Re: [AMRadio] Question about ferrite rods
Hi Conor, A ferrite rod antenna should be perpendicular to the oncoming signal wavefront, and also perpendicular to its electrical field (or parallel to its magnetic field). Because you would ordinarily be close to the ground with a loopstick radio, signals will tend to be vertically polarized at the loopstick - so for most signals the ferrite rod would be horizontal, and perpendicular to the incoming signal. If you null a signal by rotating the rod to point toward the signal, you may find that the best null is obtained with the rod tilted slightly upward toward the transmitter. This is because the signal wavefront tilts slightly toward the earth. Loops and loopsticks can be used to null interfering stations to hear weaker signnals on or close to the strong station's frequency. Skywave peaks and nulls are less precise than groundwave - nulls and peaks vary as skywave paths vary and fade, especially at shorter wavelengths, I think. But with groundwave, the behavior of a loopstick is fairly precise. There is something about paramagnetic materials that attracts magnetic flux and concentrates it in the material, and such magnetic material will also increases the inductance of windings around it, so the coils do not have to be as large as they would be in air. This is why ferrite loopsticks are used - a very small antenna can be effective. Ferrite is useful up to the megahertz range, and some ferrites are even useful to UHF and beyond. Bacon, WA3WDR
Re: [AMRadio] Question about ferrite rods
Excellent! Thanks for all the info guys!
Re: [AMRadio] Question about ferrite rods
-Original Message- From: Bob Bruhns [EMAIL PROTECTED] snip Ferrite is useful up to the megahertz range, and some ferrites are even useful to UHF and beyond. My old Tandberg portable radio uses the ferrite up to 5 mhz then the telescoping vert. above that. Having a directional antenna for 75 mtrs is real nice unless there's a noise source in the same direction as the desired signal and for directionally different QSOs the radio must be turned to match up with the incoming direction. IE, 90 degrees to copy Ohio and MD in round-table. I have often thought that a large remotely rotatable ferrite based loop on the roof or attic would be real nice for those difficult times. _Bill KB3DKS/1 _ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb Check out AOL.com today. Breaking news, video search, pictures, email and IM. All on demand. Always Free.
Re: [AMRadio] Question about ferrite rods
In a message dated 6/16/06 11:07:53 AM, [EMAIL PROTECTED] writes: I have often thought that a large remotely rotatable ferrite based loop on the roof or attic would be real nice for those difficult times. Bill, Give a small tunable loop a try. Dennis D. W7QHO Glendale, CA
