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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.
n4qa at_hotmail.com
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 theKen 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.
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73, Willie N1JBJ On Aug 13, 2022, at 9:28 AM, n4qa at_hotmail.com <n4qa@...> wrote: |
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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.
n4qa at_hotmail.com
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
¿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 |
Wayde VA3NCA/AD2GX
Alexander
Colin Kaminski
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