OK all,
I've done some more experimenting with my TVI RFI problem I mentioned the
other day.
I've tried all sorts of ferrites, filters, etc. All to no avail in getting
the last little buzz and overload conditions (ch 2 & 6) from occuring. Not
much change in anything except for one case.
Someone mentioned to put a 1/4 stub at 10 meters in the line. They
suggested I could use one of the 2:1 splitters for CATV use and hang the
stub off of one of those (split the input cable between the cable to the TV
and the stub). Well, a 1/4 wavelength at 10 meters is about 103 inches or
so. So I tried it. Nothing. However, as I moved the cable around, I could
cancel out the buzzing sound I got while keying the TX. The overload
picture problem was still there, but I could make the buzz go away. I tried
shortening the stub to see if it made a difference, but it really didn't.
I've ended up running both coaxes (the regular and the stub) into the TV
cabinet and ran the stub once inside across the back of the TV. The buzz is
nearly gone. You can't hear it unless you pay attention to it really hard.
This is great, but my question is, WHY? What sort of cancellation is going
on here? It also seems to make no difference if the stub is open or shorted
as well.
So what gives?
Additionally, the overload/harmonic problems occur on channels 2 and 6
whether or not I have the antenna coax connected. Yes, I am filtered at the
output of my power amp. I have a 3 KW ICE bandpass filter that has very
sharp roll off after 30 MHz.
I just want to know if anyone has a clue of why moving the position of the
stub around would change the noise I am picking up.
ANY ideas?
73,
Jon
NA9D
-------------------------------------
Jon Ogden
NA9D (ex: KE9NA)
Member: ARRL, AMSAT, DXCC, NRA
http://www.qsl.net/ke9na
"A life lived in fear is a life half lived."
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