Full wave loop

[lamplighter]

Situation:

I have a full wavelength loop in my attic. SWR is good 1.4:1 in channel one, 1.1:1 on channel 40. It works fine, but is in the attic with the attendant impact on signal being there causes.

Thought:

I want to move it to the roof, but the roof line will bi-sect two of the quad shaped sides of the loop giving the loop two angled sides and two straight non-angled sides. The 5/12 pitch of the roof will give me about a 22.5* angle in those two sides.

Question:

Is this workable, and, if so, how might it affect the antenna.

The question is about expected performance due to being above the roof, and how the bending of the two sides might affect it's performance.

Currently it is mounted horizontally and fed from the corner matched with a 1/4^ 75ohm section to rg58U.

Illustration:

crude, but may help:


fig. 1 is the current shape, but on the horizontal. As in fig. 2, it would drape across the roof line like a blanket.[/b]

[Tombstone (R.I.P.)]

Loops are great when matched. Are you using this for transmit or receive, they make a great shortwave receive antenna when used with a tuner. Most indoor or attic antennas are installed because of neighbors complaing, But since you're going outside with it doesn't matter. I don't know about laying the antenna directly on the roof, it might ground out somehow. You'll have to experiment.

[Marc]

I think I would turn the loop 180 degrees from the way you are showing with the feed point on the peak.

Find a way to raise the ends on the peak about 1 foot and the ends on the slope up to the same level. For the ends on the slope maybe two large coffee can filed with cement with PVC pipe sticking up from the middle like a miniature tether ball pole.

Just a thought

Marc

[lamplighter]

great ideas...

In the attic it is suspended flat like a table top, tied off at the corners, and fed from one of the corners. It seems to be omni-directional with a vertical polarity that way.
I was hoping to sneak it above the roof without the wife noticing it using an 18guage wire and right against the roof, or very close to it.

I have plenty of antennas, but only one wife who tolerates my redneck past-time.
Trying to get an omni up without getting her temper up.

[lamplighter]

May 28, 2009 14:06:09 GMT -5 Tombstone (R.I.P.) said:

Loops are great when matched. Are you using this for transmit or receive,

For both, but primarily to try to determine which way I want to swing the quad.

[zman]

Ahhh the loop skywire! On the HF bands this antenna works slick with a transmatch! I know an OT'er that has a 160 meter full wave loop (well over 500' overall lenth) that he has up 75' and talks all over the place including some DX and on 160 meters it takes a HUUUUGE antenna for that!
If you can, get it up high outside and tie off the corners at some trees or telescopic masting. at Cb freqs getting it up over 18' (preferrably 36') the loop will perfom on DX. At heights under a 1/2 wave, the antenna is pretty much a cloudwarmer and your signal goes straight up.

[lamplighter]

Jun 1, 2009 21:36:28 GMT -5 zman said:

Ahhh the loop skywire!
If you can, get it up high outside and tie off the corners at some trees or telescopic masting. at Cb freqs getting it up over 18' (preferrably 36') the loop will perfom on DX. At heights under a 1/2 wave, the antenna is pretty much a cloudwarmer and your signal goes straight up.

I've made a few DX contacts with it in the attic. I may have to do what you suggest, out and up.

[zman]

Yeah get it up high. Thats good that it works in the attic.
I am still mulling over if i should put up my Astrobeam or my Avanti Sigma 5/8 up on my 48' tower. It still will be a while before i can get everything up though.

[lamplighter]

I'm using the two element quad as my main antenna right now, but working on modifying it for better RX/TX.

The loop acts as my omni ears to locate the best DX conditions to turn to.

There's also a wire dipole up to hear, but it is mostly north/south polarized.

I may end up with a yagi underneath the A99.

I'll see.

I have only thirty-five feet of mast currently. Got someting up and take advantage of that tower.

[swamp40]

A "LOOP" is supposed to be "ROUND", any deviation from round will cause lobes and null's.
A square loop will have a hot lobe 180 degrees from it's feed point and null will be of course 180 degrees in the other direction.
Bending the loop will also have effect on the pattern and take-off angle of the loop (such as draping it over a peeked roof).
If your serious about loops, do a web search for "W4RNL" or "S-meter.net" and read the information there on loops.
They are great antennas, but as with all antennas, they have their quirks !
73, John

[lamplighter]

Jun 6, 2009 6:31:09 GMT -5 swamp40 said:

do a web search for "W4RNL" or "S-meter.net" and read the information there on loops.
They are great antennas, but as with all antennas, they have their quirks !
73, John

Will do.

[zman]

Problem is, if you dont live in a forest its near impossible to build a TRUE LOOP! So henceforth, that's why we use a square loop or a delta loop. So how's the antenna coming Lamplighter?

[lamplighter]

Jun 10, 2009 10:20:29 GMT -5 zman said:

Problem is, if you dont live in a forest its near impossible to build a TRUE LOOP! So henceforth, that's why we use a square loop or a delta loop. So how's the antenna coming Lamplighter?

Still in the attic. With the break in the weather, I've been doing chores in the great outdoors.

Thinking of going to a Yagi and A99 over the top of it.
If I continue fooling with the loop, I've a notion to put it up over the top of the pergola on the deck. Not optimum, but outside and more-or-less out of sight.
As a square, with 9' sides it should fit nicely.

[zman]

Nice landscaping. Did you do the landscaping yourself?

[lamplighter]

Jun 10, 2009 16:23:10 GMT -5 zman said:

Nice landscaping. Did you do the landscaping yourself?

Thanks.

We do everything ourselves.

[mark]

Well? You and the wife are great at landscaping but you need to convince her that an aluminum outdoor antenna is what you need. Loops are freaking great! But the way you are utilizing that one is how they are used in much lower frequency installations where they have real value. Low bands are very noisy and the loop works great from about 10mhz down. In the Cb bands, an unterminated antenna is not problem as the band is pretty quiet already. Your installation is horizontally polarized so if you are not interested in ground wave talk to your buddy's I guess it would suffice, especially if you have issues with seeing an antenna on your property. If you are hell bent on stealth antenna's try putting up two double extended zepp dipoles at 180 from each other and you can switch them for directional control. Use like an #18 wire and RG8X coax and it'll work pretty darn good for dx. Its what I used when I had antenna restrictions. Nobody EVER saw it and I was there for 9 years!

[lamplighter]

I have no restrictions here, but she wishes I'd do something less visible. So I was experimenting. This antenna is what I currently run on the pole you see in the photo of my yard.

[cbrown]

It's tough to do something 'less visible' with an 11 meter antenna. I think the antenna you've mounted is probably the best you'll do.

Looks good, btw.

[lamplighter]

Thanks. I'm a die hard, so I'll likely continue playing around with it as the outdoor weather cools.

[mark]

looks good to me! Well then you at least have that covered for now.