How to design an Interesting inductor

Thread count? Huh?

^ Room for explanation ^

Just because I left out the details, my 4-1/2 turn inductor was a potcore inductor, easy to add that 1/2 turn.

Not like bed sheets. ;)

The inductance contributed by the toroid goes as N**2, where N is the number of times the wire goes through the aperture of the toroid. No half turns need apply.

Right. And that half turn completely changes the saturation behaviour, at least if the centre post has a gap.

Cheers

Phil Hobbs

I found something I can at least try.

I got a strong magnet to change the inductance from 100uH to 4.6uH. Mikek

A half turn in a pot core can have impressively bad effects.

Yup. Or in this case, potentially useful ones.

Cheers

Phil Hobbs

I wrote an article in part discussing that, recently:

The correct way to make half turns is to put a figure-eight winding on the legs to enforce flux balance. These can even be intentionally unbalanced (say 1:2), to get even more interesting fractions of turns (1/3, 1/4, etc.). With a corresponding hit in Phi_sat of course, because the one side saturates first. I link to a Unitrode appnote which discusses this.

Tim

I have some understanding of normal Beverages, but are there reliable comparative data for BOG or slinky antennas ? Until there are some reliable comporarative and calibrated comparison betwen real Beverages an BOGs and slinki antennas I really do not want to mess with them.

The main selling point of Beverages is that it is wide band, you definitely _do_not_ want any high-Q (i.e. low bandwidth) constructs.

A simple passive stage (such as a transformer), can have voltage or current gain but the power gain is at best 0 dB. To have real power gain, you need an active device.

Beverages are nice, _if_ you have space for 0.5 - 2 wavelengths long wires. If you don't have that space, you should seriously really study other antenna alternatives.

So a 150 m long Beverage is 0.5 wavelengths at 1 MHz and 2 wavelengths at 4 MHz.

Have you considered installing a grounding resistor at 38 m (for 4 MHz) and at 75 m (for 2 MHz) and final termination resistance at 150 m (for 1 MHz) ? The intermediate grounding resistors are then selected by relays. Feed some audio tones along the wire to activate those intermediate relays (with some audio frequency selective rectifiers).

If you use relays to select grounding point no need to worry about ferrite nonlinearity or mixing products.

If I had 1000ft to put up a Beverage, I would. I have a 10ft by

Yes but when it is short you lose directivity. Mikek

Sun streaking cold An old man wandering lonely Taking time The only way he knows Leg hurting bad As he bends to pick a dog-end He goes down to the BOG And warms his feet Feeling alone The army's up the road Salvation a la mode and A cup of tea

BOG = Beverage On Ground

A beverage antenna is generally described as a 1 wavelength antenna, (more or less) Mike