[Elecraft] KPA500 Faulting on high SWR on power rise

[Alan]

10:1 SWR implies that the impedance is 500 ohms resistive at the maximum 
point on the line.

E = sqrt(P*R) = sqrt (500w * 500ohms) = 500 Vrms, which is 707 Vpk.

So if the UHF connector happened to be located at a voltage maximum on 
the line it would see more than its rated 500V peak.

Alan N1AL


On 02/24/2018 05:11 PM, Walter Underwood wrote:
> In this case, the lightning protection is on the antenna side of the matching unit, so it isn’t at 1:1 SWR or 50 Ohms. At 10:1 VSWR, we would see 500 V peak at 500 W.
> 
> wunder
> K6WRU
> Walter Underwood
> CM87wj
> http://observer.wunderwood.org/ (my blog)
> 
>> On Feb 24, 2018, at 4:46 PM, Bob McGraw K4TAX <rmcgraw at blomand.net> wrote:
>>
>> Based on the specification of 500 volts peak,    5KW at 50 ohms = 500 volts.  It would seem the PL-259 is adequate for ham radio applications per specification to 0.3 GHZ or 300 MHz without issues. Of course one is dealing with 50 ohms, which implies essentially a 1:1 SWR.
>>
>> 73
>>
>> Bob, K4TAX
>>
>> On 2/24/2018 4:53 PM, john at kk9a.com wrote:
>>> Really?  An Amphenol UHF connector only has a 500v rating.
>>>
>>> John KK9A
>>>
>>>
>>> Bill Johnson k9yeq wrote
>>>
>>> 1000v to me could be too low for a 500W amp.  You can for the time being
>>> leave the plug out, just disconnect when you are not using your equipment.
>>> I use a remote disconnect to remove the antennas at my remote grounding
>>> panel.
>>>
>>> 73,
>>> Bill
>>> K9YEQ
>>>
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