Wifi Detector

I bought a keyfob wifi detector today to check which areas have a good
signal before assuming I can surf outside from car or train wherever I
choose. Press the button and it gives 1 to 4 green lights depending on
signal strength and a red one for none.
Strange how out of the six or so tunnels taken by my train all but one
produced maxm strength insode the tunnel, yet many areas en route in
the open produced weak detection. Have I bought a crap detector??

roaming

On 20 Oct 2006 12:17:55 -0700, (E-Mail Removed) wrote:

>I bought a keyfob wifi detector today to check which areas have a good
>signal before assuming I can surf outside from car or train wherever I
>choose. Press the button and it gives 1 to 4 green lights depending on
>signal strength and a red one for none.
>Strange how out of the six or so tunnels taken by my train all but one
>produced maxm strength insode the tunnel, yet many areas en route in
>the open produced weak detection. Have I bought a crap detector??
>

Maybe you are detecting client devices?

Mark wrote:
>
> On 20 Oct 2006 12:17:55 -0700, (E-Mail Removed) wrote:
>
> >I bought a keyfob wifi detector today to check which areas have a good
> >signal before assuming I can surf outside from car or train wherever I
> >choose. Press the button and it gives 1 to 4 green lights depending on
> >signal strength and a red one for none.
> >Strange how out of the six or so tunnels taken by my train all but one
> >produced maxm strength insode the tunnel, yet many areas en route in
> >the open produced weak detection. Have I bought a crap detector??
> >
>
> Maybe you are detecting client devices?

Define the train and route as some do now have WiFi, especially at the
posh end.
All GNER electrics do, and some diesels now.

Perhaps if the link up from inside the tunnels is also wifi perhaps you
got that ?

Bill

Mark wrote in
(E-Mail Removed):

> On 20 Oct 2006 12:17:55 -0700, (E-Mail Removed) wrote:
>
>> I bought a keyfob wifi detector today to check which areas have a
>> good signal before assuming I can surf outside from car or train
>> wherever I choose. Press the button and it gives 1 to 4 green lights
>> depending on signal strength and a red one for none.
>> Strange how out of the six or so tunnels taken by my train all but
>> one produced maxm strength insode the tunnel, yet many areas en
>> route in the open produced weak detection. Have I bought a crap
>> detector??
>>
>
> Maybe you are detecting client devices?

What about packages such as NetStumbler? Does that detect client devices as
well as access points? I've noticed several times when I've used NetStumbler
that I've continued to get as strong a signal as ever even after I've
removed the power from the router to check for weaker signals on the same
channel as the router before deciding whether a customer's router needs to
be changed to a channel that's not already in use.

I wonder if I was seeing the wireless adaptors in the customer's laptops.
Strange that the signal strength didn't drop when I turned off the router.
Do client devices continue to radiate using the router's SSID and on the
original channel even after the router that they were talking to has gone
away?

Mark wrote:

>> I bought a keyfob wifi detector today to check which areas have a good
>> signal before assuming I can surf outside from car or train wherever I
>> choose. Press the button and it gives 1 to 4 green lights depending on
>> signal strength and a red one for none.
>> Strange how out of the six or so tunnels taken by my train all but one
>> produced maxm strength insode the tunnel, yet many areas en route in
>> the open produced weak detection. Have I bought a crap detector??
>>
>
> Maybe you are detecting client devices?

That's what I reckon and the tunnels were reflecting more of those
client device signals back!

bill wrote:
> Mark wrote:
> >
> > On 20 Oct 2006 12:17:55 -0700, (E-Mail Removed) wrote:
> >
> > >I bought a keyfob wifi detector today to check which areas have a good
> > >signal before assuming I can surf outside from car or train wherever I
> > >choose. Press the button and it gives 1 to 4 green lights depending on
> > >signal strength and a red one for none.
> > >Strange how out of the six or so tunnels taken by my train all but one
> > >produced maxm strength insode the tunnel, yet many areas en route in
> > >the open produced weak detection. Have I bought a crap detector??
> > >
> >
> > Maybe you are detecting client devices?
>
> Define the train and route as some do now have WiFi, especially at the
> posh end.
> All GNER electrics do, and some diesels now.
>
> Perhaps if the link up from inside the tunnels is also wifi perhaps you
> got that ?
>
> Bill


The route is Southern Railway, London to Sussex. The signal outside of
tunnels was nearly always very weak, except for two village railway
stations en route. Since arriving home I found www.myhotspots.co.uk. -
are there any other sites that list hotspots? I did not notice any
notebook users near me, it was mid-afternoon, they usually proliferate
early morning and evening. Please elaborate on "client devices". Does a
train or even a station have wireless equipment that could be detected
by a dodgy WiFi detector? A naff detector picks up microwave ovens,
mobile phones etc I believe,

Roamer

On 2006-10-20, Martin Underwood <a@b> wrote:
> Mark wrote in
> (E-Mail Removed):
>
>> On 20 Oct 2006 12:17:55 -0700, (E-Mail Removed) wrote:
>>
>>> I bought a keyfob wifi detector today to check which areas have a
>>> good signal before assuming I can surf outside from car or train
>>> wherever I choose. Press the button and it gives 1 to 4 green lights
>>> depending on signal strength and a red one for none.
>>> Strange how out of the six or so tunnels taken by my train all but
>>> one produced maxm strength insode the tunnel, yet many areas en
>>> route in the open produced weak detection. Have I bought a crap
>>> detector??
>>>
>>
>> Maybe you are detecting client devices?
>
> What about packages such as NetStumbler? Does that detect client devices as
> well as access points? I've noticed several times when I've used NetStumbler
> that I've continued to get as strong a signal as ever even after I've
> removed the power from the router to check for weaker signals on the same
> channel as the router before deciding whether a customer's router needs to
> be changed to a channel that's not already in use.

I'm pretty sure NetStumbler (I don't use it, but I use iStumbler, the Mac
equivalent) listens solely for BEACONs from access points. This is why,
when you turn the BEACONs from an access point off, iStumbler no longer
sees it (I assume NetStumbler does the same?).

> I wonder if I was seeing the wireless adaptors in the customer's laptops.
> Strange that the signal strength didn't drop when I turned off the router.
> Do client devices continue to radiate using the router's SSID and on the
> original channel even after the router that they were talking to has gone
> away?

When you configure BEACONs from the access point off the clients, rather than
just listening for BEACONS, instead actively search for the access point by
sending PROBEs. A PROBE indeed carries the router's SSID (and is why
turning off BEACONs from an access point won't hide the SSID from someone
determined to find it). I don't believe, however, that clients send PROBEs
for an access point they expect to be sending BEACONs so I doubt you would
normally see client probes.

I suspect what you are seeing is instead just a long timeout in NetStumbler's
display of BEACONing access points. That is, while each access point sends
a BEACON every (I think) half second, NetStumbler won't be seeing all of
them because of channel scanning, and for very weak signals may only get
a BEACON once in a while. Once it receives a BEACON I think it therefore
displays the network for quite a long time, since it may take a while
before it receives another one.

The keyfob, on the other hand, may not even decode BEACONs but rather
might just detect the presence of RF. In that case it might very well
display the presence of clients.

Dennis Ferguson

Colin Forrester wrote:
> Mark wrote:
>
> >> I bought a keyfob wifi detector today to check which areas have a good
> >> signal before assuming I can surf outside from car or train wherever I
> >> choose. Press the button and it gives 1 to 4 green lights depending on
> >> signal strength and a red one for none.
> >> Strange how out of the six or so tunnels taken by my train all but one
> >> produced maxm strength insode the tunnel, yet many areas en route in
> >> the open produced weak detection. Have I bought a crap detector??
> >>
> >
> > Maybe you are detecting client devices?
>
> That's what I reckon and the tunnels were reflecting more of those
> client device signals back!

The pot thickens. Fitting my USB wifi dongle to my PC at home I get a
local wifi provider page, hence I have access to the web. Putting the
same dongle on my laptop the signal is 15% and not enough to display a
web page "Cannot be displayed". Do internal computer components differ
in their ability to process/detect the signal?
As for the keyfob it detects no signal at home, yet the PC is receiving
wifi signal. Money back I think, its a Maplin job BTW,

Roamer

<(E-Mail Removed)> wrote in message
news:(E-Mail Removed) oups.com...
>I bought a keyfob wifi detector today to check which areas have a good
> signal before assuming I can surf outside from car or train wherever I
> choose. Press the button and it gives 1 to 4 green lights depending on
> signal strength and a red one for none.
> Strange how out of the six or so tunnels taken by my train all but one
> produced maxm strength insode the tunnel, yet many areas en route in
> the open produced weak detection. Have I bought a crap detector??
>
> roaming
>

Sounds like it is just a field strength meter.

Stick it in your car, it could save you a fortune, but don't ask why!

R. Mark Clayton wrote:
> <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed) oups.com...
> >I bought a keyfob wifi detector today to check which areas have a good
> > signal before assuming I can surf outside from car or train wherever I
> > choose. Press the button and it gives 1 to 4 green lights depending on
> > signal strength and a red one for none.
> > Strange how out of the six or so tunnels taken by my train all but one
> > produced maxm strength insode the tunnel, yet many areas en route in
> > the open produced weak detection. Have I bought a crap detector??
> >
> > roaming
> >
>
> Sounds like it is just a field strength meter.
>
> Stick it in your car, it could save you a fortune, but don't ask why!

Southern rail came up with a surprisingly quick and useful reply.
"The Southern WiFi service enables users of suitably enabled laptops to
access the internet at broadband speeds before the train departs, and
during the journey."

The meter is called a WiFi Explorer to "find out whether you are under
wireless LAN service" whatever that is supposed to mean. It also claims
to "avoid other interference".

roamer