Recent posts

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21
General Discussion / Re: PLEASE READ! Welcome to Ra...
Last post by RadioRay - November 08, 2019, 06:53:15 pm
Retirement and ham radio are a good mix. 

My Wife & I saw a plaque a few days ago that said it all:

   -Retirement -
Twice the husband.
  Half the money.



Welcome aboard -
22
General Discussion / Re: PLEASE READ! Welcome to Ra...
Last post by vy2js - November 08, 2019, 04:16:31 pm
3rd generation ham... not very active.

Retiring in 3 years so starting to delve back into the hobby.
23
General Discussion / Re: Just passed the Exra-Class...
Last post by Star Rider - November 08, 2019, 02:13:22 pm
Congrats!

There is a 'prestige' having the Extra

KN4ULD
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General Discussion / Re: PLEASE READ! Welcome to Ra...
Last post by Star Rider - November 08, 2019, 02:02:07 pm
New old guy checkin in 📻
25
Antennas / Re: Magnetic antenna query
Last post by daedalus - November 07, 2019, 11:52:59 am
I posted the same query on an antenna forum and received this answer, now I just have to research to understand it ! It has also thrown a spanner in the works on my homegrown antenna theory (different thread):

"Far from sources, magnetic and electric fields are almost interchangeable: EM waves are made up of E- and H-, but if you know E you also know H. This situation does not apply near EM sources (such as antennas that radiate) or reflectors (such as conductors).

A small loop (by small we always mean the diameter of the loop relative to the wavelength of interest, so a 1 meter loop is very small at 10 kHz but very large for 10GHz) produces only magnetic fields. A small loop is basically an inductor; it has low impedance so charges cannot be separated. Magnetic fields flow around current; a loop is current and hence is circulated by magnetic field. The loop does not allow for charge separation (because it a short circuit); so very little electric fields are produced.

Contrast that with a short dipole antenna. Very little current flows, so very little magnetic fields are produced. The voltage across the dipole though can be large, since it is not shorted out. This means there is charge separation - which is what produces electric fields.

So there aren't magnetic and electric waves, but fields, that certain structures are much more sensitive too."
26
Antennas / Re: antenna theory - fundament...
Last post by daedalus - November 07, 2019, 06:56:50 am
I will do a youtube video and share the link, it's easier for me to use a whiteboard or pad and sketch it out dynamically. The challenge I am facing is how to show simultaneously time and distance so that it doesn't become a mess of squiggles !

There is one thing holding me back at the moment, how to estimate the electric field lines for a flowing current, there are plenty of static +/- charge diagrams and quite a few which show the "kink" in the field when the charge is accelerating but nothing about an electric field line for a sea of electrons flowing , any thoughts from anyone
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Antennas / Re: antenna theory - fundament...
Last post by gil - November 07, 2019, 06:05:47 am
I'm all ears...
Gil.
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Antennas / Re: Magnetic antenna query
Last post by gil - November 07, 2019, 06:04:41 am
I wish I knew...

The fact is that a radio wave is made of both an electric and a magnetic field at 90deg to each-other, since those are generated by the tank circuit, electric field by the capacitor and magnetic field by the inductor. A magnetic loop is said to "favor" the magnetic field... Whatever than means... I do not know how that happens, but it is an interesting question to investigate...

Gil.
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General Discussion / Re: Radio Preppers on Mobile D...
Last post by gil - November 07, 2019, 06:01:14 am
Hello,

I need to reinstall the module and check the listing... Will do...

Gil.
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I really like the sound of the QSX, just what I was envisaging. Would still require something external for JS8call but love that it does a lot of other digital modes.

Thanks for the steer to OH8STN, amazing info on the site

I will research the ability to transmit on any frequency and see what the possibility is
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