Yes - I'll be using the 10X probe setting and doing the measurement at
1.8mhz.
Phil
----- Original Message -----
From: "Larry Benko" <xxw0qe@comcast.net>
To: "Phil & Debbie Salas" <dpsalas@tx.rr.com>
Cc: <amps@contesting.com>
Sent: Monday, December 07, 2009 10:05 PM
Subject: Re: [Amps] FW: Decent HF directional coupler for RF power meas.
> Phil,
>
> Since the TDS-2XXX scopes are not 50 ohm input, don't ignore the
> capacitance in the probe. See the appendix in the manual on page 153.
> The capacitance will be less at the 10X probe setting but not
> insignificant at 30MHz.
>
> 73,
> Larry, W0QE
>
> Phil & Debbie Salas wrote:
>> Hi Paul - I haven't looked at the PowerMaster below 5-watts. I don't
>> believee it measures SWR much below 5-watts for that matter. However,
>> I'm curious. I'll look at it tomorrow. I have a Tektronix TDS-2022 that
>> is NIST-calibrated. I'll see what that indicates compared to my
>> PowerMaster from 1-5 watts.
>>
>> Phil - AD5X
>>
>> "Phil, Do you have a way to check the accuracy of your PowerMaster below
>> 2-watts?
>> Below 1-watt, my PowerMaster deviated substantially from the Alpha 4510,
>> LP-100, and a 200 MHz scope measured across a precision 50-ohm load, all
>> of
>> which measured very closely against one another. The PowerMaster showed
>> the
>> typical signs of inaccuracy at low power due to diode detector
>> non-linearities as discussed here:
>> http://www.arrl.org/members-only/tis/info/pdf/9002019.pdf
>>
>> I am not stating with certainty that's the cause for the deviation with
>> my
>> PowerMaster, only the behavior is identical to inaccuracies seen with
>> other
>> common wattmeters using simple diode detectors. And, as I recall, the
>> LP-100 and Alpha 4510 use more complex, temperature-compensated detector
>> designs.
>>
>> Since this is the AMPS group, not too many folks here will care about
>> low-power results. But I think it's important to note some limitations
>> of
>> the PowerMaster that are not limitations with some of the other
>> commercial
>> wattmeters.
>>
>> Paul, W9AC"
>> _______________________________________________
>> Amps mailing list
>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>>
>
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