I'm trying to match a 4 inch ferrite rod antenna stick to the 3K
balanced input of a NE602 mixer chip on the AM broadcast band (540-
1650 kHz).

The primary has about 100 turns and I've tried 25 turns on the
secondary to feed the 602 with reasonable results, but I don't know
what the optimum would be.
I added another winding of 50 turns tapped every 5 turns and
experimented with that, but it seems to work best with the maximum
turns. But there isn't much difference from 25 turns to 50 turns on
the secondary. Seems the more the better, but there should be some
optimum.

Anybody know where the best place is to locate the secondary winding,
and how to determine the optimum number of turns to yield a 3K output
impedance?

Thanks,

-Bill

try here
http://home.att.net/~ray.l.cross/murod_mm/

denny / k8do

On Feb 21, 4:44 am, "Denny" wrote:
try herehttp://home.att.net/~ray.l.cross/murod_mm/

denny / k8do


Thanks for the link. Interesting but a little bit advanced for me.

I talked with an RF engineer who worked for Collins radio who
suggested just using a JFET buffer between the antenna rod and the
mixer input so the impedance matching problem would go away, and I
would get much more signal since the antenna rod will see an open
circuit (no load) and have maximum Q.

He was right, and I was able to get about 18dB more signal from the
antenna rod without using any additional windings. But I had to add a
JFET, resistor, and two caps.

-Bill