On 11/07/2020 14:57, Jim H wrote:
===================================
Antenna Matching Units ( I prefer not to use the word "Tuner") do have
fixed resistance in inductors and wiring as has been stated in this thread.

Frank , EI7KS

Jim H wrote:
On Tue, 14 Jul 2020 18:07:01 +0100, in ,
Jeff wrote:

On 14/07/2020 14:16, wicklowham wrote:
On 11/07/2020 14:57, Jim H wrote:
===================================
Antenna Matching Units ( I prefer not to use the word "Tuner") do have
fixed resistance in inductors and wiring as has been stated in this thread.


No! The amount of inductance varies depending on how much of the
inductor is used, thus the resistance of the unit varies with the
setting. Resistance also varies with frequency since the skin effect
is "deeper" (lower resistance) with lower frequency.

And, the antenna resistance to be matched also varies. When the
antenna is too short it will have a lower resistance, and thus any fixed
losses in tuner and feeder will have a higher relative effect.

All in all it is a completely wrong assumption that the losses will
be independent from frequency, even when te resistive values in the
tuner would be the same.

Hi Rob, Jim, Jef, all.



Thanks for continuing on this small thread.
As said, I asked this as a fundamental" question, so I am really
learning a lot here.


(see inline comment)



On 15/07/2020 16:27, Rob wrote:

Antenna Matching Units ( I prefer not to use the word "Tuner") do have
fixed resistance in inductors and wiring as has been stated in this thread.

No! The amount of inductance varies depending on how much of the
inductor is used, thus the resistance of the unit varies with the
setting.

OK. makes sense.


Resistance also varies with frequency since the skin effect
is "deeper" (lower resistance) with lower frequency.

Correct me if I am wrong, but it looks to me that these two elements
(partly) counter each other.

To tune / match an antenna for a lower frequency, you need more inductor
wire (i.e. greater resistor), but the skin-effect will be lower.





BTW. I always had the idea that skin-effect was only important for
frequencies of VHF and higher, not for HF.


Are there figures of how much resistances the skin effect adds to a
wire, in respect to the frequency?

(Just to get an idea of the scale of things)



And, the antenna resistance to be matched also varies. When the
antenna is too short it will have a lower resistance
This is something I do not completely understand.


I guess you are talking the radiation resistance, correct?

As far as I understand it, the radiation resistance is a "virtual"
resistance which is created by the fact that an antenna converts
electrical energy in electromagnetic waves that are radiated, thereby
extracting energy from the wire.
This "loss of energy" in the wire is modelled as a virtual resistance.


So, saying "a short antenna has a lower resistance then a full-size
antenna", is then the same as saying "a short antenna emits less energy
then a full size antenna", which is equivalent to "a short antenna is
less efficient"



So isn't this a circular reasoning?



What exactly is the reason that a short antenna has a lower resistance?



.., and thus any fixed
losses in tuner and feeder will have a higher relative
effect.

So, are there are then two different effects at play he
- the resistance of the tuner/matching unit which changes with frequency
due to the practical way it is build
- the radiation resistance of the antenna that changes with frequency.





All in all it is a completely wrong assumption that the losses will
be independent from frequency, even when te resistive values in the
tuner would be the same.


73
Kristoff - ON1ARF

kristoff wrote:
BTW. I always had the idea that skin-effect was only important for
frequencies of VHF and higher, not for HF.

So according to you the use of litze wire in medium wave (1 MHz) radios
was a waste of effort?

You seem to have a lot of strange ideas...

Rob,




On 20/07/2020 10:29, Rob wrote:
BTW. I always had the idea that skin-effect was only important for
frequencies of VHF and higher, not for HF.

So according to you the use of litze wire in medium wave (1 MHz) radios
was a waste of effort?
You seem to have a lot of strange ideas...

Well, what did you expect? I'm just a ham.
You know: for 90 % no idea what I am doing as I am just an operator and
for 9.9 % "no idea why it is like that, but that's what they told so it
must be correct".
I'm just trying to fill that 0.1 % of *really* understanding the
technology I am using.



Usually, I am more into DSP, SDR, data-communication, signal-processing,
GNU Radio, etc.
Signal processing is based on numeric representations of voltages
(amplitude and phase), either the time or frequency-domain, at one
particular place in the circuit.

The most interesting part of this discussion here is that it requires me
to think in a different way that I am used to do, so this discussion is
very interesting to me.


The problem is that, saying "the skin-effect also has an effect" but
without really quantising it does not really help.


I still do not have an answer to my question:
Are there figures of how much resistances the skin effect adds to a
wire, in respect to the frequency? (Just to get an idea of the scale of
things)

Say for a very basic HF antenna-system: 10 meter coax, balun,
full-length dipole for -say- the 40 meter band, designed for 100 Watt RF
power.

Can you put some numbers of the impact of the skin-effect on this kind
of system?





73
kristoff - ON1ARF

kristoff wrote:
Rob,




On 20/07/2020 10:29, Rob wrote:
BTW. I always had the idea that skin-effect was only important for
frequencies of VHF and higher, not for HF.

So according to you the use of litze wire in medium wave (1 MHz) radios
was a waste of effort?
You seem to have a lot of strange ideas...

Well, what did you expect? I'm just a ham.
You know: for 90 % no idea what I am doing as I am just an operator and
for 9.9 % "no idea why it is like that, but that's what they told so it
must be correct".

Well actually this is a bit strange, because a ham usually has to pass
an exam, and the theory that has to be learned from that usually includes
the basic principles of HF electronics, including a discussion of things
like L/C circuits, Q factor, skin effect, etc.

But maybe you only did a crash course and pre-learned the 500 questions
and their correct answer, without actually understanding it.


Well, hopefully you will learn from the current discussion.

In article ,
says...

Well actually this is a bit strange, because a ham usually has to pass
an exam, and the theory that has to be learned from that usually includes
the basic principles of HF electronics, including a discussion of things
like L/C circuits, Q factor, skin effect, etc.

But maybe you only did a crash course and pre-learned the 500 questions
and their correct answer, without actually understanding it.




The test of the last 20 or 30 years have been a joke. Anyone with a
memory can pass those without knowing anything.

Around 1972 I passed the FCC First Class Radio teoephone test. There
were no books with the exact questions and answers. I did get an
Associates degree in electronics engineering about 2 years before that.
I found the test relative simple even back then.

I passed the old tech which the written was the same as a General, then
the Advanced and Extra without even looking at the questions and
answers. The tough part for me was that stupid Morse Code. Hard telling
how many hours I spent on that trying to get the receive up to 20 wpm.
Had it not been for the multiguess I never would have made that.

On 7/21/2020 1:31 PM, kristoff wrote:
Rob,




On 20/07/2020 10:29, Rob wrote:
BTW. I always had the idea that skin-effect was only important for
frequencies of VHF and higher, not for HF.

So according to you the use of litze wire in medium wave (1 MHz) radios
was a waste of effort?
You seem to have a lot of strange ideas...

Well, what did you expect? I'm just a ham.
You know: for 90 % no idea what I am doing as I am just an operator and
for 9.9 % "no idea why it is like that, but that's what they told so it
must be correct".
I'm just trying to fill that 0.1 % of *really* understanding the
technology I am using.



Usually, I am more into DSP, SDR, data-communication, signal-processing,
GNU Radio, etc.
Signal processing is based on numeric representations of voltages
(amplitude and phase), either the time or frequency-domain, at one
particular place in the circuit.

The most interesting part of this discussion here is that it requires me
to think in a different way that I am used to do, so this discussion is
very interesting to me.


The problem is that, saying "the skin-effect also has an effect" but
without really quantising it does not really help.


I still do not have an answer to my question:
Are there figures of how much resistances the skin effect adds to a
wire, in respect to the frequency? (Just to get an idea of the scale of
things)

Say for a very basic HF antenna-system: 10 meter coax, balun,
full-length dipole for -say- the 40 meter band, designed for 100 Watt RF
power.

Can you put some numbers of the impact of the skin-effect on this kind
of system?





73
kristoff - ON1ARF

Here ya go... you can put in the numbers yourself.

https://chemandy.com/calculators/ski...calculator.htm

On 7/21/2020 1:31 PM, kristoff wrote:
Rob,




On 20/07/2020 10:29, Rob wrote:
BTW. I always had the idea that skin-effect was only important for
frequencies of VHF and higher, not for HF.

So according to you the use of litze wire in medium wave (1 MHz) radios
was a waste of effort?
You seem to have a lot of strange ideas...

Well, what did you expect? I'm just a ham.
You know: for 90 % no idea what I am doing as I am just an operator and
for 9.9 % "no idea why it is like that, but that's what they told so it
must be correct".
I'm just trying to fill that 0.1 % of *really* understanding the
technology I am using.



Usually, I am more into DSP, SDR, data-communication, signal-processing,
GNU Radio, etc.
Signal processing is based on numeric representations of voltages
(amplitude and phase), either the time or frequency-domain, at one
particular place in the circuit.

The most interesting part of this discussion here is that it requires me
to think in a different way that I am used to do, so this discussion is
very interesting to me.


The problem is that, saying "the skin-effect also has an effect" but
without really quantising it does not really help.


I still do not have an answer to my question:
Are there figures of how much resistances the skin effect adds to a
wire, in respect to the frequency? (Just to get an idea of the scale of
things)

Say for a very basic HF antenna-system: 10 meter coax, balun,
full-length dipole for -say- the 40 meter band, designed for 100 Watt RF
power.

Can you put some numbers of the impact of the skin-effect on this kind
of system?

73
kristoff - ON1ARF

There is abundant information of the Web about skin effect. Have you
even tried searching? Or are you just trolling?