[Elecraft] KPA-1500 failing on 160...AGAIN!

[Walter Underwood]

From the Amphenol data sheet, UHF connectors are rated for 500 V peak, so they are marginal for use at that power level. Type N connectors are rated at 1500 V peak.

https://www.amphenolrf.com/connectors/uhf.html
https://www.amphenolrf.com/connectors/n-type.html

wunder
K6WRU
Walter Underwood
CM87wj
http://observer.wunderwood.org/ (my blog)

> On Sep 27, 2019, at 7:41 AM, Jim Miller <jim at jtmiller.com> wrote:
> 
> Although the RMS voltage is pretty high. The peak voltage is higher
> especially if SWR isn't 1:1 along the transmission line.
> 
> It could easily be above 1Kv and causing arcing.
> 
> 73
> 
> jim ab3cv
> 
> 
> On Fri, Sep 27, 2019 at 10:35 AM Michael Walker <va3mw at portcredit.net>
> wrote:
> 
>> Like others have said
>> 
>> Even though your analyzer says the antenna is ok, that is only one part.
>> It can still be part of the problem at 1500 watts and if memory serves me
>> well, that is about 275V (RMS) at 50 ohms.
>> 
>> Something could be breaking down at that voltage so a good visual
>> inspection would help.  Look for arcing at each connector, Ununs, Baluns,
>> etc.
>> 
>> Mike va3mw
>> 
>> On Fri, Sep 27, 2019 at 9:18 AM Bob McGraw K4TAX <rmcgraw at blomand.net>
>> wrote:
>> 
>>> Check for burn marks or carbon traces, both on the inside and outside,
>> of
>>> the SO-239 connectors.  These may look good with the antenna analyzer but
>>> fail under power.
>>> 
>>> I've also had PL-259's arc from center pin to shell on the inside. These
>>> required removal/ disassembly of the coax in order to actually find the
>>> fault.
>>> 
>>> In all cases, once a flashover occurs, replacement of the connector is
>> the
>>> only solution.
>>> 
>>> Bob, K4TAX
>>> 
>>> 
>>> Sent from my iPhone
>>> 
>>>> On Sep 27, 2019, at 6:00 AM, John Langdon <WOYB10051 at outlook.com>
>> wrote:
>>>> 
>>>> If it also happens with a dummy load, and the antenna analyzers shows
>>> the same graph as before for R, X, then it is likely one of the
>> connectors
>>> between the KPA1500 output and the antenna. The one such problem I had
>> was
>>> old jumper I had put in to add an SWR bridge/monitor. It looked okay, and
>>> was finger tight, but when I replaced it in an A/B test, the problem went
>>> away.
>>>> 
>>>> The other time, the antenna had changed its impedance curve, but was
>>> still 'okay' and the tuner was trying to retune for it.
>>>> 
>>>> 73 John N5CQ
>>>> 
>>>> 
>>>> -----Original Message-----
>>>> From: elecraft-bounces at mailman.qth.net <
>> elecraft-bounces at mailman.qth.net>
>>> On Behalf Of Jim Brown
>>>> Sent: Friday, September 27, 2019 4:19 AM
>>>> To: elecraft at mailman.qth.net
>>>> Subject: Re: [Elecraft] KPA-1500 failing on 160...AGAIN!
>>>> 
>>>>> On 9/26/2019 10:26 PM, Peter Dougherty wrote:
>>>>> Any idea where to start looking here?
>>>> 
>>>> And if it's a vertical, what about the radial system?
>>>> 
>>>> 73, Jim K9YC
>>>> ______________________________________________________________
>>>> 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 woyb10051 at outlook.com
>>>> ______________________________________________________________
>>>> 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 va3mw at portcredit.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 jim at jtmiller.com
>> 
> ______________________________________________________________
> 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 wunder at wunderwood.org