But what worries me, the very thin coaxial inner conductor is in
series with the main loop conductor. It may have a loss resistance
several times greater than the large diameter main loop. You could
be losing a lot of decibels.

=====================================
Lee,

If you cut the length of coax into, say, 7 equal lengths and connected
them in parallel you will have a capacitor of the same value but with
a loss resistance only 1/7th of the single length.

More compact too. 6 fit very nicely round 1. Bundle them up in a
plastic bag to keep off the rain.
----
Reg, G4FGQ.

"Reg Edwards" wrote in message
...
Lee,

Using the loop indoors, at ground-floor level, at 20MHz, on a
groundwave path, is not inconsistent with what you get. Get it
high-up, outdoors, and it will make a big difference.

Next, after testing 2` above ground.......

The capacitor is made from a length of coax. I wonder how long it is
and how it is located relative to the loop? Wherever it is, being
unbalanced coax it will unbalance the loop.

Isn`t a variable butterfly vane capacitor unbalanced also as is the co-axial
trimpot and the compression piston cap?..they are all used on magloops Reg.

But what worries me, the very thin coaxial inner conductor is in
series with the main loop conductor. It may have a loss resistance
several times greater than the large diameter main loop. You could be
losing a lot of decibels.

I`m listening

Lee....G6ZSG.....

"Reg Edwards" wrote in message
...


Lee,

If you cut the length of coax into, say, 7 equal lengths and connected
them in parallel you will have a capacitor of the same value but with
a loss resistance only 1/7th of the single length.

RG8 / UR213 would be more convenient i should think Reg if i were running a
bit more QRO......

More compact too. 6 fit very nicely round 1. Bundle them up in a
plastic bag to keep off the rain.

I`ll try that Reg..... i have an old QRP atu with air spaced variables
around 350pf with slow motion drive i could use on a more ambitious project
a little later....good for 100watts or so SSB...Yes?

Lee...G6ZSG.......

Dear Lee (G6ZSG):
Please do note that I was commenting on a receiving antenna, which is in
need of an antenna mounted amplifier. The amplifier does not have
hard-to-accomplish requirements for gain (20 db is good) or for input
impedance. However, the amplifier does need to have very high IM
performance and at least a high-pass filter to reject signals from the AM
broadcast band.

Using a small, horizontal loop antenna as a transmitting antenna can be
done. As you are finding out, coupling power into the loop is a challenge.

Good luck. 73 Mac N8TT
--
J. Mc Laughlin; Michigan U.S.A.
Home:
"Lee" wrote in message
k...

"J. Mc Laughlin" wrote in message
...
I second what Irv (VE6BP) has suggested. The modeling that I have done
of
small loops (just plain loops, no magnetic materials involved) placed
horizontally (above earth) suggest the same pattern in all directions
with
a
significant dip towards the zenith - just what one's receiver likes in
order
to receive signals from far away.

73 Mac N8TT

--
J. Mc Laughlin; Michigan U.S.A.
Home:
"Irv Finkleman" wrote in message
...
Lee wrote:


I`ll try that Mac and see if it is worth the effort of a much larger
project.... like 10ft square multiband!!.

Thanks Mac & Irv..

Lee....G6ZSG......

The intermod performance of a receiving pre-amplifier is of no
consequence with a magloop.

The Q and selectivity (of the order of 1000) of the loop at the wanted
frequency easily reject local high-power MF broadcast frequencies.

On 160m, It's difficult to hear any stations only 3 kHz away from the
wanted frequency.
----
Reg.

"Reg Edwards" wrote in message
...
The intermod performance of a receiving pre-amplifier is of no
consequence with a magloop.

The Q and selectivity (of the order of 1000) of the loop at the wanted
frequency easily reject local high-power MF broadcast frequencies.

On 160m, It's difficult to hear any stations only 3 kHz away from the
wanted frequency.
----
Reg.


Hi Reg....

I took my little 1 meter dia ( 10 ft circ ) loop outside lunchtime and
mounted it verticaly 2ft off the lawn and tested it, not expecting anything
special and found that comparing it to the G5RV that there was no noticable
difference between the two!!...my friend and i switched out our preamps and
attenuator in.

I even turned the loop face on and edge on with a change of 2-3 S points..
So, needless to say, i am rather impressed with the performance and
bandwidth of 2:1 SWR about 180k.....so much so that i am thinking seriously
of going for a 20 ft circumference or larger for 80 and 40 metres....

Regards.

Lee....G6ZSG.....Well impressed!!! :-)

Dear Reg (G4FGQ):

I note with interest that your note was written in the early afternoon.

The subject of my communication is: small (much smaller than a
wavelength) - non-resonant (input impedance almost entirely inductive if one
looks into a single opening in the loop) - horizontal - loop antenna (no
substances with significant magnetic properties are in the vicinity of the
loop antenna) - used to receive incident EM waves (which have both E and H
components). SNRHL receiving antennas

I do not know the definition of a "magloop." Apparently, such a beastie
comprises a resonant loop antenna.

No knowledgeable person would disagree that a single tuned network with
a Q of 1000 is "narrow."

My interest in SNRHL receiving antennas comes from an interest in
practical HF receiving antennas that are resistive to types of noise that
appear only to be present at isolated, open, rural, otherwise-low-noise
sites. The noise involved does not occur in urban areas or even rural sites
with many trees.

Consider some of the excellent wine from Michigan this evening. This
state, with a coastline almost the same length as that of the island of
Great Britain, produces some excellent products for your enjoyment.

73 Mac N8TT
--
J. Mc Laughlin; Michigan U.S.A.
Home:
"Reg Edwards" wrote in message
...
The intermod performance of a receiving pre-amplifier is of no
consequence with a magloop.

The Q and selectivity (of the order of 1000) of the loop at the wanted
frequency easily reject local high-power MF broadcast frequencies.

On 160m, It's difficult to hear any stations only 3 kHz away from the
wanted frequency.
----
Reg.

Hello Lee,

Thanks for letting me know that by giving your magloop half-a-chance
it performs according to expectations.

You have also demonstrated that the G5RV is not so hot as it is made
out to be by salesmen and they who have never tried anything else.

No disrespect intended to G5RV himself, now deceased, who claimed only
that it had a nice radiation pattern on 14.15 MHz which enabled him to
work both Europe and North America from South America without having
to climb ladders and change anything.

The magloop is by far the most efficient of all the antennas of
roughly the same physical size. Both theoretically and in practice. It
will do even better if you can get it well above ground in the
vertical plane.

In the horizontal plane it works best at the higher heights, above
surrounding obstructions like buildings. But in such surroundings
there is room to erect full-size dipoles anyway, which will obviously
do better still.

The main disadvantage on the 160 and 80 meter bands is the size,
physical and capacitance-wise, of the variable tuning capacitor. You
need a vaccuum capacitor of about 1000 pF max. By correct choice of
loop dimensions and minimum capacitor setting the 40 meter band can
also be covered. On 40 meters a small magloop can be highly
efficient. Investigate using program MAGLOOP4.

Are you using the small internal coupling loop, about 1/5 diameter of
main loop, to match to a 50-ohm feedline? This is the best and most
simple way to go,

A different ratio small loop diameter is needed for other feedline
impedances. The circuit behaves as if the turns ratio on a
transformer is being changed.

Let us know how your experiments proceed.
----
Reg, G4FGQ.

"J. Mc Laughlin" wrote

Dear Reg (G4FGQ):

I note with interest that your note was written in the early
afternoon.

==========================================
My Dear J. Mc Laughlin,

Thank you for your interest in my early afternoon state of health. It
is now 19.15 hours and I have just started on a bottle of Sierra
Valley, Californian, Ruby Cabernet.

The subject of my communication is: small (much smaller than a
wavelength) - non-resonant (input impedance almost entirely
inductive if one
looks into a single opening in the loop) - horizontal - loop antenna
(no
substances with significant magnetic properties are in the vicinity
of the
loop antenna) - used to receive incident EM waves (which have both E
and H
components). SNRHL receiving antennas

I do not know the definition of a "magloop." Apparently, such a
beastie
comprises a resonant loop antenna.

=======================================
"Magloop" describes a small, single-turn, thick conductor, usually
made from copper water pipe, circular, hexagonal or square in shape,
loop. The two ends of the loop are connected together via a variable
capacitor. The capacitor tunes the inductance of the loop to a
resonant frequency at which everything happens.

The term "magnetic" arises because the near-field of a transmitting
loop is mainly magnetic as distinct from the electric field. On
receive it is more sensitive the magnetic field than the electric
field.
=======================================

No knowledgeable person would disagree that a single tuned
network with
a Q of 1000 is "narrow."

My interest in SNRHL receiving antennas comes from an interest
in
practical HF receiving antennas that are resistive to types of noise
that
appear only to be present at isolated, open, rural,
otherwise-low-noise
sites. The noise involved does not occur in urban areas or even
rural sites
with many trees.

=====================================
The noise in rural, open, oceanic areas is just the same sort as in
built-up, residential, city and industrial areas. It is all random but
there is just a lot less of it.

An antenna of any sort is just as sensitive to noise as it is to
signals provided both noise and signals are coming from the same
direction and elevation.
======================================

Consider some of the excellent wine from Michigan this evening.
This
state, with a coastline almost the same length as that of the island
of
Great Britain, produces some excellent products for your enjoyment.

=======================================
Everybody has heard of the State of Michigan with its capital city of
Detroit. I have always thought of it as an industrial state similar to
my own area of the city of Birmingham and the surrounding Black
Country of England. It is the manufacuring areas which produce the
REAL wealth of this World of ours. Not forgetting the farmers.

Never having had the opportunity to visit Michigan it has not occurred
to me that the land could also grow grapes and produce wine.
(Actually, we do produce respectable wine here in cool-climate
industrial England. But not much of it.)

It is now 20.00 hrs and too late to go shopping at my local
super-market. Nevertherless, at my next visit I shall keep my eyes
open for "Michigan" on the wine bottle labels.
----
Reg, G4FGQ.

Hi Lee,

I'm a little confused about the bandwidth that you're getting. Maybe it
can be attributed to losses which widen the SWR bandwidth. That's not
necessarily a bad thing. I have used an AEA IsoLoop antenna that is
about the same size as your loop antenna but has a low loss butterfly
capacitor for tuning 10-30 MHz. On 20 meters the bandwidth is only about
20 or 30KHz(can't remember exactly since I haven't used it for a couple
of years). It works great if you park yourself on a frequency but it is
a pain to use for hunt and pounce.

Besides the null using vertical polarization, is it possible that for
your local friend you may have been cross-polarized. Usually direct wave
cross-polarization is on the order 20db which accounts for the 2 to 3 S
units of change from vertical to horizontal.

Have fun with your new toy!

73 LT

Hi Reg....

I took my little 1 meter dia ( 10 ft circ ) loop outside lunchtime and
mounted it verticaly 2ft off the lawn and tested it, not expecting
anything special and found that comparing it to the G5RV that there
was no noticable difference between the two!!...my friend and i
switched out our preamps and attenuator in.

I even turned the loop face on and edge on with a change of 2-3 S
points.. So, needless to say, i am rather impressed with the
performance and bandwidth of 2:1 SWR about 180k.....so much so that i
am thinking seriously of going for a 20 ft circumference or larger for
80 and 40 metres....

Regards.

Lee....G6ZSG.....Well impressed!!! :-)