RE: Bandwidth of crystal ladder filters CW and SSB


From: Prof. Arnaldo Coro Antich (
Date: Sat Sep 28 2002 - 12:45:08 CDT

Hi all !
As more and more precision and at the same
time rather low cost per unit quartz crystals
become available, the design of homebrew
ladder type or "" ladder type assymetric sideband
filters"as one of my colleagues likes to call them,becomes a very attractive
and interesting
plus cost saving challenge.
I have several questions regarding those filters
1. crystals must be properly matched to within
a very narrow frequency range .. OK, but does
the accuracy of the match influence the wider
bandwidth SSB filter less than the CW much narrower filters ??
2. Is it true or not, that no matter how you work
around with these ladder filters, your response
will ALWAYS be assymetric , in favor of the
lower sideband ?
3. Is it true that the SSB filters ( typically designed
for between 1.8 kHz up to 3.2 kHz bandwith)
produce much higher insertion losses than
the narrower ( 100 hZ to 500 or 750 hZ wide )
CW filters ???
4. What would be the simplest and lowest cost
design for a SSB filter... and by this I mean using
the least number of crystals and other parts ?
( this question is intended to gain knowledge towards the design of the
HURRICANE TWO, a natural replacement for our HURRICANE ONE
double side band rig , used here in Cuba during
the hurricane season .... )
5. Which are the more popular and lower cost
frequencies available from suppliers around the world ??? I understand that
3579 and 4433 are
two of the most popular ones, but now it seems
like there are many more frequencies that are mass produced for
microprocessors and other
applications that has lowered the cost down
a lot
HOPE this is accepted as a QRP related topic
and that it may generate a LOOOONNNG and interesting thread...

`72 and DX
Thanks in advance for your answers and
thoughts about the topic

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