On Fri, 19 Sep 2003 16:16:36 GMT, Gregg wrote:


. Your winding will be determined by the mu and Al value of the core.
Amidon supplies those values and the math.

Thanks, after playing with a toroid I pulled from a power supply I
gave up after realizing it had a Al of 79 - way too much to be useful.

To get 3uH with that I would need about 1.5 turns...he,he.
Not easy to get six taps on that.

PI network is great if both the source and load impedances are unknown.

Yes, its pretty cool how it balances my Sony input very nicely.


Arnie says this tuner will work down to 5kHz.

Not unless your inductance in in the hundreds of mH and you have uF of
capacitance.

After a few trial and error sessions I used a suite of calculators I
found he http://eweb.chemeng.ed.ac.uk/jack/radio/projsoft.html

The result of my labor is a 6 inch piece of PVC pipe wraped for 4
inches with 15 turns of 12 guage speaker wire. My thoughts are its
pretty darn close to 3uH given it resonates down to 4800kHz. It
suprised me.

AM band is easy to reach. Wind your coil for the lowest frequency you
expect to receive.

I probably will order 2 toroids and wind one for AM and the other for
SW then connect them to a toggle with the other end connecting to my 6
position tap switch. That should bring my random wire to life.

I suggest you go to your library and read an older (mid 80's) ARRL Radio
Amateur's Handbook. They have a lot of vanluable information on this
tiopic, with the related math, even charts for Amidon toroids.

I guess with the advance of the internet and satellite, homebrew is
not so common anymore. However, I find them complemtory with the
plethera of info thats online. I found the charts you mentioned online
which helped me realize my torroid was useless.

If I had shopped around for better prices I could have assembled my PI
tuner for 35 bucks or less using the air form coil. Given nothing at
Radio Shack is cheap, my total is about 50 bucks.

It works great.

Thanks for your help,

Mike