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Re: BPF Peak Issue / Question
Ronald, I think I might be having a similar problem. I'm not able to get the BPF to peak at more than 3.
I ran these voltage checks you suggested and I only have 0.8 v on pins 1 & 7 of ICs 5, 6, 7 & 8. I have a solid 5 v (not 4.8 v) on pin 1 of IC9.? Any help is appreciated! 73 Levi |
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QCX+ Trouble Aligning BPF
#qcx
Just finished assembling my 20m QCX+ and in the process of calibrating it.? In the process of adjusting C1 for peak, I am unable to get BPF amplitude scaling factor above 3. Twisting C1 brings it up and down between 0-3.?On key-down, I have output of ~4 watts while supplying it with 13.8 volts DC.
Any suggestions to boost the amplitude scaling factor above 3? |
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Re: Ten meters?
Hi Steve. That's a very interesting issue. I was thinking that if you haven't fitted the AGC option in there, then you might take that little circuit board included?with the kit for the purpose?of doing the SSB modifications, or cut a small board of equivalent shape and size and maybe build?a little preamp on that with SMD parts. Electrically it would?need to fit between Q5 and the input winding of T1, with DC continuity to ground on the input of the amp to allow A DC path for the switching?function of Q5. That might be as simple as a 1:1 transformer on a tiny ferrite toroid.? You are right that it is a tight fit?for anything?added to a Mini. But an external amp would require you to forgo the full break-in keying of the mini.... unless you could connect the amp internally between Q5 and T1 via a modification to the CAT and PTT jacks in case you aren't planning to use those features on this rig.? Interesting possibilities... Good luck with this project ... 73 ... Ron On Sat, Feb 4, 2023 at 5:58 PM GM0HUU Steve <gm0huu@...> wrote: I just finished building a QCX-mini for 10m. |
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Re: QCX Mini On Screen Measurement Not Changing
#bpf
#troubleshooting
Jake, on that IC6 pin 5 short to ground, can you verify the actual resistance?being measured to ground with the ohm meter from pin 5 when you get a chance? Some continuity meter measurements will give the shorted?indication with a couple hundred ohms resistance. I don't know if that short would cause the oscillation or if that is in some other part of the circuit but the first step now is to find out what's causing this and fix it before proceeding to anything else. In the earlier messages above you indicated the voltages were good on this IC, but pin 5 should have measured zero volts to ground if it was shorted. Please measure all the voltages on IC6 again. After that, and with the unit turned off, please make resistance measurements around IC6 as follows: pin 6 to 7 ? ? ? 3.3K pin 6 to 5 ? ? ? 3.3K to about 11K depending on setting of R17 ?(phase Hi) pot. Look for variation with adjusting pot pin 6 to IC5 pin 7 ? ? 3.3K Pin 7 to 2 ? ? ? 3.3K Pin 2 to 3 ? ? ? 3.3K to about 11K depending on setting of R24 ?(phase Lo) pot. Look for variation with adjusting pot Pin 1 to 2 ? ? ? 3.3K Also look at C12. You will have to consult the board layout drawings to find it. Make sure it isn't somehow shorted. It goes from pin 5 pf IC6 to ground. Is it damaged, or solder splashed?? Good luck Jake. 73 ... Ron On Sat, Feb 4, 2023 at 5:38 PM <jake__donnelly@...> wrote: After further checking using the continuity tester on my multimeter, it appears that pin 5 of IC6 has continuity to ground whereas pin 3 does not. I would assume that this should not be the case, and I will investigate further tomorrow what may be causing this. |
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Re: Ten meters?
I just finished building a QCX-mini for 10m.
I ended up with: ?
T1 T50-6 (yellow)
Primary: 4T
Secondary 1: 4T
Secondary 2: 4T
Secondary 3: 14T
?
L4 T37-6: 5T
L1 & L3 T37-6: 9T
L2 T37-6: 10T On RX alignment, I can peak the BPF with the modified T1. Note that I swapped the supplied T1 T50-2 core for a T50-6. I also swapped supplied L4 T37-2 core for a T37-6. On TX I get 5W out with supply of 14.4V (protection diode fitted). So all good on TX. The only problem is that RX sensitivity a little low. Comparing it to my old Ten Tec Corsair 2, the QCX-mini is definitely a bit deaf and cannot hear weaker signals at all. I did read a post from Hans where he suggested power out on 10m may be lower and an RX pre-amp may be desireable. Has anyone had the same issue with lower RX sensitivity on 10m? Has anyone got any suggestions for a pre-amp circuit? Alternatively, any suggestions for improving sensitivity? If I go down the pre-amp route, I am thinking that an external amp with bypass on TX could be tried. I could get 5V power and T/R switching for the pre-amp from the PTT socket. Maybe a common gate FET pre-amp circuit could be used? I suspect that only 12dB of gain might be enough. As the QCX-mini is in the little QRP enclosure, it might be a struggle fitting an amp inside. Hence, the thinking to go for the external option. Despite the low RX sensitivity, I have made a few QSOs and, as with the other QCXs I have built, really enjoy using this rig. In fact, before I "tweaked" the various inductors as above, it was only putting out about 1.25W and I manged a couple of QSOs with NA ?. |
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Re: QDX V4 after changing out the finals with 4 new transistors noted the unit dont seem to receive any Ft8 Signals but does TX at the full 6W
On Sat, Feb 4, 2023 at 07:31 AM, ajparent1/kb1gmx wrote:
Hint 12V is really 12V, use a meter to verify that, or risk another failure.Extra style points for monitoring the power supply with a 'scope to catch any overshoot on turn on/off. 73, Don N2VGU |
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Re: QCX+ - 20M L3 Coil Question
Jim, I¡¯ve tuned up several 20 meter QCXs and all but one required 2 less turns on L3. But it¡¯s always easier to remove turns than to add them so keep That in mind.? 73¡ Ron On Sat, Feb 4, 2023 at 14:41 Jim Bennett / K7TXA via <w6jhb=[email protected]> wrote: I'm building my third QCX+, this one for 20 meters. Getting close to the point where I wind L3. On my 30 meter unit I had to clip a lead, remove two turns, and re-solder the coil to the board. As Hans noted in one of his videos, this is a first step in getting more power out of the 30 and 20 meter versions. What is the general consensus of this for you who've built the 20 meter version - (1) did you end up removing one or two turns to get better output, (2) just wind L3 with two less turns to begin with, or (3) did you get 4+ watts out winding it as the instruction manual indicates? |
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Re: QCX Mini On Screen Measurement Not Changing
#bpf
#troubleshooting
With it in the condition you mention where it¡¯s generating what sounds like the 700 Hz test tone even though you aren¡¯t in that test mode, it would be best to use a scope and see which stage is oscillating. Barring that, maybe a little audio test amp / signal tracer probing ins and outs of each stage around ICs 8 and 9 might locate it. You can also do some resistance measurements around those ICs following the schematic and see if something isn¡¯t right. Even look for possibility of a smd resistor or capacitor knocked off the board during construction or shipping. Those things are rare but do happen.? Ron On Sat, Feb 4, 2023 at 14:31 <jake__donnelly@...> wrote: Factory resetting didn't help. |
Levi ¨C K6LCM
Ronald Taylor
Colin Kaminski
GM0HUU Steve
Donald S Brant Jr