Cophased Biquad Vertical (QST?)

[C2]

A fellow ham was describing a pair of vertically oriented biquad antennas cophased on the same mast with their planes 90 degrees, and a coax phasing feed to one of the antennas.

This would result in an omni directional pattern with moderate gain.

Does anyone have the details?

 

[W5LZ]

What is a 'biquad'??
- 'Doc

 

[C2]

basically two loops oriented in a figure 8 and fed in the center,

usually constructed with two quads,

double diamonds,

a bow tie antenna?

 

[mackmobile43]

does it make it omni-directional for vertical or horizontal?

 

[RickC.]

I know of a Bi-Square from old antenna handbooks that can be suspended from the same mast at right angles and fed seperately for about 4 dBd gain broadside, but I don't know of anyone who's ever used them since they're twice the size of a regular quad loop-- two full wavelengths each.

Can you give us any more hints? Any idea the date (what year) QST? I'll look around.


Rick

 

[C2]

It would be the current issue, but I'm just getting the info 2nd hand. It might be the previous issue.

polarization--I'm thinking it would be whatever polarization a typical quad would be fed at the bottom...errr, horizontal?

 

[RickC.]

I just re-upped so I may not get that particular issue. Don't think current issues are available online, but will look.

Sounds like an interesting antenna, but also sounds like a lot of trouble to get an omni antenna!

(Just checked, it's on page 30 of the August issue. I don't have it yet, and you can't read the article online. 2m antenna.)


Rick

 

[jazzsinger]

a link to the general construction technique of biquad antennas,would love too see one of those built for 10/11m

Biquad Antenna Construction

 

[W5LZ]

I think that when scaled up for lower than microwave frequencies, that thing would start getting kind'a big real quick! Might be practical for VHF, but I don't think I'll worry about it ever being used on HF.
- 'Doc

 

[RickC.]

I think that when scaled up for lower than microwave frequencies, that thing would start getting kind'a big real quick!
- 'Doc

Yeah!

 

[Beetle]

The "Diamonds in the Sky" article is on page 30 of the August 09 issue. This is a Double Diamond Turnstile" (DDT) antenna, not a "cophased biquad" or whatever. Excellent antenna for VHF and above; I've used similar antennas. For 11 meters, multiply all dimensions by four or five.

 

[C2]

maybe for 10 meters, after all, a cubical quad has 4 loops, why not just reorient them?

 

[C2]

The "Diamonds in the Sky" article is on page 30 of the August 09 issue. This is a Double Diamond Turnstile" (DDT) antenna, not a "cophased biquad" or whatever. Excellent antenna for VHF and above; I've used similar antennas. For 11 meters, multiply all dimensions by four or five.

Your diamond is my quad, or square...While all squares may be diamonds, not all diamonds are squares.

The way I look at it, a quad is a square, full wave loop. I deduce this by the multiple articles about two element quads and cubic quads, etc...

Therefore, a biquad is two square, full wave loops. I'm not sure about the double biquad, but it seems to be an extention of the biquad with four linear loops built from a single wire.

Now, for the "Diamond in the Sky" you have two biquads, one is fed 90 degrees out of phase, at least that is the jist of what I've been able to determine. Is this not to some extent cophasing? Well, maybe the double diamond is not cophased with the other, but perhaps the the double diamond is a cophased arrangement? Or is that colinear?

Hello Lucy...

 

[Beetle]

maybe for 10 meters, after all, a cubical quad has 4 loops, why not just reorient them?

My quad (not "cubical") only has two loops.

 

[C2]

I got the article. Looks exactly as I invisioned.

I was dissapointed to read the expected 3.5 dBi gain figure. Isn't a typical 5/8 wave ground plane vertical higher gain? IIRC, that is only about 1.5 dBd...

I was considering an improvement by making it out of two double biquads, but that is as far as I got...

What are other options for higher gain omni's?