Is resonance really where you get best antenna performance?

[freecell]

in the case of either the center fed dipole or the common 1/4 ground plane worked against a ground system when the voltage and current traverse the distance from the feedpoint to the ends of the elements they are now (@ the ends) out of phase with the current and voltage @ the feedpoint. when the current and voltage return to the feedpoint they are in phase once again. @ a frequency of let's say 27 mhz. this cycle repeats itself 27,000,000 times every second. the phase shift occurs every 1/4 λ or every 90 degrees. for reference a full λ is = to 360 degrees.

 

[TheBlaster]

I have never seen that written in any reference material so far so thank for the explanation..however illogical and unimaginable that may be. Thanks

I cannot seem to imagine why that is the case... I thought they had a fixed phase relationship.

edit 2 add : Again I think I can visualize it now. Quite complex imagery especially when you start thinking about electric and magnetic fields as well and their relationship to each other, but we can leave those out of it, enough food for thought right there.

 

[freecell]

"I thought they had a fixed phase relationship."

if that were really the case then there would be no transverse electromagnetic "radiation." radio frequency signals are (alternating current) ac signals. current and voltage had better both be "changing."

 

[TheBlaster]

Yes the statement seems obvious when I read it now (in fact I did write that in my last post but lost confidence in what I was writing as I was not sure so deleted it). I think my brain is a bit visual based for radio and I try to imagine how these things look and until I have some imagery it just seems so abstract.... even if you cannot see oscillations beyond a few 10's of Hz.... other than light itself of course.

 

[freecell]

try this, the blue area is the (electric field) e-plane and the red area is the (magnetic field) h-plane. an antenna is a transducer, during transmitter operation it converts current and voltage into transverse electromagnetic energy while in receive mode it intercepts varying amounts of transverse electromagnetic energy and converts this back into current and voltage

 

[Wire Weasel]

Yes Yes very interesting lab experiment. With my comment earlier I was attempting to offer some simple and practical general guidance that the common street variety cb'er could understand seeing as this is in the CB Antenna Forum. But by all means you big brains carry on

 

[TheBlaster]

try this, the blue area is the (electric field) e-plane and the red area is the (magnetic field) h-plane. an antenna is a transducer, during transmitter operation it converts current and voltage into transverse electromagnetic energy while in receive mode it intercepts varying amounts of transverse electromagnetic energy and converts this back into current and voltage

Yes I can get to that in the mind from understanding your terminology. It's the traveling so far bit and miniscule amounts of energy at the RX that really fascinates me, and clearly so many others. It can be a very long journey that a voice makes and we are never 100pct sure quite how.

I never really saw myself as a particularly big brain, there are people who have got a much better grip on this stuff than I do.. but I do enjoy it nonetheless and try and pick up some knowledge when a stand out topic comes along... if you can be a bit better wherever you are on the radio knowledge scale, that's a good thing.

I will try and get my head around that GIF a bit later on, thanks.

 

[Handy Andy]

voltage and current traverse the distance from the feedpoint to the ends of the elements they are now (@ the ends) out of phase with the current and voltage @ the feedpoint. when the current and voltage return to the feedpoint they are in phase once again.

And it's the "ping" energy that if this wave is not collapsed correctly - causes a condition we see as a mis-match or high VSWR
Or do we?

Once the concept of Element location in respect to the field they generate gives us various "ohmic" results of an event - played out 27 million times a second or if you.re into the moment - movement...
Roughly 37 Pico-Seconds (One Trillionth of a Second 10-12) for one cycle.

But...​

I want to read this - in your own words, not Maxerlls, ARRL, AARP - FCC, ITU or otherwise...

Your words...as the above...

And it's the "ping" energy that if this wave is not collapsed correctly
- causes a condition we see as a mis-match or high VSWR
Or do we?​

Why do I ask, several reasons really...

Why the various impedance changes cause the SWR condition - even though antennas are using a Resonant Length of 1/2 Center-Fed antenna elements...

It is ok to show just cause of the "apparent" discrepancy - being coax and or otherwise...​

Since Transmitter output is determined to be 50 ohms - why the implications of even having poor SWR even though we are using resonate lengths?

Is it - Only by Coax mis-match or are you suggesting another ethereal event is taking place?​

​

​

 

[TheBlaster]

Could the coupling with the ether from the antenna conductors be less efficient so the RF naturally.. stays on the outside surface of this nice easy electron rich conductor and coax ? Just throwing a thought out there.

The GIF makes some sense now, clearly a parallel tuned circuit following through to an antenna (and an antenna being part of a tuned circuit coupled to its surroundings including ground in the reactive near field). I was reading that in this reactive near field taken to be 1/2 wavelength approx the system behaves like a lumped capacitor storing energy. (and losing energy in the earth below). And the earth is like a lossy capacitor. It seems the dipole elements appear as capacitive elements. And at resonance at the correct frequency electromagnetic waves are efficiently emitted into space/gasses around.

Diagrams are very helpful... it is like revision.. and supplementation. Surprising how fast the basics vacate the brain once you pass an exam and start making contacts.

 

[TheBlaster]

I just clarified in my mind why a 1/4 wave is called a 1/4 wave and a 1/2 wave dipole a 1/2 wave despite both being current fed antennas with 2 parts. It seems the dipole bottom element is also radiating and it seems radials on a 1/4 wave vertical monopole are not actually radiating. So the 1/4 and 1/2 namesake's probably come from elements that are actually radiating.

 

[freecell]

dipole antenna animation:

+ = charge, - = discharge, charge to charge or discharge to discharge = one cycle. at a frequency of 27 mhz. one complete cycle occurs every 3.703 nS. (nanoseconds) this is only 1/2 the picture since the magnetic (current) h-field component has been omitted.

 

[TheBlaster]

I had seen on a YT video that radials laid on the ground don't radiate with a monopole, someone sat there with a field strength meter and it never registered... which kind of makes sense as they would be radiating into the earth. The moving image makes sense for dipoles.

This clears up the naming convention.

 

[nfsus]

This is my 102 steel whip I've used a nano vna to tune it by adding a shunt coil at the feed point. I have no idea what length of rg8x I've used, but it's enough to get where I needed to be. The hardest pic to see is the one I took before I started tuning. Sorry about the quality.

Edit, after all guards shields and toolbox closed up I achieved a 50.0 and 1.06 whole driving

 

[ForestRunner98]

This is my 102 steel whip I've used a nano vna to tune it by adding a shunt coil at the feed point. I have no idea what length of rg8x I've used, but it's enough to get where I needed to be. The hardest pic to see is the one I took before I started tuning. Sorry about the quality.

Edit, after all guards shields and toolbox closed up I achieved a 50.0 and 1.06 whole driving

That looks great!!! Ya that shunt coil sure did the trick...you’re spot on!!!

 

[AudioShockwav]

This is my 102 steel whip I've used a nano vna to tune it by adding a shunt coil at the feed point. I have no idea what length of rg8x I've used, but it's enough to get where I needed to be. The hardest pic to see is the one I took before I started tuning. Sorry about the quality.

Edit, after all guards shields and toolbox closed up I achieved a 50.0 and 1.06 whole driving

Nice job on the toolbox mount.
The drop in cost on these nano vna's really makes them handy tools.
73
Jeff