75 V (100V)

• UF: 1 V (same)

• IF(AV): 0,15 A (same)

• IFSM: 2 A (1A)

• IR: 0,1 ?A (5?A)

• Temp: -65 ... +175 °C (same)

What worries me the most are the much lower IR and lower URRM.

Any comments on that? - Will that work or fry the diode and possibly more?

Thanks a lot and Vy73
Stefan.

Hi John & Evan,

Am 15.01.24 um 22:00 schrieb Stefan U. Hegner:

If the above checks, test that Q508 is turned on while receiving.? The source and drain should be close to zero volts.

Not so sure on this one: Drain 0.64V, Source 0.07V, Gate 0.69V - no matter what band I select. - Is this maybe the suspect? Strange, as there was no re-soldering in that vicinity.

But my interpretation would be a fried Q508 ... so change one BSS123 MOSFET.

Replaced my Q508 and now all the sweeps look good to me. - I think I maybe post them later for reference.

Thanks a lot for you help, that is appreciated.

Vy73

Stefan.


--
Stefan U. Hegner <db4st@...>
* * *
DB4ST --- German Ham Radio Station
D-32584 L?hne ----- Locator JO42IE
* * *
GPG-Key | C3CC 23A4 FBA8 622B 48AE
F-Print | 4F19 D0EE E39E ABDC 2BCE

Hi Peter Li,

I think the Zeners will provide some protection against SWR that results in high voltage, not in SWR that causes excessive current.? A bad SWR can cause either, depending on the impedance.? So, yes, 50% of the time, it will help ride through a bad SWR.

I do not equate the TN0110 and Zener combination to be the same.? I have measured spikes over 100 volts on the bench when testing for the Ldi/dt issue that the diode eliminates.? The spike is still there.? The TN devices are just better able to handle it.

At some point, the capability of the Zener to handle the excess energy could be exceeded.? When it does, hopefully, the failure mode is a short (most common for Zener failures) and protects the rest of the QDX.? It is easy enough to replace the Zeners.

Reducing the power to handle SWR mismatch better is a tentative alternative.? There is a minimum power the ATU needs to be able to operate.? A signal above that, yet low enough to prevent damage, is the juggling that needs to be done.? Reduced power for ATU tuning is what all of the commercial rigs do.? They have other protection mechanisms in place as well.

73
Evan
AC9TU

Thanks (again) Evan! For voltage, don't the Zeners give SWR protection that the L14 diode does not give??Do you think doing both Zeners and TN0110/TN0106 is also perhaps belt-and-suspenders?

For power/heat, I'm still working on my TN0110 heat dissipation for higher bands during operation. For?tuning specifically, isn't lowering supply voltage an easy protection?

On 19/01/2024 13:27, Lynx BG7JAF wrote:

the strange thing is, am I the only one who has this problem?

I've just checked my V3..Firmware 1.10. I guess I fixed the audio short if that was relevant It has a clock buffer like the V4, .I do not think that will make a difference.
I did audio and RF scans that look good so I have no problem.

73 Alan G4ZFQ

Simon & Randy - thanks for the replies to my post. I understand the dangers of auto-tuners with the QMX/QDX rigs. And it is unfortunate that the little PA units aren’t robust enough to withstand the rigors of an autotuner like the IC-705 can. Anyway, I’ve been using an MFJ-929 with my low band QMX for quite some time and with some care the QMX is able to deal with it. I was hoping to eliminate some of the equipment clutter on my desk and just use the MAT-705 for both. But without PTT in the firmware yet, it is not gonna happen!

Anyway, it was worth a shot. I might just try a manual tuner to see how easy it is to integrate into the equipment.

Thanks & 73
--
Jim / K7TXA
Eagle, ID

SKCC 10447C
BUG 301

Hi Bob. thanks for the idea.
Its called contrast <improvement> in the manual but either way it certainly effects brightness at extreme settings.
I'm okay with it as is. I found a 220k in the junk box and thought I'd put it in. It just didn't have the expected result.?
I wired the extra front panel switch to turn it off but will repurpose that as soon as I find another use for it; I dont need it for that after all.

Not to derail the thread but I'm working on thermometers now. I want to install one inside the QCX+ to monitor BS170s on wspr. we will see if rf upsets them.?

These kits are so fun and versatile. Hans has sure cornered the market on cool toys to learn with.
--
regards,
Bryan, N0LUF

Lynx,

Have you tried returning to 1_05 to verify it is a software issue?? It could be that the Si5351 has failed.? If you return to 1_05, please post a screenshot of the oscilloscope trace.??

Of note is that the 60-meter traces show that the green trace is missing, yet there is a decent discrimination of the sideband.? This could point to a measurement issue.

Suggests only.
73
Evan
AC9TU

Today I use firmware v1_10 do some test again. I use a?oscilloscope watching R41 and R40(CLK0 and CLK1), and found something strange.?In theory, CLK0 and CLK1 should have the same frequency but be 90 degrees phase different. But when doing audio filter sweep what I saw is like this:






The yellow channel is CLK0 and green channel is CLK1. From this images we can see that frequency and phase are totaly wrong. Then I return to firmware v1_05, everything return fine. So I think it's probably a firmware incompatibility issue.?But the strange thing is, am I the only one who has this problem?
Here is my QDX PCB's photo:

Hope who use the same version PCB can give me some feedback about firmware v1_10. Thanks

I use a cheap (47 EUR ) 858D clone I bought in my my local electronics shop with no problems, so far. It's really a big ?helper enabling to avoid mess on your pcb when it comes to removing microchips, relays, USB connectors, etc. I have just replaced, easily, a micro USB socket on my wife's tablet computer and a fried ?microchip IC05 in my Hi-band QDX transceiver . It's especially useful for removing these components , for soldering in the replacement parts I like to use a conventional soldering iron. But the hot air station would work equally good for that too. Good luck! 73! Linas LY2H

Great news!
Have fun with it!

Regards,
YO3GFH
op. Adrian

Thanks very much Adrian! Now have a fully working QMX!