[Milsurplus] Ferrite Loop Antennas

[J Forster]

Brooke Clarke wrote:

> Hi John:
>
> Yes, for LORAN-C it must NOT be reasonant. Those pulses take up a lot of
> bandwidth.  See: http://www.prc68.com/I/Images/Da100nf.GIF

In fact, I read in a manual, the pulse envelope is specifically amplitude shaped to
reduce bandwidth.

> But for a narrow band VLF signal you could add a bunch of caps in the radio
> room (the capacity of the coax would be small by comparison.

I'm not so sure I want to do that. Among other things, the transmission will be at 03:00
local, and I somewhat lack ambition at that hour.  8=)) I may even choose to sleep
through it b!

> An improvement would be to change from a square to a hex or octagon and space
> the wires to raise the Q.

I'm certainly not going to rewind the loop for a half hour test. Among other things,
it's in continuous use for checking and locking my local frequency standards and it
works very well for LORAN.

Best,
-John

>

> Have Fun,
>
> Brooke Clarke
> http://www.PRC68.com
> http://www.precisionclock.com
> http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam
>
> J Forster wrote:
> > The loop I'm using is not resonant. I figured that would not be a good thing for
> > LORAN, since it's a pulsed signal. The last thing I wanted was a bunch of ringing.
> > As I remember, I designed the loop to look like roughly 50 ohms at 100 KHz...  the
> > LORAN pulse frequency.
> >
> > Best,
> > -John
> >
> >
> >
> >
> > Brooke Clarke wrote:
> >
> >
> >>Hi Hue:
> >>
> >>They have small effective areas so are not optimal for weak signals.
> >>
> >>The attic antenna descrebed by J Forster sounds good.  It might be improved by
> >>spacing the wires from each other about one wire diameter to lower self
> >>capacity.  Reasonating would give you a nice high Q antenna.  A problem might
> >>be the nulls.
> >>
> >>Have Fun,
> >>Brooke Clarke
> >
> >