So here's the deal. I want to sit in my car in a parking lot and access
wi-fi legitimately in a nearby building.
(I'm authorized to use the system and have a password.)

The device is similar to an ipod (no phone).

I used a passive RF sniffer around the case and found a sweet spot that has
significant RF output.

What I want to experiment with is a coupling loop over the case sweet spot
going to a coax and then a directional antenna.

It would be acceptable to simply scotch tape the loop on the case.

Any suggestions on the antenna would be appreciated.

Wayne
W5GIE

On 3/26/2016 2:43 PM, Wayne wrote:
So here's the deal. I want to sit in my car in a parking lot and access
wi-fi legitimately in a nearby building.
(I'm authorized to use the system and have a password.)

The device is similar to an ipod (no phone).

I used a passive RF sniffer around the case and found a sweet spot that
has significant RF output.

What I want to experiment with is a coupling loop over the case sweet
spot going to a coax and then a directional antenna.

It would be acceptable to simply scotch tape the loop on the case.

Any suggestions on the antenna would be appreciated.

Wayne
W5GIE


You may have thought about this... You might need to amplify your
receive signal, the device (whatever it is) needs to talk both ways.
Bob W

On 3/26/2016 6:02 PM, Bob Wilson wrote:
On 3/26/2016 2:43 PM, Wayne wrote:
So here's the deal. I want to sit in my car in a parking lot and access
wi-fi legitimately in a nearby building.
(I'm authorized to use the system and have a password.)

The device is similar to an ipod (no phone).

I used a passive RF sniffer around the case and found a sweet spot that
has significant RF output.

What I want to experiment with is a coupling loop over the case sweet
spot going to a coax and then a directional antenna.

It would be acceptable to simply scotch tape the loop on the case.

Any suggestions on the antenna would be appreciated.

Wayne
W5GIE


You may have thought about this... You might need to amplify your
receive signal, the device (whatever it is) needs to talk both ways.
Bob W

Whatever you do with the antenna should work in both directions, no?

--

Rick

"rickman" wrote in message ...

On 3/26/2016 6:02 PM, Bob Wilson wrote:
On 3/26/2016 2:43 PM, Wayne wrote:
So here's the deal. I want to sit in my car in a parking lot and access
wi-fi legitimately in a nearby building.
(I'm authorized to use the system and have a password.)

The device is similar to an ipod (no phone).

I used a passive RF sniffer around the case and found a sweet spot that
has significant RF output.

What I want to experiment with is a coupling loop over the case sweet
spot going to a coax and then a directional antenna.

It would be acceptable to simply scotch tape the loop on the case.

Any suggestions on the antenna would be appreciated.

Wayne
W5GIE


You may have thought about this... You might need to amplify your
receive signal, the device (whatever it is) needs to talk both ways.
Bob W

Whatever you do with the antenna should work in both directions, no?

That's the plan. A bidirectional passive system with maximum coupling of
the ipod to transmission line.

Today I tried a loop pickup at the ipod to some RG-58 that has a pickup loop
at the other end.
I'm getting nearly the same level with the RF sniffer at the ipod or at the
remote end of the cable.
One difficulty is that the ipod doesn't transmit all the time, and that
affects attempts to optimize the coupling.

If I can optimize the pickup loop, I could permanently attach it inside a
slip on cover I have for the ipod.

I'm drawing a blank on a good/easy to build antenna.

Wayne wrote:
So here's the deal. I want to sit in my car in a parking lot and access
wi-fi legitimately in a nearby building.
(I'm authorized to use the system and have a password.)

The device is similar to an ipod (no phone).

I used a passive RF sniffer around the case and found a sweet spot that has
significant RF output.

What I want to experiment with is a coupling loop over the case sweet spot
going to a coax and then a directional antenna.

It would be acceptable to simply scotch tape the loop on the case.

Any suggestions on the antenna would be appreciated.

Wayne
W5GIE

Have you tried making a corner reflector out of something cheap and
holding the device inside it as a test?

I've done that with cell phones in weak areas; sometimes it works, sometimes
it doesn't.


--
Jim Pennino

Wayne wrote:
I'm drawing a blank on a good/easy to build antenna.

It of course depends on the frequency you are going to use.
WiFi antennas with gain (both directional and omni) are available
off-the-chinese-shelf (i.e. at prices you are not going to beat), but
of course you can always use one of the wellknown technologies to
make one yourself. i.e. a yagi, loop, doublequad, dish, etc.

But first find out on what frequency you are!

wrote in message ...

Wayne wrote:
So here's the deal. I want to sit in my car in a parking lot and access
wi-fi legitimately in a nearby building.
(I'm authorized to use the system and have a password.)

The device is similar to an ipod (no phone).

I used a passive RF sniffer around the case and found a sweet spot that
has
significant RF output.

What I want to experiment with is a coupling loop over the case sweet spot
going to a coax and then a directional antenna.

It would be acceptable to simply scotch tape the loop on the case.

Any suggestions on the antenna would be appreciated.

Wayne
W5GIE

@ Have you tried making a corner reflector out of something cheap and
@ holding the device inside it as a test?

@ I've done that with cell phones in weak areas; sometimes it works,
sometimes
@ it doesn't.

Thanks, I didn't think of that. Obviously, I'm just having fun playing
around.

I looked on Amazon and saw some 2.4G yagis at a pretty low price.
If I get lazy that seems like a reasonable approach.

On 3/26/2016 2:43 PM, Wayne wrote:
So here's the deal. I want to sit in my car in a parking lot and access
wi-fi legitimately in a nearby building.
(I'm authorized to use the system and have a password.)

The device is similar to an ipod (no phone).

I used a passive RF sniffer around the case and found a sweet spot that
has significant RF output.

What I want to experiment with is a coupling loop over the case sweet
spot going to a coax and then a directional antenna.

It would be acceptable to simply scotch tape the loop on the case.

Any suggestions on the antenna would be appreciated.

Wayne
W5GIE

You could maybe try one of those very large metal salad bowls from
WalMart as sort of a dish reflector.. It helped me considerably in one
situation. Good luck.

On Sat, 26 Mar 2016 18:31:40 -0400, rickman wrote:

Whatever you do with the antenna should work in both directions, no?

No. The gain can be quite different between tx and rx. The usual
symptom of a badly designed reflector antenna is that it can hear/see
wireless access points at considerable distances, but can't connect to
very many of them.

Let's take a parabolic dish reflector as an example. The general
assumption is that the transmit and receive gains are identical.
That's true only if ALL the RF produced by the feed hits the dish and
does NOT spill over the edges of the reflector. See Fig 6.0-1 at:
http://www.w1ghz.org/antbook/chap6-0.pdf
http://www.w1ghz.org/antbook/contents.htm
Any transmit RF that goes over the edge is lost and useless.

You can also screw things up by using an excessively high gain antenna
for the dish feed. Such antennas have a narrow illumination angle,
producing a "spot" on the surface of the dish. That reverses the
tx/rx situation. In transmit, all the RF produced by the narrow feed
hits a spot on the dish, and is reflected in the desired direction.
Nothing is lost. However, in receive, the feed only sees RF coming
from the spot. The rest of the dish is wasted as any rx RF that hits
outside of the spot, will not be "seen" by the feed.

Putting a USB dongle at the focus of a dish reflector is the common
way to obtain some additional gain. Everything that hits the
reflector is reflected towards the feed. So in receive, the gain
calculations are fairly close to the theoretical maximum values.
However, in transmit, much of the RF emitted by the USB dongle goes in
directions that do NOT hit the reflector. Some of these might
accidentally go in the desired direction, but most of the RF is lost.
What's left hits the dish reflector, goes in the right direction, and
if you're lucky, provides some gain. I posted some calcs for this in
alt.internet.wireless a few years ago, but of course, I can't find
them. I'll try again later.

For the tx gain to equal the rx gain, something will need to be done
about the tx RF going in random directions. The basic idea is to
match the "illumination angle" of the feed with that of the dish.
That's done by making the feed directional and setting the beamwidth
to match the f/D ratio of the dish. See:
http://www.w1ghz.org/antbook/chap4.pdf
Putting a reflector about 1/2 wave behind the USB dongle will help
some, but a properly matched feed will work much better.


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

On 3/27/2016 1:39 PM, John S wrote:
On 3/26/2016 2:43 PM, Wayne wrote:
So here's the deal. I want to sit in my car in a parking lot and access
wi-fi legitimately in a nearby building.
(I'm authorized to use the system and have a password.)

The device is similar to an ipod (no phone).

I used a passive RF sniffer around the case and found a sweet spot that
has significant RF output.

What I want to experiment with is a coupling loop over the case sweet
spot going to a coax and then a directional antenna.

It would be acceptable to simply scotch tape the loop on the case.

Any suggestions on the antenna would be appreciated.

Wayne
W5GIE

You could maybe try one of those very large metal salad bowls from
WalMart as sort of a dish reflector.. It helped me considerably in one
situation. Good luck.

I used a reflector from a work lite and it seemed to help. I was able
to pick up the signal from a restaurant across the street maybe 200 feet
away. One of these. I think it was under $10. Knowing how cheap I am,
it may have only been $5.

http://www.walmart.com/ip/Bayco-8.5-...Light/14003467

--

Rick