Hi Wolfgang,

have a look at Spectran or Argo by I2PHD http://www.weaksignals.com

My old (2006) SAQrx also contains a simple audio spectrum analyzer, 0-22 kHz https://sites.google.com/site/sm6lkm/saqrx/

73 de SM6LKM Johan

I've had something similar with one of my QCX radios. In it early days, it had the misfortune to be switched on on the bench without a load and since it had been operating as a beacon, it returned to beacon mode after a short period and went into tx with an open antenna socket. This didn't do the PA or Q6 any good, needless to say. 

So I replaced Q6 and the PA mosfets, but have had continual problems with the mosfets failing. Quite a few of my Ebay sourced BS170s were duds right out of the packet. Others failed pretty soon in wspr mode. I'm afraid I hit on one of those sellers from far away over the sea  who peddle junk on ebay. Recently, in desperation, I fitted two 2N7000 mosfets which came from a more reputable source. The 2N7000 has a lower power dissipation and a different pin out, but the rig has worked fine ever since even with a more puny pair of PA helpers. So I now have 2x 2n7000 and 1x BS170 in there. I have some authentic BS170s on the way.

With the duds in place, there was plenty of heat and very low or no output. The drains on key down were at about 2 volts with a multi meter and the gate was only showing 0.8v (DVM) instead of about 2.5. I know the real square wave voltage on the gate is about 5v, but the dvm won't measure rms. My thoughts are that one or more of your pa fets has failed short circuit and it is sinking the drain current to ground and also the driver energy. You could have more than one dud in there. I have had. I bet Q6 is running hot as hell too. Oddly - in my case all the output mosfets were hot. You can take them out one at a time and test them. There are some youtube videos on how to test a mosfet with a dvm online.

 

Thanks Alan,

I have turned on those sentences with the config tool, so will see how it goes.

Cheers,
Glenn VK3YY. 

On Sat, Mar 6, 2021 at 06:56 AM, Lee Hooper KG5VU wrote:

It would seem that most operators will never use the PTT and CAT connections.

Objection My Lord

- Licensed since more than 50 years (and never used CW for different reasons) I use CAT controlled CW only.
Had many CW QSO with my QCX+ 30m kit on 30m and 40m (yes, that works) and now also with a QCXmini 20m kit on 20m & 30m

How do I do that? Perfect CW decoding (!) by the QCX on the display + a little bit of help with an audio spectrum display for exact
tuning on the PC. To key the QCXs via CAT in CW I wrote a software, includes logging, macros etc. Early version published in the
group, enhanced in the meantime with many options I considered helpful for me. Now more functionality than fashionability ;-)

'Many roads lead to Rome'

73's de OE1MWW

Wolfgang

P.S. I am still looking for a simple audio spectrum display, no bells & whistles, no db scale, just something between 300 to 1500 Hz

I set up the GPS to send only NMEA RMC sentences via the configuration tool.   I couldn't find which sentence(s) the QCX uses in the comprehensive docs, but RMC seems to work ok.

Glenn,

I've just checked the module type used in the new QLG2 so have a note. It is somewhere in the vast documentation!
GGA, GSA, RMC, GSV are output on the QLG1.

73 Alan G4ZFQ

Hi Allen,

I set up the GPS to send only NMEA RMC sentences via the configuration tool.   I couldn't find which sentence(s) the QCX uses in the comprehensive docs, but RMC seems to work ok.

Cheers,
Glenn VK3YY.

I interfaced an old Trimble ACE III GPS to the QCX and it seems to be working as expected.  The time syncs after the first WSPR cycle.
After it has done a WSPR cycle, the display lower line  often has just has a 5 or 6 shown, nothing else.

Glenn,

It may be that the Trimble sends too many NMEA sentences.
4 specific ones are used by the QCX, others may confuse it.
If you can check the NMEA then maybe you need to reconfigure it for proper operation.

73 Alan G4ZFQ

On Sat, Mar 6, 2021 at 12:31 PM, N8DAH wrote:

LCD is one line of blocks. I have soldered a spare LCD to the back of the pins and everything works as it should so its not the radio or anything else other than the LCD.

Weird.  Looking at the trouble shooting guide (click here) indicates the LCD is working, but not receiving commands from the processor.  Look at heading:  "LCD top row is blocks, bottom row is blank"

Since the LCD soldered to the back of the pins worked, I would try adding jumpers from the back of the pins to the from of the LCD for LCD pins 4 & 6.  Also verify pin 5 is grounded.   Check for cold solder joints on front LCD.

I will have to destroy parts or the PCB to remove it. Looking for some help.

I messed up my front panel pretty good removing an LCD...  I got it working using jumper wires.

Now, the QCX+ front panel PCB is available to order for $2 (plus shipping of course...)


73,
km6wt

Just to be clear, I came here for help with a kit I bought as a customer it has nothing to do with my small website. I am more than sure Hans does not view me as a threat to his company cause I'm not.

I am not here to slander anyone. It's pretty sad I feel like I even have to write this but I have had about enough of the hate mail.

I have been a long time supporter of QRP-Labs, I have built a vast majority of his kits and will continue to support him.

After reaching all options I could do myself I asked for help at the website...hearing nothing for a few days I posted here to see if maybe the mails just didn't make it and Hans would see it and toss me a mail.

To the gents spamming my inbox with hate mail. Just stop this is ridiculous.

I don't come here for this and if it continues I will just leave.

--
David

  N8DAH

Kit-Projects.com

Shop is now open!

Hi All,

Question on the QCX display when used with WSPR and GPS.
I interfaced an old Trimble ACE III GPS to the QCX and it seems to be working as expected.  The time syncs after the first WSPR cycle.  
After it has done a WSPR cycle, the display lower line  often has just has a 5 or 6 shown, nothing else.  If I hit the back button, the display restores to normal showing UTC time and time to next beacon and sometimes alternates with just a 5 or 6.
Is the lower line display with a single digit indicating a correction from the GPS?

Cheers,
Glenn VK3YY.

Thanks, That is the dummy load I’m using!  I completely overlooked the V vs Watts curves.  Ugh!  Talk about a short between the headphones!  So at 20.2vdc measured with my multimeter, running a 12V supply, I’m at 6W or thereabouts, and everything is A-ok on output power.

I still wonder what’s up with the QRC+ J17 DVM circuit.  It reads correctly and steady when I measure +12V test points in the QRC+.  I.e my 12.2v supply minus some drop over power input protective diode D4.  But when I clip the DVM pin over to the dummy load, the QRC+ says 11V and drops fast, and my multimeter, also looking at the dummy load, also shows 11V and dropping.  When I remove the QRC+ DVM probe, the multimeter, still on the dummy load jumps up to 20.2v and is steady.   I’m going to let it go as I don’t see an immediate need for that bonus QRC+ functionality.  I clipped back the end of the wire soldered into J17 RF Pwr, which was poking kinda long out the bottom of the pwb, and called it quits.

Sorry to run people around in circles, but I learned a lot, so thanks all. I was “that guy” that posted a fraction of the relevant information.   Dang!  Anyhow, next up is to source about 70ft of RG8U and hang a dipole.

None of what I found matches the issues I am having with my QCX+ this is not a mini. I will spend the next few hours reworking it and just hope I don't stress the plating to much trying to remove it.

This is a 1st for me in regards to a DOA LCD 2x16 but I guess it happens. I was hoping for a reply from Hans.

As a side note to others that may read this consider putting R48 and R65 on the back of the board, if you get a DOA LCD you will be able to get at the pins with a cutter or Dremel.
--
David

  N8DAH

Kit-Projects.com

Shop is now open!

Do a quick search others had this issue and it was the small tabs on the back of the display that holds it together.

--

QRP-Labs has a very nice dummy load kit with an RF>DC voltmeter output. Hans even includes a neat chart to convert voltage to watts. I found it to be very accurate as it corresponds very well with a Bird wattmeter (+/-5%) and an Elecraft Wattmeter (+/-2%). I put it in a small plastic box with sockets for my DVM. Works great. I taped a copy of the conversion tables on the box for quick reference. Picture attached. 
--
73, Dan  NM3A

I have tried to contact Hans via the website and heard nothing back. Anyone know an actual e-mail that I can get a hold of him at?

LCD is one line of blocks. I have soldered a spare LCD to the back of the pins and everything works as it should so its not the radio or anything else other than the LCD. I will have to destroy parts or the PCB to remove it. Looking for some help.
--
David

  N8DAH

Kit-Projects.com

Shop is now open!

After building my 40m QCX-mini, I was able to successfully tweak the BPF, IQ balance, and audio phase shift high/low. After a couple tweaks of the coils I was getting about 4 watts out into the QRPLabs dummy load. Output was measured somewhere around 18V on my DMM. At that point, TX and RX were both good and all was right with the world. I wanted to learn a little more about the circuits so I started probing around a bit. I was trying to check the output at each drain of Q2-Q4 but in a tragic slip of the hand I shorted two of leads on one of the MOSFETs (Q3) and the magic smoke came out of Q6. I should have left well enough alone, but what fun is that?

Checking things out, I still had RX and everything except output seemed to still be in order. After pulling and testing them, Q6 was definitely blown as was Q3. I ordered a set of MPS751 and BS170 replacements.  I replaced Q6 and Q2-Q4 just to be safe. After bringing everything back up, I'm only seeing 1.5V output into the dummy load. I repeated the alignment and adjustment steps and no change.  Reviewing section 5.5 of the assembly manual, I checked output on the drains of the BS170s (More CAREFULLY this time!) and they are all only at 1.5V as well. I checked continuity on L4 and it is as it should be.

I'm still quite new to RF circuits, but to me it looks like I'm getting output through the entire signal path just not getting any amplification from the PA. The switching seems to be working as I go from 0 to 1.5V when I key up. All this points to something aside from Q6 or the PA transistors having been damaged as well. What else can I check to find the fault? Any other ideas?

I'd better get another mini on order "just in case" :)

73
Bob -- N8ZVX

Ha!  I think maybe it’s fine.  The dummy load has a diode detector.  And so does the RF Pwr pin in the QRC+.  So the 1.7W I reported above was erroneous.  DVM pin in the QCX+ hooked to the dummy load detector measures about 11v and it drops steadily.

Using my cheap harbor freight DMM on the dummy load detector, I get a steady 20.2v.  And that’s 4W, right?

Something odd about my QCX+ onboard DVM, but I’m thinking my output power is fine.