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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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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 |
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I misspoke. I enlarged a washer hole to mount the regular BNC.?
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72, Bob KI0G On Friday, August 12, 2022, 4:25 PM, Bob Cutter <ki0g@...> wrote:
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I had a similar problem.?
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With metal snips I cut off the circuit board corner where the BNC went, enlarged the case hole to fit a regular BNC and soldered wire from the lead to the center pin point?on the board and the ground.? The portion cut off the board allows the standard BNC to fit and clear. An added bonus, I don¡¯t have to worry about breaking the BNC/board joint by repeated connections.? Worked JA several times in CQWW with it plus many SOTA Q¡¯s.? 72, Bob KI0G On Friday, August 12, 2022, 4:08 PM, Ben Guansing <kn6qwp@...> wrote:
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Re: What to do when the moderator is busy working VK* on 20m.
#qdx
Hi Tony Hi hi, yes you are right, I was having a nice chat with VK5CZ. I think it's the 4th time I've QSO'ed with him on JS8 with my QDX at 5W to OCFD antenna. He uses 50W and a simple dipole at his end. Well... you prompting me with a JS8 mail was certainly a novel way to prod the moderator to do his group approvals!? used to send a notification email whenever any moderator approval was needed. Seems to have stopped! What changed? Now no moderation happens unless I got into the group on the web and do the approvals there. I have now set myself a reminder to do this every morning.? It does appear that the text and photos for L12 are not consistent and i should fix this discrepancy. However - it isn't going to make any difference which way the winding goes, as long as it is all the same way. And a half turn or a whole turn also isn't going to make much difference. So I just wouldn't worry about it.? 73 Hans G0UPL On Sat, Aug 13, 2022 at 1:08 AM Tony GM0DHD via <tony.lymer=[email protected]> wrote: Thanks for letting me into the group @Hans. I was the source of the JS8 message reminding you to approve new members. ;7) |
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Re: Si5351A output buffer
Did the last message have a picture attached to it?? If so, it doesn't come up in my browser.? I have been able to follow most of the description of the circuit from the text but a picture of the circuit would be useful as there are some interesting details.
I've just joined up.? So, I may be missing something. |
Colin Kaminski
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