Yesterday I wrote, in part:
> It has been suggested that Ten Tec's crystal lattice filters
> perform better than the INRAD [ladder?] filters for ultimate
> attenuation (TT filters retain steep skirts continue on down
> past -40dB).
> I was told that Ten Tec has made a good choice with the
> lattice filter design they have used. The thought:
>
> "Again a good choice on TenTec's part in spite of the push
> by some folks to value steep close in skirts over best
> rejection past 40 db down."
1. Ladder Filters
I have been searching about for info on this topic. Lots of stuff
out there about ladder filters, e.g.:
http://www4.tpgi.com.au/users/ldbutler/LadderFilter.htm ,
and
http://www.pan-tex.net/usr/r/receivers/cryfil.htm ,
which has several QST article references about ladder filters
listed.
2. Lattice Filters
So far, not found a lot about lattice filters. Did find a bit about
R. L. Drake's use of lattice filters, in the R-4C:
"a Crystal Lattice Filter gives superior shape factor and ultimate
selectivity for better adjacent channel rejection.."
this from,
http://www.dproducts.be/drake_Museum/r-4c.htm
at the Drake "Virtual Museum".
A lattice filter is a bit more complex, as the crystals sort of
"criss-cross" in the set up, quite unlike a straight forward
ladder structure, as discussed above. For example see
the 5th and 7th "frames" of this .pdf paper:
www.tfrtech.com/pds/TFR-2L.pdf
However, I can find no direct comparative data about the two
types of crystal filter designs.....oh well.
73, Jim KH7M
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