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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
¿ªÔÆÌåÓýPeter,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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Re: Si5351A output buffer
Hi Richard,
I have added a 50 Ohm buffer?to my VFO-SigGen (Si5351A) using the two 74LVC2G17 in parallel.? Actually four drivers in parallel.? See the attachment. It works very well for me.? In the attachment there is a schematics which I use.? This is a part of a buffer amplifier for the 10 MHz distribution from Brian Dorey.? I have used a part of his PCB for a square wave output.? The measured spectrum of a VFO 200 MHz output?signal is added. 73 Bojan? S53DZ |
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Re: #qdx for 40, 30, 20, 17 +
#qdx
Hi Alan and Sverre, your comments inspired me to try modifying my QDX for the higher bands. I figured how to use ELSIE and came up with an LPF that rejects third harmonics from 18-10m, AND includes the Rx BPF. I did a 'broad banded' BPF centred around 26MHz to cover 18-10m and dumped the 80m winding and wound a new 15 turns in the 'spare' room on L12, replaced C30 with 22pf (thanks Sverre for initial calculations). Reconfigured the 80m slot to cover the new bands (that was fun!) Some fine tuning needed for the tx spectrums, getting around 2.5W on 10m at 12v (12v build), but was rewarded last night by working across the pond and around Europe, on all the new bands, using a combination of 10m attic dipole and an ATU-100. best 73 Ken G4APB |
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Re: Win7 + QDXv2 not recognised
#troubleshooting
#qdx
#w7
I appreciate all the help guys.? I could never get the software to work for the QDX so I gave it to a coworker who's a digital guy. He's made a bunch of contacts. All's good.?
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Re: QDX: Receiving great but needs more audio output gain in order to xmit for more than 250 milliseconds.
Willie,
This first step is to do a very close and?thorough inspection of the board for shorts or bridges between traces.? What happens when you use the Terminal Transmitter Test program?? Does it still drop out? I think you might have a short occurring when you go into transmit mode.? That could be across the 5volt regulator output as it supplies all of the QDX logic ICs.? Can you monitor the output of IC2 when you go into transmit to see if there is a sudden drop, and then it comes back?? This could be an IC5 failure.? Does the LED continue with the 3 pattern flash? If you have a hot air SMD rework station, I would remove IC5 to see if the transmitter drops out after the 1/4 second.? If not,? then replace IC5 and remove the BS170s.? Try again,? If you can, test the BS170s with a transistor tester.? Replace all 4 if one is bad. The above are just suggestions.? I could be misinterpreting the symptoms you are describing.? Please proceed at your own risk. 73 Evan AC9TU |
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Re: Questions about adjusting QDX RF output by changing supply voltage
On Fri, Aug 12, 2022 at 05:57 PM, Charles Johnson wrote:
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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Re: QDX burned on start-up
Hello Alexander,
Sorry to hear that your QDX failed.? Based on what you have described, I believe that Q7 failed when or more of the BS170s failed.? I would be prepared to replace all 5 of the transistors.? This was most likely caused by a higher than tolerable VSWR. To start, remove Q7 and see if the BS170s drain pads still show as shorted to ground.? If so, then remove all 4 of the BS170s.? With them removed, and Q7 is repaired or replaced with a temporary diode for reverse voltage protection, power up the QDx, and see if the current has dropped to below 150ma and the LED comes on solid.? The next step would be removing IC5 if the LED did not come on.? Verify that IC2 output is now 5volts after removing IC5.? If so, the LED should come on, and the receiver should work. If the LED does not come on, then most likely, there are many more failures, and I am not sure it is worth trying to repair. 73 Evan AC9TU |
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Re: QDX: Receiving great but needs more audio output gain in order to xmit for more than 250 milliseconds.
n4qa at_hotmail.com
Hey Willie ( Willie or Will is what my dad, W4MAI,sk 2006 used to call me ).
My linear regulated supply is a 15 volt max, 2A max jobby that seems to be working nominally. Presently set for 12 vdc, 1 adc, QDX pulls 130 ma rcv, 550ma xmit. No dips in output v under load etc. 73, Bill, N4QA |
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Re: QDX: Receiving great but needs more audio output gain in order to xmit for more than 250 milliseconds.
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Show quoted text
On Aug 12, 2022, at 7:03 PM, n4qa at_hotmail.com <n4qa@...> wrote:
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Re: QDX burned on start-up
Alexander,
Sorry that you ran into trouble with your QDX. I think the first place to look is whether or not Q7, the reverse polarity protection FET has shorted to ground. That would give you the low Ohm reading at the power socket.? If it is the culprit, then it would be best to remove it from the circuit board and see if there's still a low resistance at the input to the 5V regulator, IC2, mainly to ascertain whether or not there is a problem with 12/9V distribution in the unit.? If there's a reasonable resistance reading at the input to the regulator, I've read others suggesting to jumper across Q7 to reestablish operation of the unit. Of course, care must be taken to make sure correct polarity is observer. Another suggestion is to replace Q7 with a diode rated at more than 1 amp. I hope that helps! I'm sure others with more troubleshooting experience will help. --Al WD4AH? |
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Re: QDX with Bluetooth?
#qdx
#bluetooth
Mine runs off a raspberry pi. Why not put it at the antenna then just use wifi of the pi to remote desktop into it from a tablet or laptop? David W5CWT On Fri, Aug 12, 2022, 2:03 AM Bela Mucs <mucsb@...> wrote: Hi Folks,? |
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I just bought a pack of 10 (identical ones) for $11 on Amazon. David W5CWT On Fri, Aug 12, 2022, 5:29 PM Bob Cutter via <ki0g=[email protected]> wrote:
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Re: QDX: Receiving great but needs more audio output gain in order to xmit for more than 250 milliseconds.
n4qa at_hotmail.com
Thanks fellas but no joy.
No rf feedback, no audio processing, all volume settings at max.? 2 repetitive Status LED flashes each time she trips until I stop the xmsn. The thing is, for a quarter of a second or so, power out is at 2 watts with 10 vdc, 3+ watts with 12 vdc. Sounds great in the FT-450D, Tune and normal xmit - can hear a couple of fq shifts b4 she drops out in normal xmit. Everything sounds beautiful, if only for a short while ! Any other thoughts? Thanks & 73, Bill, N4QA |
Alexander
Colin Kaminski
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