Re: #QDX rev3 Q7 burned #qdx

Vojtech Bubnik

I have connected my QDX to an unregulated 12V power supply that produced around 16V without load. I was not worried much because I have inspected the whole circuit and I have verified all the capacitors, FET drain to source and source to gate voltages. However the Q7 polarity protection FET failed and emitted the magic smoke.

I studied the same polarity protection circuit around a year ago. Reading the forum it looks I am not the only one with Q7 shorted and burned. The safe version of the polarity protection as in
protects the FET gate over voltage with a zener diode, however the simple polarity protection does not. While Q7 absolute maximum rating of Vgs is +-20V, gate to source impedance is undefined before the input voltage is applied and the FET opens. I don't pretend I do fully understand what may have gone wrong, however a year ago when I applied the same protection circuit as in QDX I  added a 10k resistor between the gate and source of the protection FET just to not let the gate float as I had a bad feeling the maximum gate to source voltage of a floating gate may get violated.

73, Vojtech OK1IAK

Re: QCX+ to 50w Amplifier connection #20m #50w

Evan Hand

I also use the RG316 with BNC connectors.  6" is the most common, though I do then to grab whatever is close ;-)


Re: Removing solder from holes

Charles Johnson

It's expensive but a HAKKO FR301 solder removal tool is the best way I have found to remove solder either from a hole or for component removal.

I second this, though my unit is a Hakko 808. I don't recall exactly what I paid for it, but it's worth every penny. The only thing that's more valuable in terms of price vs performance is my thermal wire stripper. I recall it costing ~$400 USD, but it's more than paid for itself and makes wire stripping so much easier and precise!

Charles Johnson

Re: can you use a qcx 50 watt amp for qdx?

Evan Hand

Hi Mark,

I have the AmateurRadioKits WA2EBY amp as well.  I can state that it is a Class AB amp, NOT a class C.  It is suitable for SSB as well as FT8 and other digital modes.  I have not seen an actual power rating but would suspect that it must be derated for digital modes.

Because the PTT software is not ready, I have not yet tried one of the 50watt PAs I have from QRP-Labs with the QDX.  I have used a 40meter 50watt amp with the QRPGuys Digital III kit, which passes all spectral purity requirements.  Since the QDX is the same basic technology, I expect it will also pass inspections.


QDX V3 - Correct power but higher current draw #qdx


I've been struggling to figure out what is causing my high current draw on a QDX that produces an acceptable output.

Receiving current draw is 170ma with a 9v stable supply.
 80M 4.52 @1133ma
 40M 4.53 @1182ma
 30M 4.13 @1015ma
 20M 4.41 @1025ma

I have made contacts on FT8 on all bands.

But as I gather, my current should be closer to 140ma and 1000ma on receive and transmit.

I had had two separate mysterious failures: the AO3407 failed when I first tested the QDX. Later, when I had replaced the AO3407,  L1, a 47uH inductor, got extremely hot and failed.  ("And I wasn't doing a thing!")

I have replaced the AO3407, but since I do not have a 47uH inductor here, I used what I had - an 18uH inductor -  tacked on the board. The output/current numbers above were made with the 18uH inductor not the correct 47uH one. 

Can anyone suggest what may be the cause of my 30ma increase in current draw? Or how I might be able to troubleshoot it?  The RF filters and the AF filters look similar to what I've seen others posting.

Also if someone has a 47uH inductor I would be appreciative.

Phil K3UT

Re: @QDX Callgroup in JS8Call

Ron Lambinon

@QDX is not a normal used group and because of that you won’t get  many replies. But when you get a reply on an snr? You can make a decision which station in which mode (slow, normal, fast or turbo) you can reach/work under the condition on that moment.   

73 Ron

Op 6 jul. 2022 om 15:15 heeft Al Holt <grovekid2@...> het volgende geschreven:

On Wed, Jul 6, 2022 at 08:50 AM, Ron Lambinon wrote:
When you use @QDX  as a group and send an SNR? You will get from each of the stations with @QDX an snr reply...
Wondering what might be a better query other than SNR?  @QDX CQ? doesn't seem to fit. I'll have to look at what's listed...


Re: @QDX Callgroup in JS8Call

Al Holt

I hope more QDX owners will give it a try. It quickly gives you a common point of interest to start a chat.

JS8Call has good potential. I get a pretty good response when I send a heartbeat. My problem is I just don't send CQ's. That's on me.


Re: Series of boards for Ultimate 3S and relay switched PPF


Hi Dave....based on the time frame (2017), you should be using "QCU Rev 3 or 4" instructions.  You can verify by checking the main PC board, it should either "QCU - Ver 4" ....right around the center of the board.

Hope that helps.  I just finished this little kit a couple of months back.  Lot's of fun!  I'm getting reports from VK/ZL on 250mw (on 20 meters)



Re: @QDX Callgroup in JS8Call


That would be great .... as soon as I get the kit assembled and tested ... received it yesterday in the mail .... also have a ready (Tr)uSDR waiting to try out =)

de N5VMO Pat

Re: Update - QDX v3 - Serial Port Driver problem

Alan G4ZFQ

On 06/07/2022 16:58, W6ZZ wrote:
Thanks, Lee.
I followed your steps and it's leading me to 2 OLD STM Drivers. Doesn't say if they are for 32 Bit or 64 Bit machines, warning that it may load incompatible driver:
As I posted before all is described here
My first post is on the QDX page, this is a more detailed update. I have installed the driver using this method on two W7 machines.
"Note that you may have to dismiss Windows warnings, it may say it is not the correct driver."

73 Alan G4ZFQ

Re: Substitute for BS170?

Ed Kwik

Re: Substitute for BS170?

Ed Kwik

Parts and Kits has BS170s in stock

Re: QDX 13 Colonies clean sweep #qdx

Mark Earnest

Looking over my log sheet, it was an almost perfect 50/50 mix of FT8 and FT4. Mostly 40m and 20m, but I did make a couple of 30m contacts as well. 


I have not tried JS8 with this yet, that's next on my list after Hans gets the transmission audio popping issue resolved. 

Re: QCX+ to 50w Amplifier connection #20m #50w

R. Tyson

On Wed, Jul 6, 2022 at 04:54 PM, kf7rcm@... wrote:
What type and how long a coax did you use to connect the transmitter to the amplifier? 
I have 3' jumpers that I don't think will do the job. In addition, which coax have you found to be the best performer for these little rigs?
I have three of the 50w amps for 40,30 and 20m. I just use RG58 patch leads 3ft long for each of them. They work perfectly fine.

Reg                           G4NFR

Re: 4 progrock kits

Colin Kaminski

Sweet! I was hoping to have one as a bench tool. 

Thank you,
Colin - K6JTH 

On Wed, Jul 6, 2022 at 8:15 AM Hans Summers <hans.summers@...> wrote:
Hi all

The ProgRock kit has been out of stock for a while. I have found four more ProgRock kits hiding. I have added them to the shop.

Re: Substitute for BS170?

Colin Kaminski

I have been getting them from 

Colin - K6JTH 

Re: #qdx #building #qdx #building

tim born

Thanks all.  I'm learning much.

While waiting for my query to post on (what's with the delay?), I just rewound the torrid.
I didn't know what else to do, and I had enough wire to make this work.  Next time it will be nail polish (use it to color code long wire runs).

QDX working MOST EXCELLENTLY, although I'm getting < 3W on all bands (12.3v).
Was able to contact Japan from Phoenix with an EFHW only 6' off the ground (I know, I know.  I'm working on it.)

BTW I also gave QDX the "heat test".  I live in the desert and work outdoors.  We have been hitting 113F/45C pretty often, and while the case is too hot to hold, the radio keeps on a cranking.  Reliability possibly related to lower power output (3W)?  I measured the power using a dummy load before I deployed it, so the low power is not caused by the heat, but perhaps the low power is benefiting the radio to be able to work in such temps?

Years ago working on telecom equipment for Saudi to be deployed in containers in the desert, we quickly learned the value of WIDE component spacing to help the boards survive.


Re: Coax between the rig and antenna preference

Steve K0STK

"kf7rcm@... via" said:

I will be needing a length between 30' and 50' or more.
What type of coax has been the best for your setup in the field or home?
Which rig ?

Steve K0STK // k0stk@...

Re: Coax between the rig and antenna preference

William Smith

I prefer RG-8x, The different vendors have different qualities, so I tend to prefer Belden, though it is more expensive.

73, Willie N1JBJ

On Jul 6, 2022, at 1:05 PM, kf7rcm@... via <kf7rcm@...> wrote:

I will be needing a length between 30' and 50' or more.
What type of coax has been the best for your setup in the field or home?

Re: Update - QDX v3 - Serial Port Driver problem



Usually a manufacturer will let you know if a driver is made for 32 or 64 bit machines only. Check by going to your System and checking the About section - It will tell you where you are at. I'd load the older driver, check to ensure it works after a re-boot, then ask Windows to look for an update through Device Manager. Or - load the older one, and if it works, stick with it. -)

I'm not surprised the driver is old - Windows 7 is an older system and the manufacturers usually expect somewhat newer hardware and software.


On Wednesday, July 6, 2022, 12:58:56 PM EDT, W6ZZ <w6zz@...> wrote:

Thanks, Lee.
I followed your steps and it's leading me to 2 OLD STM Drivers. Doesn't say if they are for 32 Bit or 64 Bit machines, warning that it may load incompatible driver:
(1) STMicroelectronics Virtual Com Port v1.3.1.0 [4/25/2010]
(2) STMicroelectronics Virtual Com Port v1.3.1.0 [8/2/2013]
I previously installed the STM W7X64 Bit Serial Port Driver.

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