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Discussion in 'Amateur Radio Antennas' started by AE5RD, Mar 16, 2010.
Want a good 'all band' antenna? Boy! You have some decisions to make with that one! A 'fan' dipole, multiple 1/2 wave elements from the same feed point is probably about the 'best'/simplest/cheapest if you can string it up.
I like loops and ladder line and don't think using a good tuner is all that 'bad'. So a loop resonant on the lowest frequency you'll ever use normally works on a lot of other bands too (not all of them, but most). In general, the longest, tallest, biggest antenna you can accommodate for the space you have is the 'best' for you.
I'd love to be able to afford a couple of 'Stepper' antennas. Not that I'd ever buy them, I just wish I could afford them!
And just for grins, that G5RV was designed as a 20 meter antenna, that's where it was meant to work best. That it will 'work' on other bands is just incidental, and very over-rated.
If your gonna use the loop on 20 I would suggest lader line feed. Just 40-80 coax fed will do fine. Coax will work on 20 but will have losses.
A double extended zepp will provide more gain but will be bi directional."single band"
you might want to research the NVIS type antennas.
they are great for ragchewing due to the high radiation angle and are simple to erect because they are close to the ground.
the DXer types call them "cloudwarmers", but they provide consistant signals out to about 800 miles radius or so with little QSB
Wire antennas are a comprimize unless you cut an antenna for each band you are wanting to work..That takes alot of wire and feed line though
But I am happy with the antenna that I use,but make sure you have a decent tuner
SUPER loop????? yee haw
seriously,..... i don't think i've ever heard of one. do you have a link. i'm puttting up a loop this summer.
i have found sites with a "mini super loop",.... is this the same animal?
Should that twin-lead/ladder-line/whatever hang straight down? Yes, it should, and not be near other things. That parallel feed line portion is the impedance matching device for that antenna and has to be treated as such (as in tuned). It should be mounted high enough where the coax is the only part of the feed line near the ground.
Just how bad is the SWR?
thanks for the site info
YIKES!!!! i just checked their site..............$175.......... i don't think so
i've got a 100 feet of new 450 ohm ladder line and a 500 foot spool of insulated wire. a 4:1 balun isn't too costly.
only issue i have is that i would perfer to feed it with ladder line and not coax.
i think i'll keep looking at ladder line fed delta loop plans.
How much area do you have to put one up in? That's the biggy. From there it's merely a matter of having enough wire to put up. If you have the option, two or more times the full wave length of whatever the lowest frequency you'll be using is VERY nice to have! That typically means some 'gain' on bands higher than the design frequency/band. It also means one heluva big loop, lots of area required. But in most cases, it's worth it.
The shape of a loop, round, square, rectangular, triangular, some 'other' weird shape isn't all that important, sort of. The more area -inside- that loop the more efficient it will be. That difference in efficiency isn't going to be huge, but there is a difference. A triangular shaped loop is probably the least efficient, but the easiest to get up. That round loop is the most efficient, but the hardest to get up. A rectangular (or close to sort of rectangular) shape is probably the most common. Until that rectangular thingy gets real 'skinny', that loop ought'a work okay. When it get's real 'skinny' you ought to call it a 'folded dipole', sort of, and then things start changing rapidly.
Can you have stuff inside that loop, like a house, trees, and like that? Yes. That stuff does affect things to some extent, but probably not all that 'badly', sort of. (Tear that house down and live in a cardboard box? You gotta put priorities where they belong!)
A typical horizontal full wave loop has an input impedance somewhere around 100 - 150 ohms (give or take a little). Feeding a loop with coax can certainly be done if you use an impedance matching device of some kind (gamma? 75 ohm electrical 1/4 wave section?). That pretty well limits you to one band though. If you can, feed the thing with ladder line through a tuner and use it on any higher bands. You are going to loose some efficiency (power transfer) with any multi-band antenna like that so it's not really a big deal, sort of.
Polarity with horizontal loops depends on where you feed the thing and it's general shape. Square loops are easy to figure for polarity. A corner means vertical polarity, the center of one side means horizontal polarity. When the loop's shape isn't exactly 'regular' that polarity thingy gets more complicated. This is one of those 'generalized' thingys, meaning it just depends on a lot of factors, and is going to be different for each installation because of what's around it. So change the feed point till you find the 'sweet spot' you're looking for.
Ladder line and tuners.
Lots of misinformation about those things. Is there losses when using a tuner? Sure, but not as much as you might think. Is ladder line difficult to 'work' with? I wouldn't say it's more difficult than coax but it's certainly different. Just a different set of "do's" and "don't do's". What's the advantages? Biggest one for me is that it doesn't really matter what that SWR is, it isn't going to hurt/damage the ladder line like it can coax. If that tuner can handle whatever the impedance mismatch is, then who cares! The typical $19.95 tuner isn't gonna work in most cases, so get ready for it. 'Nuther one'a them 'bigger is better' thingys.
And lastly, tuners and ladder line don't do miracles, they have limits. Sometimes those 'limits' can be in unexpected places, not where you'd expect them to be. Most of those limits deal with the harmonic relationships between bands. Or maybe the different portions of bands?
Loops are not the best answer for -every- antenna choice/requirement. They do have some characteristics that are nice, and I've found that they will usually work fine for most of my antenna requirements. I like them! (You couldn't tell that, could you?)