[Amps] low pass filter fail

[Ian White]

VE7RF wrote:
>##  whoa.  The amp generates harmonics.... it doesn’t amplify harmonics
>from the driver.
>
Sorry, I didn't meant to imply that. What I meant to say was "You should only need to attenuate the harmonics of the signal frequency". The PA will not generate any other signals in between those harmonics, which is why a multiple-notch filter may be an easier option than a classic lowpass.

G3RZP wrote:
>Can you get 43 + 10log P dB attenuation (not exceeding 70dB) for each harmonic up to the 10th using stubs? 
>(as required by ERC/REC 74-01)

The answer will obviously depend on the type of PA including its output matching network, as well as the performance of the filter that follows. 144MHz DXers tend to operate within a narrow frequency range, so a stub filter can easily provide notches of 40dB at the harmonic frequencies, and closer to 50dB with a little care. The stubs for 2f, 3f, 4f and 5f will also provide notches at 6f and 9f, so a 144MHz version will cover every harmonic up to 1GHz. That still cannot guarantee regulatory compliance, of course... but it is a big step along the way.


73 from Ian GM3SEK