electronic components using moebius strips?

Apparently you've never seen twinlead. It is a wide, flat ribbon cable with no room for moisture or dirt between the conductors.

This style was preferred for UHF:

Did you read that last paragraph you wrote?

300 ohm twinlead and even shielded 300 Ohm twinlead was common on UHF antennas in the '60s & '70s. The run was usually around 25 feet, and it worked very well where I lived, about 30 miles from the closest UHF TV transmitter. Most TVs had seperate terminals for VHF & UHF. The newer TVs used 75 ohm for VHF, but retained the 300 ohm for UHF which contradicts your theories. Early TV coax was the crappy copper braid shielded RG-59 which was barely good enough for security cameras. It took the addition of a foil shield inside the braid to make it useful at UHF, let alone VHF. The loss was horrible, and cheap brands allowed the copper to corrode, making it useless for any RF applications.

--
You can't fix stupid. You can't even put a Band-Aid? on it, because it's
Teflon coated.

Casual observers will note how easy it is to roll 300 Ohm twin-lead into a Mobius configuration; and then will see how easy it is to analyze... unless your name is Larkin ;-) ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

      Remember: Once you go over the hill, you pick up speed

But very repetitious.

I wonder if he keeps his marbles in a Klein Bottle?

--
You can't fix stupid. You can't even put a Band-Aid? on it, because it's
Teflon coated.

Bwahahahahahaha! Good one, Michael! ...Jim Thompson

-- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

| 1962 |

Remember: Once you go over the hill, you pick up speed

Apparently you do not understand how the electromagnetic wave propagates in a twin-lead transmission line.

It propagates in the space _between_ the two connectors in a more or less circular pattern. Thus, part of the field is below the insulator and some above. When the insulator between the conductors get dirty or wet, it will create additional losses.

There was some attempts to avoid this problems with tubular twin-lead constructions, in which the conductors were on opposite sides of the tube and most of the EM field was within the air space within the tube. Of course, when installing such lines, care is needed to avoid any moisture or dirt intrusion into the tube.

This problem seems to have been a known since a long time ago, since Popular Mechanics Nov 1949 has a picture of a tubular twin-lead on page 237 (Fig. 2) and explanation on page 244. Check books.google.com

Sure. But you could just use parallel sheet conductors with a thin insulator between, shorted on the far end, and it would be about the same. That's actually done.

John

Div, Grad, Curl and all that:

This has changed a lot in just the past decade or so -- PCs are fast enough now that full-wave EM analysis is de rigueur. And not just for, e.g., antennas -- connectors and many things found in a microwave circuit on a PCB are now par for the course...

Check the links you deleted.

--
You can't fix stupid. You can't even put a Band-Aid? on it, because it's
Teflon coated.

Yes, but that means I don't have to do the vector math myself. A good grasp of the concepts is all I need.

John

I once again checked out those three links and this time they all appeared to work OK.

Unfortunately, I did not find anything in those links that would contradict my original postulate that dirt/moisture upon the flat dielectric between the two conductor would cause additional losses.

Gee. The photo in the last one shows an oval shaped twinlead made for UHF, similar to what were were selling and installing in the mid '60s. We also sold UHF standoffs for UHF twinlead, and combo versions to hold both VHF/FM and UHF cables. It was well known even to competent TV techs over 50 years ago how the transmission line worked. It was covered in early ARRL handbooks, as well.

Belden has dropped twin-lead from their current catalog, because it was a small market item like CATV converter control cable or studio TV camera cable.

All of that will take some time to wade through, but it looks interesting. :)

You all missed the smiley, but most TV antennas were just sets of dipoles for different channel groups on a single boom, and connected together. Since both sets were brought to the reciever, it was a balanced 300 ohm feed. A few were designed for 75 ohm use, and connected the shield to the boom and used one side of the dipoles for the signal. These were more common for FM radio antennas but I saw a few TV antennas made that way.

There were other types, like the 'Double Lazy X', and some that were a large pair off wire loops, but they were only good in zone A locations.

--
You can't fix stupid. You can't even put a Band-Aid? on it, because it's
Teflon coated.