[Elecraft] Bandpass filters

[Ken Kopp]

A current posting paints a totally incorrect picture of the relationship
between HF and VHF/UHF filtering methodologies.  

A typical VHF repeater TX runs 50 -110 watts and the spacing
between TX and RX is 600 kHz.  At UHF/450 the spacing is 
5 mHz.  (I'm a career two-way radio technician and have been 
the repeater coordinator for Montana for 30 years.)

The set of six 160 - 10 meter bandpass filters that I use for HF 
contesting and DX-peditions would all fit in the case of a K2 or 
K3 and do function perfectly well in the same room with several 
multi-op stations with KW transmitters.  SO2R is the proverbial
"piece of cake".  In addition, there are dedicated RF input limiters 
available for the antenna inputs of radios if one wants additional 
protection or doesn't have bandpass filters.

There is little, if any, relationship between the resonant cavity type 
of band-pass, band-notch technology used in VHF/UHF duplexers 
and the capacitor/inductor technology used in HF band-pass filters.

73! Ken Kopp - K0PP
k0pp at arrl.net