[TenTec] Filters: Ten Tec vs. INRAD

Jim Reid jimr.reid@verizon.net
Tue, 3 Dec 2002 11:10:42 -1000


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