On 22 mar, 16:17, Leon wrote:
On Mar 22, 9:49*am, Jean-Daniel HB9AKQ wrote:





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.

The questions I am facing are these:
1) Do the MQF (Monolytic Crystal Filter) withstand high level signals,
like 1 mW or more, and what is their shape on the frequency domain (do
they go steeply down and do they have parasitic responses) ?

2) I am actually ready to try one of the lattice crystal filters as
described by Rhode in his may 1981 article (I can send you a copy for
the asking), where there are 4 crystals in 2 pairs separated in
frequency by about the 2 thirds of the desired passband. I would find
the crystals by sorting out batches of crystals on the frequency
meter. One can put 2 of these filters in series separated by a 1-dB
resistive pad (8 crystals total). Any experience to report on these
filters?

3) How good are ladder filters with overtone crystals? I do know that
ladder filters with such crystals are excellent on their fundamental
(3rd overtone crystals), but can you have them filter on the overtone,
with a tuned circuit up front ?

It's quite easy to buy 40 MHz fundamental crystals, which could be
used for a ladder filter.- Masquer le texte des messages précédents -

- Afficher le texte des messages précédents -

Oh, I'll check that out, the highest I saw was around 24MHz at 1mW,
but I also quite a few at Digikey's going to 50MHz,but I do not know
if they are overtone or not. In any case they withstand only 50 or 200
uW, which is not enough for an up-conversion roofing filter that gets
dBm galore