On Fri, 28 Oct 2005 14:19:14 -0400, TRABEM wrote:
With the current model of parallel loop...

If my receiver was 2K input impedance (whether tuned input or not),
could I connect it to my loop with a piece of 2000 ohm open wire line
and expect the net (or loaded) Q to be around 100 (assuming a 2K
impedance open wire line could be built and that my unloaded antenna Q
was 200 to start with).

Yes or No?

You have too many suppositions to give a straight answer. First,
there is no such thing as a 2000 Ohm open wire line. As for the gist
of the question:
Yes.

With the current model of parallel loop...

If I elected to use a buffer amp with megohms of input impedance,
would I preserve the unloaded Q and end up with a net Q of about 200
because I haven't loaded the loop?

Yes or No?

Yes.

However, as Tom has pointed out separately, this may not be the
optimal solution.

I believe my receiver is microvolt sensitive and that the loop will
deliver a relatively good signal to the receiver even though the loop
isn't terribly efficient. If I build selectivity into the front end of
the receiver, do I really need high Q (200)??

I think the answer is NO.....

Well, this is a good opportunity to examine that tumble down the slope
to the Q = 2 (caused by the severe loading of your proposed design).

The correlative to this is, how much selectivity do you need in a
field where stateside VLF is relatively rare? Further, by the action
of the strong filtering that usual attends the "I" and "Q" channel
processing, you could easily repair any shortfall.

However, back to that Q = 2. That still offers respectable (not
fantastic) selectivity against signals out at the bottom of the AM
band which is 10f (one decade) away.

OK, I am with you with respect to the brain filtering out unwanted
conversations to let you focus on your conversational partners distant
voice. But, I thought traditional binaural receiver meant that the
frequencies higher than a certain point went to one ear and that the
all the frequencies lower than the same frequency went to the other
ear. In this manner the listener has a feeling of 'depth' or
'richness' that isn't present in a mono setup.

Binaural is what the fellows in white coats mean by listening with two
ears.

This is interesting though.

And rarely reported for this style of detection. What a pity.

Are you suggesting that the brain can also process the I/Q output
streams and provide opposite sideband rejection as well as selective
frequency and adaptive filtering?

The rejection is psychological, not actual. It is what I meant by
"mind-space." The vectors do not add up to zero, the mind simply
ignores the off-band content like you would at a party listening to
that cute office temp's whispers when your wife is yelling across the
room at you.

Listen to a recording of that same scenario in mono and you WILL hear
your wife!

The brain reassembles all delay/phase information content at the party
to sort out what to pay attention to. When that same information is
passed through a monaural channel, the phase information is lost and
everything competes equally lousy given the S/N ratio.

73's
Richard Clark, KB7QHC