[Elecraft] KPA500 SWR Calibration

[AJ8MH Radio]

I know I've seen an explanation somewhere, but it's common to have 
different readings between the tuner, amp and rig when connected to an 
antenna. Readings seem to even out when connected to a dummy load...at 
least in my case. 20 meters is my worst, and the amp will kick out at times.

On 11/17/2019 2:19 PM, Bob McGraw K4TAX wrote:
> Jack, et.al.
>
> Thanks,  Yes I see from the circuit it is not a Breune.   I have 
> calibrated the indications for power and all is well in that regard.  
> I just see a higher SWR that actually exists.  That under certain 
> conditions causes the amp to fault.   I'll figure a work-a-round and 
> be able to deal with it.
>
> 73
>
> Bob, K4TAX
>
>
> On 11/17/2019 10:12 AM, Jack Brindle wrote:
>> Bob;
>>
>> The KPA500 does not use a Breune style bridge, but rather a true 
>> directional coupler. It does not need to be nulled; there is no 
>> adjustment.
>>
>> There is an adjustment for the power; see the PWR ADJ setting in the 
>> manual.
>>
>> 73!
>> Jack, W6FB
>>
>>
>>> On Nov 17, 2019, at 6:58 AM, Bob McGraw K4TAX <rmcgraw at blomand.net> 
>>> wrote:
>>>
>>> I need to null the SWR detector on my KPA500.   I've not found any 
>>> adjustment procedure as such.   And from the schematic, there is none.
>>>
>>> I do have a rather precise Bird 50.5 ohm dummy load.  I see SWR 
>>> values higher than 1:1 on the LED display and also on the LCD 
>>> display on higher frequency bands.   I've found that the PWR ADJ 
>>> does affect not only the indicated power but the FAULT values as 
>>> well.   I am suspect that the  SWR error likewise affects the Fault 
>>> actions.
>>>
>>> Any thoughts?
>>>
>>> 73
>>>
>>> Bob, K4TAX
>>>
>>>
>>>
>>>
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>
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-- 
Joe Hutchens
AJ8MH - Radio
Marquette, MI