[RFI] Re: Radio Frequency Interference (RFI) Digest V3 #89

[J. Bradshaw]

: Subject: [RFI] Follow up to TV RFI

Jon,

Rather than using a 2 set splitter, you should use a T connector (If you 
could ever find one.  Alternately you could open up the "splitter" and 
remove the broadband transformer and hard-wire the center connections 
together.  The splitter as it is will only drop about 6db out of the main line.  
Also as was mentioned, the velocity factor will find resonance with a 
physically shorter length of coax, but may drop some of your intended 
signal on some channels.  I'm still looking for a decent F- high pass filter. 

The most difficult thing for most hams, is to actually identify whether 
there is actually a spurr at Fo, but it is unlikely to be significant if you're 
on cable, and have a LP filter on the radio.  You can assume that 
fundamental overload is the culprit, forcing circuits into non-linearity.  
I have been able to get rid of the 2 and 6 interference with a twin-lead 
type hi-pass filter, but I am using coax now so it's back.  You're on 
cable though, so you shouldn't even have this problem.  If your cable 
signal isn't dirty, the only thing left is to keep the RF away from the 
vicintity of the cabinet.  Have you tried ferrites back in the wall plate 
or outside?  It used to be popular to have a large steel plate at the shack 
entrance with bulkhead feedthrough connectors to act as both a single
point ground, and to suppress shield currents on the coax. 

This may or may not help, but you really don't need an amp on 10 meters 
at all.  Five or 10 watts is sufficient with the band opened, but you just 
can't get anywhere with any amount of power if the ionesphere won't give
you a path.  For local communication, VHF/UHF is quite a bit more 
efficient because ground absorption is much less severe.  

Having said that, If you have TVI on 10 with an amp, you probably still 
have some with only 10 watts.

Good luck.





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