[Elecraft] KPA1500 PA Current

Sun Mar 17 18:43:36 EDT 2019

By and large the response to my technical question regarding the behavior of my KPA1500 have been good, technical information and hints.  Your posting, Dave, is of the form of a lecture and comes across as anything but responsive to the topic at hand.  Whether I wish to squeeze the last dB out of my signal or not is not yours to comment on.

Please confine your postings to being responsive to the thread.

73,

Gary W2CS

> On Mar 16, 2019, at 5:13 AM, David Wilcox <djwilcox01 at yahoo.com> wrote:
> 
> Try 1000 watts for one month.  Then  500 watts for the next month.  Don’t tell anyone. 
> 
> Unless you are trying to get that last country for your stats you won’t see any difference in your enjoyment and contact ratio.  How often do we turn our receivers, stereos, ovens, microwaves, irons, or even car engines up to their max just “because we can”?  Not trying to start a flame war here but to me it does make sense to give our equipment some breathing room? 
> 
> Yesterday while monitoring a group of guys around Michigan on 75 meters one of them dropped down from his KW to 12 watts and everyone was amazed he was still 20 dB over S9.  They were over 100 miles apart too.
> 
> Many of my friends have over 300 countries or have worked all counties and have never used over 500 watts, mostly 100 watts.
> 
> Yes, it is good to experiment to find out why this is occurring, but after that give your amp some room to breathe.  I watch this list for education and haven’t ever seen a rating of how high the Elecraft 1500 watt amp is tested at, what is its actual max output and for how long.  I would guess that if it’s designed to handle 3000 watts then 1500 watts is conservative and this problem shouldn’t be happening.  If it is tested and burned in at 2000 watts then it is being pushed and heating might be a problem on some amps.  I have watched a few other comments on the Elecraft 100 watt amp and they have troubles getting an actual 100 watts out all the time too.  Rain, ice, and other factors change things too.  Isn’t this hobby fun?
> 
> Just a thought.
> 
> Dave K8WPE
> 
> David J. Wilcox K8WPE’s iPad
> 
>> On Mar 15, 2019, at 9:27 PM, K9MA <k9ma at sdellington.us> wrote: comeer, it’s possible you have hit just the wrong phase angle.  If your 1.2 SWR resulted in a load impedance of 42 Ohms, the current could go up 20 percent. On the other hand, 55 A into 50 Ohms sounds a bit high. Make sure the voltage isn’t dropping more than a couple Volts.
>> 
>> 73,
>> Scott K9MA 
>> 
>> ----------
>> 
>> Scott Ellington
>> 
>> --- via iPad
>> 
>>> On Mar 15, 2019, at 1:25 PM, Gary J Ferdinand <alaparos at w2cs.net> wrote:
>>> 
>>> I’m in the process of checking out my amp.  I have two dipoles (40 and 80).  At resonance both show a 1.2:1 SWR with ATU totally bypassed.  With ATU on, it remains bypassed on 80, but shows only the ATU ON LED on 40.  In both cases the resultant SWR is 1.2:1.   SWR measurements are from the KPA1500 display.
>>> 
>>> When I use the amp with my K3 and drive it up to 1500W, I am occasionally getting an excessive PA current fault at 63A.  From a cold start it’s 60A, but as it warms up in contest usage I find the power drops off, so I have to adjust the K3 to bring it back up to 1500W.  At that point the PA current goes over 60A.
>>> 
>>> Interestingly, into a dummy load the 1500W point shows a PA current of only 55A.  So the 1.2:1 SWR, be it via a bypassed ATU or using the ATU, is sufficient to raise the PA current eventually to excessive levels.
>>> 
>>> Suggestions?   I don’t want this to be flipping out during a contest.  I also don’t want to reduce power into what should be a totally acceptable load.
>>> 
>>> 73
>>> 
>>> Gary W2CS
>>> 
>>> 
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