Re: [amsat-bb] Transverters with *70cm* IF\'s

[Zack Lau <zlau@xxxxxxxx>]

The exact frequencies are quite important when deciding how
practical it is to make a transverter.  A typical worst case is a
432 to 1296 transverter--no amount of filtering will separate a
the 1296.000000MHz mixing product from the 1296.000000MHz
harmonic.  A few MHz offset and tight filters may turn an impossible
project to something that can be built by a serious designer.  For
instance, an 8 x 8 x 1 inch interdigital filter will easily remove a 142 x 3
or 426 MHz harmonic from a 432 MHz desired signal.  OTOH, trying
to notch out the harmonic with stubs or using a more conventional filter
just wasn't up to the task. It should be pretty easy to make a 3 MHz wide
1269 MHz filter using WR-650 waveguide.--Zack Lau W1VT

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