It doesn’t have to be that expensive. I have built several. DIY is as good as
buying the finished product.
Sent from my iPad
> On Jul 23, 2019, at 11:16 AM, Bob McGraw K4TAX <rmcg...@blomand.net> wrote:
>
> Yes a calorimeter is the better way to measure power. Not inexpensive
> however.
>
> Bob, K4TAX
>
>
> Sent from my iPhone
>
>> On Jul 23, 2019, at 10:07 AM, W2xj <w...@w2xj.net> wrote:
>>
>> If you really want precision, use a water cooled load. Measure the flow rate
>> and input and output temperature. You can precisely calculate power.
>>
>> Sent from my iPad
>>
>>> On Jul 23, 2019, at 9:38 AM, Bob McGraw K4TAX <rmcg...@blomand.net> wrote:
>>>
>>> Since power meter systems are calibrated at a known impedance {usually 50
>>> ohms}, and they are voltage sensing devices, any deviation from the
>>> calibration value will introduce an error in power indication. It just
>>> depends on how precise one prefers to be with power measurements.
>>>
>>> 100 watts into 50 ohms is 70.71 volts
>>>
>>> 100 watts into 55 ohms is 74.16 volts
>>>
>>> 100 watts into 45 ohms is 67.08 volts
>>>
>>> 73
>>>
>>> Bob, K4TAX
>>>
>>>
>>>> On 7/23/2019 5:43 AM, CUTTER DAVID via Elecraft wrote:
>>>> I often wonder just how useful a precision dummy load really is in the
>>>> amateur service. I picked up home brew dummy load at the club the other
>>>> day. It measured 57ohms dc and comprises 4 wire-wound resistors attached
>>>> in a cluster across the end of the coax. After lots of disparaging
>>>> remarks I put it on the VNA and it didn't look at all bad out to 30MHz:
>>>> nothing over 1.5:1 and no spikes or dips to indicate resonances. I'll have
>>>> to do it again and make a print-out for posterity.
>>>> I've heard that salt water in a bucket works after a fashion.
>>>> So the question is: how good do you need it to be?
>>>> David G3UNA
>>>>
>>>>
>>>>> On 22 July 2019 at 23:58 "hawley, charles j jr" <c-haw...@illinois.edu>
>>>>> wrote:
>>>>>
>>>>>
>>>>> Used Bird Attenuator is a good deal.
>>>>>
>>>>> https://nm3e.com/AttenuatorSampler.htm
>>>>>
>>>>> Then you’ll have a sample to plug into your counter or scope
>>>>>
>>>>> Chuck Jack Hawley
>>>>> KE9UW
>>>>>
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>>
>
>
>
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