Concepts that I did not learn in the seventies...

Thread Starter

Externet

Joined Nov 29, 2005
1,960
Greetings.

If I find a dozen new explanations for return loss and radiation resistance, perhaps I will someday grasp the concepts... It used to be standing wave ratios and feedpoint impedances...
There is teachers with a lot of clear knowledge and poor teaching skills; as there is great teachers with unclear concepts.
Finding the best of both is uncommon. People that only know to toss links are too abundant.

Can you attempt to formulate your own explanations ?

----> https://www.w8ji.com/radiation_resistance.htm
----> https://antennatestlab.com/antenna-education-tutorials/return-loss-vswr-explained
 

nsaspook

Joined Aug 27, 2009
10,698
A rough analogy that hopefully won't muddy the water too much?

1651868739660.png
Z = ROhmic + Rrad + iXantenna,
"where ROhmic is the ordinary resistance of the conductors of the antenna as measured at its terminals, and Xantenna is the (capacitive and inductive) reactance of the antenna"
1651868838843.png

Antennas are a type of transformer/transmission that converts near-field EM energy into far-field EM energy and back. Look at it mechanically as a system with an engine (RF transmitter), coupled to a transmission (RF match), to drive shafts, differential, to drive wheels (antenna system) on the road (free-space). You can see radiation resistance as the power transfer match-up in motion from the shaft torque (from engine power) on the wheels to the traction of wheels hitting (friction) the road. Radiation resistance is a type of geometric (voltage/current ratios of the same power with higher currents causing more non-radiation ohmic losses) coupling of forces with slip. Tiny skinny tires on a large heavy truck would have low Radiation resistance. You can change everything in the motor/transmission system but it won't change the fact you're movement power transfer limited by the tires (radiating part of the antenna). The mismatched shaft power to the wheel will be wasted as heat and burned rubber (antenna losses). A suitable set of tires matched (free-space resistance) to the shaft torque and tire friction will be able to transfer more power with fewer losses.

This guy can explain reflections VSWR.
 
Last edited:

Ya’akov

Joined Jan 27, 2019
6,856
A rough analogy that hopefully won't muddy the water too much?

View attachment 266587
Z = ROhmic + Rrad + iXantenna,
"where ROhmic is the ordinary resistance of the conductors of the antenna as measured at its terminals, and Xantenna is the (capacitive and inductive) reactance of the antenna"
View attachment 266588

Antennas are a type of transformer/transmission that converts near-field EM energy into far-field EM energy and back. Look at it mechanically as a system with an engine (RF transmitter), coupled to a transmission (RF match), to drive shafts, differential, to drive wheels (antenna system) on the road (free-space). You can see radiation resistance as the power transfer match-up in motion from the shaft torque (from engine power) on the wheels to the traction of wheels hitting (friction) the road. Radiation resistance is a type of geometric (voltage/current ratios of the same power with higher currents causing more non-radiation ohmic losses) coupling of forces with slip. Tiny skinny tires on a large heavy truck would have low Radiation resistance. You can change everything in the motor/transmission system but it won't change the fact you're movement power transfer limited by the tires (radiating part of the antenna). The mismatched shaft power to the wheel will be wasted as heat and burned rubber (antenna losses). A suitable set of tires matched (free-space resistance) to the shaft torque and tire friction will be able to transfer more power with fewer losses.

This guy can explain reflections VSWR.
This film is probably my second favorite instructional video after the reference frame one of a slightly later vintage and possibly a couple of others from that series, in any case it is very good and it also shows the evolution of knowledge as new things were learned about the equivalence of mechanical and electromagnetic waves.
 

nsaspook

Joined Aug 27, 2009
10,698

MrSalts

Joined Apr 2, 2020
2,618
Yes. I wish people produced content like that now. That they used purely practical demos is great. Computer animation is a great thing but a physical demonstration is much more enlightening to the careful observer.
I seem to find good to excellent content every day on YouTube. It takes time, effort to create search terms and discipline to not go down rabbit holes of Autoplay that end up taking you to kitten videos.
 

nsaspook

Joined Aug 27, 2009
10,698
Yes. I wish people produced content like that now. That they used purely practical demos is great. Computer animation is a great thing but a physical demonstration is much more enlightening to the careful observer.
People do produce good content like this today that try to explain complex concepts in a practical way.

The Classic
The Big Misconception About Electricity
With 14 million views and

How Electricity Actually Works
5 million views

are good examples.

But, even if you're actually an expert:
https://en.wikipedia.org/wiki/Derek_Muller
Muller was born to South African parents in Traralgon, Victoria, Australia, and moved to Vancouver, British Columbia, Canada, when he was 18 months old.[3] In 2000, Muller graduated from West Vancouver Secondary School.[4] In 2004, Muller graduated from Queen's University in Kingston, Ontario, with a Bachelor of Applied Science in Engineering Physics.[5]

Muller moved to Australia to study film-making, but instead enrolled for a Ph.D. in physics education research from the University of Sydney, which he completed in 2008 with a thesis: Designing Effective Multimedia for Physics Education.[6]
there are legions of nitwits that will treat your educational series like dog poop.
 
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