> ANYTHING with a software tuned front end is considered
> broad when talking about hi-level rf site performance.
I wouldn't say "anything"... many receiver front-end filter
sections are designed to electronically adjust and optimize...
aka a "tracking receiver pre-selector front end". I have
seen some pretty neat'o tracking receiver filter sections
with impressive performance values....
> That is why helical resonator front ends are desirable.
The helical front end receivers are no free lunch deal.
Fixed tuned helical front ends as found in many of the
GE and Motorhead Radios (and repeaters) are often a few
MHz wide.
The previously mentioned Toko Brand helicals are even
wider (lower Q, less number of sections, great taste,
less filling) than the typical GE, Motorhead assemblies
we find in front of our favorite surplus commercial
receiver.
While a few MHz band-width might be OK in many classic
base and repeater station applications... persons trusting
helical filters with pre-amplifiers in/at really busy
close spaced ("on the margins") situations are often in
for a surprise visit from Mr. Gremlins N Grunge.
There is smart information, engineering and application
information available on the web... to make a really
high performance "smokin" repeater receiver system. I've
just not found it all in one place yet.
cheers,
s.
