45-70MHz crystal filters, MQF,lattice,ladder?
Jean-Daniel HB9AKQ ) writes:
Hello,
I am in the process of choosing a technology for a crystal filter in
that frequency range. I am facing the choice of buying a filter and
paying the price, or to build a filter myself.
Are you hoping/expecting to get a narrow filter out of this, or will
it be a roofing filter, with the real selectivity at a different frequency?
I thought there were limitations on selectivity at those frequencies.
I can't recall ever seeing a narrow filter up there (and while it's been a
long time since I read that QST article, which is the only article in
the ham magazines that I've seen about making crystal filters that high
up, I thought it addressed that issue).
If it's just a roofing filter you need, you can pull one out of an older
cellphone. The big clunky kind have parts that are recognizable.
Michael VE2BVW
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