Iane:

- thanks for posting this, it is very helpful..

Dan


In article ,
(RHF) writes:

Subject: Homemade AM ferrite antenna question
From: (RHF)
Date: 20 Oct 2003 20:24:28 -0700

ELFA,

"BA" gave you some good advise.

Before you start the windings.

* Find a 6.5" to 8" Ferrite Rod Antenna (FRA).

* 10 Feet of Wire (Magnet or Litz)

* Cut a 2" X 2" piece of Typing/Copier Paper 20/24LB)

* Wrap the Copier Paper around the FRA
(About Two(2) Layers & Tape the Joint)
- - - The Copier Paper will 'form' a "Tube" that can be moved on the
FRA.

* Wrap 50-80 Wire Windings over the Copier Paper Tube to form a
"Moveable Coil Assembly (The Coil).

* Set the Windings at the very tip of one of the Ends of the FRA.

* Connect the Variable "Tuning" 360-400pf Capacitor (VTC) to the Leads
from the Windings.

# Place the FRA and VTC next to a Radio: Ideally you would use a
Radio with a Digital Frequncy Display and a "S" Meter.

* Starting-Mid-Point: "Tune" the Radio to a medium strength AM/MW
Radio Station at the Middle of the AM/MW Band 800-1000 kHz.
- Set the VTC to its Middle/Center Position.
- - Very Slowly 'move' The Coil from the Tip of the FRA towards the
center of the FRA.
- - - Try to identify by Ear or Eye an change in the Quality and
Strength of Reception.
- - - - Mark-Measure-Record this 'position'.
Note: If you 'find' a "Sweet Spot" on this first try: You have
Luck-Out !

* Top-End-Point: "Tune" the Radio to a medium strength AM/MW Radio
Station at the High-End of the AM/MW Band 1500-1700 kHz.
- Set the VTC to its Fully "OPEN" Position.
- - Very Slowly 'move' The Coil from the 'prior' (Starting-Mid-Point)
position towards the Tip of the FRA and then towards the center of the
FRA.
- - - Try to identify by Ear or Eye an change in the Quality and
Strength of Reception.
- - - - Mark-Measure-Record this 'position'.

* Bottom-End-Point: "Tune" the Radio to a medium strength AM/MW Radio
Station at the Low-End of the AM/MW Band 550-700 kHz.
- Set the VTC to its Fully "CLOSED" Position.
- - Very Slowly 'move' The Coil from the 'prior' (Top-End-Point)
position towards the Tip of the FRA and then towards the center of the
FRA.
- - - Try to identify by Ear or Eye an change in the Quality and
Strength of Reception.
- - - - Mark-Measure-Record this 'position'.

NOTE: Ideally these three points are within a 1/8" of each other and
you would set The Coil in the the middle of the three.

However the reality is that this will not be the case and you will
have to REMOVE/ADD a few Windings and try the above process again.

TIP: If you can "Tune" the Low-End and/or Middle of the AM/MW Band
then REMOVE a few Windings. Or, if you can "Tune" the High-End and/or
Middle of the AM/MW Band then ADD a few Windings.


iane ~ RHF
.
.
= = = "Brenda Ann"
= = = wrote in message ...
"elfa" wrote in message
...
I appreciate your offer of instructions re the ferrite bar antenna but I
think
I'll just skip it for now. This was the wrong group for this kind of
request.
It should have been in an electronics group.

elfa

The number of turns necessary for a loopstick antenna depends on several
factors.

1) the frequency range required
2) the permeability of the ferrite core
3) the spacing of the turns

For experimentation purposes, you might start with about 80 turns of AWG 30
enameled or cloth covered wire, contiguously spaced, near one end of the
core. With this, use a ~360 pF variable capacitor.

If you have a grid dip meter, you can easily find where this is resonant.
If
you don't, then you have to poke about on the AM dial of a cheap radio, and
see where you can tune it.