Types of Open Wire Line (

Teodor, 2E0GIY, is curious. "Why 450 Ohms?" He is wondering why it became such a commercial type when it is rarely a viable solution. Dave here to help explain.
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[@brianveitenheimer4492]

I’ve been licensed a little over a year. I wanted a true multi band antenna and soon got frustrated with trying to tune configurations with coax. Big losses. I decided to go back to what worked for people 90 years ago and home brewed my own open wire line ,1:4 and roller tuner. Total success.

[@graeme9184]

Make your own twin, The formula is so easy. Insulators made from air line with a cable tie passed through it. Formula is twice the distance between the wires. Divide by the wire diameter Log of the result Multiply by 276 = impedance of the open wire

[@davidc5027]

That's what I did, made my own 600 ohm open-wire / ladder line, and it works great! It's basically what Dave said, for a all band antenna. I really don't care about SWR too much because I know nearly all of the signal will be radiated. Don't get me wrong, I'm not going to run the tuner at 9:1 SWR.. but I really don't care if it's 2:1 or 3:1, and with the tuner I rarely have a situation where it's going even be 2:1, so win win. I remember when I first got my tuner, I was so worried about a 1:1 or 1.3:1 tuning as I always wanted 1:0.. However, these days, for example, I'm looking at my tuner right now, and see on 10 Meters, it is set to 1.5:1 with 4.7W reflected... and I say to myself "who cares".. lol So, I'm not so anal about SWR anymore.

[@jptucsonaz8503]

Hi Dave, Very nice coverage on 300/450 & 600... thank you. And they do have some advantages... However, how about the trade off's? A few off the top of my head... A) No shielding; i.e. prone to r.f.i. from outside sources - interference! B) more difficult & expensive to protect from static & lightning. C) the flip of a & b- above... the no shielding thing also presents a r.f. exposure issue to us & creates r.f.i. in the shack (& home). Flickering lights, tripping gfci & afci breakers, etc. Back to rule #1 of antennas... everything affects everything! ... and non-shielded open line is very much a part of the antenna system. And respectfully, from what I've seen; window line is not cheap at a buck or more per foot. Maybe in comparison to LME-400? But about the same as good RG-213. I do miss 11 cent per foot RG-8 & really dirt cheap 300 twin lead. I used the latter to make fan dipoles for shortwave listening back in the 70's thru 90's.

[@g0fvt]

There is a lot going for it, a well balanced system will not significantly radiate from the feeder despite the lack of shielding. Of course with imbalance in the system the twin feeder can become part of the antenna. This assumes that the spacing between the conductors is small relative to a wavelength.

[@chrisk0blu594]

Dave, rather than i^2/R, I think you want the Equation Power P= E^2/R to explain the lesser power loss for a given EMF with window line with a higher R than 50 ohm Coax cable.

[@Pelnied]

You had the Power Loss right at 5:45 as I^2*R, but changed it when accidentally writing E = I/R at 6:11 which made it accidentally turn into P=I^2/R

[@ericdee6802]

What i understand about open wire line is that it DOES NOT leak RF energy even though the wires are in the open free space, unlike unballanced feed line (shielded coax) does leak RF. Very strange Phenominon!!! Stan Gibilisco W1GV (silent key) has a very informative video regarding open wire line here on youtube.

[@sinatralala]

Fantastic presentation!!!!!!!

[@kentk9aee898]

Kudos for differentiating ladder line from window line. Calling window line ladder line has long been a pet peeve ov mine. 73 K9AEE

[@allenmiddendorff2068]

I learn something, thank you!

[@poorman-trending]

So, For a non-resonant EFHF , could I skip the 9:1 unun and just use 450 line?

[@cbGamer481]

@ David Casler I have a cb base station setup. Would the window line make a difference in hearing other and does it handle power better than the thickest coax i can find? i also planned to top out the tallest tree on my land and putting my cb antenna on the top of it. The putting the antenna in the tree, will this hurt me any? the antenna is 18 foot ground plain type.

[@dougtaylor7724]

I was confused by the ohm rating myself. My electrical background is boats and cars. So I hear 50 ohms, I naturally think measured with an ohm meter. Nope. Has nothing to do with resistance as one would think. It’s relative. Two conductors this far apart is this measure, the farther away the conductors are from each other, the higher the ohms.

[@izzzzzz6]

I think i'll make some 500 ohm. Is it ok to use 1.5 mm stainless cable or do i need to adapt the formae for braided stainless?

[@DonzLockz]

I remember internal TV aerials having 300 ohm ribbon cable, thats what we called it here. Old tv's only had inputs for ribbon cable, no PAL coax socket. Some newer tv's had input options for both. I didn't understand 300 ohm ribbon cable at the time as i was young.

[@darinhitchings7104]

Very good video. Learned a number of things. Crazy question... what would be the consequence of running window line or ladder line inside of a galvanized steel pipe or another type of metal to insulate it from the external environment a la Gauss's Law (that electrical currents travel along the surface of a conductor...). Would that be helpful? Or would that cause chaos / adverse coupling effects?

[@n0vty873]

Use dual coax lines spaced correctly

[@donschneider7252]

Thank you Dave! That clears up some ? I had about the feed lines. P.S. I like the way you spell shades of my own method of over coming a poor memory for detail... KI7RJS

[@ernestb.2377]

I had a trouble by following this explanation. P = I^2/R? And about what power-losses we are talking? Due to..? Current? Higher R lower I at the same P, V must go up. I was looking for the explanation of the 9:1 UnUn needed for the LongWire antenna and can not understand why is 49:1 used with EndFed which have similar lengths... and so on. How is impedance of the wire determined?

[@nevmarr]

Maybe I need to get out a bit more ... my observation is open wire lines are used at HF but I've never seen them used at VHF or UHF. Is there a reason(s) to use coax rather than open wire at VHF UHF? Thank you Dave and any commenters.

[@rogerlafrance6355]

Open wire was popular on VHF before good quality and cheap low loss coax. Many of the antennas were made 300 ohms into the 60's, But what a pain, fragile, broke with ice and stopped working when wet. Forget using a rotor.

[@nevmarr]

@@WECB640 Yeah, I'd assumed it would work, I was more curious why "no one" uses it ... or as I say, maybe people do use it and I just need to get out more :) And I'd assumed wire feeders would be (a lot) less lossy than coax, so there must be benefits of coax that outweigh the benefits of wire. Roger (other commenter) has pointed out some of the problems with wire (thank you Roger).

[@OzzieKev]

Yes, 300 ohm line was originally the standard for TV antennas. Coax started to be used in the 70's but 300 ohm twin was still common. By the 1990's, coax was standard for New installations. I remember an electrician telling me he had been taught that coax was "better", as it was easier to run. He was surprised when I showed him the different loss figures.