[Moon] Looking for anti-TVI filters

[M. Watanabe]

Bruno and all: 

I made a mistake in spelling.  
>    If you like to reduce the second harmonic, simply put a 
> electrically-a-quater-wave shortened coax stub.  

It's not a shortened stub, but a shorted stub.  Electrically and 
mechanically shorted stub at the end.   Put this like a T on your 
coax line.  

Mike  JH1KRC  


---- "M. Watanabe" <jh1krc at syd.odn.ne.jp> wrote: 
> Hello Bruno, 
>    If you like to reduce the second harmonic, simply put a 
> electrically-a-quater-wave shortened coax stub.  
> It works as a half-wave short circuit for the second harmonic. 
>  
> Use a coax of good quality (i.e. low loss on the higher frequency) 
> and make a good short (i.e. a low impedance short on higher 
> frequency).  
> 
> You would easily get over 30dB notch on the second harmonic.  
> But it is very sharp notch.  So tune it (cut it) carefully. 
> You had better use a tracking generator, or impedance analyser 
> anyway.   It shows almost zero ohm at resonant frequency.  
> 
> If you like to make another notch on the third harmonic, build up 
> another notch for it.  But a simple short stub may rise a little 
> reflection.  Still, it works!     Modification is needed for complete 
> matching for the third harmonic stub notch.  
> 
> Mike JH1KRC  
> 
> 
> 
> 
> ---- F1MPQ - 2m MS EME <f1mpq at orange.fr> wrote: 
> > Hi all,
> > 
> > I'm looking for filters against TVI for 144 Mhz and 432 Mhz for powers till 500w on the twice bands. Good filters easy to buid.
> > 
> > Thanks for your help
> > 
> > 73's Bruno de F1MPQ
> 
> 
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