RF-Board - inductance values?

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DL7AQT
 

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Joined: 07 Jan 2022, 22:27

RF-Board - inductance values?

Post by DL7AQT »

My PA delivers different output powers depending on the band:

80m - 1,0 W
60m - 0,8 W
40m - 1,8 W
30m - 4,6 W
20m - 3,5 W

All measured @13,8 V on a 50 Ohm dummy load.

The value of 4,6W on 30m appears to indicate that the PA is ok and able do deliver sufficient output power, so it seems that in some bands the attenuation of the low pass filter is to high.

I suspect that the inductance of one or both of the toroid coils in the low pass filter of the bands with low power is to low/high, i.e. not at the design value.

Unfortunately only the number of windings for the toroid coils is given, not the value in µH. Only for L15 the value of 200µH is given - I measured for my L15 185µH

Could the developers provide the µH values of the low pass filer toroid coils ?

Thanks!

73 de Frank, DL7AQT
mm0gyx
 

Posts: 83
Joined: 30 Dec 2021, 20:22

Re: RF-Board - inductance values?

Post by mm0gyx »

DL7AQT wrote: 04 Feb 2022, 21:04 My PA delivers different output powers depending on the band:

80m - 1,0 W
60m - 0,8 W
40m - 1,8 W
30m - 4,6 W
20m - 3,5 W

All measured @13,8 V on a 50 Ohm dummy load.

The value of 4,6W on 30m appears to indicate that the PA is ok and able do deliver sufficient output power, so it seems that in some bands the attenuation of the low pass filter is to high.

I suspect that the inductance of one or both of the toroid coils in the low pass filter of the bands with low power is to low/high, i.e. not at the design value.

Unfortunately only the number of windings for the toroid coils is given, not the value in µH. Only for L15 the value of 200µH is given - I measured for my L15 185µH

Could the developers provide the µH values of the low pass filer toroid coils ?

Thanks!

73 de Frank, DL7AQT
Using the windings from schematic I found I had to evenly spread the windings fully around the core to get the expected power. Did you check, and check again to be sure you got number of windings correct?

My power is 4 - 6 watts at 13.8 volts.

Ian MM0GYX
DL7AQT
 

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Joined: 07 Jan 2022, 22:27

Re: RF-Board - inductance values?

Post by DL7AQT »

Yes, the windings are evenly spread and the number of windings is ok. Checked before soldering and again now.

Frank
dc8lz
 

Posts: 41
Joined: 31 Dec 2021, 01:35

Re: RF-Board - inductance values?

Post by dc8lz »

Hello!

Looks like a wrong cap from my #1 round... I have sent all OMs a mail. So just to inform all others here... It is not a truSDX problem. Sorry.

73, Stephan
2M0ufo
 

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Joined: 31 Dec 2021, 12:52

Re: RF-Board - inductance values?

Post by 2M0ufo »

Nice catch Stephen

It would be nice to have inductor values
Cheers
Stevie
2M0ufo
va3rr
 

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Location: FN25eg
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Re: RF-Board - inductance values?

Post by va3rr »

You could use the WA0ITP spreadsheet. Of course, the spreadsheet produces ideal capacitor and inductor values which may not exist. Fractional turns aren't possible with toroidal inductors.

http://www.wa0itp.com/class%20e%20design.html

I used toroids.info to come up with uH values for the number of turns for the inductors, and they compared pretty closely with the WA0IPT spreadsheet for everything but 80M.

I may try building a 2nd (Tr)uSDX with yellow 6 mix toroids on 10MHz and 14Mhz and white 7 mix toroids on 7MHz, just because I have some available...
Slava Ukraini!
DL2MAN
 

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Re: RF-Board - inductance values?

Post by DL2MAN »

I would like to give the Inductance Values, but I don´t have them.
I only have the theoretical Values.
While trying to measure them, I figured that my measurement equipment is not accurate enough.
It would vary too much. And that´s only on my device.
Now imagine the differences between 2 devices (yours and mine).
I think this will create more confusion, than it actually helps....
So I went to publishing only amount of turns, which is what everyone can reproduce...

73 Manuel; DL2MAN
va3rr
 

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Re: RF-Board - inductance values?

Post by va3rr »

DL7AQT wrote: 04 Feb 2022, 21:04
Unfortunately only the number of windings for the toroid coils is given, not the value in µH. Only for L15 the value of 200µH is given - I measured for my L15 185µH
I'm measuring 170 uH at 100 Hz and 158 uH at 100 kHz on my DE-5000 LCR meter. However, one L15 inductor measures 399 uH at 100 Hz and dropping to 246 uH at 100 kHz.

I realized it must be from old stock #43 ferrite. Both batches of ferrite came from Kits and Parts.

Owen Duffy says that Fair-Rite changed the permeability of that ferrite in 2020.

https://owenduffy.net/blog/?p=19138
Slava Ukraini!
DL7AQT
 

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Joined: 07 Jan 2022, 22:27

Re: RF-Board - inductance values?

Post by DL7AQT »

Meanwhile the issue with the wrong capacitors on my RF Board is fixed. The output power is now on all bands in the expected range of >5 W a 13,8 V.

For winding the toroids I followed the instructions of the video. The wire has been tightly wound and the windings are evenly spread on the toroids.

I removed the insulation and tinned the wires in one step using the "solder-blob" method, teached by DL2FI (sk, RIP). In this method you heat the wire close to the toroid with a larger tip of the soldering iron (I used a 2mm screwdriver style tip), add a larger amount of solder so that a "blob" of solder encloses the wire. As soon as some smoke indicates that the insulation burns, move the iron slowly about one centimeter towards the end of the wire. The result is a perfectly tinned wire. You may try whether this works for you if you fear scratching the wire.


73 de Frank, DL7AQT
va3rr
 

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Re: RF-Board - inductance values?

Post by va3rr »

I placed my inductor measurements at www.qsl.net/va3rr/xls/trusdx_inductor.csv

i used #24 AWG wire, so ymmv...
Slava Ukraini!
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