On Feb 2, 3:42*am, "Antonio Vernucci" wrote:
Tom,

the story began when, a few days ago, I was going to replace a trap of my HF
yagi. Not to make mistakes, I consulted the antenna assembly manual where I
found a big banner: do not invert traps otherwise the antenna will not work.

So, I thought, this is a case in which a bipole cannot be inverted.

This is clearly due to the fact that the external body of the trap (an aluminuim
can about 2 feet long), which contains two coils resonated at different
frequencies by means of built-in capacitors, is effectively part of the antenna
radiating element. So, the trap is a bipole not only comprising lumped elements,
and that is the reason why it cannot be inverted.

So, as K1TTT has pointed out, a bipole can be inverted without consequences only
if it has only 2 ports, has only passive linear components, and is small enough
to be considered a lumped element.

73

Tony I0JX
Rome, Italy

A bipole is symmetrical, obviously the internal circuity of the trap
is not symmetrical .

Jimmie

A bipole is symmetrical, obviously the internal circuity of the trap
is not symmetrical .

Jimmie, that is not the point.

- if the bipole is made of lumped components, then it can be freely reversed
without consequences, independently of whether it is symmetrical or asymmetrical

- a trap, which instead contains a distributed element (that is the radiating
trap body), can be freely reversed without consequences only if it is
symmetrical (which is not my case).

73

Tony I0JX

Hello Tony,

On 2 feb, 19:14, "Antonio Vernucci" wrote:
A bipole is symmetrical, obviously the internal circuity of the trap
is not symmetrical *.

Jimmie, that is not the point.


At some frequency, everything becomes a distributed component, it
depends on size/lambda ratio and application. Many distributed
components can be modelled based on theoretical lumped components
(with sufficient accuracy), but a ground for modelling stray
capacitance is frequently required.

True lumped component behaviour, in my opinion, only applies to
networks with size=0.

- if the bipole is made of lumped components, then it can be freely reversed
without consequences, independently of whether it is symmetrical or
asymmetrical

What do you define as "lumped component"?

- a trap, which instead contains a distributed element (that is the radiating
trap body), can be freely reversed without consequences only if it is
symmetrical (which is not my case).


I agree on the above.


73

Tony I0JX

Best regards,


Wim
PA3DJS
www.tetech.nl
without abc, PM will reach me

On Feb 2, 7:06*pm, Wimpie wrote:
Hello Tony,

On 2 feb, 19:14, "Antonio Vernucci" wrote:

A bipole is symmetrical, obviously the internal circuity of the trap
is not symmetrical *.

Jimmie, that is not the point.

At some frequency, everything becomes a distributed component, it
depends on size/lambda ratio and application. *Many distributed
components can be modelled based on theoretical lumped components
(with sufficient accuracy), but a ground for modelling stray
capacitance is frequently required.

True lumped component behaviour, in my opinion, only applies to
networks with size=0.

'True' or theoretical versus 'practical' is a very important
distinction that is, or at least was, taught in engineering classes.
it is very important to know when you can apply the practical
simplifications that allow you to do design work without worrying
about insignificant phenomena in the problem domain you are working
in... so if i am designing an HF antenna I know that objects below a
given size can be safely ignored, but if i'm doing a microwave design
i have to take into account much smaller objects.