[Elecraft] KPA100 recommended max power for digital modes?

[Edward R Cole]

Glenn,

My guess is most figured you were referring to the KXPA100, but your 
question even has more general reach.

Since full output for the KXPA-100 is cited with 10w drive, it is a 
good guess that 3w => 30w, 4w=> 40w, etc.  In reality the gain curve 
for amplifiers is not that flat and often you get a little more gain 
at lower inputs.  One advantage is that linearity is usually much 
better when an amp is driven below its max specs, so that is good for 
running psk-31 and other digital modes.  The K3 and KX3 are much 
better transmitters than most so maybe that is not as much of a concern.

Just a general comment about digital modes:  psk-31 was something I 
tried when it was fairly new and I generally ran at 15-25w with my 
FT-847.  I did well with a 20m dipole running at that level.  There 
were no locals to cause me grief so power level was not an issue.  I 
recall most contacts as nice chats and not certificate chasing.  I am 
looking forward to returning to psk-31 or its variants with 10w from 
my K3 or 3-5w from my KX3.  On 20-10m bands I use a three element 
yagi at 50-feet so that gives gain advantage of more ERP and 
selective reception if a neighbor is operating (I now have a 
multi-multi class station located about 12mi north of me).  But then 
I am not on for the contests so we have no issues (not even heard 
him).  He is big on RTTY and CW.

WSJT suite of digital modes was primarily developed for super 
weak-signal operation such as meteor scatter or eme.  They have 
evolved to weak-signal proponents on HF and LF, and up to mw, so I 
agree that a plain-text version is needed for "chat" style 
operating.  There are so many different digital modes these days so 
one has more to chose (eg: FLdigi).

73, Ed - KL7UW
17 bands: 600m - 3cm

--------------
From: WA7SPY <wa7spy at comcast.net>
To: "elecraft at mailman.qth.net" <elecraft at mailman.qth.net>
Subject: Re: [Elecraft] KPA100 recommended max power for digital
         modes?
Message-ID: <4144055F-7458-437A-A581-459369ADD617 at comcast.net>
Content-Type: text/plain;       charset=us-ascii

Thank you for all the replies they were very informative. In my 
original post I stated KPA100. It should have been KXPA100 my bad on 
my part. Most of you figured out what I meant.

I agree about the hi and bye PSK31 QSO's these days. That being said 
I will say I have had some really nice rag chew QSO's lately on 
PSK31. I typically start turning my power down during a QSO to see 
how low I can go and still have a good copy.

I do have my KX3 connected to a Hard Rock 50, 50 watt amplifier. I 
run the Hard Rock at 20 watts or less on PSK31.

In regard to the KXPA100 my original question was to find out what 
the max output power would be safe to go to without causing damage to 
the amp. If I am correct the answer is the amp will protect itself 
and automatically throttle itself back if the temp to the finals gets too hot.

Now in regard to the KX3 without the amp 2-3 watts is recommended for 
PSK31. What does 2 -3 watts driving the KXPA100 equate to for output 
power from the amp. I will be using the Elecraft cable set to 
integrate the amp. So from what I have read that means the PA menu is 
selected to on on the KX3. That means the power control on the KX3 is 
re-indexed. So does that mean it is safe to run in the 20-30 watt 
range with the amp without over driving the KX3 for PSK31?

Thank you
Glenn Maclean WA7SPY



73, Ed - KL7UW
http://www.kl7uw.com
     "Kits made by KL7UW"
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