Jonny in the UK,

Check-Out - This "Frequency Wavelength Calculator"
http://www.csgnetwork.com/freqwavelengthcalc.html

The One Wave Length Measurement for 5.680 MHz
is 173.24 Feet or 52.84 Meters.

A Quarter Wave (1/4 WL) Length Vertical Wire Antenna
would be 43.31 Feet or 13.20 Meters.

THE SLINKY QUARTER WAVE LENGTH (1/4 WL)
SHORTENED {LOADED} VERTICAL WIRE ANTENNA :

A "Shortened" {Loaded} Quarter Wave Length (1/4 WL) Vertical
Wire Antenna : [Using One Long Bottom Loading Coil ]

Requirement - This Shortened Quarter Wave Length (1/4 WL)
Vertical Wire Antenna Requires a Vertical Support-Point of at
least 25 Feet and up to 45 Feet high above ground level; with
about 27 to 33 Feet being about the right height.

First use a Coax Cable Feed-in-Line running out along the
ground or under the ground from your Radio about 45-50 Feet
(15-17 Meters) from the House to the Base of the Antenna.
* If space is limited 20-25 Feet (6-8 Meters) will do OK.

Use a Four to Eight Foot (4-8 Ft) Ground Rod at the Base
of the Vertical-Up-Leg of the Antenna.

Use a standard Full Size Slinky as the Variable Loading Coil
for the Quarter Wave (1/4 WL) Length Vertical Wire Antenna.

NOTE - The standard Full Size Slinky has about 100 Turns
with a Diameter of 2 3/4 Inches and a Circumference of
8.64 Inches for a Total Wire Length of 72 Feet.

How Long Does a Slinky Get ? - I Calculate that the Optimum
"Stretched-Out" Length of a Slinky would be about 22.9 Feet.

Connect {Solder} a 23 Feet (7 Meter) piece of Insulated Stranded
Copper Wire to one end of the Slinky.

To the free-end (Far-End) of this Copper Wire tie a 50 Foot piece
of Nylon-Poly Rope to Rig the Wire Antenna Element.

Connect (Solder) the free-end (Bottom-End) of the Slinky to
the Center {Inner} Conducter of the Coax Cable.

Connect (Clamp) the Outer Shield of the Coax Cable to the
Ground Rod.

Rig the Nylon-Poly Rope to your Upper Vertical Support and
Stretch-Out the Copper Wire up to this Support-Point.

Note - The Radio-End of the Coax Cable should have a
Coax Cable Connector to 'fit' your Radio.

Connect the Coax Cable to your Radio and Tune to 5.680 MHz.

Use the Nylon-Poly Rope to Shorten or Lengthen the Length
of the Antenna to Receive the Maximum Signal {best sounding}
on 5.680 MHz.

Note - If the Upper Support-Point is only about 25 Feet high :
Then the Far-End (Top-End) of the "Insulated" Copper Wire
may go through or over the Upper Support-Point and be angled
down at about 45 Degrees from the Vertical Wire Antenna.

Trimming the Wire Antenna Element - If necessary the Copper
Wire Antenna Element may be Trimmed {Cut} from the Far-End
by Three Feet (3 Ft) or One Meter; and then the Length of the
Antenna may then be Adjusted for the best signal on 5.680 MHz.


hope this helps - iane ~ RHF