Re: QDX PTT to QRP LABS Amp
I measured the voltage at the red TX led on the amp trigger by the QDX. ?It was only 0.89 volts.
The voltage on the red TX led on the amp triggered by the QCX Mini was 1.94 volts.
¡ ? Now, what is the best solution¡ ??
Regards, NT5AT - Will
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On Aug 13, 2022, at 2:22 PM, Ronald Taylor < wa7gil@...> wrote:
Hi Bojan. Interestingly, I breadboarded the keying circuit including the Red LED and resistors and there is still something like 3.3 volts available to the gates of the two BS-170 switches in the PTT circuit of the amplifier with the 470R current limiting resistor at R10 in the QDX. Since the Gate threshold?of these MOSFETS is around 2.5 volts, 3.3 volts should still be enough to turn them on I would think. The BS-170 I was testing saturated at something just greater than 2.5 volts on the gate.?100R in parallel with R10 increased that voltage going to the MOSFET Gates to 4.4 volts in my test setup. That won't hurt anything but your new short circuit current limiting/protection in the QDX is higher than before the mod. Did you do any before and after voltage measurements, especially at the gates of Q5 and Q6 in the?amplifier PTT circuit? Just curious as to what is causing the need for the modification.
Thanks ... Ron Sorry again, quicky fingers on a mobile phone... Hi.
Just wanted to conclude that's why I prefer an active 0 Ohm PTT (inactive = open circuit) instead of an active +5V PTT (inactive = 0V).? QDX is capable of doing that.??I will add one P-channel MOSFET to the 50W PA PTT input in the future.
73 Bojan S53DZ
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QRP Labs VFO/Signal generator and Kenwood TS-520 VFO
Hello Hans and all,
I built the QRP Labs Si5351A VFO/Signal Generator QCU Ver. 4
for use in a Kenwood TS-520SE, for replacing the Kenwood VFO that
lacks frequency stability.
I have a single 60 meter LPF.
Can you please tell me the location for RF Out and if any
jumpers are required (W0-W1, W2-W3) for routing RF with the
single 60 meter Low Pass Filter.
Thank you.
Charles Brown
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Re: QDX PTT to QRP LABS Amp
Hi Bojan. Interestingly, I breadboarded the keying circuit including the Red LED and resistors and there is still something like 3.3 volts available to the gates of the two BS-170 switches in the PTT circuit of the amplifier with the 470R current limiting resistor at R10 in the QDX. Since the Gate threshold?of these MOSFETS is around 2.5 volts, 3.3 volts should still be enough to turn them on I would think. The BS-170 I was testing saturated at something just greater than 2.5 volts on the gate.?100R in parallel with R10 increased that voltage going to the MOSFET Gates to 4.4 volts in my test setup. That won't hurt anything but your new short circuit current limiting/protection in the QDX is higher than before the mod. Did you do any before and after voltage measurements, especially at the gates of Q5 and Q6 in the?amplifier PTT circuit? Just curious as to what is causing the need for the modification.
Thanks ... Ron
Sorry again, quicky fingers on a mobile phone... Hi.
Just wanted to conclude that's why I prefer an active 0 Ohm PTT (inactive = open circuit) instead of an active +5V PTT (inactive = 0V).? QDX is capable of doing that.??I will add one P-channel MOSFET to the 50W PA PTT input in the future.
73 Bojan S53DZ
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Re: Questions about adjusting QDX RF output by changing supply voltage
On Sat, Aug 13, 2022 at 04:49 PM, William Smith wrote:
Hi Peter,
?
Sorry, what I meant was to use only one Grove MOSFET board, to supply 12V to the QDX when it's on.
?
When that one MOSFET board is off, the QDX is powered by the string of diodes.
Yes, that would certainly work, but I needed to be able to turn off the power completely by remote control (this was so that I could switch to using an SDR receiver instead of the QDX over the USB extender).? Hence I needed 2 MOSFET switches and they could be in parallel or series, it doesn't make much difference.? Incidentally, the Grove MOSFET boards are pretty cheap - only ?3.80 each here i.e. a handful of dollars, so they didn't break the bank! ? -- Peter Lee G3SPL
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Re: QDX: Receiving great but needs more audio output gain in order to xmit for more than 250 milliseconds.
More later.
Multi-year class reunion inside my old high school today
Dublin High School, VA ( Dukes ) Class of '70 here. Lettered in varsity track- can only walk fast these days.
73,
Bill, N4QA
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Re: QDX PTT to QRP LABS Amp
Sorry again, quicky fingers on a mobile phone... Hi.
Just wanted to conclude that's why I prefer an active 0 Ohm PTT (inactive = open circuit) instead of an active +5V PTT (inactive = 0V).? QDX is capable of doing that.??I will add one P-channel MOSFET to the 50W PA PTT input in the future.
73 Bojan S53DZ
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Re: QDX PTT to QRP LABS Amp
... just to add...?
The reason for the 100R parallel to 470R is actually the PTT input in the 50W PA, which is over 470R and a red LED in series tied to the GND.? This way those +5V from the QDX is no more +5V but less.
73 Bojan S53DZ
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Re: QDX PTT to QRP LABS Amp
Hi,?
I had to improve the QDX PTT +5V output line for that to work well:- 100R 0604 parallel to R10 470R,- 1k from Q12 drain to GND.This was necessary to come closer to the QCX PTT like output.
This is what I have done to get the reliable PTT trigering of a 50W PA from the QDX.? The reason is that the QCX's PTT is a direct logic output with either 0V or +5V level whereas the QDX PTT is "only" active +5V over 470R resistor.? In my case that was not enough.? Now it works.? And yes, it is a ring to ring 3.5mm connection.? 73 Bojan S53DZ
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Re: QDX: Receiving great but needs more audio output gain in order to xmit for more than 250 milliseconds.
I would add using a dummy load to reduce RFI as an issue.
73
Evan
AC9TU
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Re: QDX PTT to QRP LABS Amp
Will,
Note that the QCX+ rev 1 has the PTT signal on the TIP, and the others, including the QDX, have the PTT on the RING of the 3.5mm jack.? If you are using the same cable as a rev 1 QCX+, then it will not work.? Try a stereo extension cable.? That worked for me.
73
Evan
AC9TU
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Re: QDX PTT to QRP LABS Amp
Hi Wil. It sounds like something might be loading down the 5 volts. You should find a way to measure that voltage while transmitting with the QDX PTT connected to the amplifier. I recall reading a thread on this group just a few days ago about something similar where a resistor was soldered across R10 to lower the resistance of this current limiting resistor and lessen the voltage drop to the amplifier PTT circuit but I can't think why that would be necessary since it is working?for most folks as designed. Anyway, there is no current limiting resistor in the PTT 5 volts coming from a QCX so that may explain why it works for one and not the other...
73 .. Ron
Too keep is short,?
QDX Rev 3 with the 1.04 firmware is providing 5 volts to the ring of the PTT cable, but not triggering the QRP Labs¡¯ 50w Amp. ? What should I be checking?
more details:
- ?QDX wired for 12volts. ?
- ? QDX fully functional at low power. ?(Made numerous contacts on FT8 and RTTY)
- ?Using 2 different amps (40m and 20m) with same results, PTT voltage present, but amp not turning on.
- ?Amps turn on when QCX Mini or QCX+ is used to provide PTT signal
- ?Voltage from QCX Mini and QCX+ are approximately 4.98 volts
- ?Voltage from QDX is approximately 5.04 volts
- ?Voltage on tip from QCX radios has 5 volts present, QDX does not have that 5 volts (amp does not use tip, so should not be an issue)
- ?When checking QDX, identified Q7 was fried and shorts closed.? Replaces with a diode, but results remains unchanged for amp not turning on.
- ?My assumption sitting here typing is that another component fails when Q7 failed.? Thoughts?
I would like the option to use with amp on occasion. ? But, not sure where to go from here.
Any help would be appreciated. ?
NT5AT - Wil
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Re: Questions about adjusting QDX RF output by changing supply voltage
Hi Peter,
Sorry, what I meant was to use only one Grove MOSFET board, to supply 12V to the QDX when it's on.
When that one MOSFET board is off, the QDX is powered by the string of diodes.
Put them in parallel, so the minimum voltage is "diode string" and the maximum voltage is "MOSFET Board On".
Does that make more sense?
73, Willie N1JBJ
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On Aug 13, 2022, at 11:43 AM, G3SPL < leepd60@...> wrote:
On Sat, Aug 13, 2022 at 10:53 AM, William Smith wrote:
Peter,
?
Could you leave the diode string in-line at all times and short it out with the Grove MOSFET swich, or do you need to be able to turn all the power off at times?
?
73, Willie N1JBJ
Willie.? Yes, you can absolutely operate the switches in series, with the second switch just short circuiting the diode droppers. In that case, you would need to short circuit D3 in both of the Grove MOSFET boards as this Schottky diode drops about 0.3 to 0.4 volts otherwise. Doing it my way saved me about 10mm of wire for the short circuit!? Oh, and of course the series arrangement has another MOSFET "on" resistance added which drops a few more millivolts.? Either way is fine. Peter Lee G3SPL
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Too keep is short,?
QDX Rev 3 with the 1.04 firmware is providing 5 volts to the ring of the PTT cable, but not triggering the QRP Labs¡¯ 50w Amp. ? What should I be checking?
more details:
- ?QDX wired for 12volts. ?
- ? QDX fully functional at low power. ?(Made numerous contacts on FT8 and RTTY)
- ?Using 2 different amps (40m and 20m) with same results, PTT voltage present, but amp not turning on.
- ?Amps turn on when QCX Mini or QCX+ is used to provide PTT signal
- ?Voltage from QCX Mini and QCX+ are approximately 4.98 volts
- ?Voltage from QDX is approximately 5.04 volts
- ?Voltage on tip from QCX radios has 5 volts present, QDX does not have that 5 volts (amp does not use tip, so should not be an issue)
- ?When checking QDX, identified Q7 was fried and shorts closed. ?Replaces with a diode, but results remains unchanged for amp not turning on.
- ?My assumption sitting here typing is that another component fails when Q7 failed. ?Thoughts?
I would like the option to use with amp on occasion. ? But, not sure where to go from here.
Any help would be appreciated. ?
NT5AT - Wil
+
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Re: QDX: Receiving great but needs more audio output gain in order to xmit for more than 250 milliseconds.
Hi Other WIllie,
Sorry, I misunderstood, thought it was working on 30M, but on closer reading it turns out it was only for a brief moment, my mistake.
OK, now we're into shotgunning the problem:
As Alan said, use a terminal program to transmit and eliminate your PC as a source of the problems.
As someone mentioned (can't find it now), check the post-regulator supplies on the QX to make sure they aren't dropping as you start transmitting.
Check all solder joints and visially inspect the board and all components for anomalies.
Can you select speakers or a headset as the output of your WSJT-x program and try the 'Tune' function to see if it stays steady?
When you say '2 repetitive blinky LED flashes' do you mean it flashes twice at the beginning of the transmission and then never again, or it flashes twice, stops, flashes twice, stops, and repeats that during the entire time it should be transmitting (either FT8 or Tune)?
73, Willie (the Other Other WIllie) N1JBJ
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On Aug 13, 2022, at 10:58 AM, n4qa < n4qa@...> wrote:
Hi ya same name !
That's right ! - no rf feedback. I'm confident that my Bird dummy load prevents rf feedback.
Also, still getting 2 repetitive blinky LED flashes which, according to the ops manual indicates insufficient 'gain'.
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Re: Questions about adjusting QDX RF output by changing supply voltage
On Sat, Aug 13, 2022 at 10:53 AM, William Smith wrote:
Peter,
?
Could you leave the diode string in-line at all times and short it out with the Grove MOSFET swich, or do you need to be able to turn all the power off at times?
?
73, Willie N1JBJ
Willie.? Yes, you can absolutely operate the switches in series, with the second switch just short circuiting the diode droppers. In that case, you would need to short circuit D3 in both of the Grove MOSFET boards as this Schottky diode drops about 0.3 to 0.4 volts otherwise. Doing it my way saved me about 10mm of wire for the short circuit!? Oh, and of course the series arrangement has another MOSFET "on" resistance added which drops a few more millivolts.? Either way is fine. Peter Lee G3SPL
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Re: QDX burned on start-up
Congrats on getting your QDX back on the air, Alexander! I use the following SWR bridge and tuning indicator with mine so that the max SWR 'shown' to the QDX will be 1:2... A fun and easy kit build and seems to work well as insurance for me!
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Re: QDX: Receiving great but needs more audio output gain in order to xmit for more than 250 milliseconds.
On 13/08/2022 14:58, n4qa at_hotmail.com wrote: Also, still getting 2 repetitive blinky LED flashes which, according to the ops manual indicates insufficient 'gain'. Bill, Did you check using the terminal program as Evan suggested? This would confirm a PC problem (or not). Operation manual section 4.1 PuTTy is available for Windows. 73 Alan G4ZFQ
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Re: QDX: Receiving great but needs more audio output gain in order to xmit for more than 250 milliseconds.
Hi ya same name !
That's right ! - no rf feedback. I'm confident that my Bird dummy load prevents rf feedback.
Also, still getting 2 repetitive blinky LED flashes which, according to the ops manual indicates insufficient 'gain'.
I understand, Hans, that this is not *audio* gain...just gain :0)
The plot thickens.
73,
Bill, N4QA
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Re: Qdx terminal tx test
#qdx
Now another 'feature request' for you to consider....I have modified my QDX to cover from 80m to 10m but I need to switch antennae as I change bands. Could a band dependent configuration option be added to allow the Ken Is X6 the answer? The LPF signals are brought out, I thought to do just this sort of thing. 73 Alan G4ZFQ
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Re: QDX: Receiving great but needs more audio output gain in order to xmit for more than 250 milliseconds.
I know you said there's "no RF Feeedback", but this is classic symptoms of RFI, which can be disconcerting on QDX as even brief transmissions into a mismatched load (which usually causes RFI) can blow up (at least) your finals.
73, Willie N1JBJ
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On Aug 13, 2022, at 9:28 AM, n4qa at_hotmail.com <n4qa@...> wrote:
On second thought, opening QDX probably won't help.
Today, I'm on 30m and pwr out is 5 watts with 12 vdc at 750 ma.
Power supply steady - no trips nor dips- just short xmsns !
Sure is a mystery !
Gonna have to pull down my thinking cap a bit tighter !
73,
Bill, N4QA
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Ronald Taylor
Wayde VA3NCA/AD2GX