QDX High-band Digital Transceiver. Problems you didn’t expect.
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- čas přidán 17. 06. 2023
- This video deals with some unexpected problem faced by almost one third of all High-band QDXs manufactured - low power output on 10m band.
QDX High-band digital transceiver for Ham Radio covers amateur radio digital modes frequencies in 20,17,15,12,11 and 10 meter bands. 11m band is not a Ham Radio but CB band, nevertheless, there is, obviously, some FT8 mode activity among non-amateurs too, so this radio for them also.
I have tested my own 9V QDX and you can see the results of my tests.
I also discuss the possible ways to cure the problem. The QRPLabs is aware of the problem and working busily to come up with the solutions. Below is the link to the article by Hans Summers G0UPL , the father of all the QDX/QCX,QMX radios himself (copy this link into your browser , if needed):
groups.io/g/QRPLabs/message/1...
Here is al link to my other video on the FT8CN app for Android:
• Pocket FT8 for Android...
Please consider subscribing if you like my videos. Buy me a coffee is you want to support this channel:
buymeacoffee.com/ly2h
Thank you!
73!Linas LY2H - Jak na to + styl
Awaiting arrival of my High band QDX. Currently have the low band and really am impressed with it. Have used FT8CN and WJST-X with the low band. VY1FC
Good luck with your High band! 73! Linas LY2H
They changed to blue/yellow cores in a later version of the high band. I had a wrong mterial core when they were all black. Both work fine. These are great rigs. 73
Thanks for the info! Yes, you are right, I think the info on the changed toroid colors was explained by QRPLabs as changed suppliers etc. Have fun! 73! LInas LY2H
Very nice! hope to get one soon!
Hope to catch you on FT8 also!
DV1K 73
because of your videos I ordered the 5 band (low band) rig !!! ...... thanks !!! .... de George , N2JNZ
Very insteresting. Great job! Nice vídeo. I'm subscribe
Great video, I will have to check bands for you ft8.
Thanks Brian! Good idea! With your new 3-ele vertical super-yagi it shouldn't be a problem :). What time UTC you hear area of my location best? 73! CUL Linas LY2H
@@Linas_LY2H I normally gets spots in Scandinavia jeans my evening greyline.
@@brianfields4479 Cool, keep on checking!
Thanks for video Linas. Hoping to build a QMX soon and get it connected to my Android phone like this for some portable digi ops. Alas, currently, QMX is like Low Band QDX and only goes up to 20m. I know that I will miss 17m. However, Hans has indicated he may produce a Mid/High band QMX. 17m has been a fantastic band recently for QRP and portable/mobile operation.
Absolutely, Steve! The same’s here- I’m in a process of building the QMX and I’m , too, already missing the 17m band :). No doubts, there will be High band version of QMX too, Hans seems serious about that ! So, let’s solder and wait :) 73! Linas LY2H
Linas, thank you for your videos!
Can you tell me what cable youre using between the QDX and SWR meter? That looks really nice!
Also what antenna do you use? EFHW? Any particular kit? In an inverted-v, or just thrown up in a tree?
Thanks!
Hi Tedd, thanks for watching! The cable is home made of two BNC 90 degree angle connectors and a short piece of cable :) I failed to find in my junk-box SMA patch cables of a right size, so I went DIY BNC :) 73! Linas LY2H
Sorry Tedd, I've missed the antenna part of your question :). The antenna is a vertical described in detail in this video czcams.com/video/9ob7RVwbkOU/video.html
HTH, 73! Linas LY2H
@@Linas_LY2H all good, thank you for your replies :). I've been checking out all your videos, I think I want a kit very similar to what you have for your "portable POTA ops", but I'm having a hard time getting some of the pieces together. This is my first adventure into HF so I'm hoping to get it right.
Cheers, 73!
Hans and friends have a new winding scheme on the binocular transformer that cures the low power on 10m. I have chosen not to rewind my because I get 3.5W. The new winding scheme overcomes a self resonance that causes the power reduction on some units.
Currently the new QMX has some issues with FT8CN that will probably get resolved in firmware upgrades - works fine with WSJTX.
Thanks for the info! I'm currently in a process of assembling the QMX and the "weird" transformer is to be wound soon. Looking fwd to making a review on my QMX if all is gonna work ok,:) 73! Linas LY2H
Nice video and thank you for sharing. How do you tune with the tuner? Do you use another rig to tune it to the band you want first and antenna, then use the qdx or do you have another method? 73 Jason, WV3V
Thanks Jason! In this particular case I've been using my Nano VNA to tune my vertical whip to resonance before running the QDX. In other cases when I can't use any resonant antenna, I would use one of my tuners I have, like T1 , N7DDC or manual Z-match, etc. The FT8CN app does not have the Tuning function to generate the signal, unfortunately, so it would probably take just to call CQ :). Again, the resonant antenna would make things much easier and safer for the finals, but on the other hand , my personal impression is that the BS170 transistors stand a short-term over-SWR which might appear during tuning quite OK. HTH, 73! Linas LY2H
Nice little setup. I have 2 version 3 QDX kits to put together, so I'm going to steal ideas from you. :)
I think I'd use Mix-6 on 10 meters, though anything over 3 watts is fine as far as I'm concerned. High efficiency matters more o me than high power. I don't know what black toroids he's using, but I've had good luck on 10 meters with the efficiency of Mix-6 toroids in other small project builds.
Thanks John! And good luck in your kit building! I see no reason why your mix-6 toroids should not be good, number of turns adjusted accordingly. 73! Linas Ly2H
What are you using to power that transceiver? I just took delivery of a low band model designed for 12 V supply. But I'm being advised not to run it at 12 V because that may blow up the finals. I had intended to use a 12 V Talent Cell battery from Amazon that is switchable between 5 V and 12 V. But maybe I should get a 9 V battery instead. What do you think?
Hello, I think the power supply voltage is not causaly related to the death rate of the final transistors :). There are many more other ways to kill the BS170 :). I'm running my QDX's off 9V but due to other reasons which seem important for me, like, being able to use a wider range of batteries, including partially depleted 12V batteries :), etc. I'm using an in-line DC/DC downconverter to get my 9V in a compact way. It's desribed in detail here:
czcams.com/video/9dobqEHw9Ks/video.html
But 12V is fully legit and has its own benefits, like you can get the power output reduced easily ( if you want even more QRP than it is) by feeding the12V radio with 9V power supply . I'm building the new QMX now and I think I'll make it 12V as I'm planning to use it also on WSPR and other beacon modes where you only need the power of 1-2W or less. HTH, 73! Linas LY2H
My 12v low band QDX seems to be a good performer on output power. 5.25watts on 10m and 3.5watts on the remainder of the bands. It is very poor on the receive side of things. I had to increase the gain on the band configuration to 95 to get the slider to reach 30dB. Can't figure out what the issue is. Band pass filter maybe. You know your way around this unit very well, any suggestions would be appreciated.
Hi Raith,
you mean your 12V HIGH band QDX? 5.25 W on 10 looks nice to me but 3.5 on all the rest a bit too low . I would try to tweak the windings on the LPFs to get more even power output on all bands. As to the poor reception, well, the BPF on L12 would be the first candidate to look at for me. Most trivial reason is a low quality soldering of contacts on L12. I would re-heat these contacts and let the solder "eat" the enamel on the wire for some 15-20 seconds. Also, the QDX troubleshooting article on QRP-labs site and the great group community on iogroups would be my favorite places to look for advise. Good luck, let us know here how's it going! 73! Linas LY2H.
@@Linas_LY2H Thanks Linas. Will give it a go when I get back to civilization. Currently 700 km north of my home qth at my remote cabin. Using starlink internet for coms and of course my ham radios. Appreciate the input.
@@raithjames860 Whaw! Fantastic! Have a great stay there in the cabin and many DX! 73! Linas LY2H
Love your videos !!! ..... wondering how long a 9V battery would last on a QDX ?? ... thanks !!! de N2JNZ
Thanks for watching George! And thanks for a good question. Best of all if I (or you too) could just hook the 9V alkaline up and see how long would it last with QDX, but I have no such battery at hand at the moment :) So I can make some rough calculation instead. 9V alkalines are said to be about 500mAh of capacity, accordingly to some specs. So, my QDX power draw is ~140mA on RX, 850mA on TX. In FT8, we have 50% duty cycle, i.e., 50% of time we transmit, 50% we receive (we may, of course, be receiving all the time, or transmitting just a bit, but still when we make a QSO, it’s 50% duty cycle). It means, my average TX current will be 425mA, RX-70mA, total - 495mA. If battery’s capacity C=500mAh, then it would last 500:495=1.01 hours. In theory! That is, assuming the battery would be supplying the same 9V at the same current all this time. Which is NOT true in the real life. First, we can only use the battery until it discharges up to 7.5V (despite the battery’s full discharge is at 6.5V) as this is the lower limit of supply for QDX, it stops working at a lower voltage (not enough of voltage for the internal 5V buck converter). Secondly, the 9V alkalines are NOT designed for such a high current draw, so it may die much quicker then this calculation due to overheating of the junctions between the individual cells in the battery, depending on brand, probably. Thirdly, the discharge curve is not gonna be flat because of the high current, so the 7.5V could be achieved suddenly, on transmit only first, but it will already disturb the work of the QDX. So, not much left of our theoretical 1 hour! 10-15 minutes? I don’t know, it’s my guess. Anybody reading this, have you done that, probably, practically? Please drop a comment here! 73! Linas LY2H
What cable are you using to go between android and QDX. Thanks Joe
Hello Joe, thanks for watching. It's a two-part cable comprised of an micro USB to USB-A female OTG pigtail (available in all places selling smart phone accessories) and a short USB- B to A cable which I made myself of a 20 cm piece of a standard B-A signal cable with self-installed A end. I DIY-ed as I hate these long "printer" cables coiling around :) HTH, 73! Linas LY2H
@@Linas_LY2H Thanks very much. 73
Is there a way to tell if it uses 9 volts or 12 volts power by looking inside? Thanks K7WHN
Hello Joseph! It's a very good question! Just I'm not sure there is a good answer to it :). The only thing which differs between 12V and 9V versions is the T1 transformer. It has 3 turns of secondary winding for 9V and 2 turns secondary for the 12V. So, theoretically, you could try to take a peek into one end of the transformer and see how many windings in general do you see -5 or 6. But practically, it would be very difficult to do, IMO :). I think, the easiest way is to feed the radio with 9V power supply and see what RF output power you have on the dummy load. If you measure full 4-5W, it's a 9-volter, if only some 2W, it's a 12V radio. I think, this would be the safest way, as 9V is harmless to any version. I personally, always mark the top of the T1 during the assembly process with white Sharpy pen what voltage is it wound for , and I put the same mark on the radio case near the power supply jack. HTH, 73! Linas LY2H
@@Linas_LY2H
Thanks I will try 9v first. 73
I’m not surprised about the low output power. I received my QDX kit without the PA transistors and upon writing an email back about this I got no response. I ordered them myself and finished the build and the radio works but I would not buy it again…
Hello and thanks for sharing your experience ! I have been buying 5 or 6 kits from this company and, luckily, there was no single case of missing parts. But I always have a handfull of BS170 transistors handy, in case some of them decide to kick a bucket :). 73! Linas LY2H
That's weird. I thought I ordered my QDX with 4 day shipping instead of 7 day (turns out I'm in DHL zone 4 and FedEx zone 7) . When I emailed QRP Labs/Hans, to check the status, he informed me he thought I ordered another product that's currently out of stock, then ended up sending out my QDX right away. He even switched me to FedEx shipping since it would be quicker, and refunded me the difference.
Now that's a Customer Service! I'm glad you got your QDX, finally! 73! Linas LY2H
Hi Linas, I'm Paulo, CB entusiastic, using a QDX high frequency too. Mounted by me, my very first kit😊. Mine have an output in all bands of 2W, not afraid about, because I have a lot of contacts. I'm using 11 meters only in JS8Call frequency 27,245 USB. We are a lot of stations using this beautiful mode. 3 years ago trying using FT8, but the program do not recognize our call signs. We only use js8call at the moment and Varac. I'm very happy about all information that you put on the video, about this wonderful rig, that work's amazingly beautiful. Only one question what kind of power supply are you using? Tks 7351 Paulo.
Hello Paulo! Thanks for watching! Nice to hear CB people also active on digital modes! For my power supply I use a DC/DC buck converter in my own designed 3D printed enclosure. Please check this other video of mine here with all the details : czcams.com/video/9dobqEHw9Ks/video.htmlsi=guPcme9cunEDntSx
HTH, 73! Linas LY2H
@@Linas_LY2H Yes inspired in your videos I have DC/DC buck converter too. I'm my home using power supply of 13,8V, when go to the field, using the battery of my car. But now I'm interested in more mobility in the field, so I have to doing a battery, what kind of battery you have? Tks Paulo.
@@antenaseinterfacescb Hi Paulo, in my outdoors operations, I'm using my home made battery packs for low power (5-10W) and up to 50 W operation, and for my 100W portable go-box I use more powerfull Bioenno 20Ah LiFePo4 battery. My low power Li-Ion battery packs are featured here:
czcams.com/video/fgkG5EZklFA/video.htmlsi=EeCn9vGjl7Z46O4G
My medium-power home-made 12Ah LiFePo4 battery pack is featured here:
czcams.com/video/DI8yfxBGDJ4/video.html
The 20Ah LiFePo4 battery is most probably described on the Bioenno website. HTH, 73! Linas LY2H
QDX Rev 5 High Band 9 Volt
Nissei DG-503 Watt Meter/SWR
SDS 1102CML+ Scope
MFJ-264 50o Dummy
EVENTEK KP3010D
20m 4.91W Nissei 22.8VRMS Pre Filter 18.8V RMS at BNC -17dB RX 1.10A
17m 4.07W 17.2V RMS 18.8V RMS 0dB 1.15A
15m 3.11W 15.2V RMS 15.2V RMS +4dB 1.05A
12m 2.11W 15.6V RMS 12.8V RMS -2dB 0.92A
11m 2.58W 13.6V RMS 15.6V RMS +0.5dB 0.96A
10m 2.67W 14.4V RMS 16.1V RMS +0.5dB 0.93A
RX 0.160A @ 9V