When are ferrite beads the most approproate component to use?
in [Design]
|
Prev: Idiots
Next: Looking for photo frame that does GIF...
From: Joerg on 27 Dec 2009 15:06 Tim Williams wrote: > "Paul Keinanen" <keinanen(a)sci.fi> wrote in message > news:ma1ej51jo38s7s2utdfa28f1tpci4uevnj(a)4ax.com... >>> Story: the college radio station antenna is right on top of my dorm... >> If this was a vertically polarized antenna, the radiation pattern has >> a null directly downwards. To reach your room, the signal would have >> reflected from the surrounding buildings, creating a large number of >> multipath nulls (selective fading). With one such null at or close to >> the transmitter frequency, the received signal amplitude will change >> depending the instantaneous frequency, which varies with the audio >> waveform. > <snip> >> Some old Revox FM-receivers even had an oscilloscope CRT driven by the >> audio voltage (instantaneous frequency deviation) on the X-plates and >> the corresponding RF/IF signal strength on the Y-plates. With no >> multipath, there would be a horizontal line, but with multipath, the >> IF-amplitude varied within the FM-channel. > > Oh, so multipath causes AM? That's neat... > > I'm about 70 feet (~23m?) below the antenna, which I think is a vertically > oriented dipole. I assumed near field was either blasting its way down the > building, or conducting through various dubiously grounded structures (I > have reason to believe the steam radiator along the outer wall carries more > RF than the nearby outlet). Oh well, in the city there's certainly no > shortage of reflection paths. There's an apartment building the same height > just a block away. > With GSM the trouble is more in the negotiating sequence where you see multiple bursts of carrier. This gets rectified even in circuits where you thought they'd never "see" 1.8GHz stuff. But they see enough to cause the rectified rat-tat-tat in the signal. All it takes is one BE junction, somewhere in the path. Beads are typically not terribly effective up there, I use RC or dedicated GHz-mufflers such as the Murata line for that. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Nico Coesel on 27 Dec 2009 15:34 "mook johnson" <mook(a)mook.net> wrote: >I've never found an application where a I felt a ferrite bead as head ahd >shoulders over a resistor or some other means filtering the signal. Most of >the develpments Im involved with are power conversion and data acquisition >(ADCs and DSPS)from various sensors. > >For lowish frequency stuff (say sub-10MHz) in what applications would a >ferrite bead be the bees knees? I use ferrite beads liberally. Everything that goes outside gets a ferrite bead. I also use ferrite beads to decouple power supply sections (analog / digital). -- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico(a)nctdevpuntnl (punt=.) --------------------------------------------------------------
From: Joerg on 27 Dec 2009 16:10 Nico Coesel wrote: > "mook johnson" <mook(a)mook.net> wrote: > >> I've never found an application where a I felt a ferrite bead as head ahd >> shoulders over a resistor or some other means filtering the signal. Most of >> the develpments Im involved with are power conversion and data acquisition >> (ADCs and DSPS)from various sensors. >> >> For lowish frequency stuff (say sub-10MHz) in what applications would a >> ferrite bead be the bees knees? > > I use ferrite beads liberally. ... We don't want no liberal beads out here :-) > ... Everything that goes outside gets a > ferrite bead. I also use ferrite beads to decouple power supply > sections (analog / digital). > Hint to others (I am sure you know): Put a dab of softish glue on it so it won't rattle on the wire. Nothing as aggravating as a notorious rattle or, worse, shattered beads. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: qrk on 27 Dec 2009 18:04 On Sat, 26 Dec 2009 21:33:16 -0600, "mook johnson" <mook(a)mook.net> wrote: >I've never found an application where a I felt a ferrite bead as head ahd >shoulders over a resistor or some other means filtering the signal. Most of >the develpments Im involved with are power conversion and data acquisition >(ADCs and DSPS)from various sensors. > >For lowish frequency stuff (say sub-10MHz) in what applications would a >ferrite bead be the bees knees? > >Just want to make sure I'm not overlooking a useful electrical component. > >thanks guys. > > I use ferrite for religious purposes on most of my boards.
From: Joerg on 27 Dec 2009 18:38
qrk wrote: > On Sat, 26 Dec 2009 21:33:16 -0600, "mook johnson" <mook(a)mook.net> > wrote: > >> I've never found an application where a I felt a ferrite bead as head ahd >> shoulders over a resistor or some other means filtering the signal. Most of >> the develpments Im involved with are power conversion and data acquisition >> (ADCs and DSPS)from various sensors. >> >> For lowish frequency stuff (say sub-10MHz) in what applications would a >> ferrite bead be the bees knees? >> >> Just want to make sure I'm not overlooking a useful electrical component. >> >> thanks guys. >> >> > I use ferrite for religious purposes on most of my boards. Prayer beads? :-) -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |