RadioBanter - View Single Post

September 25th 03, 02:06 AM

On 24 Sep 2003 22:04:06 GMT, (Avery Fineman)
wrote:

You could simple attach the 300-to-75 Ohm matching thing to the long
wire and use the coax...provided that the Z-changing-transformer can
handle HF. It won't be good if it's just a TV accessory; those seldom go
down to 30 MHz.

You might check the "300 Ohm" side of the transformer to see if it
actually has a DC path across it (an Ohmmeter will show that). Such an
accessory doesn't always have a DC path there. If it ain't there, no sense
in using it for your application.

The long-wire's impedance is going to range all over the place on HF so
it won't make much difference to a 75 Ohm coaxial cable feed. Most
frequencies will be way off in impedance matching regardless of the ultimate
impedance of the receiver.

Keeping the coax feedline offers some protection from household QRM
that is between receiver and antenna.

Len Anderson
retired (from regular hours) electronic engineer person

It does have a DC path so I went ahead and gave it a whirl, plus added
another 60 feet or so to my antenna, which probably didnt help.

Seems to be working OK.

I found a cheap source of T68-2 toroids so I going to pick up 5 or 6
and wind up several giving me an assortment of matching posts like the
ICE transformer. This would allow me to create an internal inductor
for my tuner as well.

mike