I used a Bird dummy load, rated to above 1 GHz. The Scope was a
recently calibrated Tek 2465B. I'd estimate overall measurement
accuracy to about 3%.
73,
Jim w8zr
Sent from my iPhone
> On Jun 19, 2017, at 2:37 AM, Roger (K8RI) <k8ri@rogerhalstead.com> wrote:
>
> Be careful of the scope across a known load. Accuracy depends on the
> precision of the resistor and on many bands may require compensation. If you
> have a good dummy load, there is the calibration of the load.My DL5K requires
> compensation above 40 meters. It's great on 160, 75, and 40, but the SWR goes
> up in a hurry from there.
>
> 73, Roger (K8RI)
>
>> On 6/18/2017 Sunday 9:36 PM, Jim Brown wrote:
>> Hi Jim,
>>
>> You've pointed out the obvious problem -- man who has more than one watch
>> never knows what time it is. :)
>>
>> My LP100A came from the estate of an SK, with one coupler. I sent the
>> LP100A and the coupler to Larry to cal for me, and to cal the second coupler
>> that I bought. So I know it's calibrated. For the LP100A, the cables between
>> the coupler and the unit are part of the calibration, and they're labeled.
>>
>> Your MB-1 calibration using the scope across a known load is pretty good, as
>> good as the calibration of the scope and the load.. :) It really does come
>> down to using the tools and instrumentation in our own personal labs to get
>> as close as practical to the fundamentals of what we're measuring.
>>
>> 73, Jim K9YC
>>
>>> On Sun,6/18/2017 5:28 PM, MU 4CX250B wrote:
>>> I have an LP100A wattmeter and like it very much. But how do any of
>>> you know how accurate it really is? The only way to know is with a
>>> calibration standard, and RF power is notoriously difficult to measure
>>> accurately. I've compared the LP100A to the Alpha 4510, and a
>>> MeterBuilder MB-1, and by measuring the RMS RF voltage (with a
>>> calibrated Tek oscilloscope) across a 50 ohm dummy load. There's no
>>> obvious consistency among these wattmeters. The readings vary from one
>>> another with frequency and power level, by as much as five percent. My
>>> guess is that the MB-1 is likely the most accurate, based on the
>>> calibration curves and methodology supplied by the manufacturer. But
>>> that is still just a guess.
>>
>>
>> _______________________________________________
>> Amps mailing list
>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>
>
> ---
> This email has been checked for viruses by Avast antivirus software.
> https://www.avast.com/antivirus
>
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|