[Elecraft] KPA1500 - temp reading drops 10C when under power

[K9MA]

Elecraft has a fix for this. 

73,
Scott K9MA

----------

Scott Ellington

 --- via iPad

> On Aug 18, 2018, at 1:55 PM, Paul Baldock <paul at paulbaldock.com> wrote:
> 
> I just checked mine on 40M and when on CW Temp is bouncing all over the place. Same into a dummy load as the antenna 300ft away. It also does it to a lesser extent on 80M and a little bounce on 17M and 10M.
> 
> I suspect its in the amp and not related to common mode RF in the coax.
> 
> Probably a cap in the right place would fix it.
> 
> - Paul
> 
> 
> At 11:20 AM 8/18/2018, you wrote:
>> Some baluns offer good common mode current rejection while others offer virtually no common mode rejection.   {See DJ0IP site and discussion on baluns.}  Since the feed line from the balun runs down the tower to the point where the feedline runs underground, that segment of feedline is exposed to radiation from the antenna.  Certainly common mode current can be a very realistic occurrence in this case. ..........." it's some sort of new hyper-super-ultra-infina-deluxe type never before discovered on earth."   Nope,  it is just basic physics regarding the properties of RF induced currents.    Depending on band, a choking impedance of 300 to 5000 ohms may be needed to resolve the issue.   Since it was disclosed as power related, this supports the issues of common mode currents. Good luck in finding and correcting the matter. 73 Bob, K4TAX On 8/18/2018 12:20 PM, Jeff Blaine wrote: > Odds are not good there.  The antennas have a balun at the feedpoint, > are on a tower 500 feet from the shack and the hardline runs under > ground.  If there is common mode involved, it's some sort of new > hyper-super-ultra-infina-deluxe type never before discovered on earth. > > 73/jeff/ac0c > alpha-charlie-zero-charlie > www.ac0c.com > > On 18-Aug-18 7:12 AM, Bob McGraw K4TAX wrote: >> I'd say a bit of common mode current on the feed line.    I see that >> from time to time with my KPA500 on certain bands/antennas. >> >> 73 >> >> Bob, K4TAX >> >> >> On 8/17/2018 11:45 PM, Jeff Blaine wrote: >>> While running the KPA1500 in the SARTG tonight, I noticed that the >>> temp reading drops about 10C when transmitting.  min fan speed 1. >>> >>> Seems to be related to power - at 1500W it's pretty close to 10C. At >>> lower powers, it's less of a difference.  I don't recall seeing that >>> before. >>> >>> Normal? >>> >>> 73/jeff/ac0c >>> alpha-charlie-zero-charlie >>> www.ac0c.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 keepwalking188 at ac0c.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 paul at paulbaldock.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 k9ma at sdellington.us