On 11/11/2014 2:42 PM, Lostgallifreyan wrote:
Wimpie wrote in :

Never mind Maxwell, why is no-one asking "why is an electromagnet not
used as an antenna when driven by AC?" That should be a basic reality
check because I've neve heard of such a thing working, and if it did it
would be widely known.

You may know that an AC current through a loop does generate near
fields, and far (EM radiation) fields. This follows from Maxwell's
equations. The solution for radiated power from a loop carrying AC
current is:


I did know, but I didn't think it through. What I had in mind was the kind
of electromagnet usually used to simulate a magnet, one with a big
lump magnetic material to guid the flux and concentrate it, etc. I imagine
the moment you do that, you get closer to a normal magnet, but it probably
makes the coil unusable as an antenna at the same time.

I think there are a lot of things you don't think through, lol. Ever
hear of a ferrite core antenna? Not much different. Why would an iron
core make a poor antenna?

--

Rick

rickman wrote in :

I think there are a lot of things you don't think through, lol. Ever
hear of a ferrite core antenna? Not much different. Why would an iron
core make a poor antenna?


Fair enough. I'll plead diminished responsibility though. I repaired an
amp during 5 hours at a house yesterday where the guy smokes. I don't, but
passive smoking does my head in sometimes. I fixed the amp just fine, but by
the time I got back here my brain was mush.

On 11/12/2014 5:43 AM, Lostgallifreyan wrote:
rickman wrote in :

I think there are a lot of things you don't think through, lol. Ever
hear of a ferrite core antenna? Not much different. Why would an iron
core make a poor antenna?


Fair enough. I'll plead diminished responsibility though. I repaired an
amp during 5 hours at a house yesterday where the guy smokes. I don't, but
passive smoking does my head in sometimes. I fixed the amp just fine, but by
the time I got back here my brain was mush.

Most of the posts in this thread are jim and Gareth arguing so I'm going
to killfile it. If you have anything else to say I won't see it unless
you start a new thread.

--

Rick

"rickman" wrote in message
...
Most of the posts in this thread are jim and Gareth arguing

Incorrect.

The onslaught of abuse comes only from Jim, whereas I play the
role of the patient schoolteacher dealing with the unruly disruptive
infants that are Jim (and you, and Lostie).

In your own case, see above.