Dave Platt wrote:

Is it any more efficient to use copper foil or PCB material as the reflector
rather than wire?

I believe not.

PCB material will probably be less efficient - standard FR-4
fiberglass-and-epoxy has significant losses at 2.4 GHz. Also, the
presence of the FR-4 will change the effective length/diameter of the
reflector loop... you might have to change the loop diameter to
compensate.


I would think so, at 2.4Ghz there is, no doubt, "only skin effect."
Although, I doubt you would notice a great change in efficiency, it
should be prove-able, at least on paper. The biquad uses a solid
reflector plate for good reason, wire is cheaper/easier to obtain. If
the foil side faces the element, I should doubt any rf gets past it to
the fiberglass-epoxy to be "lost" in efficiency.

Foil would probably be bit less efficient than wire, assuming that the
width of the foil was the same as the diameter of the wire - less
surface area for the current to flow through, and perhaps more current
crowding to the edges of the foil due to skin effect. It'd also be
significantly less rugged.


My statement above applies here ... all the wire element can "see" is
reflector, with foil.

Once again, neither of these losses of efficiency is likely to be
terribly important in this application, but why run the risk?

I'd just stick with solid copper wire of a reasonable diameter/gauge,
as it'll be electrically efficient and mechanically strong and rigid,
easy to get, and inexpensive.


Tear apart some LNA/satellite feeds to the dish, you will not see them
using wire reflectors there; I think there is good reason.

Just my opinions drawn from my readings/study, looking at commercial
equipment and hands-on ...

One thing I do totally agree with, it WILL work well with just a wire
reflector.

Regards,
JS

John Smith wrote:

...
One thing I do totally agree with, it WILL work well with just a wire
reflector.

Regards,
JS


I built this, actually, a while back. Toss in a director (what is one
more wire?); I found that to be a worthwhile mod ...

Regards,
JS

I built this, actually, a while back. Toss in a director (what is one
more wire?); I found that to be a worthwhile mod ...

Regards,
JS

Suggestions re. dimensions and location of a director?

Thanks.

SparkyGuy wrote:
I built this, actually, a while back. Toss in a director (what is one
more wire?); I found that to be a worthwhile mod ...

Regards,
JS

Suggestions re. dimensions and location of a director?

Thanks.


I believe I tried lengths of a 3% to 5% shorter length with the
director, than the drive element (i.e., the one in front of the
reflector), settling on a 4% shorter length ... anyway, that is common
in HF parasitic arrays ... this is equiv. to a 3-element quad on HF.

I just dug it out and measured it, this is what it appears to be,
alright. With a spacing between driven element and director of ~0.2
wavelength, center-to-center.

Regards,
JS

I believe I tried lengths of a 3% to 5% shorter length with the
director, than the drive element (i.e., the one in front of the
reflector), settling on a 4% shorter length ...

So about 26.8mm square?

With a spacing between driven element and director of ~0.2
wavelength, center-to-center.

So the director should be 25 mm forward (toward the uwave source) of the
driven element? (3e8 / 2.4e9) x 0.2 = ~25mm

Do these numbers look right?

Thanks.

SparkyGuy wrote:
I believe I tried lengths of a 3% to 5% shorter length with the
director, than the drive element (i.e., the one in front of the
reflector), settling on a 4% shorter length ...

So about 26.8mm square?

With a spacing between driven element and director of ~0.2
wavelength, center-to-center.

So the director should be 25 mm forward (toward the uwave source) of the
driven element? (3e8 / 2.4e9) x 0.2 = ~25mm

Do these numbers look right?

Thanks.


My elements are made from #14 bare copper wire. It is difficult to
measure each side, individually, when constructing the antenna. Better
to cut the wire to 1 wavelength, then make your bends forming it into a
square. Of course, every attempt possible should be made to keep each
side 1/4 of this length, exactly.

In measuring the one before me, which I constructed, this total length,
about the quad, is ~12.5cm.

However, here is a calculator I referenced in my constructions:

It is a java application, you must have java on your computer. Let me
know if you can't access it and I will give you the figures it spits
out, 2.4ghz = 2400mhz. Just let me know what wifi channel you wish to
center on (frequency.)

Regards,
JS

John Smith wrote:

...
However, here is a calculator I referenced in my constructions:

It is a java application, you must have java on your computer. Let me
know if you can't access it and I will give you the figures it spits
out, 2.4ghz = 2400mhz. Just let me know what wifi channel you wish to
center on (frequency.)

Regards,
JS

Well, da! It would help if I cut loose with the URL. sheepish smile

http://www.n6mrx.com/Antenna/Cubical-Quad1.htm

Regards,
JS

SparkyGuy wrote:

...
Suggestions re. dimensions and location of a director?

Thanks.


Had company today, been in and out all day ... sorry I didn't offer more.

A wavelength at 2.4Ghz will be approx. 12cm, half-wave ~6cm, 1/4 wave
~3cm. (with a very thin wire 1/2 wave monopole-omni-element I find
~12.25cm works for me, element dia. will affect this, as other factors ...)

Anyway, I looked though my old emails for something a friend sent me,
thought if you were interested in the 2.4g fsm, you might be interested
in this, if nothing else, just because the dude is so complete!:

http://www.users.bigpond.com/darren....enna_for_2.htm

You will notice, he uses a plate reflector ...

Regards,
JS

On Sun, 07 Dec 2008 21:40:38 -0800, John Smith
wrote:

A wavelength at 2.4Ghz will be approx. 12cm, half-wave ~6cm, 1/4 wave
~3cm. (with a very thin wire 1/2 wave monopole-omni-element I find
~12.25cm works for me, element dia. will affect this, as other factors ...)

Anyway, I looked though my old emails for something a friend sent me,
thought if you were interested in the 2.4g fsm, you might be interested
in this, if nothing else, just because the dude is so complete!:

http://www.users.bigpond.com/darren....enna_for_2.htm

You will notice, he uses a plate reflector ...

Regards,
JS

I also noticed that he cut his elements to a precision of 0.1mm. That
would be correct if the boom were an insulator or the elements were
inserted in insulating sleeves. However, since the 10mm square boom
is metal and effectively "shorts" part of each element, the actual
element length includes part of the diameter of the boom, thus adding
approximately 5mm to each element length (not including the reflector
and driven element). A VSWR sweep test would have shown the problem.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann wrote:

...
I also noticed that he cut his elements to a precision of 0.1mm. That
would be correct if the boom were an insulator or the elements were
inserted in insulating sleeves. However, since the 10mm square boom
is metal and effectively "shorts" part of each element, the actual
element length includes part of the diameter of the boom, thus adding
approximately 5mm to each element length (not including the reflector
and driven element). A VSWR sweep test would have shown the problem.


I have always used #8 wire as a boom on ghz yagis' (constructed a 7
element once.) Since the boom is at a current antinode (voltage node),
I ignored the boom.

The boom you mention is rather LARGE, give the freqs in question.

One of my next projects is a GOOD VSWR meter for ghz ... unfortuantly,
on the list of priorities here, it is low on the list ... :-(

I have just tended to take the % signal readings on the chans as good
enough, and trimmed my antennas accordingly. I know, this does NOT take
into account the functioning/power-fluctuations/antenna(s)/etc. of the
AP over these ranges ...

But, excellent point, glad you mentioned it ... but you are right, my
elements end up being filed down a bit from the figures the calculator
spits out ...

Warm regards,
JS