Date   

Re: QDX arrived but Q4 is damaged

Steve Z
 

Looks like if I try leaving the damaged transistor in place that I should first check for shorts across its terminals and to ground.

Thanks to the family for all this great info!

Steve N9SZ


Re: QDX Binocular alternative to deburr

Jim Strohm
 

LOL!!

Actually, that "rock"may be a chip off of one of the deburring stones that are put into a vibratory polisher with the ferrite cores. 

I had not thought about checking every ferrite before inserting wires, but I'm sure that any obstruction would be obvious.

Using little sleeves of heatshrink tubing inside a binocular ferrite is a good idea.

73
Jim N6OTQ


Re: Welcome Lawrence G4GZG

Steve
 

Hi Curt,  The odd couple, I love it!  I'm 62 now and remember as a kid looking in the back of the tv set with all those glowing tubes and the heat coming off of them; it looked like a cityscape of skyscrapers lit up at night in there!   As I grew I'd thumb through my dad's electronic books.  The most interesting were the home brew radio equipment "build this" books.  They were all tube based at that time naturally.  I can still remember being intrigued while reading about how those circuits worked, often each tube did multiple things.  Since then I guess I resigned to using solid state devices, but tube circuits will always have a "warm" place in my heart.


Glory to God in the highest, and on earth peace, good will toward men. Luke 2:14


Re: QDX acceptable swr #qdx

ke9uw
 

I ran mine with 3:1 on 20M yesterday and the finals got pretty almost hot at 4.9W. Didn't break it though.


Re: Regarding Finals in QCX+

Ronald Taylor
 

Hi Keith. The final transistors are common, low cost, available parts. It's easy to replace them. If you don't have a good desoldering tool, then the best way to replace them, in my opinion, is to just snip off the leads at the top of the board and solder the new parts to the same points on top of the board. That will avoid potential board damage. With the right tools it is possible to cleanly remove them and solder the new ones in the holes, but it isn't necessary to do it that way to make it work well. The best thing to do, though, is to NOT destroy those parts on the first place... Hihi .. 73 ..Ron


On Wed, Jan 12, 2022 at 7:57 AM Keith Davis <islandpiper51@...> wrote:
Good morning.  Although my QCX+ 40M is running fine, it only takes one (old man) screw up to cook the finals in almost any radio.  Looking ahead here, and hoping I'll never need to proceed.....if I do create a situation where that happens, how much of a job is it to replace them?  Specialized components or "off the shelf" transistors? My 40 was purchased "built", and I have a new 20 in the box, on the bench, so I've never built one.  No doubt, I'll have a better understanding of the issue after I do.  Many thanks in advance for any info.  73 Keith AG5GW


Re: QDX Binocular alternative to deburr

Steve
 

If it's for sale I'd like to purchase that "rock".  The way Han's new kits sell out, I figure I'd have a chance of making the new kit with components on hand.



Glory to God in the highest, and on earth peace, good will toward men. Luke 2:14


Re: QDX Binocular alternative to deburr

John AE5X <ae5x@...>
 

It looks like Hans inadvertently sent you one of the components from his upcoming kit:



--
John AE5X
https://ae5x.blogspot.com


Re: QDX arrived but Q4 is damaged

Keith AG5GW
 

This group is more like family than some families are.  


Regarding Finals in QCX+

Keith AG5GW
 

Good morning.  Although my QCX+ 40M is running fine, it only takes one (old man) screw up to cook the finals in almost any radio.  Looking ahead here, and hoping I'll never need to proceed.....if I do create a situation where that happens, how much of a job is it to replace them?  Specialized components or "off the shelf" transistors? My 40 was purchased "built", and I have a new 20 in the box, on the bench, so I've never built one.  No doubt, I'll have a better understanding of the issue after I do.  Many thanks in advance for any info.  73 Keith AG5GW


Re: QCX-mini Ultimatic keying not working

Daniel Walter
 

Mike,
JP17 in the mini is the 4 pin male header at the back edge of the main PCB. It is for the on-board RF Power Meter (pin 2) and the on-board DVM (pin 2). Pin 1 is +12V and pin 4 is GND. If you want to monitor your input voltage, you can jump pin 1 to pin 3, then turn  Battery ON in menu 7.2 and set the Full and Step in menu items 7.3 & 7.4. 
--
73, Dan  NM3A


Re: Welcome Lawrence G4GZG

Ed Kwik
 

A good home build learning experience build would be:
https://www.k8iqy.com/qrprigs/2n240+/2n240+page.html
There is a lot of info on how everything works. It was a very popular project in the qrp community back in the late 90's
Ed
AB8DF


Re: Welcome Lawrence G4GZG

Tech Guy
 

I got my novice license in 1981. Same first rig!
40 meter dipole made of used house wiring pulled from a friends defunct chicken house! 
73s John N4HNO 


QDX Binocular alternative to deburr

Gregg Myers
 

Someone on here mentioned the use of slightly long pieces of heat shrink tubing to avoid accidentally scraping off enamel while making the binocular transformer for the QDX. The manual says to gently deburr the holes but since I wasn't confident I was having success with that method I thought I would try the tubing.

The tubing ended up working very well! As a side note, there was also a small rock inside one of my binocular holes (I don't know where that came from!). Good thing I was able to poke it right out.

My transformer was built for 9v and all the wire squeezed inside the tubing fine. The heat shrink tubing was slightly undersize of the binocular hole and the length just a bit long as you can see in the picture.

Gregg
W7GRM


Re: QDX acceptable swr #qdx

Dave VE3GSO
 

Allison
The user might think of the EFHW transformer as “a tuner”. 
My experience with a 1:49 transformer fed half wave antenna is that there is some residual SWR that can be easily matched with an LNetwork or the more common C-L-C tuner.  Once it is tuned up the SWR detector shows no return power and no heating of the QDX PA components, at least as far as my fingers can detect.

Dave

On Jan 12, 2022, at 06:46, ajparent1/KB1GMX <kb1gmx@...> wrote:

Tom, M7MCQ

Your using a EFHW and a tuner (antenna matching unit)...
So let me get this straight you have a tuner and then another tuner at the antenna?

I'm puzzeled by that.

If the EFHW was reasonably tuned you would not need the tuner at the rig. 
One of the most common errors with EFHWs is to not correct the length of
the wire to get a reasonable SWR.  The match box at the antenna is there
to avoid that.

If the antenna was not a EFHW but instead it was a EF-RW fed with a
1:9 transformer (a non resonant antenna) then a tuner makes a bit of sense.

An no while they work about the same as an antenna the difference is
significant from their behavior for SWR and how they are matched to t
he transmitter.

Allison
-------------------------------
Please reply on list so we can share.
No private email, it goes to a bit bucket due to address harvesting


Re: Photo PowerModsSM.jpg uploaded #photo-notice

Dave VE3GSO
 

You are very welcome.  You may want to file it back if you are putting it in the cute QDX case, as it otherwise will exert strain on the ground solder joint, which could fail, and then in turn cause the output pad to fail.

Sandpaper or a small fine flat file will work well.

Dave

On Jan 12, 2022, at 06:48, clacey@... via groups.io <clacey@...> wrote:

Many thanks Dave for the photo posted of your powermod to the QDX v1 which inspired me to find a 78M05 and fit it to my QDX for the same reasons. Fitting was a bit tricky mostly to get the tab soldered onto the pad but the end overlapping the board helped to solder it in place and I didn't file it back. A nice little mod!
73 Chris G0IMX


Re: Photo PowerModsSM.jpg uploaded #photo-notice

clacey@blueyonder.co.uk
 

Many thanks Dave for the photo posted of your powermod to the QDX v1 which inspired me to find a 78M05 and fit it to my QDX for the same reasons. Fitting was a bit tricky mostly to get the tab soldered onto the pad but the end overlapping the board helped to solder it in place and I didn't file it back. A nice little mod!
73 Chris G0IMX


Re: QDX acceptable swr #qdx

ajparent1/KB1GMX <kb1gmx@...>
 

Tom, M7MCQ

Your using a EFHW and a tuner (antenna matching unit)...
So let me get this straight you have a tuner and then another tuner at the antenna?

I'm puzzeled by that.

If the EFHW was reasonably tuned you would not need the tuner at the rig. 
One of the most common errors with EFHWs is to not correct the length of
the wire to get a reasonable SWR.  The match box at the antenna is there
to avoid that.

If the antenna was not a EFHW but instead it was a EF-RW fed with a
1:9 transformer (a non resonant antenna) then a tuner makes a bit of sense.

An no while they work about the same as an antenna the difference is
significant from their behavior for SWR and how they are matched to t
he transmitter.

Allison
-------------------------------
Please reply on list so we can share.
No private email, it goes to a bit bucket due to address harvesting


Re: QDX acceptable swr #qdx

ajparent1/KB1GMX <kb1gmx@...>
 

kc0gkf,

Why isn't the SWR perfect?  I presume you means not 1:1
as anything below 1.5:1 is fine.

For a given band the SWF should easily be below 1.5:1
unless the wire part of the antenna is too long or short.
An SWR higher is not because its an EFHW its because
its not tuned as would be the case for a dipole.

Allison
-------------------------------
Please reply on list so we can share.
No private email, it goes to a bit bucket due to address harvesting


Re: Welcome Lawrence G4GZG

tony.volpe.1951@...
 

I well remember the blind panic as my first HF CQ call on CW was answered, though the logbook is not available to me right now in this qth. It must have been about 1982 or thereabouts, and I was using a very much second hand, all valve/tube rig - a Yaesu FT200, manufactured around 1969. I later managed a two way CW QSO - UK to VK on that rig with a ridiculous G5RV 'antenna'.  The quotes there are deliberate. It was a terrible travesty of an antenna, and I would have been far better off with as big a doublet as I could manage, fed with open wire or 300 or 600 ohm ribbon cable. Lots of my signal would have been eaten up by the high swr in the coax section.

I should maybe say that the FT200 did have one transistor, which was used in the local oscillator - apart from that, it had sixteen valves or tubes if you like. 

Tony G0BZB


Re: QDX arrived but Q4 is damaged

Johan Bodin
 

Steve,

2N7002 may work well as Q4 but it has a higher turn-on Vgs threshold than BSS123.

From Onsemi data sheets:

BSS123: VGS(th) = max 2V at VDS = 2V for 1mA drain current

2N7002: VGS(th) = max 3V at VDS = 3V for 1mA drain current

Q4 will have to sink quite a lot of current to ground when the 40m LPF is selected, about 77mA in case of 12V QDX supply. The gate drive is only 3.3V from the processor and this may not be enough to saturate the transistor. Anyway, it could be worth a try. Tune to a 40m frequency and measure the voltage over Q4 (between Q4 drain and ground). If it's less than a volt or so, you are good to go.

73 SM6LKM


Steve Z wrote:

Hmm, I just realized that I do have some extra SOT-23 sized 2n7002 transistors left over from repairing the keyline out on my KX3. Does anyone know if I can use the 2n7002 in place of the BSS123 for Q4 in the QDX. Seems like it is just a switching transistor for the low pass filters, no?

9261 - 9280 of 86581