tell her NO.

Doing things properly can take time, and you are not going to be rushed in to a bad decision.


Anthony - N1IG

I've built two QCXs and agree that the C1 peak is not very pronounced. I also agree that it is unlikely the C1 is bad. What is much more likely is that T1 does not have the proper number of primary windings. I agree with the others that recommend continuing with the alignment. In my experience, the C1 setting makes very little difference in the performance of the receiver.

Steve N9SZ

Any chance of there being a QSX xcvr kit in 2022?

73,
Randy, KS4L?

The total payload weight for my lora tracker including pcb supercaps and solar cell is 13 gms .Am? I likely to get a stable float height of about 12000 meters with a single 32 inch diameter fully spherical balloon? using Helium

R

I suggest continuing with the alignment and see how that goes.? Maybe some stage further down the line is in saturation throwing us off the track.

I built my last QCX+ up as a uSDX.? I have the C1 part left over.? Send me a PM with your address and I will mail it to you.

Lora tracker now working OK on solar. Needed the inclusion? of 2 supercaps in cct Thanks to all the help from Mustapha Tan. Any progress on the integration from Helium to aprs-fi

Thanks?

Richard

Thankyou Gyula, I have downloaded the file and will get round to reading it
tonight.
73, Mike

Mike,
i built this on a pcb board, you can see it here:
/g/SoftwareControlledHamRadio/topic/85716281#13067
You will find what you need to build in the article above.
--
Gyula HA3HZ

Greetings Folks.
I need an AM lf/hf signal generator to make my life easier when re-aligning a
9R59 receiver, FM might be useful too.
Has anyone achieved this with the SI5351 or an AD9851 ?

tnks, Mike

开云体育

Looking at the solder side of the board I spotted a few solder shorts + lots of suspicious joints.

?a deck of playing cards is about the same size as a QDX. Buy a pack of cards and paint the box black and you have a reasonable model of a QDX for planning shelf space etc. and appeasing partners.

This exactly. I could've been less laconic about it, but that's all I was saying. It's the size of a deck of cards.?

--
Ryan Flowers - W7RLF

Thanks for taking the trouble to answer my questions, Bill; everything sounds reasonable. You didn't tell me about the impedance of the headphones; the QCX doesn't like low impedance headphones or speakers, and they could cause grief..

Yeah, I know the term "motor-boating", and it helps to know because it's often a slow enough oscillation that can be detected by a DVM...
Would you be up for some DC voltage checks on the pins 1 and 7 of the op-amps? You've probably seem the good values written here enough times...
IC5 through IC8 pins 1 & 7 and IC9 pin 7 should be close to 2.5,
IC pin 1 should be 5V,
IC110 pins 1 and 7 should be half supply voltage.

If the measurements are not as above, that's a very strong clue.

I'd be VERY interested to see what happens to those voltages during the motorboating...

Also check to make sure there's no DC voltage on the pins of the volume control with the slider a 50%.

If we can't resolve it, just drop it in a padded bag and send it to me and I'll swap out the suspect op-amps (9 & 10). I won't be able to get around to it until early May because of backlog, but better late than never...

--
Julian, N4JO.

Bryan,

Point F should be close to the supplied voltage when keyed without any RF input to the amp.? This is because there is no RF pumping to get the voltage up using D2, D9, D10, D4, and C10 as a voltage doubler.? 9.3 volts seems low.? It should be closer to 12.75-1.4=11.35volts though not too low.? I would verify that the diodes are installed correctly.? Also, check the D4/D8 junction to confirm that there is supply voltage there when the PTT is enabled, and no RF is being fed to the input BNC.? Finally, check on Q3 Drain voltages.? It should be the same as point F.

What happens to point F when you supply RF to the input?? It should be over 2x the peak RF voltage to ensure that the diodes remain off.

You may have stated what band it is built for, but could you please repeat it as I can not seem to find it.? Higher frequencies will act differently than lower frequencies.? I am comparing it to my 40meter QCX and Amp.

73
Evan
AC9TU

Keith

I think we may be giving the cap too much attention. Possibly all but one or two connections may be good. Prime suspects include not have conductivity one or more spots on T1 or one or more pins are not really connected on those trim pots. Even if that variable cap were faulty, as long as it isn't shorted some signal should get through.?

It is a bit tricky to get the hang of the nullify procedure.?

Most likely there are one or more connections are open. Possible also to have one or more shorts. If rig is not receiving, 98 percent of time or more its a misconception. It's there someplace. First be convinced that T1 is really electrically installed. Suspect it may not be and play detective.?

Curt

Agreed. Don't pull that capacitor until absolutely sure it's bad. Highly likely that it's OK. Did you do the continuity test I mentioned from the hot side of C1 (pointed end) to ground? That will prove continuity from the capacitor, to the large T1 winding and through that winding to ground. If that is not the case, you need to find the cold solder joint that's causing the problem. If there is continuity but you still can't adjust it, it might mean that C1 is indeed shorted, but that is so unlikely, I think you should first carefully look for solder shorts all around that area to make sure something else isn't causing it.?

If you were seeing even a slight increase in test signal strength on one end or the other of the capacitor adjustment, then you would need to add or remove turns on the coil to get alignment within the tuning range of C1, but I've built and/or repaired many 20 meter QCXs of all three models and never had to adjust the inductance of the large winding of T1 to get the bandpass filter tuning within the adjustment range of C1.?

Good luck ... Ron

Ya, Ron, I wondered about that. ?But, I'm a little concerned that if I pull it, it'll be the dog's butt trying to get it or a replacement back in. ?

Hi Juliann
The oscillation or squeal has always been present in this build. I have an original 30 m QCX and a 17m QCX mini that have no problems. The intermittent nature of the problem is frustrating, you think it’s gone and during a QSO it comes back.
to answer your questions;
changing power supplies makes no difference
RX current is .055 ma. Tx current .500 to .570 depending on swr
there is no voltage drop on Tx
volume control- affects volume of squeal, when turned down very low squeal is not present and strong signals can be copied. As the volume is turned up the oscillation seems to pulse, almost “motor boating” to use an old term.I think this is overload or the installed AGC?
I do note that after the squeal has started that it is not present during Tx, only the side tone is heard?
Removing and reinstalling headphones doesn’t stop the squeal
Voltage at Q6 end of L4 is 12.9v during Tx and 0v during Rex using inexpensive VOM
When the squeal isn’t present the receiver works very well.
The squeal doesn’t start as often when using “semi QSK”
I hope I answered your questions. ?I agree that if it is an op amp, it’s probably something ?I can’t address, hate to see this little rig in the scrap box.
thanks
Bill

Curt, many thanks for your suggestions. ?Yes, working from the TOP of the board, and checking just the visible solder pads around the inside and outside circumference ?of T1, I have continuity end-to-end of each of the four coils. ?That's not even checking on the back side of the board where a bit of exposed wire-end might be touched with the probe. ?

Ron, if it's a bad C1 then probably I made it that way. ?Using the Capacitance ?function on my DVM, which works fine for the little ceramic caps, I can't get any readings between the center and either of the two side terminals aside from a "blink" of the meter occasionally. ?I used small alligator clips and connected to my meter, and turned the core of C1.....nothing. ?So, I"m pretty suspicious of it. ?