Jack is right. Please use an oscilloscope if you need accurate reading, unless your multimeter can handle high current. If you know your electronics, you can use the regular multimeter only at the entry point before the transistor or the diode and work your calculation across the transistor. Since we're into real technical issue here, the 5 to 7 db gain on the antenna is being amplified usually by mosfet. Most of the multimeters built today are capable of handling 10A, which is well beyond the current supplied by the adapter or the antenna end of the transistor. I don't want to scare everyone out there, but please follow the safety procedure for both electrical and communication standard. Unless you're working with wireless bridges that carries higher power, most AP are consider low risk as far as electrical shock or rf energy. Jack, I love your book and our role is to help readers here. I apologize for the long email, but I just want to help. I hope everybody can enjoy the fun.
Steve -----Original Message----- From: Jack Unger <[EMAIL PROTECTED]> To: [EMAIL PROTECTED] Date: Thu, 26 Jun 2003 23:32:36 -0700 Subject: Re: [SOCALWUG] Low Power AP's using solar > NO - do not connect the multimeter to the antenna end... > What comes out at the antenna end is radio-frequency (RF) energy. > The multimeter is not made to read RF. Putting it at the antenna end > may zap it and certainly will not provide an accurate voltage or > current > reading. Instead, look at the manufacturers specs for the supply > voltage > (E) and the current (I). The current spec will usually be the maximum > current draw under load (when transmitting). Multiply E times I and > you will have the peak power in watts used by the AP. Buy a power > supply (if needed) that provides the required voltage and the required > (or a little higher) current and everything will work OK. > > jack > > Steve Chen wrote: > > > Hi guys, I couldn't help myself to reply on this topic. Everyone is > > correct about what they know already, and yes P=I*E. The most > important > > part of finding out power consumption is to know how much power is > being > > pump into the antenna. > > > > You can open the AP and stick this $20 multimeter at the antenna end > to > > find out the amp and volt it sucks up, then apply the wonderful power > > formula above to find out the approximate consumed power. To be more > > accurate, you may want to check out the amp and volt over a period of > > time since the output may vary against time. > > > > The fact about the amp and volt on the ac adapter reflects to the > > maximum power required by the unit plus about plus/minus 5%. All > > electronic devices has a minimum operational power requirement, which > is > > known to manufacturer only. But the ac adapter usually provides the > > unit with maximum amount of power equal to how much the unit will > > consume. > > > > I'm in the manufacturing industry and I hope this information will > help > > everyone to clearify the confusion. Enjoy! > > > > Steve > > > > -----Original Message----- > > From: Kenneth Crudup <[EMAIL PROTECTED]> > > To: [EMAIL PROTECTED] > > Date: Tue, 17 Jun 2003 18:10:29 -0700 (PDT) > > Subject: RE: [SOCALWUG] Low Power AP's using solar > > > > > > > > On Tue, 17 Jun 2003, Mike Outmesguine wrote: > > > > > > > You are right about P = I * E and your assumption of the answer. > But > > > > as you said, the power capacity of the DC supply is not the > actual > > > > power *draw* of the access point. > > > > > > What, none'a you's got a $20 RatShack multimeter?! > > > > > > -Kenny > > > > > > -- > > > Kenneth R. Crudup Sr. SW Engineer, Scott County Consulting, Los > > > Angeles > > > H: 3801 E. Pacific Coast Hw #9, Long Beach, CA 90804-2014 (888) > > > 454-8181 > > > W: 2052 Alton Parkway, Irvine, CA 92606-4905 (949) > 252-1111-X240 > > -- > Jack Unger, President-Wireless InfoNet ([EMAIL PROTECTED]) 818 227-4220 > Vendor-Neutral WISP Training - http://www.ask-wi.com/2002workshops.html > Author - "Deploying License-Free Wireless WANs" > http://www.amazon.com/exec/obidos/ASIN/1587050692/ > >
