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Old October 28th 05, 09:23 AM
Reg Edwards
 
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Default HIGH Q CAPS FOR VLF LOOP ANTENNA?


TRABEM wrote in message
...


I think you are heading down the wrong path with the series circuit

as your
fighting a loosing battle. Assuming a perfect coil and capacitor

you create
an infinite Q circuit. Now you hook it up in your circuit. First

there has
to be enough resistance to develop the voltage , and here is the

rub, as you
increase the resistance to develop a voltage you decrease the Q.

Yuk!

Go with a parallel circuit like the rest of the world uses and you

will be
going in the right direction.



I think I'm starting to get it. Am I cutting off my foot to spite my
face::

Comments made by you and a few others have nudged mein the right
direction.....

The higher I make the series resonant Q, the lower the impedance

goes,
hence it's almost impossible to get a lot of voltage out of it??

Not sure why it matters that much. But, I was under the impression
that a perfectly matched antenna and front end would only decrease

the
Q by a factor of 2.

Follow along with Richard's comments if you like and add your

comments
as I check here often and read everything, sometimes many mant y
times::

Regards,

T

PS:I had begun thinking that the higher imedance presented by a
parallel loop was harder to match with a balun, which is why I

started
thinking of a series loop. I'm gettin there, thansk again.

=======================================
Trabem,

This discussion is getting you nowhere very fast.
So let's summarise.

I don't have your exact dimensions but the following are good enough.

L = 27uH, Reactance = j10 ohms, Conductor loss = 0.05 ohms, ESR =
0.01 ohms, Radiation ohms = 0. Receiver input = 10 ohms, Ground
loss ohms = 0.01

The intrinsic Q of the loop is 10 / 0.05 = 200.

The working Q of the loop, when series connected, is Reactance divided
by the SUM of all resistances including the receiver.

Working Q = Reactance / ( 0.05 + 0.01 + 10 + .01 ) = 10 / 10.07 =
0.993

Take note of the ridiculous low value of working Q due to the loop
being in series with the receiver.
----
Reg.


 
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