On Sun, Apr 13, 2025 at 10:42 AM, dl8lrz Reiner wrote:
The 20-17-15m filter (and higher) in particular can cause a lot of trouble afterward.
Hello Reiner and all,
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With 3 x 2 BS170's and using 10V on a 9V build, power out is 5.3W on 20M, 3.7W on 17M and 5.2W on 15M.
Fiddling with the low pass filter did not improve P-out on 17M.
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I duplicated the original 20 / 17 / 15 M LPF on a small PCB.
The frequency response is flat +/- 0.1 dB from 14 - 21 MHz.
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This filter was used to replace the original filter, mounted directly after L501.
Though having a perfect flat frequency response, the same lower output showed up on 17M.
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I have also measured the input signal at the gates of the BS170's and the amplitude is very similar over the whole frequency range.
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Does someone have an idea what might cause this lower output on 17M and not on 20 and 15M?
Just curious.
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73,
Roelof, pa0rdt?
