11m delta loop question

[Crasher]

I am going to attempt to build an 11m delta loop, but have a question.

On this style, do all 3 wires connect together? Also, the 75ohm coax..can this be coiled or have to be left straight? I am going to try to get this up as high as possible and hopefully outperform my vertical for DX and long distance. Thanks!

 

[Robb]

11 Meter Loop Antenna

This page has the best explanation that I'd seen.

Gives the formula to determine the length of the 75 ohm matching section.

 

[Crasher]

Perfect!
Thanks for the info!

 

[vkrules]

Yes it's 1 wire ,hence the name loop, the 75 ohm cable can be coiled.When configured as in your diagram the loop will be horizontally polarized .Great DX aerial.

 

[vkrules]

Also the 1/4 wave 75 ohm matching section length is 1/4 x propagation factor not a straight 1/4 wave.

 

[Robb]

For the 75 ohm coax with a velocity factor of .66, the length is 5 ft 10 in.

Using the formula, you could use other types of 75 ohm coax with a different velocity factor and the result will have a different length.

To calculate the length of wire needed for a 11 meter loop antenna, we must use a formula. Divide 1005 by Frequency in Mhz will give you length in feet.
For example, if we wanted our loop to receive on 27.555 Mhz we would divide 1005 / 27.555 = 36.47 feet or 36 feet, 6 inches.

Before we attach this loop to our 50 ohm coax we need to put a matching section in between the loop of wire and the 50 ohm coax.

This matching section is a section of 75 ohm coax.
(Same as cable tv coax. If you are unsure of the coax's velocity factor, go online and look up the codes printed on the side of that coax first.)

To figure the length of this 75 ohm coax matching section:

This 75 ohm section will be a quarter wavelength of the operating frequency.
To get this we calculate 246 Divided by frequency.
In this case it's 246 / 27.555 = 8.93 feet or approximately 9ft.

Now we need to figure the "Velocity Factor" before we cut this 75 ohm piece.
The velocity factor of your coax is either .66 or .80.
Most RG-59u is .66 so we will use that.

Now take that 8.93 feet from above and multiply that by .66.
For this the answer is 5.89; or 5 feet 10 inches.

If you have .80 velocity factor coax, just multiply 8.93 by .80.
For this the answer is 7.14; or 7 feet 2 inches.

Note:
This 75 ohm coax is a tuned length and acts as an impedance transformer. Without it, the loop antenna will not have a usable impedance and the SWR will be way off scale.

 

[BJ radionut]

This will give slightly more gain than a Delta Loop...and requires no matching stub it's direct feed with 50 ohm coax
To change calculations to 11mtr's add approx. 4% to the total length...
ie: 152" vs. 146" for the long side
ie: 76" vs 73" for the short side
These lengths should be close for 27.2mc....
Just a thought
All the Best
Gary

 

[vkrules]

If you have only 1 high mounting point you can turn the delta upside down ,apex up base down and feed from the center of the base ( you can feed at any point on the loop but it will change your polarization ).Here is a variation you might want to try. make the loop a rectangle 12 ft high and 6 ft wide ( use the same formula for exact length)feed at the center of the bottom leg with 50 ohm coax, this configuration is 50 ohm so no matching section is required and it provides about .5 db more gain.

 

[vkrules]

You beat me to it.

 

[wavrider]

I have a pair of co phased delta loops.

They work fantastic on 10 meters. Very broad banded.

 

[nosepc]

I am going to attempt to build an 11m delta loop, but have a question.

On this style, do all 3 wires connect together? Also, the 75ohm coax..can this be coiled or have to be left straight? I am going to try to get this up as high as possible and hopefully outperform my vertical for DX and long distance. Thanks!

If you want to overcome any vertical antenna with some directionality, use the antenna in this manner. Just a single square.
The polarization is vertical.
After many tests with loops is the best configuration achieved.
This is simmilar to a "hentenna"

 

[W5LZ]

Wasn't too long ago one of the antenna manufacturers made a similar antenna but it was switchable in direction, a N-S and E-W sort of thingy.
The only significant difference in the 'Hentenna' and a differently shaped 'quad' is in it's input impedance and it's method of being supported (only needs one support 'pole' and a couple of cross arms).
I think it's an interesting antenna and still plan to make one if I ever get a round to it...
- 'Doc

 

[nosepc]

Wasn't too long ago one of the antenna manufacturers made a similar antenna but it was switchable in direction, a N-S and E-W sort of thingy.
The only significant difference in the 'Hentenna' and a differently shaped 'quad' is in it's input impedance and it's method of being supported (only needs one support 'pole' and a couple of cross arms).
I think it's an interesting antenna and still plan to make one if I ever get a round to it...
- 'Doc

Take you any wire, lined or not of length 37 '
With 12 'high enough to get a very good lobe.
Hang it in this manner from anything and be surprised.

 

[Henry HPSD]

Hello,

Most certainly a fun antenna.
Its always most fun if you construct it your own !
On the SWR plot you can see the rather small swr bandwidth (50 ohms set for 27,555 Mhz which is the int dx freq)

Perhaps a possible option could be the bi square.
A antenna i tend to use most often for portable use.

Attached a pdf with some info how to make one...

Hope it is of use...

Kind regards,

Henry 19sd348