A caveat with higher current capacity power supplies (esp. replacing one
kind of battery chemistry with another) is their internal impedence
characteristics may vary, and if the electronics being run assume a certain
impendence, things may go awry.  A specific case is replacing alkaline
batteries in some electronics that depend upon the internal
current-limiting impedence characteristics of alkaline batteries.  In those
electronics, if you try to use NiCads or NiMH batteries, the device
sometimes misfunctions.  (Alkaline batteries have a (much) higher impedence
than NiCads or NiMH batteries, as a result alkalines don't like
high-current loads like digital cameras.  I think certain older film-camera
flashes were among devices that don't repond well to NiCad/NiMH batteries).

As far as using a higher current power supply on an AP, I don't think this
will be a problem.  For long runs it may be necessary to use a higher
voltage (but same or slightly higher current) power supply than the
original in order to overcome the voltage drop over the CAT5 run.  If you
use a power supply that puts out enough voltage but not enough current, the
voltage will drop (to some degree) in order to make up for the current
shortfall (basically you have a brownout).

You can find voltage drop calculators using Google.  Most CAT5 is 24 gauge
wire.  The AP should have an on board voltage regulator to bring the
incoming voltage down to whatever the chipset needs, so being a few volts
(say < 3) above the specified voltage at the end of the 300 foot run likely
is good enough.  If you open the AP and identify the regulator IC (possibly
a three-legged 7805 or 7812), you can then look up its spec sheets for its
acceptable input voltage range.  That said, the closer your input voltage
is to the regulator's output voltage, the cooler the regulator will run and
the happier it will be.


At 09:43 PM 2/4/2006 +0100, you wrote:
>Increasing the Voltage beyond the specifications will kill the radio. 
>Putting a higher power - (current) PSU shouldn't hurt the radio. The radio 
>will 'draw' the needed current only.
>The power consumption if assumed constant,
>P (Power) = I (Current) x V (Voltage)
>----- Original Message ----- 
>From: "Brian Rohrbacher" <[EMAIL PROTECTED]>
>To: "WISPA General List" <wireless@wispa.org>
>Sent: Saturday, February 04, 2006 9:34 PM
>Subject: Re: [WISPA] OT amps and volts
>> It's not actually mine.  It's another's from the list.  We were talking 
>> about it.  But I am sure that on my 230 ft run of cat 5 that I had to 
>> replace an 18v 1a with an 18v 2a to get the radio to stop rebooting.  The 
>> individual I was talking to thought if you up the amps it will kill the 
>> radio.  I thought if you up the volts it kills the radio.  Who is right?
>> Well, actually I know what the cat 5 is.  It's comscope 25 pair.
>> Which brings up another question.  Who does this?  Run a single bundle of 
>> 25 pair up towers and use punch down blocks.  Any issues with this?
>> Brian
>> Sean S gayle wrote:
>>>   I'm normally a lurker, but maybe your problem is in the 300' run of 
>>> CAT5.
>>>What kind is it?  You may be getting signal degradation which is causing 
>>>sporadic radio behavior.
>>>JohnnyO's evil twin
>>>-----Original Message-----
>>>Behalf Of Brian Rohrbacher
>>>Sent: Saturday, February 04, 2006 2:01 PM
>>>To: wireless@wispa.org
>>>Subject: [WISPA] OT amps and volts
>>>I'm a little confused here.  I'm working on a 300 ft run of cat5 and have 
>>>a question.  The radio is acting sparatic.  The power supply has already 
>>>been upped from a 18v to a 24v.  Both 1 amp.  Will it hurt to put a 24v 2 
>>>amp power supply in?  If I "over do" on amps or volts, what blows a radio. 
>>>One or both?  I seem to remember being told that a radio only takes what 
>>>amps it needs, so putting a higher amp power supply in won't hurt, but if 
>>>you put too many volts in, that will fry them.  Please clarify me on this.
>> -- 
>> Brian Rohrbacher
>> Reliable Internet, LLC
>> www.reliableinter.net
>> Cell 269-838-8338
>> "Caught up in the Air" 1 Thess. 4:17
>> -- 
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