And the narrow notch for the harmonic is not required anyway, since the
fundamental is fare enough, therefore a high Q LC trap will work
better, also with the setting of the biasing af the active devices the
spures could be reduced to [ just observe the output with a spectrum
analyzer and set the bias of one site to minimum harmonics, there will
be no common optimum for all harmonics, but a good compromise could be
achieved ]
73
Alex KJ6UHN
On 1/29/2015 2:16 PM, Richard (Rick) Karlquist wrote:
On 1/28/2015 11:28 AM, Charles Steinmetz wrote:
Gerhard wrote:
It is a different game when you want to notch away sub/harmonics.
One problem with using crystals as traps (notch filters) is that the
series resistance of a crystal is several orders of magnitude higher
than that of a good series-resonant LC -- generally in the 50-100 ohm
range. So, although the notch is very narrow, it will not be very deep
unless it is in a high-impedance circuit. For example, in a 50 ohm
It is very straightforward to use LC networks to transform the
impedance of the crystal to a much lower value and get around this
problem.
Rick Karlquist N6RK
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