On Nov 18, 3:14 am, Tony Giacometti wrote:


how do I calculate the dimensions of the coupling loop?

It's really not that critical. But there is a "sweet spot"
where you get the maximum coupling.
The best way is to just test it and see where you get
the strongest level, and nail it down.
I'm looking at my 44 inch per side loop, and the coupling
loop is about 5 inches inside of the main loop windings.
It's a plain single wire.
On my 16 inch loop, it's a circle, and is built on a
plastic humidifier blower housing. The motor mount
acts as the boom to attach to the mast.
When it's on the stand, it almost gives the impression
of some kind of perverted microwave dish at first
look... :/
It's coupling loop is a three turn coax shielded loop
that is appx three inches away from the main coil.
It's also slightly less across, and is about a 12 inch
loop inside the 16 inch loop. Yes, it has a gap in the
shield at the top, which is the center of the total
length of the coax.
I tested various coupling loops on that one, and
got the best level using the three turns, and the
use of a "shielded" coax loop just aids in better
balance. The main coil is plain insulated #12 wire.
As you can tell in the recordings, my nulls are deep.
In most cases with groundwave path signals, I can
make an unwanted station vanish if I want.
That applies to local single source noise too..
My usual culprit is line noise due south or north
or me. But I can kill 95% of it. I'm lucky it seems
to come from one location.
In general, the nulls are not near as good with actual
skywave signals late at night. But they can still
help a bit, as they tend to reject a bit of unwanted
crud vs a larger wire antenna.
If I'm listening to the BC band, I'm always on the loop,
no matter what the time of day. I prefer it even with
skywave signals. But due to the generally lower
signal levels on the weaker 160m band, it's a bit
different animal.
You might have better luck on 160 using say a set
of phased short verticals.
There was a thread talking about those just the other
day. I think W8JI uses those quite a bit, and I
know he often works stuff I don't even hear on the
transmit vertical, or one of my loops.
On 160, I think just being vertical is an advantage
for long haul DX.
Either that or use beverages, which I'm gonna assume
are probably not possible at your QTH...
BTW, one time I hooked the 16 inch loop to a
AC/Delco car radio in a truck.. Worked great.
MK