[CQ-Contest] Band-pass filters -- insertion loss

[i4jmy at iol.it]

>One well-known SO2R op commented that he got only 80 watts out
> of the bandpass filters that follow his 100-watt class radios, which 
in
> turn means he can not drive his 3-500Z amps to full output.
> 
> Is this typical of the bandpass filters available today -- ICE, 
Dunestar,
> Array Solutions?  Anything to choose among them in this respect, or 
others?
> 
> Thanks in advance.
> 
> 73, Pete N4ZR
> Contesting is!

I don't know about commercial products but the insertion loss of a 
filter is function of components losses and design parameters, in other 
words the chosen filter configuration, the number of poles and the 
desired off band attenuation.
Of course, an alignement that insures good return loss and tuning is 
required but I wouldn't trust with the long term stability of a 
critical design while a good mechanical strenght and filter capability 
to dissipate energy (i.e. when antennas coupling is very tight) is 
instead a primary key for reliability.
Basically, if the filter works as required in terms of out band 
attenuation and its inherent loss doesn't stress the internal 
components, an higher insertion loss is probably a more 
acceptable "feature" than a smaller off band attenuation with a filter 
with the same number of poles but optimized for a minimal insertion 
loss (sometimes required when the filter components aren't oversized 
and couldn't dissipate a consistent power).
In my opinion any filter that's less than half dB insertion loss (about 
10%) is practically acceptable, if the other goals are obtained and 
stable.
 
73,
Mauri I4JMY
 


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