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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Re: QDX burned on start-up
Alexander,
Good news! Just want to mention, the diode will drop 0.7V across it in this application. This is the reason the FET is used since it has a lower voltage drop across it.?
This is will contribute to the lower current draw in Transmit (0.69 A). It's lower than what's usually seen.
I built my QDX for 9V operation. In transmit I read ~0.97 A and in receive it draws 0.14 A.?
Do you have a way to measure transmit power out in Watts into a 50 Ohm (dummy) load? I'm just wondering if maybe one of the PA FETs (BS170's) is open and giving you the lower current reading. I don't want to be an alarmist, but it's something to consider.
--Al
WD4AH
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Re: QDX: Receiving great but needs more audio output gain in order to xmit for more than 250 milliseconds.
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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Re: QDX burned on start-up
Hello Al and Evan,
thank you both so much for your kind replies and detailed explanations, Q7 was the right guess!
Wit Q7 as a search string I greped through the archive and found the other failures and fixes mentioned.
Luckily I found an 1N4007 diode which I used instead of the AO3407 and all seems to work now.
When connected to a dummy load sending FT8 on 40 m I observe 0,69 A at 8,9 V and 0,16A on receive.
Now I will replace my old PSU with one that does not change the set parameters on it's own and look into either building a new antenna or an antenna tuner to be able to send without fear.
73 Alexander DM8TE
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Re: Artwork for "Manual Days" Chinese Antenna Tuner
Helmut
Nice work to redeem that tuner, I bought one someone had partially assembled at a hanfest for a couple dollars, just to save another person from its limitations. Try opening your original message I think there is an edit function. Change to message view, not topics, perhaps to find it easier.?
I has a friend and coworker also named Helmut, came to US as young boy from Berlin. Went by Hal and was one of the designers of AWACS antenna, no surprise his father was a machinist.?
Yes a quality toroid is necessary to tune things well on lower bands.?
Curt wb8yyy?
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Re: Qdx terminal tx test
#qdx
Hi Hans,
Should anyone want to know this, I figured out a way to keep the QDX tx on during a remote terminal tx ptt test. On my Raspi 4 loaded a keyboard programme called 'Onboard', then configured from its own menu for a 'long key press' to give 'repeating keys'. This allows me to keep the tx on longer for spectrum and other power measurements.
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 PTT output to give either polarity (as already has) but in receive mode as well? i.e NOT just a PTT function only on transmit. For those wanting to use the PTT function as original, just disable the rx ('PTT') mode. This would allow me to switch antenna three changeover relay drivers (from pull up, pull down and disable states).
whadderya think?
73 Ken G4APB
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Re: Questions about adjusting QDX RF output by changing supply voltage
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
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On Aug 12, 2022, at 8:52 PM, G3SPL < leepd60@...> wrote:
On Fri, Aug 12, 2022 at 05:57 PM, Charles Johnson wrote:
1) For those who have done the 12V build and adjust the supply voltage to change the RF output, what problems (if any) have you had? ?
2) Is the QDX tolerant of supply voltage change while powered up or do I need to turn it off before I make a change?
Charles.? There is no problem in changing supply voltage while the? QDX is on or indeed transmitting.? That is provided you can do this without any spikes that take the voltage above the appropriate supply level (e.g. 9 or 12V).? I am thinking here about maybe a defective variable resistor which causes brief high voltage excursions as it is adjusted! The clever bits are all fed off 5V or 3.3V regulators which easily handle variations in input voltage.
I regularly switch my QDX between 12V (the supply I built it for) and about 8.2V in my remote "bottom of the? garden" installation.? I use 2 Grove MOSFET switches (see attachments), one of which switches the full 12V to the QDX (note: Schottky diode D3 short circuited in this case) or the other which has a series of silicon power diodes as a voltage dropper. The switches are controlled by my Arduino telemetry/remote control system from the shack PC.
The attached diagram and picture show the arrangement.? Note that the Grove MOSFET switch is a commercial unit.? I have added some RF decoupling to input and output and also use 200uF of electrolytics on the output of the switches to ensure continuity of supply in case of brief periods when both switches are open (not that I believe this happens from the way the Arduino is programmed) and also to maintain a low impedance source for the QDX.? This extra capacitance is almost certainly not really necessary, but it doesn't cost much to add it in, so I did! My main use of the "reduced power" feature is to check the antenna match at the start of an operating session to ensure that the load is OK before switching to full power, and also when changing bands. Peter Lee G3SPL
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Ronald Taylor
Wayde VA3NCA/AD2GX
Alexander