My Vertical Loop Antenna for 80 Meters

hooked it up and got infinite SWR until I unwound the extra turns from the two posts. Was able to get a SWR of about 1.2:1 with the MFJ Versa Tuner 2. This was at 3.913 MHz. Will try to make a contact soon. Probably next week.

From the following site I determined to feed the antenna directly with 50 ohm coax

http://www.qsl.net/kd4sai/loopant.html

"The feed point can be anywhere along the wire, but is normally made near one of the supports simply to lend stability to the antenna system. A loop is a loop, so anywhere you "break" it for the feed point, it's still a loop! The use of a balun is controversial. Some argue that the feed point impedance must be compensated for through the installation of a balun. Others argue that the installation of a balun will result in the radiation of undesirable harmonics and the loss of power. Tests that we ran way back when I was in college at the antenna laboratory at O.S.U. resulted in the determination that directly feeding the loop with 50 ohm co-ax was most desireable. A quarter wave length of 75 ohm co-ax may be inserted in the feed line for a closer match if you desire."

Directly feeding the loop antenna is obviously the simplest, however, you be your own judge and feel free to try it both ways. All 3 of my loops are directly fed with 50 ohm co-ax. My 17 and 10 meter loops are both vertically suspended and are relatively in the clear but low to the ground"

http://www.eham.net/ehamforum/smf/index.php/topic,23606.0.html

"To Balun or Not To Balun feeding a full wave loop?
« Reply #3 on: June 22, 2004, 05:58:20 PM »

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"To be
honest, the physical environment, height above ground,
ground conductivity, and other factors make a bigger
difference in performance than the feedline type.

If you read through the articles on horizontal loop
antenna from W4RNL:

"So it comes down to a personal preference. At low
heights the 50 ohm coax is likely to give you a better
match on 80m, while with a higher antenna a 4 : 1 may
have a lower SWR on 40m. But for initial testing
you can just put it up with direct coax feed (50 or
75 ohm) and use it without a balun."

Category:

Science & Technology

Tags:

• HAM radio
• Versa Tuner
• SWR
• Amateur Radio
• Velocity Factor
• VF

[lukedoc12345]

Build a center fed dipole and feed it with open wire or ladder line. Either go into the back of the tuner with it, or connect it to a 1:1 current balun close to the house, and run a short low loss coax to your tuner. The way you have your antenna now is not efficient. It's like a side ways vertical with no ground radials. And fed with coax using it on a frequency other than where it's resonant, the line loss will be great and not much power will make it to the antenna.

[Lockemeister]

@lukedoc12345 sounds good

[umajunkcollector]

A BalUn (coax to antenna transformer - coupler) is not as important with a receiver. All those COILS wrapped around the posts will have an effect. Zigzag the wire with bungies is much better, or go around the yard a couple of times, i.e. two or three loops, is better than those coils that act like a trap or choke. Ferrite beads on the coax at the antenna feedpoint is also a good simple BalUn, if the antenna is used for transmitting. Full wave folded dipoles and loops usually work very well.

[Lockemeister]

@umajunkcollector i meant to say i want to try also the 40 meter band, not 4 meter band! I mainly want to use the 80 meter band though.

[Lockemeister]

@Lockemeister It won't work on 40 meter. It's only good for 80 meter band. that's Ok though, It's what I wanted. I make tuning adjustments with a MFJ Veersa tuner II.

[battlestarone]

you have a massive back yard,i would but the antena up horizontal,and feed it with 450ohm ribbon and a length of coax,this will make it multiband from lowest freq up,you will also need a 4:1 balun,load of more info on the net for multibanding loop antennas.,wrapping stuff round fences is not a good idea,if you have kids or humans around.

[Lockemeister]

@OH2FFY see description for comments from eham...

[Lockemeister]

@OH2FFY see links posted in the description

[Lockemeister]

@umajunkcollector Thanks! Ferrite beads is a great idea. I'm going to check the SWR across the entire 80 meter band and then try the 4 meter band as see what the SWR comes out to be. I was able to get 1.2 :1 so I hope it's not a fluke