Re: I think something has blown on my QMX
Excellent possibility, Dav. High heat for an extended time can cause a ceramic smd cap to crack.? Transmit power might have been the last straw. That should be an easy repair, thankfully.
JZ
Thanks John.?
There's continuity through T507, but I wonder if C526 might be damaged? Everything (tx and rx) goes through that cap to the antenna.
C526 is right next to the solder pads of T507 where?I had to apply a lot of heat to get the enamelled?wire to bond to the pad because I hadn't scraped off the enamel?sufficiently.
Perhaps the cap finally gave up the ghost when I was sending tx power through it.? Perhaps there's just enough capacitance between the pads to allow a fraction of the signal to get through, which is why I can still hear very strong signals faintly.
I've been thinking about this a bit more. Your BPF sweep looks a lot like those produced by others who had forgotten to put on a dummy load.?
The path from the internal signal generator (CLK2) through the receiver chain appears to be working well.
The net is that an open path through T507 to the antenna is looking more probable.
JZ
On Thu, Jul 27, 2023, 5:48 AM John Zbrozek < jdzbrozek@...> wrote: Dayfidd,
T507 itself is in one of those high leverage positions. A failed solder joint there might also be responsible. It is worth checking.
JZ
On Thu, Jul 27, 2023, 5:18 AM John Zbrozek < jdzbrozek@...> wrote: OK and Good Luck! I would think that T507, the transformer in the SWR bridge, should provide a static drain path for QMX that QDX does not enjoy.?
Regardless, damaged transmit and receive function on all bands requires the failure of a very well placed component. The T/R switch is in the right spot for that. Testing it for shorts using an ohmmeter while QMX is without power may be a good idea.?
73 OM. I look forward to hearing of your positive results. JZ
Thanks for your suggestions Alan and John.
The receive (as well as transmit) performance has plummeted?on all bands. Rx is not broken completely, but now the familiar?FT8 drone at 7.074 MHz sounds very faint, for example (same on the other bands).
The RF filter sweeps (image in my original email) also now have that unusual double-hump profile on all bands, with the peaks at a positive value (e.g. 7dB). When everything was working, the sweeps showed a single peak, at a small negative number.
I will try replacing Q508 John. Thanks for that suggestion. It'll be a couple of days until I get the BS170s and the BSS123s, I'll report back with an update when?I've replaced them.
If all bands are weak on both transmit and receive I would advise checking Q508, a BSS123? MOSFET functioning as a T/R switch. On another fellows QDX I have seen a jolt of static electricity from the antenna take out the T/R switch.
JZ KJ4A?
On Thu, Jul 27, 2023, 1:17 AM John Zbrozek < jdzbrozek@...> wrote: Dafydd,
Are all bands affected?
JZ?
I received my QMX kit a few days ago. I must say?I'm very pleased with?it. It's a fabulous?little transceiver, and when all the firmware features are complete it's going to be a cracker! I assembled it per the latest instructions (which include the 20m sensitivity mod) and I conducted successful?preliminary tests on receive on an active loop antenna, and on transmit into a dummy load.
The RF filter sweeps shown in the terminal all looked nice and uniform, the output power was good (it varied a bit from band to band between around 4 and 5 watts) from a 12V power supply, and according to my TinySA the harmonic suppression was excellent (the worst measurement I observed was on 60m, and even then the second harmonic was 57dB down from the fundamental; fantastic).
So the next step was to hook up to a transmitting antenna and get on air with the QMX. As soon as the antenna was connected I could immediately hear loads of CW signals on 40m; sensitivity seemed great. Unfortunately, I believe the SWR may have been high and shortly after I started transmitting (CW) I think something on the board went?pop, because?the transmit power dropped off a cliff. Interestingly the receiver stopped picking up anything but the strongest signals at this point. When I hooked up my PC again, I also noticed that the band filter sweeps shown in the terminal are now very irregular (I've attached an example), even when connected to a dummy load.
My first thought was that I must have blown one or more of the BS170s. However when I pulled them from the board and put them on my tester, they didn't seem obviously fried (see photo attached). I've ordered some replacements in any case.
Given that the receiver sensitivity also seems to have been lost, could it be that some other component could be damaged? I'd be grateful for any thoughts on this.
Many thanks.
73, Dav M0WDV
|
Re: I think something has blown on my QMX
Thanks John.?
There's continuity through T507, but I wonder if C526 might be damaged? Everything (tx and rx) goes through that cap to the antenna.
C526 is right next to the solder pads of T507 where?I had to apply a lot of heat to get the enamelled?wire to bond to the pad because I hadn't scraped off the enamel?sufficiently.
Perhaps the cap finally gave up the ghost when I was sending tx power through it.? Perhaps there's just enough capacitance between the pads to allow a fraction of the signal to get through, which is why I can still hear very strong signals faintly.
I've been thinking about this a bit more. Your BPF sweep looks a lot like those produced by others who had forgotten to put on a dummy load.?
The path from the internal signal generator (CLK2) through the receiver chain appears to be working well.
The net is that an open path through T507 to the antenna is looking more probable.
JZ
On Thu, Jul 27, 2023, 5:48 AM John Zbrozek < jdzbrozek@...> wrote: Dayfidd,
T507 itself is in one of those high leverage positions. A failed solder joint there might also be responsible. It is worth checking.
JZ
On Thu, Jul 27, 2023, 5:18 AM John Zbrozek < jdzbrozek@...> wrote: OK and Good Luck! I would think that T507, the transformer in the SWR bridge, should provide a static drain path for QMX that QDX does not enjoy.?
Regardless, damaged transmit and receive function on all bands requires the failure of a very well placed component. The T/R switch is in the right spot for that. Testing it for shorts using an ohmmeter while QMX is without power may be a good idea.?
73 OM. I look forward to hearing of your positive results. JZ
Thanks for your suggestions Alan and John.
The receive (as well as transmit) performance has plummeted?on all bands. Rx is not broken completely, but now the familiar?FT8 drone at 7.074 MHz sounds very faint, for example (same on the other bands).
The RF filter sweeps (image in my original email) also now have that unusual double-hump profile on all bands, with the peaks at a positive value (e.g. 7dB). When everything was working, the sweeps showed a single peak, at a small negative number.
I will try replacing Q508 John. Thanks for that suggestion. It'll be a couple of days until I get the BS170s and the BSS123s, I'll report back with an update when?I've replaced them.
If all bands are weak on both transmit and receive I would advise checking Q508, a BSS123? MOSFET functioning as a T/R switch. On another fellows QDX I have seen a jolt of static electricity from the antenna take out the T/R switch.
JZ KJ4A?
On Thu, Jul 27, 2023, 1:17 AM John Zbrozek < jdzbrozek@...> wrote: Dafydd,
Are all bands affected?
JZ?
I received my QMX kit a few days ago. I must say?I'm very pleased with?it. It's a fabulous?little transceiver, and when all the firmware features are complete it's going to be a cracker! I assembled it per the latest instructions (which include the 20m sensitivity mod) and I conducted successful?preliminary tests on receive on an active loop antenna, and on transmit into a dummy load.
The RF filter sweeps shown in the terminal all looked nice and uniform, the output power was good (it varied a bit from band to band between around 4 and 5 watts) from a 12V power supply, and according to my TinySA the harmonic suppression was excellent (the worst measurement I observed was on 60m, and even then the second harmonic was 57dB down from the fundamental; fantastic).
So the next step was to hook up to a transmitting antenna and get on air with the QMX. As soon as the antenna was connected I could immediately hear loads of CW signals on 40m; sensitivity seemed great. Unfortunately, I believe the SWR may have been high and shortly after I started transmitting (CW) I think something on the board went?pop, because?the transmit power dropped off a cliff. Interestingly the receiver stopped picking up anything but the strongest signals at this point. When I hooked up my PC again, I also noticed that the band filter sweeps shown in the terminal are now very irregular (I've attached an example), even when connected to a dummy load.
My first thought was that I must have blown one or more of the BS170s. However when I pulled them from the board and put them on my tester, they didn't seem obviously fried (see photo attached). I've ordered some replacements in any case.
Given that the receiver sensitivity also seems to have been lost, could it be that some other component could be damaged? I'd be grateful for any thoughts on this.
Many thanks.
73, Dav M0WDV
|
I build my QMX yesterday. After tracking down a broken L504 and borrowing one from my QCX-Mini, I have a working rig. turns out that without the L504 everything works except transmits, it appears.
SMD components are new for me, can anyone provide a mouser/digikey/manufacturer part number for L504 (QMX) or L4 (QCX-Mini).
Also looking for the encoder/click mart number. Can anyone source that? My volume adjustment just does not work as it should. I traced the lines and all seems okay so guessing the encoder may be an issue. adjusting the volume is not consistent, some times it goes up, sometimes down, some loud pops, some times it will drop in volume....
I have to say, nice work Hans, this is an incredible design with countless hours behind it no doubt. Thank you!
After replacing the inductor, I was able to hit the RBN on 80, 40, and 20m, which of course put a big smile on my face. Also receiving WSPR from over 2,000mi away, testing that now. I will try some FT8 while I'm at it (BTW the CDX is incredible for this, again, nice work Hans!)
Looking forward to additional firmware releases. Yes the CW keying bug is there. Will try an external keyer for now, assuming that will do the trick, so i can try some of the other features (batter, s-meter, decode etc.). With all these things turned off the keying tone in the headphones seems fine. I am lead to believe the transmit is still okay when the headphone feedback is off as I did not hear properly what i was sending last night but the RBN decoded properly.
I'm assuming the GPS frequency adjustment is not yet implemented. I built my first QCX-Mini day before and its not working yet, but the GPS frequency calibration worked find. I tried the same process with the QMX and not joy.
I really look forward to further development of this rig, its great!
Joshua
N5FY
|
Re: Here's what QSOs look like from the W4MAI ( SK 2006 ) Memorial Sun room monitoring station.
Addio Signore Giuseppe? depuis Guillaume, N4QA et 72 !
|
Re: I think something has blown on my QMX
I've been thinking about this a bit more. Your BPF sweep looks a lot like those produced by others who had forgotten to put on a dummy load.?
The path from the internal signal generator (CLK2) through the receiver chain appears to be working well.
The net is that an open path through T507 to the antenna is looking more probable.
JZ
On Thu, Jul 27, 2023, 5:48 AM John Zbrozek < jdzbrozek@...> wrote: Dayfidd,
T507 itself is in one of those high leverage positions. A failed solder joint there might also be responsible. It is worth checking.
JZ
On Thu, Jul 27, 2023, 5:18 AM John Zbrozek < jdzbrozek@...> wrote: OK and Good Luck! I would think that T507, the transformer in the SWR bridge, should provide a static drain path for QMX that QDX does not enjoy.?
Regardless, damaged transmit and receive function on all bands requires the failure of a very well placed component. The T/R switch is in the right spot for that. Testing it for shorts using an ohmmeter while QMX is without power may be a good idea.?
73 OM. I look forward to hearing of your positive results. JZ
Thanks for your suggestions Alan and John.
The receive (as well as transmit) performance has plummeted?on all bands. Rx is not broken completely, but now the familiar?FT8 drone at 7.074 MHz sounds very faint, for example (same on the other bands).
The RF filter sweeps (image in my original email) also now have that unusual double-hump profile on all bands, with the peaks at a positive value (e.g. 7dB). When everything was working, the sweeps showed a single peak, at a small negative number.
I will try replacing Q508 John. Thanks for that suggestion. It'll be a couple of days until I get the BS170s and the BSS123s, I'll report back with an update when?I've replaced them.
If all bands are weak on both transmit and receive I would advise checking Q508, a BSS123? MOSFET functioning as a T/R switch. On another fellows QDX I have seen a jolt of static electricity from the antenna take out the T/R switch.
JZ KJ4A?
On Thu, Jul 27, 2023, 1:17 AM John Zbrozek < jdzbrozek@...> wrote: Dafydd,
Are all bands affected?
JZ?
I received my QMX kit a few days ago. I must say?I'm very pleased with?it. It's a fabulous?little transceiver, and when all the firmware features are complete it's going to be a cracker! I assembled it per the latest instructions (which include the 20m sensitivity mod) and I conducted successful?preliminary tests on receive on an active loop antenna, and on transmit into a dummy load.
The RF filter sweeps shown in the terminal all looked nice and uniform, the output power was good (it varied a bit from band to band between around 4 and 5 watts) from a 12V power supply, and according to my TinySA the harmonic suppression was excellent (the worst measurement I observed was on 60m, and even then the second harmonic was 57dB down from the fundamental; fantastic).
So the next step was to hook up to a transmitting antenna and get on air with the QMX. As soon as the antenna was connected I could immediately hear loads of CW signals on 40m; sensitivity seemed great. Unfortunately, I believe the SWR may have been high and shortly after I started transmitting (CW) I think something on the board went?pop, because?the transmit power dropped off a cliff. Interestingly the receiver stopped picking up anything but the strongest signals at this point. When I hooked up my PC again, I also noticed that the band filter sweeps shown in the terminal are now very irregular (I've attached an example), even when connected to a dummy load.
My first thought was that I must have blown one or more of the BS170s. However when I pulled them from the board and put them on my tester, they didn't seem obviously fried (see photo attached). I've ordered some replacements in any case.
Given that the receiver sensitivity also seems to have been lost, could it be that some other component could be damaged? I'd be grateful for any thoughts on this.
Many thanks.
73, Dav M0WDV
|
Re: Main microprocessor failure
#qmx
It sounds like he programs them in-circuit, so even Hans couldn¡¯t sell you a programmed/unsoldered CPU. Yeah, he may have a programmer with an appropriate socket, but that¡¯s a lot of work for a very low volume part¡
73, Willie N1JBJ
toggle quoted message
Show quoted text
On Jul 27, 2023, at 7:26 AM, Jeffrey W Moore via groups.io <jeffreymoore@...> wrote:
Hi Don,
I've seen this on a couple of QMX rigs that I¡¯ve tried to repair for other hams. In both those cases 12v got connected by accident to one of the cpu pins through probing around on the system. Its usually one of the power boards. It¡¯s easy to bridge 2 pins on the power board to cause this. But I¡¯m sure that¡¯s not what happened to you.
My understanding is that Hans programs these CPUs with a boot loader. I¡¯m sure he doesn¡¯t distribute that. So getting a cpu without the boot loader would be useless. Maybe Hans would sell you one but I doubt it and that he even has stock in Turkey. The best you could hope for is to salvage one from another QMX and install into yours. That¡¯s fun - removing two 100pin packages and RE-soldering all without damaging anything else. I¡¯ve done it but I find it stressful.
|
Re: Main microprocessor failure
#qmx
Hi Don,
I've seen this on a couple of QMX rigs that I¡¯ve tried to repair for other hams. ?In both those cases 12v got connected by accident to one of the cpu pins through probing around on the system. ?Its usually one of the power boards. ?It¡¯s easy to bridge 2 pins on the power board to cause this. ?But I¡¯m sure that¡¯s not what happened to you.
My understanding is that Hans programs these CPUs with a boot loader. ?I¡¯m sure he doesn¡¯t distribute that. ?So getting a cpu without the boot loader would be useless. ?Maybe Hans would sell you one but I doubt it and that he even has stock in Turkey. ?The best you could hope for is to salvage one from another QMX and install into yours. ?That¡¯s fun - removing two 100pin packages and RE-soldering all without damaging anything else. ?I¡¯ve done it but I find it stressful.
|
Re: Main microprocessor failure
#qmx
Everyone,
To close this topic; On another topic thread Hans explained that replacement of the MCU by us customers is not an option. QRPLabs flashes and locks the bootloader on the assembled boards therefore it is not possible for us to replace it even if we wanted to risk doing that with such a tiny fine-pitched device.
The only fix is a new kit.
Good thing that it is so inexpensive. Think about what it costs to return any other rig for such a repair! Yep, still a bargain folks!
72, Don
|
Re: QMX Pulling Current on First Power Up
Thanks Hans. I was afraid that might be the case. Although I might be able to replace it since I have the tools, I'm sure that the best route would be an entire new kit. Drat!
clansd: An afterthought here. Try those USB-C cables with another data device and make sure that they are good for handling data. Unlike previous USB cable formats, there are a great many USB-C cables on the market that are only wired for charging and not data. That seems to be a common problem now and VERY frustrating! The data capable cables usually cost more. Test them with some other devices and tag 'em to prevent future waste of time. Around this house, mine are big red woven sheathed for easy spotting. Been there, done that, too darned often!
|
Re: QMX Pulling Current on First Power Up
Hi all
The microcontroller has a flashed bootloader and is then locked, we do that here,?on the assembled boards (I mean, with the SMD assembly completed). So it isn't possible to replace it with a Digikey one. It's pretty hard for many of us to replace a QFP-100 anyway, for most of us the probability of a successful swap would be not great.?
The current sounds pretty normal at this point. Other threads address the voltage checks that you might follow but require that the case be removed and great care performed. First confirm that the USB connector is solid and anything like that is considered. If you have another computer or a tablet with OTG cord try that first.
My MCU is toast but that showed up entirely differently, so I don't believe that is your problem. That chip seems to be out of stock everywhere (if it is indeed what Hans addressed in his FDIM presentation) but I have not received a reply about it or any specific requirements yet.
Take your time. Take a break. Then try the hardware jumper forced boot. I'm pretty sure that it's just that the computer isn't displaying the connection. If it's a Windows OS, look in the "Device Manager" tab. If it's a linux OS, try lsusb command. There are a host of different tools available so slowly work through those. These bumps in the road are usually great learning experiences.
73, Don
|
Re: QMX Pulling Current on First Power Up
The current sounds pretty normal at this point. Other threads address the voltage checks that you might follow but require that the case be removed and great care performed. First confirm that the USB connector is solid and anything like that is considered. If you have another computer or a tablet with OTG cord try that first.
My MCU is toast but that showed up entirely differently, so I don't believe that is your problem. That chip seems to be out of stock everywhere (if it is indeed what Hans addressed in his FDIM presentation) but I have not received a reply about it or any specific requirements yet.
Take your time. Take a break. Then try the hardware jumper forced boot. I'm pretty sure that it's just that the computer isn't displaying the connection. If it's a Windows OS, look in the "Device Manager" tab. If it's a linux OS, try lsusb command. There are a host of different tools available so slowly work through those. These bumps in the road are usually great learning experiences.
73, Don
|
Re: I think something has blown on my QMX
Dayfidd,
T507 itself is in one of those high leverage positions. A failed solder joint there might also be responsible. It is worth checking.
JZ
On Thu, Jul 27, 2023, 5:18 AM John Zbrozek < jdzbrozek@...> wrote: OK and Good Luck! I would think that T507, the transformer in the SWR bridge, should provide a static drain path for QMX that QDX does not enjoy.?
Regardless, damaged transmit and receive function on all bands requires the failure of a very well placed component. The T/R switch is in the right spot for that. Testing it for shorts using an ohmmeter while QMX is without power may be a good idea.?
73 OM. I look forward to hearing of your positive results. JZ
Thanks for your suggestions Alan and John.
The receive (as well as transmit) performance has plummeted?on all bands. Rx is not broken completely, but now the familiar?FT8 drone at 7.074 MHz sounds very faint, for example (same on the other bands).
The RF filter sweeps (image in my original email) also now have that unusual double-hump profile on all bands, with the peaks at a positive value (e.g. 7dB). When everything was working, the sweeps showed a single peak, at a small negative number.
I will try replacing Q508 John. Thanks for that suggestion. It'll be a couple of days until I get the BS170s and the BSS123s, I'll report back with an update when?I've replaced them.
If all bands are weak on both transmit and receive I would advise checking Q508, a BSS123? MOSFET functioning as a T/R switch. On another fellows QDX I have seen a jolt of static electricity from the antenna take out the T/R switch.
JZ KJ4A?
On Thu, Jul 27, 2023, 1:17 AM John Zbrozek < jdzbrozek@...> wrote: Dafydd,
Are all bands affected?
JZ?
I received my QMX kit a few days ago. I must say?I'm very pleased with?it. It's a fabulous?little transceiver, and when all the firmware features are complete it's going to be a cracker! I assembled it per the latest instructions (which include the 20m sensitivity mod) and I conducted successful?preliminary tests on receive on an active loop antenna, and on transmit into a dummy load.
The RF filter sweeps shown in the terminal all looked nice and uniform, the output power was good (it varied a bit from band to band between around 4 and 5 watts) from a 12V power supply, and according to my TinySA the harmonic suppression was excellent (the worst measurement I observed was on 60m, and even then the second harmonic was 57dB down from the fundamental; fantastic).
So the next step was to hook up to a transmitting antenna and get on air with the QMX. As soon as the antenna was connected I could immediately hear loads of CW signals on 40m; sensitivity seemed great. Unfortunately, I believe the SWR may have been high and shortly after I started transmitting (CW) I think something on the board went?pop, because?the transmit power dropped off a cliff. Interestingly the receiver stopped picking up anything but the strongest signals at this point. When I hooked up my PC again, I also noticed that the band filter sweeps shown in the terminal are now very irregular (I've attached an example), even when connected to a dummy load.
My first thought was that I must have blown one or more of the BS170s. However when I pulled them from the board and put them on my tester, they didn't seem obviously fried (see photo attached). I've ordered some replacements in any case.
Given that the receiver sensitivity also seems to have been lost, could it be that some other component could be damaged? I'd be grateful for any thoughts on this.
Many thanks.
73, Dav M0WDV
|
Re: QDX Terminal Emulator - problem editing values
It all works for me exactly as previous software releases.All my previous settings transferred on the recent upgrade and I can change values on all settings.
Not familar with MobaXterm, I use PuTTY or Tera Term.
Taking PuTTY as an example, you have to highlight the value you want to change using the UP/DOWN/LEFT/RIGHT keys then use the backspace key to delete the valuebefore entering the new value.
For the settings that are ENABLED or DISABLED, highlight the field using the same method, then if you want to change from ENABLED to DISABLED, type the letter? "D "or "E"? to change from DISABLED to ENABLED.
You must use Ctrl-Q to quit each page and Exit terminal to close the application.
Geoff
|
Re: Here's what QSOs look like from the W4MAI ( SK 2006 ) Memorial Sun room monitoring station.
Thank you Bill.
Well no.
You are in my killfile now.
Hope you won't have much else to post, I will miss you.
On 7/27/2023 2:16 AM, Bill, N4QA wrote:
toggle quoted message
Show quoted text
|
Re: Here's what QSOs look like from the W4MAI ( SK 2006 ) Memorial Sun room monitoring station.
Thank you Bill.
On 7/27/2023 2:15 AM, Bill, N4QA wrote:
toggle quoted message
Show quoted text
OOPS! Wrong >PNG!
Tnx QSO, WI4E
72,
Bill, N4QA
|
Re: Here's what QSOs look like from the W4MAI ( SK 2006 ) Memorial Sun room monitoring station.
Thank you Bill.
On 7/27/2023 2:08 AM, Bill, N4QA wrote:
toggle quoted message
Show quoted text
Tnx QSO, W1WRA.
72,
Bill, N4QA
|
Re: I think something has blown on my QMX
OK and Good Luck! I would think that T507, the transformer in the SWR bridge, should provide a static drain path for QMX that QDX does not enjoy.?
Regardless, damaged transmit and receive function on all bands requires the failure of a very well placed component. The T/R switch is in the right spot for that. Testing it for shorts using an ohmmeter while QMX is without power may be a good idea.?
73 OM. I look forward to hearing of your positive results. JZ
Thanks for your suggestions Alan and John.
The receive (as well as transmit) performance has plummeted?on all bands. Rx is not broken completely, but now the familiar?FT8 drone at 7.074 MHz sounds very faint, for example (same on the other bands).
The RF filter sweeps (image in my original email) also now have that unusual double-hump profile on all bands, with the peaks at a positive value (e.g. 7dB). When everything was working, the sweeps showed a single peak, at a small negative number.
I will try replacing Q508 John. Thanks for that suggestion. It'll be a couple of days until I get the BS170s and the BSS123s, I'll report back with an update when?I've replaced them.
If all bands are weak on both transmit and receive I would advise checking Q508, a BSS123? MOSFET functioning as a T/R switch. On another fellows QDX I have seen a jolt of static electricity from the antenna take out the T/R switch.
JZ KJ4A?
On Thu, Jul 27, 2023, 1:17 AM John Zbrozek < jdzbrozek@...> wrote: Dafydd,
Are all bands affected?
JZ?
I received my QMX kit a few days ago. I must say?I'm very pleased with?it. It's a fabulous?little transceiver, and when all the firmware features are complete it's going to be a cracker! I assembled it per the latest instructions (which include the 20m sensitivity mod) and I conducted successful?preliminary tests on receive on an active loop antenna, and on transmit into a dummy load.
The RF filter sweeps shown in the terminal all looked nice and uniform, the output power was good (it varied a bit from band to band between around 4 and 5 watts) from a 12V power supply, and according to my TinySA the harmonic suppression was excellent (the worst measurement I observed was on 60m, and even then the second harmonic was 57dB down from the fundamental; fantastic).
So the next step was to hook up to a transmitting antenna and get on air with the QMX. As soon as the antenna was connected I could immediately hear loads of CW signals on 40m; sensitivity seemed great. Unfortunately, I believe the SWR may have been high and shortly after I started transmitting (CW) I think something on the board went?pop, because?the transmit power dropped off a cliff. Interestingly the receiver stopped picking up anything but the strongest signals at this point. When I hooked up my PC again, I also noticed that the band filter sweeps shown in the terminal are now very irregular (I've attached an example), even when connected to a dummy load.
My first thought was that I must have blown one or more of the BS170s. However when I pulled them from the board and put them on my tester, they didn't seem obviously fried (see photo attached). I've ordered some replacements in any case.
Given that the receiver sensitivity also seems to have been lost, could it be that some other component could be damaged? I'd be grateful for any thoughts on this.
Many thanks.
73, Dav M0WDV
|
Re: QMX Pulling Current on First Power Up
If it turns out that somehow the MCU is fried, is it possible to replace it with one ordered off Digikey? Or is there some sort of software lock installed from the factory necessary in order to upload the firmware?
I hope that is not what has happened but would like to know either way.
|
Re: I think something has blown on my QMX
Thanks for your suggestions Alan and John.
The receive (as well as transmit) performance has plummeted?on all bands. Rx is not broken completely, but now the familiar?FT8 drone at 7.074 MHz sounds very faint, for example (same on the other bands).
The RF filter sweeps (image in my original email) also now have that unusual double-hump profile on all bands, with the peaks at a positive value (e.g. 7dB). When everything was working, the sweeps showed a single peak, at a small negative number.
I will try replacing Q508 John. Thanks for that suggestion. It'll be a couple of days until I get the BS170s and the BSS123s, I'll report back with an update when?I've replaced them.
If all bands are weak on both transmit and receive I would advise checking Q508, a BSS123? MOSFET functioning as a T/R switch. On another fellows QDX I have seen a jolt of static electricity from the antenna take out the T/R switch.
JZ KJ4A?
On Thu, Jul 27, 2023, 1:17 AM John Zbrozek < jdzbrozek@...> wrote: Dafydd,
Are all bands affected?
JZ?
I received my QMX kit a few days ago. I must say?I'm very pleased with?it. It's a fabulous?little transceiver, and when all the firmware features are complete it's going to be a cracker! I assembled it per the latest instructions (which include the 20m sensitivity mod) and I conducted successful?preliminary tests on receive on an active loop antenna, and on transmit into a dummy load.
The RF filter sweeps shown in the terminal all looked nice and uniform, the output power was good (it varied a bit from band to band between around 4 and 5 watts) from a 12V power supply, and according to my TinySA the harmonic suppression was excellent (the worst measurement I observed was on 60m, and even then the second harmonic was 57dB down from the fundamental; fantastic).
So the next step was to hook up to a transmitting antenna and get on air with the QMX. As soon as the antenna was connected I could immediately hear loads of CW signals on 40m; sensitivity seemed great. Unfortunately, I believe the SWR may have been high and shortly after I started transmitting (CW) I think something on the board went?pop, because?the transmit power dropped off a cliff. Interestingly the receiver stopped picking up anything but the strongest signals at this point. When I hooked up my PC again, I also noticed that the band filter sweeps shown in the terminal are now very irregular (I've attached an example), even when connected to a dummy load.
My first thought was that I must have blown one or more of the BS170s. However when I pulled them from the board and put them on my tester, they didn't seem obviously fried (see photo attached). I've ordered some replacements in any case.
Given that the receiver sensitivity also seems to have been lost, could it be that some other component could be damaged? I'd be grateful for any thoughts on this.
Many thanks.
73, Dav M0WDV
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Re: QMX Pulling Current on First Power Up
Thank you Don,
?
I set the voltage on the variable supply to 12.0V, and with the QMX "on" (encoder long pressed), it is drawing around 160mA of current.
Plugging it into my computer, I do not see anything popping up. I have tried multiple USB C cables with no luck.
Any ideas what to look for next? I have a scope and DMM, etc.
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Dafydd Walters M0WDV
Don, ND6T