[AMPS] Band Pass Filtering

[Ian White, G3SEK]

Peter Chadwick wrote:
>I guess the bottom line is that Jon needs a decent filter at the output - a
>single cavity  would probably do it. Of course, Jon, you could roll your own
>- there have been a number of designs in the older RSGB VHF Manuals

Aaaargh - those ultra-sharp single-cavity bandpass filters are a
disaster! 

They combine all the worst features that a bandpass filter could have:
touchy tuning, poor stopband rejection, hit-and-miss impedance matching,
high voltages and high circulating currents. In particular, the very
rapid variation in impedance with mis-tuning is a recipe for IMD. 

I'm not normally one for burning books, and especially not VHF Manuals,
but...

73 from Ian G3SEK          Editor, 'The VHF/UHF DX Book'
                          'In Practice' columnist for RadCom (RSGB)
                           http://www.ifwtech.demon.co.uk/g3sek

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