Different TX Power Issue?

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KD9BXR
 

Posts: 7
Joined: 21 Nov 2024, 19:41

Different TX Power Issue?

Post by KD9BXR »

Greetings all,

I know that TX power problems are not that strange, and a number of posts have already been written on this subject. However I have spent a good amount of time reading these posts and checking various details and trying the usual remedies to no avail and I'm hoping the community can help me out.

For background I'm building up a set of 5 TruSDXs for myself and other Hams in my family. The PCBs were purchased with SMT parts from JLC using the files generously provided by DL2MAN (Thank you sir!). Toroids came from KitsandParts.com, and everything else was sourced from Mouser, Digikey, and Amazon.

Assembled everything using the video instruction. Was able to program without issue with the exception of one reversed CH-340. Finally tuned the filter using a VNA again following the video instruction. Everything was good up until this point, and then I went to test TX power using CW mode on the unit. On 80m I am seeing around 1w, and just slightly less for 60m. On 40m, 30m, and 20m its around 100mw - 150mw. Measurements are being taken with an Aeroflex service monitor that I have access to, and I've also been using a Bird wattmeter on the bench for a quick check. The TruSDX displays this power output accurately, and it gives an efficiency of 40% on 80m. The finals do start to get warm after TXing for a few seconds.

I've tried a new set of BS-170s, and these have been matched as per the proscribed method. I've also attempted using an FTD-86256 after removing the BS-170s with no notable change. I've populated a second RF board being very careful to make sure every step of the process was correct, and only using the 20m band section. Finally, a third RF board was built this time removing the relays (bypassed with jumpers for band selection between 20m and 80m only) and the SWR/Pwr measurement circuit to remove variables from the equation. I'm seeing identical performance out of all 3 boards, and I verified the my main board is supplying 12v. I also replaced the JLC capacitors on one board because I wondered if there was a chance that maybe I did not have the correct values placed after the incident with the improperly placed CH-340. These were replaced with good quality parts from Mouser, and the values were triple checked before being placed.

Is there something I have missed on the RF board that might be the issue? Should I look at the RF and Drive lines from the control board and if so what should I look for? Like I said I have access to a variety of test equipment which is a benefit I know most builders don't have, but I'm hoping it will make the troubleshooting process less painful. I could test both boards independently if needed, but it would be good to have some direction before doing so. My skills are more that of a repair tech, and not an engineer. I understand the concepts at play, but electronics theory is not my strongest skill.

Please let me know your thoughts, and I thank you for reading my long adventure into the TruSDX builders world.

'73
Dave/KD9BXR
KE0QQQ
 

Posts: 65
Joined: 02 Aug 2022, 00:41

Re: Different TX Power Issue?

Post by KE0QQQ »

Hello,

You describe me to a T , I'm just a person who knows which end of the soldering iron to grab. I have built five of these things since Covid, they all worked to start out with. Three still survive. Careful on how you grab the 12v plug, the connector on the board is not easily repaired.
Screenshot 2024-08-08 140809.jpg
Screenshot 2024-08-08 140809.jpg (121.39 KiB) Viewed 507 times
And install a diode to protect the finals
diodejpg.jpg
diodejpg.jpg (107.83 KiB) Viewed 507 times
And never, never plug it in without a antenna or dummy load
And always start out with USB power till you can confirm SWR and function
<<<< all my mistakes :)

Have you built a kit from an approved provider? You offer so many variables to the mix.
I assume the reversed chip was not from an approved vendor?

If you have built a number of the these from the same sources and they all are mis-behaving, I'd be changing my parts source

Can you offer a pic of your build, T1 and T2 can be a bear to get right
winding1.jpg
winding1.jpg (213.24 KiB) Viewed 507 times
KD9BXR
 

Posts: 7
Joined: 21 Nov 2024, 19:41

Re: Different TX Power Issue?

Post by KD9BXR »

Greetings,

Thanks for the advice! can you tell me what flavor of diode you used for your Mod?

With respect to my builds, they aren't a kit from any of the suppliers, but rather a small group by using the process provided by DL2MAN. The PCBs were built by JLC, and up to this point I have had great success using them as a supplier for similar projects. The issue definitely appears to be the same with every combination of RF and Main board I have tried up to this point. I've even considered ordering a kit from Sunny to have a known good example to help me track down what might be wrong with my current project. The beautiful thing about these radios is how simple they are, but any electric circuit can have a fault. There is always a chance its a problem with the PCB itself and not any of the components, I have seen that happen before, particularly when RF is involved. However the most likely situation is something wrong with either a part or a connection somewhere along the line.

My next thought was to verify the RF coming out of the main board to make certain its on frequency. Even though I'm seeing a little bit of output power on 80m I'm not completely sure its transmitting a good signal on the correct frequency. Hoping to have answers to that later today. See attached images of the RF board. I'm very confident my T1 and T2 are working well because the radio reports out more or less the same amount of TX power I am measuring on my wattmeter, and this output level does not change when that circuit is removed entirely on my other RF board.
Attachments
RF board
RF board
2.jpg (221.03 KiB) Viewed 483 times
T1/T2 again
T1/T2 again
4.jpg (225.33 KiB) Viewed 483 times
T1/T2
T1/T2
3.jpg (233.9 KiB) Viewed 483 times
KE0QQQ
 

Posts: 65
Joined: 02 Aug 2022, 00:41

Re: Different TX Power Issue?

Post by KE0QQQ »

hello again,

The easy answer first, I saw some post that pic is in within
https://forum.dl2man.de/viewtopic.php?p ... ener#p8033

Thank you to AC8L

The diode came from Buy N Large (Amazon) I had to buy 20 for like 10 buck including shipping.
The exact listing is gone now.
Diode Zener 1N4756A 47V 1W is the quest

I do have spares I can mail ya if you find my Email on the ZED. No biggie

They do work, This summer I pounded on my radios with FT8. Full Throttle on 3 cell lipos all day long. You have to when using a couple watts to get thru. The only time one failed was doing a couple QSO's on 17m when I had a 15m dipole up. I checked the SWR once I fried them and it was like 7:1 << opps, darn tiny display

L51 looked a little funny, Is a loop doubled over another? That one is for 80m. I can't tell you if that is a bad thing or not.
And of course you scrap the coating off the wire and tin before soldering ?

And to anyone else, does it matter how tight you make the loops? I really tried using a dowel to make the loops as tight and flat as possible to the iron, both over the top and thru the middle. I broke a few wires tugging to make them tight

I wish I could be more helpful, these little things are the bees knees. Thank you for the conversation !

I hope this guy gets better and offers this product again for us from QRPguys
https://qrpguys.com/bs170-socketed-heatsink
KD9BXR
 

Posts: 7
Joined: 21 Nov 2024, 19:41

Re: Different TX Power Issue?

Post by KD9BXR »

Many thanks! I've got some of those diodes laying around in my vast collection of parts.

Yes L51 has a twisted coil and I just haven't spent the time to pull it off and rewind it. Based on my understanding this changes its value, but it will still function for the most part. I did scrape and tin all the wires before populated the coils on the PCB so I am very confident that they are making good contact.

See images below for scope measurement of output into a dummy load and RF pin from Main to RF board. Near as I can tell the 1w of power out is essentially broadband noise.
Attachments
RF pin between Main and RF PCBs
RF pin between Main and RF PCBs
5.jpg (215.57 KiB) Viewed 461 times
RF out into dummy load
RF out into dummy load
6.jpg (211.69 KiB) Viewed 461 times
KE0QQQ
 

Posts: 65
Joined: 02 Aug 2022, 00:41

Re: Different TX Power Issue?

Post by KE0QQQ »

Hello,
I started out buying the first radio shown here.
I tried to mimic what shown when winding the coils as a guide
That is some tight winding
Tight.jpg
Tight.jpg (83.45 KiB) Viewed 454 times
Now help me. I stared at your SMA connection. It might not matter, but do you see the difference.
SMA.jpg
SMA.jpg (92.29 KiB) Viewed 454 times
Its like an eye trick on the mind

I hope to see more information using your scope!
KD9BXR
 

Posts: 7
Joined: 21 Nov 2024, 19:41

Re: Different TX Power Issue?

Post by KD9BXR »

Good morning,

Yes those are definitely some tightly wound coils :) I always leave a little give on my so that they are easier to move around while tuning. Learned that the hard way while working on my uBITX :lol: After I'm very happy with everything I will use a drop or two of hot glue to help keep them in place while the rig is bouncing around in my backpack.

Your eyes aren't deceiving you, my SMA connector does not have the same leg pattern as yours. The lower pair of legs is soldered on the pads on the opposite side, and the other two are floating. Not ideal perhaps since we lose some mechanical strength, but its good enough to make the connection.
KD9BXR
 

Posts: 7
Joined: 21 Nov 2024, 19:41

Re: Different TX Power Issue?

Post by KD9BXR »

Update:

Still no success finding any obvious issues with any of my main boards. I've decided to order a kit from Sunny to at least have one good working unit that can be used as a point of comparison for further troubleshooting. Imagine this will not happen until after the holidays, but things are always better when they are not rushed.
KE0QQQ
 

Posts: 65
Joined: 02 Aug 2022, 00:41

Re: Different TX Power Issue?

Post by KE0QQQ »

Hey, I hope your new build goes well.

Keep us in the loop and show us some stuff with your scope.

I keep wishing this product would be available to us soon

https://qrpguys.com/bs170-socketed-heatsink
KD9BXR
 

Posts: 7
Joined: 21 Nov 2024, 19:41

Re: Different TX Power Issue?

Post by KD9BXR »

Update:

After a relatively busy holiday I'm back at the bench working on this project.

I recently received a commercially purchased build kit from Sunni. I echo all the positive sentiments expressed by others about this supplier and would recommend to anyone interested in doing their own build.

After assembly I was able to use the Main board from the commercial kit with the RF board from my own private build. The good news is that everything is working fine with my RF board. The bad news is this confirms that the issue I am seeing should be found somewhere on the Main boards I bought for my build. Now that I have a good working example I should in theory be able to start comparing the circuits until I find the issue. Given the amount of time this will take I do not expect to complete this task very quickly. I know its a relatively simple circuit, but I've also got some other projects demanding attention. I'm tempted to purchase a few more Main boards from Sunni to complete the rest of my units for my family to enjoy. If I repair my original boards I can keep them as spares, or purchase additional RF boards to assemble even more radios.

If anyone has any hints or suggestions on where to look on the Main board I would be most grateful. I still haven't found anyone else experiencing this particular issue with TX power.

Many thanks and 73!

David/KD9BXR
KE0QQQ
 

Posts: 65
Joined: 02 Aug 2022, 00:41

Re: Different TX Power Issue?

Post by KE0QQQ »

I had some holiday down time and assembled a main board from an Amazon sale. It mates to a classic RF board using the single FET. This display has the yellow top row and wow the pin holes are tight when its new. I assembled my last two years ago. I ripped the 12v connection off the previous board

Upgrading to the x version is done and works as expected

I was able to check into a local 80m LSB net on 3 cells using the onboard mic. They all heard me within a busy metropolitan area.. at s2

This new X software displays mic input, it helps to watch it and back down the voice when it pegs 999.

I wish there was someone who could CAD design a case in the shape of a VW bug or a bus maybe. Or a Star Trek communicator. That would be cool.. no trademark troubles there ;)
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