[Elecraft] Dummy Load recommendation

[Bob McGraw K4TAX]

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 <W2xj at 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 <rmcgraw at 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-hawley at 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
>>>> 
>>> ______________________________________________________________
>>> Elecraft mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:Elecraft at mailman.qth.net
>>> 
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>>> Message delivered to rmcgraw at blomand.net
>> 
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Elecraft at mailman.qth.net
>> 
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to w2xj at w2xj.net
> 
>