Cool Temperature Ranges Affecting USB Wireless Adapters Reception

I have been having trouble with USB adapters in colder temperature
ranges.
The manufacturers list a functional temperature range with low around
35 degrees fahrenheit.
You would not think with solid state electronics that temperature would
have a great effect.
At around that temperature ( 35 of so) the adapters power up fine. the
computer knows it is there but there is no reception of any type.
I have tried shorter usb cords and added a powered hub.
Any connections are taped in plastic so as to avoid humidity shorting
out the circuit .
Anyone have any ideas or experience in this matter.

thank you

On 25 Nov 2005 10:38:49 -0800, "(E-Mail Removed)"
<(E-Mail Removed)> wrote:

>I have been having trouble with USB adapters in colder temperature
>ranges.
>The manufacturers list a functional temperature range with low around
>35 degrees fahrenheit.
>You would not think with solid state electronics that temperature would
>have a great effect.
>At around that temperature ( 35 of so) the adapters power up fine. the
>computer knows it is there but there is no reception of any type.
>I have tried shorter usb cords and added a powered hub.
>Any connections are taped in plastic so as to avoid humidity shorting
>out the circuit .
>Anyone have any ideas or experience in this matter.

Sure. The problem is not cold but water. At temperatures just above
freezing or actually near the dew point, water will condense on your
USB adapter circuit board. It will detune antennas, short out
adjacent traces, act as an attenuator to RF radiation, and general
wreak havoc with the circuitry. If you're in a marine atmosphere, the
salt in the condensed water will do an even better job of shorting out
the board. Whatever "taped in plastic" is suppose to do does nothing
for condensation unless your box is hermetically sealed and
desiccated.

Your best bet is a polyurethane or acrylic conformal coating, such as
the various products made by Humiseal.
http://www.humiseal.com/protect/guide.htm
It comes in spray cans. You will need some tape or masking goo:
http://www.humiseal.com/temp.htm
to protect connectors, adjustments, and antenna surfaces. You'll also
need a UV lamp to inspect the results to be sure you've covered
everything. When I used to design marine radios, this was the stuff
we used to protect the boards.

You will have a big problem with circuit board antennas. The
dielectric constant of the conformal coating will probably detune the
antenna. Therefore, I suggest you consider using an external antenna.
This can simply be a half wave long dipole made from two pieces of
stiff wire. Just get the antenna off the board.

Good luck and don't do this in the kitchen.

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

Jeff,

thanks as usual you came through.
A couple questions-

the adapter used is a USB pen type adapter which allows the
length of USB wire from the computer.
Signal strength loss can be a problem with a length of wire that is
why I am trying to retain use of the simple, efective USB adapter
setup.
Could the adapter be placed in a sealed container such as a sealed
glass container to keep out humidity.
The cold in the middle of winter is actually a very dry cold- they
say it is drier than the Sahara Desert.
In the middle of the coldest weather would the adapter work if it is
really dry ?
Interestingly enough the problems started as you explained in the
temperature around freezing where moisture is a problem.


thank you




Jeff Liebermann wrote:
> On 25 Nov 2005 10:38:49 -0800, "(E-Mail Removed)"
> <(E-Mail Removed)> wrote:
>
> >I have been having trouble with USB adapters in colder temperature
> >ranges.
> >The manufacturers list a functional temperature range with low around
> >35 degrees fahrenheit.
> >You would not think with solid state electronics that temperature would
> >have a great effect.
> >At around that temperature ( 35 of so) the adapters power up fine. the
> >computer knows it is there but there is no reception of any type.
> >I have tried shorter usb cords and added a powered hub.
> >Any connections are taped in plastic so as to avoid humidity shorting
> >out the circuit .
> >Anyone have any ideas or experience in this matter.
>
> Sure. The problem is not cold but water. At temperatures just above
> freezing or actually near the dew point, water will condense on your
> USB adapter circuit board. It will detune antennas, short out
> adjacent traces, act as an attenuator to RF radiation, and general
> wreak havoc with the circuitry. If you're in a marine atmosphere, the
> salt in the condensed water will do an even better job of shorting out
> the board. Whatever "taped in plastic" is suppose to do does nothing
> for condensation unless your box is hermetically sealed and
> desiccated.
>
> Your best bet is a polyurethane or acrylic conformal coating, such as
> the various products made by Humiseal.
> http://www.humiseal.com/protect/guide.htm
> It comes in spray cans. You will need some tape or masking goo:
> http://www.humiseal.com/temp.htm
> to protect connectors, adjustments, and antenna surfaces. You'll also
> need a UV lamp to inspect the results to be sure you've covered
> everything. When I used to design marine radios, this was the stuff
> we used to protect the boards.
>
> You will have a big problem with circuit board antennas. The
> dielectric constant of the conformal coating will probably detune the
> antenna. Therefore, I suggest you consider using an external antenna.
> This can simply be a half wave long dipole made from two pieces of
> stiff wire. Just get the antenna off the board.
>
> Good luck and don't do this in the kitchen.
>
> --
> Jeff Liebermann (E-Mail Removed)
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060 http://802.11junk.com
> Skype: JeffLiebermann AE6KS 831-336-2558

On 26 Nov 2005 16:05:14 -0800, "(E-Mail Removed)"
<(E-Mail Removed)> wrote:

>Jeff,
> thanks as usual you came through.

I like to answer the easy questions and leave the tough ones for
others to answer.

> the adapter used is a USB pen type adapter which allows the
>length of USB wire from the computer.

16ft maximum USB cable. If you want to go longer, you need an
amplified cable or a few USB powered hubs. The hubs are cheaper.

> Signal strength loss can be a problem with a length of wire that is
>why I am trying to retain use of the simple, efective USB adapter
>setup.

Length of the USB cable has no effect on signal strength. However, it
does limit the location of the USB wirless adapter, which will have a
serious effect on signal strength.

> Could the adapter be placed in a sealed container such as a sealed
>glass container to keep out humidity.

Sorta. I've done quite a bit with pressurized coax and boxes.
Basically, you take a bicycle valve stem (available at auto parts
stores for some other purpose) and seal a NEMA plastic waterproof box.
These usually have a rubber seal around the cover and can easily be
made air tight. Dump some desicant (silica gel) into the box. If
it's old, bake it in a toaster oven for a while to drive off the
moisture. Seal the box and test pressurize with a bicycle pump.
Attach a tire pressure guage and measure the pressure. If ambitious,
spray the box with kids bubble mix to check for leaks. Mine always
seem to leak around the cable entry, which I like to bury in silicon
bathroom caulk. When you're sure it's air tight, install the radio,
close the cover, pressurize, and hope it lasts the winter. I usally
have a small pressure bottle and regulator attached to the bicycle
valve to make sure the pressure holds. This also works with heliax
and other air dielectric coax cables.

> The cold in the middle of winter is actually a very dry cold- they
>say it is drier than the Sahara Desert.
> In the middle of the coldest weather would the adapter work if it is
>really dry ?

Well, I don't have any experience with low humidity cold. However,
it's easy enough to test. Take a mirror or piece of glass and leave
it outside in the cold for a while. Wipe it clean. Take it inside
where it's warm. If it's instantly covered with condensed water, you
have a problem. If not, ignore my ranting and try something else like
installing a small heater (resistor) to the keep the board warm.

> Interestingly enough the problems started as you explained in the
>temperature around freezing where moisture is a problem.

Check your local weather station for the dew point (temperature).

Geobytes says 24.70.95.203 is in Edmonton, Alberta, Canada with an 88%
certainty. (How close did I guess)?
| http://www.geobytes.com/IpLocator.htm
The local weather is:
| http://www.weather.com/outlook/trave...local/CAXX0126
with a:
temperature: 35F
dew point: 25F
humidity: 65%
Humidity goes to 75% at night and 53% during the day. That's anything
but dry. What are you talking about?

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