On Thu, 10 Jun 2004 20:53:30 -0400, "lsmyer"
wrote:

I enjoy AM dxing, and I've noticed that the radios with larger ferrite rods
seem to be better for dxing than those with small ones.

I did some research on the subject, and I kept running into terms such
q-factor and flux. My 45-year-old mind only has room for so much, and I'm
afraid that anything I try to learn about electronic theory will just push
out some of the more important stuff already stored in there such as
anniversary dates and current wife's name.

So maybe somebody can answer a couple of questions for me in simple English,
and maybe help me save what few brain cells I still have left.

It's been years so the erudite here will please set me straight.

The coil-antenna combines signal gathering with tuning and
directivity. The ferrite core just increases the antenna-coil
inductance. This results in a smaller coil for tuning frequency
coverage but less antenna (the physical coil proper) for actual
signal reception. It adds to core losses but there is less wire
loss. It makes a much smaller transformer. So, there are
several tradeoffs.

The most efficient AM band ferrite coils for external antenna use
were only about an inch and a half or so as I recall. They are
variable inductance too for tweaking. Some old radios may have
them.


1) Is there an optimal length for an internal ferrite antenna?

2) If so, then why don't all radios have one that size?

3) Is ferrite expensive or something?

4) How can my little Degen 1102 (tiny ferrite antenna) do so well on MW
while my ATS505 does so poorly?

Thank you in advance for all who reply.