[AMPS] Re:Scopes/power/bandwidth

[Bill Murphy]

Reading all this info about measuring power with a high voltage  probe and 
scope, what probes do you use? As far as i know most high voltage probes 
suitable for measuring power have a limited bandwidth of about 300 Hertz, 
wide band scope probes generally have voltage limits not suited to legal 
output measurements. Jenning have a dividing probe but that looks like a 
mighty expensive sollution. Anyway just curious as i would like to check my 
wattmeters and try this method.

Bill

>From: User312627@aol.com
>To: measures@vc.net, amps@contesting.com
>CC: W8ji@contesting.com
>Subject: Re: [AMPS] Re:
>Date: Mon, 26 Jul 1999 19:08:36 EDT
>
>
>Hi All,
>Tom said:
> > A good meter is more reliable than a scope.
>What does that mean? Meters have a longer MTBF than Oscilloscopes?
>
>The waveform envelope is limited by filters to 3000 Hz, an audio limit. But
>does not the FCC regulations state that the power is to be measured over 
>one
>RF cycle?
>At 30 Mhz = 33.3 nano-seconds
>At 1.8 Mhz = 555 nano-seconds
>
>The rise time of a system is related thus:  BW x RISETIME = CONSTANT = 0.35
>
>0.35/3000 = 117 micro-seconds. The peak rectifier circuit time constant
>should be designed to get the information as quickly as possible ( but not
>quicker) , so that subsequent following pulses are not ignored. If the
>rectifier time-constant is 40 micro-seconds, then in 3 time constants most 
>of
>the prior information will be bled off and the circuit will be ready for 
>the
>next pulse. Some of the circuits I have looked at had 15 millisecond
>time-constants. Somehow either I am missing something very simple or my 
>logic
>is faulty!
>I think Rich is using a good system. The bandwidth of the scope is more 
>than
>adequate and will not miss in-between pulses.
>The FCC says power is measured over one RF cycle.
>Regards,
>BillW KB7YUM
>
>--
>FAQ on WWW:               http://www.contesting.com/ampfaq.html
>Submissions:              amps@contesting.com
>Administrative requests:  amps-REQUEST@contesting.com
>Problems:                 owner-amps@contesting.com
>Search:                   http://www.contesting.com/km9p/search.htm
>


_______________________________________________________________
Get Free Email and Do More On The Web. Visit http://www.msn.com

--
FAQ on WWW:               http://www.contesting.com/ampfaq.html
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm