Electromagnetic waves via antenna questions

[IotaYodi]

I know when an electric signal is transmitted from an antenna that the electric field and the magnetic fields alternate. A few questions I have is on the magnetic field part.
Does the magnetic field reverse polarity as it travels?

Does a pulsed dc generated signal do the exact same thing as Ac with the magnetic field?

Is the the oscillating frequency of the magnetic field itself responsible for the coupling to the receiving Antenna? 

Tried to search this but didnt find anything.
Frank

[the_big_m_in_ok]

... Does the magnetic field reverse polarity as it travels? ...

It should.  That's how a transformer works.  AC coming out of the wall reverses electromagnetic polarity with each cycle of frequency.

Does a pulsed dc generated signal do the exact same thing as Ac with the magnetic field?

An unfiltered single diode-rectified signal would be a changing magnetic field going in one direction.  If you look at it on a oscilloscope, it's a series of rising and falling voltages from 0 to the line voltage.  Capacitor filtering this reduces the voltage changes to a ripple on the scope.

Is the the oscillating frequency of the magnetic field itself responsible for the coupling to the receiving Antenna?  ... Tried to search this but didnt find anything.

Well, all kinds of competing signals would be present on a long wire, which is why a radio or TV has channel selection electronics to filter out unwanted crosstalk signals.  (Doesn't always work, from personal experience.)
To answer your question:  It should be the radio waves impacting the antenna that causes voltage fluctuations.  So, do radio waves have a magnet field, as such, as part of its manifestation as they emanate from an antenna?  Does light?

I'd say, "No".  It takes the imposition of matter in the form of a wire or antenna to manifest a magnet field in a conductor.

--Lee

[IotaYodi]

I'd say, "No".  It takes the imposition of matter in the form of a wire or antenna to manifest a magnet field in a conductor.

My interest was in the free air as far as the magnetic field and its polarity goes. From your statements the polarity of the ac/dc signals do change in free air so that does answer the question. I was trying to visualize 2 identical signals in opposite directions colliding in air creating 2 vertical and horizontal planes intertwined so to speak. I guess it would just be scattered whether they were in phase or not.
http://www.astronomynotes.com/light/emanim.gif
Thanks Lee!!
Frank   

[the_big_m_in_ok]

... I was trying to visualize 2 identical signals in opposite directions colliding in air creating 2 vertical and horizontal planes intertwined so to speak. I guess it would just be scattered whether they were in phase or not.
http://www.astronomynotes.com/light/emanim.gif

I envision two signals 180 deg out of phase to each other on the same conductor.  Is that what you meant?  Interesting graphic, though.

If so, it's something I have no experimental experience with.  The concept is a new one for me.

Thanks Lee!!
Frank   

Sure, you bet.  Glad to help.

--Lee