electronic components using moebius strips?

Moebius audio tape?

See US 4599586 (Mobius capacitor) and 3267406 (Mobius resistor).

M=F6bius resistor:

Not common, but used - typically with a graphite surface coating to give long life and ease of pulling thru the heads.

The problem is that even this design does have residual mutual- or self-inductance at high frequencies, along with shunt and stray capacitance. With care, the inductance can be rather low, but never zero.

If you apply a step of voltage, it takes time to make it around the loop, past the twist and back to the input. Until then, the step doesn't know how long the loop is. So initially, the step sees two lossy transmission lines in parallel, headed in opposite directions. A lossy transmission line's impedance varies with frequency. So it doesn't look purely resistive.

I think you'd get pretty much similar results if you cut the strip at the twist and flattened it out and shorted the ends.

It would be fun to Spice this.

John

-- Boris

What does a "300 ohm Möbius loop" mean? Of course the DC resistance would be 300 ohms, but what would the transmission line impedance be?

John

Recordgraph loops were available as normal loops and as 'long-play' Moebius loops.

nce.

Yabut, I think then you have an additional constraint of getting the input terminals, not only opposite each other but also opposite the short.

Surely someone looked at the frequency response.

George H. (Thanks for the link Spehro)

It looks like the patent claims there is decreased coupling (which I took to mean far-field inductive coupling), and that much is true. But that doesn't really depend on Mobius geometry, any odd number of half-twists would do the same.

If you used that geometry with no twist, there would still me no net loop magnetization... the currents flow in the sheets in opposite directions and - as long as the insulator is thin - their loop fields cancel.

Make a tight twisted pair of resistance wire and short the far end. It's pretty much the same.

There is a real resistor used that is a strip of manganin or zeranin, folded over into a very tight U shape with a thin insulator to keep from shorting. Same idea.

My company makes low-inductance, high current shunts that have nearly zero magnetic coupling to the outside world. There are lots of ways to do that. Mobius seems about the least practical. I've never seen a Mobius resistor in real life.

John

or

tance.

We buy twisted pair phosphour bronze wire, solder one end together and make non-magnetic heaters.

I was thinking about making a Mobius 'strip' from just two wires... like old 300 ohm twin lead .. Make a loop, a twist in the middle, solder two of the four end wires together... It looks a bit different than the twisted pair. (the joint is back at the input) Does that make a difference?

George H.

Look again at the patent; if there were no twist, the two conductors would not connect at all, and it'd be a capacitor, not a resistor. The band is a sandwich, with resistive film faces and an insulating core.

Should have been more explicit. I was referring to 300 Ohm flat transmission line used for TV antenna feed many moons ago.

-- Boris

or

itance.

Yeah, TDR a 300 ohm piece of twin lead from one end with the other end shorted. And then take the same piece and make it into a Mobius loop. You could use a piece of coax too.

George H.

capacitance.

You would think an EE would know what TV antenna wire is. :(

capacitance.

You'll obviously see Zo initially (or Z0/2 if you start in the middle) and the wire's DCR after things settle down. The transition could be messy. The Spice lossy line model should give some idea.

A transmission line with significant ohmic losses TDRs as Zo followed by a ramp of increasing impedance. A mobius resistor will initially look like that, at least until the tdr step makes it around the loop. For a really lossy line, the initial step of Zo can be tiny, so all you see is a ramp.

I'm not sure how a mobius resistor would TDR. It's complicated by the possible values of Zo and resistive losses per unit length.

Seems like a silly idea to me.

John

capacitance.

What's a TV antenna? ;-)