Loop or dipoles?

[KB2WIG]

Watt to do. Hacking and burning the envyronment for my new 80/40m fan dipole. Laying pvc pipe.  As I looked up, I began to wonder if other things were possible...  Such as tossing the 10m clothesline dipole in the basket and putting up a 10m loop. As Clint would say, Hang it High. It looks like I may get 30, maybee 40 feet up in a branch to play with. I've got the PVC.

But the mind is a terrible thing to lose. I'm wondering if  hanging two dipoles, one above the other, may be the better way.

The loop is nice; using the oblong configuration, its feedpoint Z is around 50 Ohms. 73 inches on the top and bottom and 144ish on its sides. The bottom of the loop would be around 20 feet above the ground - about 1/2 wavelength above the ground. And no phasing stuff to play with.

The dipoles would be about 1 wavelength and 1/4 wavelength above ground, respectively. Hanging the loop or the dipoles from the tree allows for a a steering line and wadeing through the snows to turn  'em.

Both the antenna designs would be out of sight from the house and driveway,this means there is no Xyl approval needed.

Someday, i'll breakdown and play with computor design antennas, but that's not today. Any comments or alternatives apreciated.


klC

[Steve - K4HX]

There won't be a lot difference between the oblong loop and the stacked dipoles. You'll want the dipoles to be at one wavelength and one-half wavelength. The wider spacing doesn't do much for you and the bottom dipole would be too close to the ground.

The stacked dipoles will have a little more gain (a dB or so) and a cleaner pattern. The loop is simpler, especially the feed arrangement. Below is a comparison of the two. The top of each antenna was at 40 feet. The solid line is the dipoles and the dashed line the loop.

[kb3ouk]

if you really want some gain and have the space, why don't you go with a lazy H?

[KL7OF]

Resonant Loop is more broadbanded than resonant dipole when coax fed
Vertical Loop takes up less space between supports
loop can be mounted vertically and polarized horizontally or vertically
loop has no coronal discharge when using high power at high altitudes

[WZ5Q]

For Multiband use,

I have found the best all around performance out of a 288' 160 meter Doublet fed with 124' of 600Ω OWL and using a LCT.

The Doublet is up at about 70 feet. The South Leg is flat topped, and the North Leg is bent in on itself at a 45 deg acute angle and down at a 45 deg angle (picture the top of a "Z"). This was done for 2 purposes:

1 - Lack of real estate.
2 - To add some NVIS radiation into the "Doughnut Hole" on 40 meters for local communications.

I used to have this Aerial configured in what I called an "Inverted Z" due to the size of my lot, with great performance. My neighbor to the south allowed me to use his trees and I was able to pull the south leg of the aerial straight out. My North neighbor also gave me permission, but when I stretched the doublet out completely Flat Topped and Straight, I lost the locals on 40 meters. After some modeling on EZNEC to see why, I bent the North Aerial Leg back into the "Z" configuration thus gaining the NVIS on 40 with minimal impact on 75 and 160m. 10m has some very low take off angles (10deg) with many, many lobes. EZNEC plots of the Azimuth and Elevation of the 160m Doublet on 10m are attached. I usually use my 3ele SteppIR for that band now.

I did have a 1058' Loop up at 110' when I owned the property on the top of the hill out of this river bottom. I also had Phased Dipoles for 75m, and a 160m Carolina Windom up at 110'. The Loop was INCREDIBLE for Low Take Off Angles and DX on all bands (especially 10m), sketchy for NVIS on 75, non existent for NVIS on 40. I would always have to switch to the Phased Dipoles for Local 40m QSO's. The 160m Carolina Windom was a poor performer everywhere. Unfortunately, Horrorcane Rita destroyed all of the 120' Pine Trees on that property, and it was sold.

All in all for multiband use, I like the performance of the 160M Doublet with OWL and a LCT the best.

Take Care,

[KB2WIG]

Thanks for all the input.

I think I'll go fer the loop. --- Not a lot of performance difference. The added complexity of phasing for the dipoles throws the balance for a loop. I've got the pvc, and it seems like I can do the antenna in about an hours worth of work.  Placing it in the jungle will take longer.

I'm too lazy for the "H" thing for now.

Watt I may do later on in the year, if and after the 160m El goes up, I'll go looking for a tall tree and maybee try the 2 dipole stack. Or a extended double zep, or a bisquare.


klc

[flintstone mop]

LOOP triggered Magnetic loop antenna in my brain.
This month I'm (attempting) to build a Helical wound magnetic loop antenna good for 80-20M. It is 6 feet in dia. of 2" flex PVC. Vacuum variable cap and 30rpm motor. Hopefully I'll remove my defective Cushcraft A3S............
Link:
http://www.qrz.com/db/K8NDS

Maybe some here have read about this approach. Takes full legal limit. Only needs to be 6 feet from the ground.
The Yahoo group for this antenna is always growing and results are usually very surprised Ham ops.

[Opcom]

Also here but for RX only. I bought a receiving magnetic loop from Pixel and it makes a difference getting rid of much of that buzzing noise from power lines and that sort of junk. Now that I have done a/b test with both, the answer is; I need both. In some cases it is better signal strength than the dipole and in other cases the incoming signal is weaker. One thing noticed is the null is apparently steeper than the peak. Do these magnetic loops perform better if they are bigger? Mine is 1 meter diameter with the 27dB preamp.

But the talk is about a regular loop, I have no experience there other than for SWL where I got mixed results, same as a dipole.