[Lowfer] Really big coils- VA3LK

Larry Kayser kayser@sympatico.ca
Tue, 1 Aug 2000 11:01:51 -0400

Paul es group.....

>I wonder if anyone has tried building a really big coil out of CATV line.
>I can easily be formed into 3 or 4 foot dia circles and even more. With the
>right lenght to
>dia. ratio yield a very hi Q coil.  The cable diameter .5" to 1.125" and is
>relatively light.
>Might be OK for base loading.  Any ideas on this crazy scheme.

I have tried using some black jacket aluminum shield coax here at the 4 ft
diameter and I was not able to in the few hours I had to work on it make the
coil perform.  I unrolled the coax and used it as a radial were it made a
measureable contribution.  IF I have the sense right very high performance
coils, Hi Q included are when the coil approaches square, diameter by
length.  The Q seems to improve quickly when one goes to an odd number of
vertical winding posts and creates what I think is called the basket weave.
My next series of loading coils here will be LITZ wire on a basket weave in
a square format with a small variometer at the top for screwdriver motor
tuning under PC control.

>Also has anyone heard VA3LK on 137.710.   I am very dissapointed that I
>cannot hear/see him using
>Spectran 4.0 and a 200 foot long wire.  I heard that there was a good
>in Western PA and also that someone
>1100 miles away recently copied him  I gotta be doing something wrong.
>137.710 correct with 800 Hz  CW note?
>Also no sign of his friend 14 Hz down.

There are a number of issues for this, not sure of all of them but a 200 ft
long wire is from my experience here a lousy LF receiving antenna.  My best
results last winter were with a 1000, 2000, and 4000 ft Beverages laying on
the ground, terminated in about 500 ohms and using copper pipes bashed into
the ground - which is really horizontal under the soil and above the rock
hi.  I have an email from a chap in Maine who copies the test signal on his
speaker most of the time, his antenna is very significant, ie big.  From my
meager experience it is essential to go through a very hard learning curve
with this LF receiving bit, hearing weak signals is a complete layer of
significant effort under the general listening on LF.

I offer this hint.  I have a large coil and capacitor that is series
connected on any broadband antenna to resonate on 137 kHz.  This assembly
makes and amazing difference for weak signal reception.

The last point was that I have learned that the use of the DSP programs Gram
etc. need to be diddled a lot to get the last few dB out of them.  When I
was looking for WA2XTF (AMRAD beacons in the Washington area) I spent months
seeing a faint line that I came to know was them, the second signal 5 Hz
away was similarly there but not readable (and it never has been readable
here).  One after noon I looked up and there on the screen was the complete
call sign.  The point of this comment is that I was near the threshold for a
long time before I managed to pull them out of the mud.  My total of heard
reports for the test transmissions from here on 137.710 is now over 20, I
know this as I am making up the SWL/QSL cards for those who have been kind
enough to send in reports.  I know that if you are not able to hear the NPG
rtty on 135.95 at times that you will not hear me.  If you need the full
data on NPG let me know I will get my log book and send you a summary of
information on that signal.

The VA3LK test signal on 137.710 continues at this time transmitting EVEN
hours UTC with .4 wpm CW.  If you are having trouble identifying the signal
I can send you a .jpg of what others are seeing so you can have a sense of
finding the signal in the noise.