double biquad

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OK, the biquad parallels two 100 ohm loops to make 50 ohms. How does the double biquad get away with 4 loops?

Reply to
miso
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If you look carefully at the double biquad, the outer two quads are connected in series with the opposite ends of the inner two quads. The result is 200 ohms on each side of the coax or 100 ohms in paralle. If you look at the NEC2 results at:

you'll notice that the impedance is 100 ohms, not 50 ohms with a resultant VSWR of 2:1. (I'll make the above URL look pretty later).

Reply to
Jeff Liebermann

I get it. Seems to me we need a double double biquad. Next time I'm at In and Out, I will see if they have one.

Reply to
miso

I was a bit sloppy with my explanation. Take a single 100 ohm quad loop element and break the end opposite the feed. That gives two 50 ohm sections. Put another 100 ohm quad loop across the break point, and we have: 50 + 100 + 50 = 200 ohms. Put two of those in parallel, and we have a 100 ohm antenna.

You could probably get it back to 50 ohms by taking two such double-double biquad antennas, placing them 1 wavelength apart on a common reflector, and connecting them together using two odd multiple of 1/4 wavelength, 75 ohm coax cables as is commonly done in collinear dipole antennas.

Here's one attempt:

which I think has a problem as he's assuming a 50 ohm feed point for each double biquad.

Now, what the deleted expletive does this have to do with In and Out burger?

Reply to
Jeff Liebermann

Does "double double" not mean anything to you? The cry of "Eight meat down!" when you order two four by fours is priceless.

Reply to
alexd

Sorry, but I'm culturally retarded.

I haven't been to an In and Out Burger in maybe 30 years. I might eat two burgers per year, and that's usually at a barbeque. I have no clue what "eight meat down" means. Google didn't help. However, I do know what's a 4 by 4. I use 4 by 4 lumber to support my house.

Reply to
Jeff Liebermann

That's all beyond my cultural experience also. Oh, I used 4x4s to hold up a fence.

But Jeff, you could do the wifi DIY's a big help if you could perfect the double double and still keep it simple.

I wonder if the pcb is a stripline that is used to transform the impedances? That would be the most difficult part for many.

If you can't design it to eliminate the stripline transformer (if that's what it is) you could sell the pcb!.

I like it because the construction is so simple. Can you really get 16-17 db gain in 7" x 7"? :-)

Mikek

Reply to
amdx

It is part of the secret menu at In and Out. It isn't so secret since you can find the "off the menu" items on the internet. Technically, I don't believe a double double is a legit meal, which is why google didn't help. You would ask for a four by four.

Reply to
miso

My idea of simple is the Franklin/Amos antenna. See various examples near the top of:

The main problem with building a double-double biquad or AMOS is the wire standoffs. Cheezy nylon doesn't work. Custom ceramic or glass are tempting if you're into pottery or working glass. It's really tempting to make the entire AMOS wire antenna out of a polysufone (not G10/FR4) PCB (printer circuit board). That's easy for the AMOS as it could be single sided, but with the double-double biquad, it would need to be etched on both sides to deal with the crossover. If you're going to build just one, all this is irrelevant. If you're going to manufacture, it's vital.

I'll throw together a proper NEC model and offer some construction ideas for do-it-thyself constructions. With semi-rigid coax, the double double biquad is quite easy. However, no now. I'm busy with paying work.

I can't figure out what he's trying to do. Each double biquad section has a 100 ohm feed point impedance. One could parallel two of these to get 50 ohms, if they were on top of each other, or separated by any multiple of 1/2 wave sections of mythical 100 ohm coax cable. (75 ohms would be close enough). Yet, the stepped PCB strip line in the photo is doing something else, which I can't guess without dimensions or a description.

The original design apparently came from this site:

but I can't find it.

No thanks. I can make money selling expensive antennas (or expensive consulting), but not cheap antennas for experimenters. If you want cheap and easy, think about multiple patch antennas on PCB material. For example:

14dBi gain is a bit optimistic, because it ignores matching section losses. My guess is 12dBi maximum on a 5.5" x 5.5" PCB. I have several of these, but have never bothered to measure the gain or sweep the VSWR.

I don't think it's that simple. Permit me to remind you that things become more critical as the gain goes up. One can be rather sloppy when building antennas with gains of less than about 12dBi. Higher gains require a pile of test equipment and some precision construction.

Close. Doubling the size of an antenna yields 3dB more gain. The model for the original double biquad claims 13.5dBi gain. Two of these, properly combined, minus about 1dB combiner loss, would yield: 13.5 + 3.0 - 1.0 = 15.5dBi gain Using lossy materials (i.e. leaky standoffs, lossy coax, and lossy PCB material) will reduce this some unknown amount. The 15.5dBi is the very best that can be done. Your mileage will be less.

Reply to
Jeff Liebermann

Be sure to ask for it "Animal Style".

Isaac

Reply to
isw

double double = two meat, two cheese

four by four = four meat, four cheese

You order two four by fours and they'll need to grill eight patties.

Reply to
alexd

I did that once. It is not my style, so I guess I'm not an animal. I don't like a lot of sauce on my food. IIRC, animal style used a lot of mustard.

Incidentally, you can ask for the fries to be well done.

While we're at it, the last tidbit of In and Out useless trivia is the bottom of the cups have bible verses on them. One of the previous CEOs was quite the bible thumper, not that it saved his arse from dying in a plane crash.

Reply to
miso

Doesn't that just mean that God wanted him NOW! And I guess everyone else on the plane too. Funny how he got them all on the same plane, but I guess he can do that too. Mikek, in an agnostic mood I think there ain't no heaven but I pray there ain't not hell.

Reply to
amdx

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