For receiving SW broadcasts a long wire from the receiver to a point as high as you can get it works pretty well. 100 feet would be a good place to start.
If you feel more adventurous you can construct a dipole from some insulators and two pieces of wire. The total length of the dipole should be calculated from the following formula:
Code:
Length(in feet) = 468 / Frequency(in MHz.)
Let us say you want a dipole to receive WWV on 10.000 Mhz
Length = 468 / 10.000 = 46.8 feet
Take the 46.8 and divede by 2 to get 23.4 feet. The actaul wire should be two feet longer or 25.4 feet. The extra length is run through the insulator and taped with electrical tape back along the antenna the same way on both ends. In the ascii graphics below W and T are insulators, * is wire and - is insulating rope.
Attach the wire to the insulators so that the distance from W to T and the distance from T to W is as close to 23.4 feet as possible. Get T up as high as you can and the tie the ropes connected to the W insulators as high as you can. It is OK to let T sag in the middle. You need some kind of feedline to connect your antenna connector to one side of the dipole. The other side of the dipole is connected to ground near the antenna connector. The feed line should have conductors that are parallel. 300 ohm TV feedline should work just fine.
One more thing, the best signal reception will be from the two directions perpendicular to the antenna. For example if the antenna runs North-South then the best reception will be from the East and the West.
That all there is. Good Luck and let me know how it turns out.
2375 mm is pretty far away from 23.4 FEET. I'm sure the hams and SWLs in countries that use the metric system have an equivalent formula, I just don't know the constant off the top of my head.
Your antenna would be resonant at about 31.57 Mhz or 9.5 Meters. I'm not sure if there is a VOA station there though.
I am sorry, I was not clear....... I was trying to show what it would look like if you put up a dipole....... I forgot that I had mesurements on the drewing...
It is for a radio telescope, but it shows the basic idea...... Having said that, you could use any reasonable size for you antenna and add an ATU (antenna tuning unit) to it...................
Oh dear, I think I just made it more complicated............
You may also wish to investigate a TTFD (Tilted Terminated Folded Dipole) shortwave antenna, here; The TTFD-2 antenna by dxzone.com
It's an extremely quiet and broad-band antenna design.
I used a high-power Amateur Radio version of the TTFD which was 90 feet long during my first three years on the air starting in 1998 and I confirmed contacts in all 50 states on 7 bands (40 through 10 meters) and well over 300 countries in a very short time.