On Thu, 27 Oct 2005 20:52:45 -0400, TRABEM wrote:

I have a series resonant loop with moderately large conductor wire and
reasonably high Q capacitors. It's tuned to resonate at 60 KHz.

A series resonant loop. First, this is a contradiction in terms and
as your interpretations hinge upon this reading, it bears examination.

A series tuned circuit is a low impedance circuit, so 60 KHz signals
from the antenna are passed to the receiver

To be in series, you have to describe the source and its common, you
simply describe the loop. With this, you neglect the coupling between
the actual source of power, a remote transmitter, and the antenna's
Radiation Resistance. This value appears no where in your analysis
and yet it is largely responsible for the atrocious efficiency of this
breed of antenna.

I've thrown together a quick model of your 5M on a side loop using
(and being generous) #1 wire. The bottom of the loop is 10M above
ground. In terms of performance relative to an isotropic antenna it
is down 60dB. It displays an impedance of:
Impedance = 0.05849 + J 10.37 ohms
An addition of a 0.2555µF capacitor draws this down to:
Impedance = 0.05851 + J 0.006073 ohms

Please note that the capacitor is perfect, no ESR whatever. In a
system with Zc = 0.0585, this antenna presents a 1.11 SWR. The half
power points of its resonance are only 600 Hz apart. Hence a Q of
100.

This is without any extraneous detector circuitry whatever. We will
see where its addition leads.

By simply inserting your 2 Ohms (I know full well where my 10 Ohms
will take us) - in series - (again, your thesis) and re-assigning the
system Zc to that same 2 Ohms, this antenna presents a 1.077 SWR.

Sounds hunky-dory, right? Except when you look at the Q which has
plunged to 2.9 and the antenna loss now compares to -75dB compared to
an isotropic.

Your receiver, in series with the loop, has just killed 15dB of gain
and wiped out the Q by 95%. Not bad for a day's work.

I will forgo the remainder of your questions to allow you to digest
the material above. You can validate these readings by using EZNEC
which in its free version is perfectly suitable to this question.

-------------------------------------

schematic I sent you by email.

Didn't get it. My Kill filters barely let your last schematic
through.


Not sure what I did to deserve an honored position in your kill file.

This is not the kill file of unsophisticates simply ignoring by
posting name. Agent has much more flexibility to read headers and
judge what is spam. Works great and eliminates that source by - well
I cannot guess the amount simply because I don't count the kills, and
none survive the trash can except those at a lower level of sifting.

I'm getting a lot of correspondence right now helping designers out.
About half a dozen posts a day. Seems to be peak season and their
mail lands in my inbox without incident.

I confess to being stubborn and cranky, but I don't think I was
disrespectful or made inappropriate comments. I won't email you
anymore schematics.

I simply pointed out I've only receive one of your emails, and the
kill files put it in the trashcan - that is one step above absolutely
erasing it. The presumption from the several kill-rules is that your
headers appear to be spoofed. Now, tell me that you aren't doing
something out of the ordinary like passing mail through an open relay.
;-)

73's
Richard Clark, KB7QHC