Adjustment of the RF section

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Posts: 63
Joined: 04 Jan 2023, 13:32
Location: brasil

Adjustment of the RF section

Post by reytek79 »

Guys, I'm trying to adjust the coils with Nanovna, but when I compress or remove the turns, it doesn't change the position of the second harmonic in the Nanovna, I can't bring it to the correct position.
80m band I'm adjusting the L52
I'm also finding the power low in 80m only has 3.6W 75% efficiency
WhatsApp Image 2023-03-09 at 08.21.13.jpeg
WhatsApp Image 2023-03-09 at 08.21.13.jpeg (111.43 KiB) Viewed 624 times

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Joined: 04 Mar 2023, 03:22

Re: Adjustment of the RF section

Post by NI6V »

You pictures show a really sharp cut off after the pass band. This is way better than mine looks. I found all the recommended number of turns through the toroids to be grossly off compared to the inductance called for on the schematic. I would desolder both coils and check them with an LCR meter.

Posts: 399
Joined: 30 Dec 2021, 22:54

Re: Adjustment of the RF section

Post by dl6sez »

Hello OM,

it is easier to remove one turn at the harmonic notch toroid you are too low in frequency, than measure again and adjust the spacing of the turns. Equally spaced around the whole core => lowers L and vice versa
increases it.
Measuring with an LCR Meter makes not really sense because for the other toroid turns it depends also on the FET impedance, most effect the output capacitance. The FETs are not equal one to each other.
If you haven't already mounted the other toroids you can measure with LCR and equal spaced turns to see if it is okay, but think about you are than at the lowest end of their inductance value and it can not be lowered with tweaking the turns together :)

73 de Chris
Chris DL6SEZ, JN48XL near Ulm, Southern Germany
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