Re: QDX PTT to QRP LABS Amp
Wilson Little <wilsonlittle66@...> wrote: Bad News is that trigger the amp immediately caused the amp to fry, and
also killed a power supply. Using another p/s, the amp immediately
pulls 10 amps, triggered or not. oops... Something went way wrong. Did you adjust the bias voltage (R5)? Amp shouldn't be keyed without setting it to minimum (counter-clockwise) first. Fortunately most probably nothing drastic happened, you just killed the final transistors (Q1 and Q2, IRF510). It happens, fortunately they're cheap and you'll be able to replace them. I'd also replace R5 and IC1 just in case, because failing transistors could've damaged them too. It's a good idea to add a fuse between the PSU and the amp anyway.
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Re: Artwork for "Manual Days" Chinese Antenna Tuner
Were you aware that you can get waterslide?decal paper that's printable with an inkjet printer?? There's both white background and clear background available.? So you can roll your own.
73 Jim N6OTQ
On Sat, Aug 13, 2022 at 7:40 PM Steve in Okinawa < sfab43@...> wrote: I'm having terrible luck with the waterslide decals, but I've squeezed the tuner into a smaller box.
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Re: Artwork for "Manual Days" Chinese Antenna Tuner
I'm having terrible luck with the waterslide decals, but I've squeezed the tuner into a smaller box.
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Re: QDX PTT to QRP LABS Amp
Ronald,
Thank you very much for this communication. ? Unfortunately, I rush to the next step before receiving. ? You can see the results¡. ? ?No so good. ? But, on a positive note, more things to play with and fix. ? :)
NT5AT Will
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On Aug 13, 2022, at 6:26 PM, Ronald Taylor < wa7gil@...> wrote:
Will, your measurements?were very thorough. Thank you for those. Those measurements are pointing to some other issue that we aren't yet seeing. You are showing almost the entire 5 volts dropped across R10. This should not be the case unless something is causing it to go to "almost" ground, i.e. very?low resistance, before going to the 50 watt amp. Please use your DVM, in current measuring mode, to measure the current going from the QDX to the amplifier on the PTT line. It should be only something in the neighborhood of 3 or 4 mA. I really think you should trace this fault before lowering the value of R10 in this case.
73 .. .Ron The answer is yes.?
Because you said that with QCX the PTT switching works and because your measurements show that the voltage drop over the 470R in QDX is too much.?
73 Bojan S53DZ
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Re: QDX PTT to QRP LABS Amp
Good News / Bad News
Good news was I found a 100 ohm resistor to tack in parallel with the QDX R10 resistor, and it enabled the QRP Labs¡¯ 50w Amp to turn on. ? The red TX led might be a little less bright than when triggered through a QCX radio, but it clearly comes on.
Bad News is that trigger the amp immediately caused the amp to fry, and also killed a power supply. ?Using another p/s, the amp immediately pulls 10 amps, triggered or not. ?oops¡ ? Something went way wrong. ?
Initial attempt with the modified QDX had the rf to a dummy load, and was triggered only for a second or two. ? The output from the QDX was just about 4.5 watts. ?I am unwilling to hook up the second amp to see if I get similar results.
It was a fun day playing and learning. ? Thanks for all the help.
Regards,? NT5AT - Will ??
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The answer is yes.?
Because you said that with QCX the PTT switching works and because your measurements show that the voltage drop over the 470R in QDX is too much.?
73 Bojan S53DZ
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Re: QDX PTT to QRP LABS Amp
Will, your measurements?were very thorough. Thank you for those. Those measurements are pointing to some other issue that we aren't yet seeing. You are showing almost the entire 5 volts dropped across R10. This should not be the case unless something is causing it to go to "almost" ground, i.e. very?low resistance, before going to the 50 watt amp. Please use your DVM, in current measuring mode, to measure the current going from the QDX to the amplifier on the PTT line. It should be only something in the neighborhood of 3 or 4 mA. I really think you should trace this fault before lowering the value of R10 in this case.
73 .. .Ron
The answer is yes.?
Because you said that with QCX the PTT switching works and because your measurements show that the voltage drop over the 470R in QDX is too much.?
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.
Oh, _that_ kind of dummy load, that everyone else in the known universe calls an attentuator. ?Makes me wonder if there's some other miscommunication going on here.
Which one of those 'dummy loads' do you use when your QDX is having this problem? ?Does it change if you use different ones?
73, Willie N1JBJ
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On Aug 13, 2022, at 6:32 PM, n4qa < n4qa@...> wrote:
10-A-MFB-10,? ?-20,? ?and -30 dB ten watters.
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Re: QDX: Receiving great but needs more audio output gain in order to xmit for more than 250 milliseconds.
Please explain about the dummy load being an issue.
BTW, this dummy load requires no interconnecting coax- has bnc male on one end, female on the other.
My combination dummy load / attenuators consist of one each Bird model:
10-A-MFB-10,? ?-20,? ?and -30 dB ten watters. I use them for running QRPp and for attenuating xmtr output for direct connection to my Spectrum Analyzer.
Oh, and as a dummy load !
BTW, the XYL & I had a great time inside my old high school today !
73,
Bill, N4QA
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Re: QDX PTT to QRP LABS Amp
The answer is yes.?
Because you said that with QCX the PTT switching works and because your measurements show that the voltage drop over the 470R in QDX is too much.?
73 Bojan S53DZ
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Re: QDX PTT to QRP LABS Amp
Ok, confession time. ? I am not an electrical engineer. ? I am a mechanical engineer. ? This might be important in that my understanding may need corrected by folks who are much more knowledgable. ? :)
First set of measurements are using the QCX Mini to trigger the amp, which triggers the amp correctly.
On the QRP Labs¡¯ 50v AMP - ?Voltage drop R16 (470 ohm) resistor is 2.13 volts. - ?The incoming voltage at resistor R16 (470 ohms) referenced to ground is 4.07 volts. - ?And, as expected the outgoing measured voltage at the resistor R16 referenced to ground is 1.94 volts. ? ? ? ? ?In - Drop = Out ?- - - ?4.07 v - 2.13v = 1.94 v?
Second set of measurements using QDX to trigger amp, which does not turn on the amp nor the red TX Led
On the QRP Labs¡¯ 50v AMP - ?Voltage drop R16 (470 ohm) resistor is 0.00 volts. - ?The incoming voltage at resistor R16 (470 ohms) referenced to ground is 0.82 volts. - ?The outgoing measured voltage at the resistor R16 referenced to ground is 0.82 volts. ? ? ? ? ? In - Drop = Out ?- - - ? 0.82 v - 0.00v = 0.82 v
On the QRP Labs¡¯ QDX with the PTT disconnected - ?Voltage input to R10 mesures 5.03 v ref to ground - ?Voltage output of R10 measure 5.03 v ref to ground - ?Voltage drop across R10 is 0.00 v ??? On the QRP Labs¡¯ QDX with the PTT connected - ?Voltage input to R10 mesures 5.00 v ref to ground - ?Voltage output of R10 measure 0.86 v ref to ground - ?Voltage drop across R10 is 4.13 v ? So is the answer still to add a parallel resistor to lower the voltage drop across the QDX R10 resistor? ??
Just for record keeping:
I made the comment that the QCX Mini and QCX+ both worked with the QRP Labs¡¯ 50w Amp. ? Another user commented that the two radios are configured differently, tip versus ring on the PTT cable to trigger the amp, which is accurate. ? However, I modified the QCX+ (per QRP Labs instruction manual) to swap to the ring configuration.?
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Re: QRP Labs VFO/Signal generator and Kenwood TS-520 VFO
Hi Charles,
Please see the U3S Assembly Manual what to add to the PCB and how to connect things and for the jumpers.
At least you will have to insert one BS170 to allow the signal CLK0 to come to the LPF.? The PCB is the same.
73 Bojan S53DZ
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Re: QDX PTT to QRP LABS Amp
Ron, of course you are right about the current protection of a BSS84 in the QDX.? It is now about 61mA instead of about 11mA.? But this current limit is used only if one does a short to GND during the PTT high state.
73 Bojan S53DZ
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Re: QDX PTT to QRP LABS Amp
Hi Will. Probably best to go ahead with Bojan's suggestion and parallel a 100R across R10 in the QDX to raise the PTT eying voltage. Hope that solves it for you .. .73 ... Ron
And Will, have you measured the voltage over the series of 470R and the red LED?
? 73 Bojan S53DZ
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Re: QDX PTT to QRP LABS Amp
And Will, have you measured the voltage over the series of 470R and the red LED?
? 73 Bojan S53DZ
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Re: QDX PTT to QRP LABS Amp
Hi Will,
generally I prefer using the active zero Ohm PTT line, as I said.? And I will do it in due time.
73 Bojan S53DZ
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Re: QDX PTT to QRP LABS Amp
Hi Ron,
No I did not do those precise voltage measurements, however I did a simple test when I was first trying to use the QDX PTT to trigger the PA.? I noticed that in that case the power did not go to the expected level as it went when I provided full +5V to the PTT input.? So I decided to make the PTT active level high enough for the T/R switch to switch solid.? Probably the red LED in my PA is working at somewhat lover voltage?? And yes at the time of that first test my PTT cable was quite long.
73 Bojan S53DZ
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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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Ronald Taylor