[RFI] TVI: suggestins needed! Help me

[Aldo Angeletti]

Hi,

we are three amateurs radio with different transceivers, 
  different antennas and ground systems but all with the
  same problem : moderate to strong interference to the video of the  
  TV channel B ( 61/68 MHz ) when we transmit on 21 MHz
  band ( 100 W ) ;in my case, the TV antenna is directly 
  connected to the TV Set ( no preamplifier on the feeding 
  line being the imput signal 1mV ).
  Connecting a Spectrum Analyser to the receiving TV antenna 
  I see the third harmonic that interferes with TV signal (it is 
  ~ 33 dB less ); connecting a Drake low pass filter the armonic 
  on HF cable decreases of 45dB but on TV cable:it has ,more 
  or less , the same amplitude .
  I tried a  TG-4 Line Isolators but nothing has changed, so I 
  have no other ideas.
  One of the test I tried it has been to use a dummy load instead 
  of antenna (Explorer 14 )and the TV channel was ok;the strange,
  in this case,is the behavior of the low pass filter:it does not work;
  all the armonics at the dummy load terminal keep the same 
  amplitude with or without it.Using a signal generator instead of the
  TX (Mark V) it works correctly cleaning all the armonics
  Can you help me ? 
  Thanks
  
Aldo IK2ANI