What do you think is the best Omnidirectional antenna for 11 meters ?

[Mudduckmobile]

MD: Delta Loop looks cool.
I have a question though, is that a metal mast?

No the mast is not metal, the mast is a "tepee pole". The Pole is 28 ft long, and it is mounted on my deck on the 2ed story. (the pully is brass).
I still need to play with the loop a bit, I need to add a few inches. I am X=0 and R= 47-52, and the swr is 1.9, 2.4 ish, I would like to get 1.1, 1.2 at 27.555 but time will tell. My roof is all metal as well.
In a few days I should be getting my Sirio 2016, I will be putting it on the top of the mast, about 5 ft higher on pvc to the mast. I will keep the pully on for diploe and other wire antennas.
I am going to put up 2 dipoles. one for 11 meters and one for 45 meters.(6670lsb).

 

[BJ radionut]

Well don't get to crazy trying to get that loop to match that low...I would bet that 1.5:1 is the best place to stop. The true impedance should be about 73 ohms (if I remember correctly but can be as high as 200 ohms or more)....feedpoint location, height above ground and other factors change this. Thus trying to tweak it down that low will most likely result in changing the electrical length shorter than it should be....
Low VSWR does not always mean best performance!
The Delta loop is an excellent performer...normally a quiet antenna when feed for Horizontal operation compared to a vertical.
So have fun and enjoy it should serve you very well as set-up.
All the Best
Gary

 

[Mudduckmobile]

Well don't get to crazy trying to get that loop to match that low...I would bet that 1.5:1 is the best place to stop. The true impedance should be about 73 ohms (if I remember correctly but can be as high as 200 ohms or more)....feedpoint location, height above ground and other factors change this. Thus trying to tweak it down that low will most likely result in changing the electrical length shorter than it should be....
Low VSWR does not always mean best performance!
The Delta loop is an excellent performer...normally a quiet antenna when feed for Horizontal operation compared to a vertical.
So have fun and enjoy it should serve you very well as set-up.
All the Best
Gary

How right you are...Maybe I should have left it as is...Now I'm at:
26.825, R=109, X=0. swr 3.0
23.344. R=23/24, X=0 swr 5.1
27.385, R=48, X=10. swr 2.7
27.555, R=38, X= 7. swr 2.6
My Yaesu ft450d can clean it up but I think I should get it better...?
My "best showing now looks like:
35.765 R=91 X=0 swr 1.5
36.182 R=86, X=0 swr 1.5
136.33 R=71 X=0 swr1.3
And so on...

 

[BJ radionut]

Frequency in MHz:

27.500 MHz



Length of full-wave loop:

• 36 feet, 6.5 inches
• 11.14 meters

The calculated length is approximate. In practice it's best to make the antenna a little longer than the calculated value and then trim it to get the best SWR value.

Feedpoint impedance and coaxial matching section
The feedpoint impedance at the design frequency is about 100 ohms, so full wave loops are often fed with an impedance-matching section made from a piece of 75-ohm coxial cable one quarter wavelength long (shortened to compensate for the velocity factor of the cable).

Length of an impedance-matching section with 75-ohm cable with a velocity factor of 0.66 (polyethylene dielectric):

• 5 feet 10.8 inches
• 1.80 meters

Length of an impedance matching section made with 75-ohm cable with a cable velocity factor of 0.80 (foam dielectric):

• 7 feet 1.9 inches
• 2.18 meters

http://www.66pacific.com/calculators/full-wave-loop-antenna-calculator.aspx

Keep going as is till you put up the other antenna...then "retweak" it for your spot...
YEP certainly looks like it's too short.
All the Best
Gary

 

[Mudduckmobile]

Frequency in MHz:

27.500 MHz



Length of full-wave loop:

• 36 feet, 6.5 inches
• 11.14 meters

The calculated length is approximate. In practice it's best to make the antenna a little longer than the calculated value and then trim it to get the best SWR value.

Feedpoint impedance and coaxial matching section
The feedpoint impedance at the design frequency is about 100 ohms, so full wave loops are often fed with an impedance-matching section made from a piece of 75-ohm coxial cable one quarter wavelength long (shortened to compensate for the velocity factor of the cable).

Length of an impedance-matching section with 75-ohm cable with a velocity factor of 0.66 (polyethylene dielectric):

• 5 feet 10.8 inches
• 1.80 meters

Length of an impedance matching section made with 75-ohm cable with a cable velocity factor of 0.80 (foam dielectric):

• 7 feet 1.9 inches
• 2.18 meters

http://www.66pacific.com/calculators/full-wave-loop-antenna-calculator.aspx

Keep going as is till you put up the other antenna...then "retweak" it for your spot...
YEP certainly looks like it's too short.
All the Best
Gary

Swamped today....Will be cutting new loop (longer) to work on after s-2016 is ready to put up. Loop as is is working well, quite, some power loss.....I'll get her fixed soon.
Thank you for your help..

 

[BJ radionut]

MD: Here is a chart , that most of the masses don't believe...and why it can be futile to try and achieve "The ultimate match."
Notice the minute difference from 1:1 to 2.5:1....Transmission dB loss of .88...(NOT EVEN 1 dB!)
100 watts in = 82 watts out.... and NOBODY on the receive end will ever know it!
Enjoy
All the Best
Gary

PS...GET YOUR GENERAL!

 

[Mudduckmobile]

MD: Here is a chart , that most of the masses don't believe...and why it can be futile to try and achieve "The ultimate match."
Notice the minute difference from 1:1 to 2.5:1....Transmission dB loss of .88...(NOT EVEN 1 dB!)
100 watts in = 82 watts out.... and NOBODY on the receive end will ever know it!
Enjoy
All the Best
Gary

PS...GET YOUR GENERAL!

Thank you very much. I just stopped by on my lunch.
Now that things are starting to slow down here, come nov. it will get real slow and I can get back to the books.

 

[sp5it]

I am X=0 and R= 47-52, and the swr is 1.9, 2.4 ish

it is impossible. SWR with that values should be 1,065. Are you sure your measurement device is accurate?
Mike

 

[bob85]

sp5it, its not impossible,

impedance measured at the input of his coax does not determine vswr,

his antenna is mismatched to the line,
as you move away from the mismatched load along the line impedance will swing up and down while vswr stays constant for lossless or short lines,

since his coax has some loss vswr will measure lower at the input end of the coax vs at the antenna,

impedance on his analyser will be whatever his length of coax transforms the mismatched load impedance into at its input end.

vswr on his analyser will be the ratio of coax impedance to load impedance minus whatever loss he has in his coax.

 

[Mudduckmobile]

it is impossible. SWR with that values should be 1,065. Are you sure your measurement device is accurate?
Mike

It is.

 

[Mudduckmobile]

sp5it, its not impossible,

impedance measured at the input of his coax does not determine vswr,

his antenna is mismatched to the line,
as you move away from the mismatched load along the line impedance will swing up and down while vswr stays constant for lossless or short lines,

since his coax has some loss vswr will measure lower at the input end of the coax vs at the antenna,

impedance on his analyser will be whatever his length of coax transforms the mismatched load impedance into at its input end.

vswr on his analyser will be the ratio of coax impedance to load impedance minus whatever loss he has in his coax.

I found that out in real time bob85. When I was putty up the loop I first put my 259C on at my feed point, ran it up and looked at with my scope.
Then I tested it with 20ft of DX Eng. 8X coax (new). I then tested with a 50 ft. DX Eng. 8x coax. And now have it on the 50 + 20 ft.
I also noted that by moving my feed point up and down the "sides" of the Delta I would get better or worse readings. As luck would have it....MY best readings came with my coax coming off the loop in a way I can not keep all the time with snow coming.

 

[sp5it]

Use 180° cable. You will see true readings at the load.
Mike

 

[Mudduckmobile]

Use 180° cable. You will see true readings at the load.
Mike

I do not know what that is...?

 

[Mudduckmobile]

I do not know what that is...?

Well I played with it to much yesterday..
I added to much wire, and moved the feed point. Feed point is at apx.42ft. now, and my loop is at:
25.584 R= 110, X= 0, swr2.2
to
26.310 R= 102, X=0, swr2.0
27.000 R=42, X=19 swr 1.8, swr1.7
27.385 R=33, X=14, swr1.7
27.555 R=32, X=11, swr1.6
My feed point is now so I am Vert. (man there is noise here),
I need to move feed point back to Horz.
I am in a Diamond shape now as well.

 

[Mudduckmobile]

Oh one more thing when I power up my computer I get 4 on the S meter, when I power off the computer it goes away...Any help?