Another "Eureka!" moment
2009-Jul-13, Monday 18:25![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
texxgadgetDont let the math & theory in this post scare you off.
Whats important to this post is where the math & theory take me.
If you dont follow the math & theory, keep reading anyway.
Im presently 1st VP & Program Chair of the East Bay Radio Club.
I booked "AWR" f4om the Alameda club to speak on antenna analysis.
Im very glad I did. Dave went into transmission line theory where
I got my latest "Eureka!" moment.
I have had a number of times when I was unable to learn a topic when
I was younger. Recently, Ive stumbled across someone who cut through
all the bull and explained it right out where it clicked. College trig,
which I flunked twice, suddenly came to me in about 20 minutes via a
Wikipedia article a couple summers back. No screwing around and I just
got it. My college prof never said "Trig is about right triangles" which
is probably the 1st & most important thing to ever say about trig.
Im becoming very critical of the teaching profession because I now
realize what dunderheads, most of the teachers Ive ever met actually are.
My AC power theory class didnt work out and that unraveled my AA in
electronics and thats there this story comes in.
In DC power, direct current, ohms law is very simple.
Voltage = amps times resistance. Watts = volts times amps.
If your circuit is purely resistive, it works for AC too.
If there is inductance or capacitance or both, then things start getting
dicey. Capacitive & inductive circuits are "reactive". Resistance in
a reactive circuit changes, depending on frequency. I got that part too.
Inductive reactance = 2 pi freq times inductance OK
Where I got all screwed up was when we had to start doing polar to
rectangular conversion. You calculate your inductive reactance and
your capacitive reactance, both expressed in ohms like resistance and
then you do this polar to rectangular conversion stuff and then you
number crunch before converting back for your answer.
Things like power factor conversion depend on this stuff.
ICK !!!
Enter Dave:
Among other things is the interesting fact that capacitive reactance
in ohms is positive and inductive is negative. This would explain
why for a given frequency, if the reactance of the inductance is the
same as the reactance of the capacitance, you have a resonant circuit.
Since the 2 types of reactance are of opposite polarity, if the values
are the same, they cancel and have resonance.
Old Man Carlson ! Why didnt you explain is this way !
Now I need to do some more reading on the subject to fill in a few
still missing pieces but this positive ohms vs negative ohms is the
glue that ties the whole thing together.
Any why do we have to do polar to rectangular conversion ?
Because AC wave forms have angles in them and thats where trig
figures into the whole mess. Im not totally there yet, but I have hopes
of it all coming to "gel" soon.
This was quite apropos, being the 153rd birthday of Nikola Tesla.
We raised our coffee cups in his honor at the break during the radio
meeting last Friday. Google had a nice piece of artwork recognizing him.
Mr Edison is a son of a bitch who can rot in hell for all I care. He
stole most of his ideas from others, but dont get me started on that not
my anger towards the Smithsonian for doing the bidding of the Edison
Institute and denying Dear Nikola his rightful place in history.
One more time with feeling:
Up YOURS ! Edison, you f'ing bastard!
Whats important to this post is where the math & theory take me.
If you dont follow the math & theory, keep reading anyway.
Im presently 1st VP & Program Chair of the East Bay Radio Club.
I booked "AWR" f4om the Alameda club to speak on antenna analysis.
Im very glad I did. Dave went into transmission line theory where
I got my latest "Eureka!" moment.
I have had a number of times when I was unable to learn a topic when
I was younger. Recently, Ive stumbled across someone who cut through
all the bull and explained it right out where it clicked. College trig,
which I flunked twice, suddenly came to me in about 20 minutes via a
Wikipedia article a couple summers back. No screwing around and I just
got it. My college prof never said "Trig is about right triangles" which
is probably the 1st & most important thing to ever say about trig.
Im becoming very critical of the teaching profession because I now
realize what dunderheads, most of the teachers Ive ever met actually are.
My AC power theory class didnt work out and that unraveled my AA in
electronics and thats there this story comes in.
In DC power, direct current, ohms law is very simple.
Voltage = amps times resistance. Watts = volts times amps.
If your circuit is purely resistive, it works for AC too.
If there is inductance or capacitance or both, then things start getting
dicey. Capacitive & inductive circuits are "reactive". Resistance in
a reactive circuit changes, depending on frequency. I got that part too.
Inductive reactance = 2 pi freq times inductance OK
Where I got all screwed up was when we had to start doing polar to
rectangular conversion. You calculate your inductive reactance and
your capacitive reactance, both expressed in ohms like resistance and
then you do this polar to rectangular conversion stuff and then you
number crunch before converting back for your answer.
Things like power factor conversion depend on this stuff.
ICK !!!
Enter Dave:
Among other things is the interesting fact that capacitive reactance
in ohms is positive and inductive is negative. This would explain
why for a given frequency, if the reactance of the inductance is the
same as the reactance of the capacitance, you have a resonant circuit.
Since the 2 types of reactance are of opposite polarity, if the values
are the same, they cancel and have resonance.
Old Man Carlson ! Why didnt you explain is this way !
Now I need to do some more reading on the subject to fill in a few
still missing pieces but this positive ohms vs negative ohms is the
glue that ties the whole thing together.
Any why do we have to do polar to rectangular conversion ?
Because AC wave forms have angles in them and thats where trig
figures into the whole mess. Im not totally there yet, but I have hopes
of it all coming to "gel" soon.
This was quite apropos, being the 153rd birthday of Nikola Tesla.
We raised our coffee cups in his honor at the break during the radio
meeting last Friday. Google had a nice piece of artwork recognizing him.
Mr Edison is a son of a bitch who can rot in hell for all I care. He
stole most of his ideas from others, but dont get me started on that not
my anger towards the Smithsonian for doing the bidding of the Edison
Institute and denying Dear Nikola his rightful place in history.
One more time with feeling:
Up YOURS ! Edison, you f'ing bastard!
