" bravely wrote to "All" (15 May 05 19:37:52)
--- on the heady topic of "Could a Balun Be Useful Here?"

ma From:
ma Xref: aeinews rec.radio.amateur.antenna:30429

ma I have a PC FM radio peripheral. It has a standard telescopic steel
ma aerial that plugs into a base. This works quite well.

ma However, I would like to recieve some signals that are too weak for
ma this arangement. I have an external TV yagi, but attaching it either
ma reduces the recieved signal or increases it only slightly.

ma Could impedence differences be an issue here? If so, what is the
ma likely impedence of the yagi and the peripheral?


Hmmm, those are usually 300 ohms at the top of the mast. What comes
into the building, is it a 75 ohm coax or a 300 ohm balanced twin lead
tv cable? If it is 300 ohm there might be a noticable difference. Have
you tried a little can tv transformer? Might there be an FM trap on
the antenna system? Do you have any idea of the input Z of the radio?
It may be 50 or 150 ohms, who knows? If your antenna cable is a 75 ohm
coax you may need to adapt this to whatever input Z the radio has but
it shouldn't be as critical as the 300 ohm balanced line in my opinion.

A*s*i*m*o*v

.... Bad day: When the bird singing outside is a buzzard!