Prev: Connecting Wireless to Public Server
Next: New AP vs.New Modem/Router
From: msg on 8 Dec 2009 15:01
Jeff Liebermann wrote:
> On Sun, 06 Dec 2009 12:37:02 -0600, msg <msg@_cybertheque.org_> wrote:
>
>> Too bad I didn't photograph the board before installing it so that now
>> I could know what parts it contained. These PDFs describe this
>> amp (I am using the 2400cx):

> "The requested object does not exist on this server."

It's been a bad week, I'm lucky to be typing complete sentences;
the urls are fixed here:

>> ftp://ftp.cybertheque.org/pub/tmp/wifi/2400cData-Sheet.pdf
>> ftp://ftp.cybertheque.org/pub/tmp/wifi/2400cAppNotes.pdf
>

>> Too bad there is no real temp data for this antenna; I also wonder about
>> moisture freezing and changing characteristics.
>
> With only 12dBi of gain, I don't think the internal parts are that
> critical. Thermal expansion isn't going to move things around that
> much.
>
> It's possible that the receive amp is unstable and oscillating. Maybe
> lowering the gain with the lower temperature returned it to sanity.
> Difficult to tell from here with near zero hardware info. However, if
> it is for real, then the receive amp is the most likely culprit.

Yeah, I might try to borrow a spectrum analyzer and do some tests
in a temp chamber sometime; it is just such a dramatic change that
your probably right that something funky is happening in there.
From: Bill Kearney on 8 Dec 2009 17:09
> Last night with temps dipping to near
> zero degrees F, there were a dozen more leases added.

Do the leases correspond to actual device connections? As in, can you ping
the devices once they've obtained an address?

Are the MAC addresses legit? That can tell you what vendor device is making
the request. Start a log collecting the MAC addresses and see what trends
appear.

Finally, consider if there are cold weather activities that might have
larger numbers of attendees that usual. Any schools nearby? Lots of people
with wifi-enabled phones and laptops might be a likely culprit. A log over
time would help reveal that.

-Bill Kearney

From: Jeff Liebermann on 8 Dec 2009 19:42
On Tue, 08 Dec 2009 14:01:03 -0600, msg <msg@_cybertheque.org_> wrote:

>Jeff Liebermann wrote:
>> On Sun, 06 Dec 2009 12:37:02 -0600, msg <msg@_cybertheque.org_> wrote:
>>
>>> Too bad I didn't photograph the board before installing it so that now
>>> I could know what parts it contained. These PDFs describe this
>>> amp (I am using the 2400cx):
>
>> "The requested object does not exist on this server."
>
>It's been a bad week, I'm lucky to be typing complete sentences;
>the urls are fixed here:
>
>>> ftp://ftp.cybertheque.org/pub/tmp/wifi/2400cData-Sheet.pdf
>>> ftp://ftp.cybertheque.org/pub/tmp/wifi/2400cAppNotes.pdf

The photo shows a Maxim MAX850 GaAs FET power supply.
<http://datasheets.maxim-ic.com/en/ds/MAX850-MAX853.pdf>
There is a discrete GaAS FET amp in there somewher. My guess(tm) is
that it's for TX, not RX. There's also an LT1632 op amp, which might
be part of the Tx AGC power control. There are a bunch of discrete RF
devices on the board, but no easy way to identify them. Offhand, my
guess(tm) is that the RX chain (two devices) is not temperature
stabilized and probably drifts. However, without a better schematic
or block diagram, there's no way to be sure. Got an FCC ID number?

Hmmm. I found an HMC174 GaAS FET T/R switch on the lower right corner.

The SMD database doesn't show anything for an "H5" marking, so I can't
guess what that does. Kinda looks like a voltage regulator. Anyway,
I don't see any fancy DC stabilization for the two RF RX xsistors,
which may explain the drift.

>Yeah, I might try to borrow a spectrum analyzer and do some tests
>in a temp chamber sometime; it is just such a dramatic change that
>your probably right that something funky is happening in there.

Well, if there's a gain change, the spectrum analyzer will certainly
show something. If the circuit is oscillating or unstable, you might
see something. However, if it's just a change in NF, the SA won't
show anything.

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com jeffl(a)cruzio.com
# http://www.LearnByDestroying.com AE6KS
From: msg on 10 Dec 2009 20:14
Bill Kearney wrote:
>> Last night with temps dipping to near
>> zero degrees F, there were a dozen more leases added.
>
> Do the leases correspond to actual device connections? As in, can you
> ping the devices once they've obtained an address?

Many have client hostname set and I can reliably ping those that renew
their leases regularly. Several are Sony game consoles (determined from the
UID) and there is a mix of iPhones, laptops and what appear to be desktops
too.

Since the temps have hit -10F, machines known to be at a winter carnival
area on the waterfront called 'Bentlyville' have been given leases, about
two miles away.

> Are the MAC addresses legit? That can tell you what vendor device is
> making the request. Start a log collecting the MAC addresses and see
> what trends appear.

See above. The dhcp leases database shows the trends and so far the
only correlation that I've been able to perceive is inverse to temperature
(and perhaps proportional to snow cover).

>
> Finally, consider if there are cold weather activities that might have
> larger numbers of attendees that usual.

Bentlyville has much less traffic in the extreme cold and was even shut
down yesterday, yet the number of new leases stays stable or even increases
in the colder weather.

> Any schools nearby? Lots of
> people with wifi-enabled phones and laptops might be a likely culprit.
> A log over time would help reveal that.

Sure, but the lease activity is inversely proportional to the temperature
and in our arctic climate this seems counterintuitive.

Michael
First  |  Prev  | 
Pages: 1 2
Prev: Connecting Wireless to Public Server
Next: New AP vs.New Modem/Router