(tr)uSDX Forum

Experiences:
Today I got a little smarter...

I now have a kit from newdiytech.com.

Since I had already waiting for the (unfortunately canceled) OE-DL Group buy and previously had very bad experiences with toroids from China (N7DDC-AT-100 project), I previously ordered all toroids from amidon.de for the (tr)uSDX . After i built the kit, the power and efficiency was bad.
At 12V 1.75W-2.5W and 30-40% efficiency depending on the band.
That was of course very unsatisfactory.
I then changed T2 from Amidon-toroid to kit-toroid with no improvement. Squeezing the coils didn't do much either. My wattmeter only starts at 2.5W and showed about 2.5 watts at 80m (strongest band), which the display also showed. So the efficiency was displayed almost correctly.
I had changed all BS170 from first "Fairchild" to "China" and now "Motorola", with not so big differences. That wasn't the breakthrough either.
All that remained was to fiddle around the toroids or replace them. And in the back of my mind I had Manuel's enthusiasm for the toroids of the kits. So today I changed first the two Toroids for 20m.
and bingo! At 20m at 12V, the power increased from 1.96W to 4.6W and the efficiency from 30.6% to 77% without further adjustment.
Loud relaxed sigh of relief!
The rest will follow soon, but I assume that was the breakthrough.
Actually, I would have expected less stress from the Amidon cores.
And now I share Manuel's enthusiasm for the toroids off the chinese kit. A big thumbs up.

Maybe this is also interesting for others.

Thanks for sharing your experience !
Yes, the toroids that Sunny is providing, are really great.
I don´t know what creatures they torture to get that much amount of fairydust, but that stuff really works spot on.
Joke aside: The Material is imported and it´s only pressed in China. Once again I´m happy, that we found a really good chinese supplier, that takes it seriously.

73 Manuel, DL2MAN

Fairydust hits it.
At some point I saw that toroids can be compared to the NanoVNA.
That might be interesting. However, the post was in Japanese...
https://mobile.twitter.com/JG1TWP/statu ... 3755765762
It needs to be translated to our small toroids.

But now the other toroids have to be exchanged when I have time...

DL2MAN wrote: ↑23 Apr 2022, 19:33
Joke aside: The Material is imported and it´s only pressed in China. Once again I´m happy, that we found a really good chinese supplier, that takes it seriously.

73 Manuel, DL2MAN

This is a very interesting development. I wonder where they source their cores? I've measured what I think is a Caracol CT-37-2 toroid that QRP Labs had provided, and it only has half the Q of a Micrometals T37-2 (red).

I've also measured Ebay-sourced T37-2s that have a Q that is extremely poor...

AFAIK, Amidon in the U.S. does not make their own toroids - they are a re-seller...

va3rr wrote: ↑25 Apr 2022, 14:42 I wonder where they source their cores?

Why don´t you ask Sunny ? I´m sure, she will sell them on request, or if not, give you the Information you need.

73 Manuel; DL2MAN

Hi all,

finally I'm now in the process of building the RF board and tried to measure the inductances before I solder them to the board. I used a 100kHz RLC meter and also a resonance method with a 0,5% Cap not far from the final target frequency. So, I always end up with much more inductance.
With the kit I received a sheet saying eg. L11, L32 should be 10T on a red T37-2 core and the schematic says 400nH. With 10T equally distributed around the whole core I ended up with 600nH. I reduced to 8T to get the 400nH. L12 came out with 5T instead of 7. The AL seems rather 6 than 4.
Also my cores look rather brown than red. But brown would be material -0 with AL=0,5.

So, is the rusty brown the new red?

Did you also have seen such deviations?

Is my measurement wrong and I should trust the 10T?

Thanks and 73, Thomas.

Update, tuning the filters it turned out the number of turns listed in the documentation is correct.
I had to add the turns again that I initially omitted.
Have fun

Suddenly it's frequency dependent ))