[Lowfer] Re: [Lowfe Worthwhile going to Shielded loop?r]

[John Andrews]

Paul,

> Why do  you suppose that there a common notion that says the shielded loop
> is quieter?

Some of it traces back to the use of shielded loops on aircraft, where they
really do help with precipitation static. Shielded loops are also used in
field strength measuring equipment, where they pretty much eliminate the
"hand capacitance" effect. It's also possible that the shield has a greater
positive effect with unbalanced loops than with balanced. As Bill noted in
his message, I see great advantage in keeping the loop balanced with respect
to ground.

>  Is your loop located far enough from the house that maybe manmade noise
is
> not a problem?

I only wish that I had your space! The loop is only about 30 feet from the
house.

> Perhaps if your only alternative to listen to LF was from an inside the
> house location, the shielded antenna have its desired effect?
> Seems to me Palomar made a shielded loop for table top use.

Could be.

> To some extent it would seem that size doesn't matter....  for loop
antennas
> anyway.  Until the antenna "gain" and system noise figure become greater
> than the noise floor, seems like the smaller antenna doesn't hurt you.

As long as the desired signal stays above the S/N threshold that permits
detection, if you increase the incoming signal+noise, you're not
accomplishing much. Of course you may wish to get rid of the preamp you'll
likely need with a smaller loop. I use a W1VD-designed model that is quiet
and robust, so it hasn't made much difference at my place.

> I have a nearly 3 foot long loopstick I could try in the woods sometime.
> Maybe I will do that.  It is tuned for about 160 to 190 Khz

Worth trying. The signal+noise will be lower than the other loops we've
talked about, so be prepared to use a quiet preamp.

John A.