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The Double Diamond

Stephen Sherer (KE4LJH) on August 16, 2013
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Here is an antenna that I designed back in the 90's for 6 meters initially and posted on a QRP forum. It has been so long ago that when I checked not too long ago the post I made of this design has now disappeared into the ether. It can be used for both vertical polarization needs and horizontal polarization needs. It can be scaled to any band VLF to 23cm and above. It has no limit.

I found someone in Europe recently, touting this same design now as the ultimate HF antenna.

In the 90's I called it and published it as, "The Double Diamond"

Two full wavelength loops in phase.

Visualize two squares, one standing on top of the other, each standing on a corner. It will look like two diamonds. Now visualize rotating the antenna into the horizontal plain. Feed in the center with ladder line.

Now visualize this antenna designed for 160m.

Draw this on a sheet of paper with a pencil. In the center, where the wires come together, (at the two corners), the wires do not cross and they do not touch. They merely converge closer together and then diverge away, within a few inches.

This is also your 52 ohm feed point.

In perfect conditions which we all know do not exist for antennas, each full wave loop has a characteristic impedance of 104 ohms. Two full wave loops in phase as described, have a characteristic impedance of 52 ohms. (At perfect elevation figuring in ground effects, soil conductivity, near by metal object and on and on. Don't worry about these two much).

How many times have I seen 52 ohms as a reference in the ARRL antenna book!

How many times have I reviewed over the years the secret knowledge the ARRL still continues to publish today, for wire antennas, the graph, "Wavelengths vs. Gain".

One does not build a 160m horizontal loop just for 160m.

Let's see. How much gain will this antenna have on 20m by virtue of the number of wavelengths per acre?

When building wire antennas of any configuration consider the following:

(1005/Fmz) X (Velocity Factor if insulated wire is used)= One wavelength in feet.

This is the ROOT equation that the 468/fmz number was derived.

The venerable equation 468/fmz was specifically designed for use with 12 gauge insulated wire with a known velocity factor. This is why every time one uses the 468 number, their antennas are cut either too long or too short every time.

This antenna is also used commercially in the microwave region, sat phones and satellite communications.

Yes, it can also be used at VLF/HF.

It is not published in so far as I know, in the ARRL Antenna Book in this configuaration. Two full wave loops in phase.

If I had a magic wand and could have everything I could possibly want.

Honey, Buy Me A Diamond...

From the antenna files of:

"The Double Diamond"

Member Comments:
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RE: The Double Diamond  
by KC8FRJ on August 16, 2013 Mail this to a friend!
The Double Diamond  
by W4UKR on August 16, 2013 Mail this to a friend!
We used a number of these, on hf, running about 5kw, in the FAA overseas. Worked great. Our were labeled such as type E or type F. Was notified by FCC that we killed the AT&T Sanfrancio- okinara circuit. This was in the sixties. Good antennas.
The Double Diamond  
by AD5VM on August 16, 2013 Mail this to a friend!
The Double Diamond  
by JOHNZ on August 17, 2013 Mail this to a friend!
Outstanding antenna! Used HF versions of it in the military during the Viet Nam War and later when employed by a government agency. A great performer, both receiving and transmitting. Using a patch panel, we had the ability to do side-by-side antenna comparisons, and the Double Diamond consistently out performed all other antennas we had. As mentioned, it will perform in the VLF range too.
The Double Diamond  
by KI5FJ on August 19, 2013 Mail this to a friend!
I use a Bow-Tie shaped DD. Three double loops nested, wires cut for a extra wide band 140-160 MHz. Fed in the center of the Bow-Tie. The nulls are great for Directional Finding. 73 Joe O NNNN
The Double Diamond  
by W0AEW on August 19, 2013 Mail this to a friend!
What are its advantages over a dipole?
The Double Diamond  
by KH6AQ on August 19, 2013 Mail this to a friend!
A picture would really help this article. Is this antenna the same as a Bi-Quad antenna?
The Double Diamond  
by KI5FJ on August 19, 2013 Mail this to a friend!
The DD is also known as a Bi-Quad.
The advantages over a dipole:
1.Wider SWR bandwidth
2.Deeper Nulls
3.Higher gain @ low TOA for DX.
Example a 30-M dipole up 20 Ft is a NVIS radiator. Not Bad if you want regional communications. Poor for DX. A Bi-Quad with feed-point @ 20 Ft is a DX radiator, 3.3 dBi @ 22 degrees Elevation.73 Joe O NNNN
RE: The Double Diamond  
by JOHNZ on August 19, 2013 Mail this to a friend!
Yes, still a very good antenna for DF use by amateur radio operators and other scenarios and applications which do not require highly sophisticated technologically advanced DF equipment, such as the military and other government agencies. The forestry & wildlife folks at a local university here have used the bow tie DD to detect and track tagged wildlife. Can still recall in the 50s when automated DF equipment was not yet available. The bow tie DD was one of several antennas we were using for close-in and long range DF applications.
RE: The Double Diamond  
by KH6AQ on August 19, 2013 Mail this to a friend!
An EZNEC model shows the antenna to have a gain of 1.8 dB over a dipole.
The Double Diamond  
by KI5FJ on August 20, 2013 Mail this to a friend!
Historically, references to this antenna type,
AKA Bi-Loop go back earlier than 1979.
Dig out your Feb 1995 or Apr 1979 issues of 73 Magazine. Also see (136-Bi-Loop)
73 Joe O NNNN
The Double Diamond  
by KE4ZHN on August 26, 2013 Mail this to a friend!
These antennas are okay, but any good yagi will blow one away.
The Double Diamond  
by AC0MP on September 11, 2013 Mail this to a friend!
Is the feed line attached across what is a continuous wire bent into a double diamond or a double loop? I think this would make it in phase.
Or are there two separate loops each fed with one side of the feed line? Much like a dipole where each side is a diamond instead of a single line.

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