[TowerTalk] Are All Low-Pass Filters Alike? -

[Don Havlicek]

Correct me if I am wrong, but aren't "harmonics" exact multiples of a 
given frequency?
As such, they should be differentiated from the spurious frequencies 
generated by an amplifier which usually are NOT an exact multiple of the 
driving frequency.
Those spurious frequencies are, correctly as stated, not filtered by a 
LP between the Xcvr and amplifier.
The original question I raised was concerning HARMONICS, not spurious 
frequencies generated by the amplifier.
Perhaps operating an amplifier ONLY within the linear portion of its 
curve would cure most of the spurious frequencies and limit the need for 
a LP filter post-amp.
As for the statement that 'amps do not amplify harmonics' that was 
posted by another submitter .. I defer to the "experts" as to why 
harmonics ARE amplified by a well-designed amplifier .. a FACT that  can 
be easily measured.
Don
N8DE

Jim Lux wrote:
> At 01:10 PM 8/16/2005, Don Havlicek wrote:
> 
>>Why don't hams place the LP filter between the Xcvr and the Amp?  That
>>way, the amount of harmonics reaching the Amp will be minimized,
>>rendering their output levels relatively the same, if not lower, than if
>>the LP filter was AFTER the Amp.
>>BTW:  this is what I have done since the 50's.  Never blew up a LP
>>filter yet!
>>Don
>>N8DE
> 
> 
> probably because the harmonics people are concerned about come from the 
> power stage, not the exciter.   
> 
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