Output power on K2 not stabel

[Dick Grolleman]

Hi All

I'm using my K2/100 to drive my Amp with 50 watts. But the output power is not stabel. When set to 50 watt the power goes from 50 to 100 and back, wich causes to much drive for my Amp. Other then that the K2 works fine with 100watts, barefood.
Any one knows this problem? And more important, how do is solve it.
My K2 is serial nr 4072. It's build in sprng 2004. Rev B  KPA100

Have the K3 on order, have to wait a few more months

73 de Dick PA3FQA
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[Darwin, Keith]

Mine was similar but only on 40 meters.  It is a known side effect of
the design.  There is one resistor you can change that will make it much
better but you may lose a bit of output on 10 meters.  I'm sure some
smart person (Don?) will jump in with the exact resistor, it's location
and a suggested value :-)

Or a search through the archives may turn up the same info.

- Keith N1AS -
- K2 5411.ssb.100 -
- K3 tbd -

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Dick Grolleman
Sent: Thursday, April 10, 2008 3:32 PM
To: [hidden email]
Subject: [Elecraft] Output power on K2 not stabel

Hi All

I'm using my K2/100 to drive my Amp with 50 watts. But the output power
is not stabel. When set to 50 watt the power goes from 50 to 100 and
back, wich causes to much drive for my Amp. Other then that the K2 works
fine with 100watts, barefood.
Any one knows this problem? And more important, how do is solve it.
My K2 is serial nr 4072. It's build in sprng 2004. Rev B  KPA100

Have the K3 on order, have to wait a few more months

73 de Dick PA3FQA
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[Don Wilhelm-4]

Dick,

Check out this application note at the Elecraft website -
http://www.elecraft.com/Apps/Power_Control_Mod.html

Each K2 is a bit different in the overall transmit gain, so for most
stable operation, the value of R98 must be determined experimentally.  
Be aware that increasing R98 too much will result in a power output drop
on 10 meters (the band with the lowest transmit gain), so some
compromise must be made - you select how much power reduction on 10
meters is tolerable for you.

73,
Don W3FPR

Dick Grolleman wrote:
> Hi All
>
> I'm using my K2/100 to drive my Amp with 50 watts. But the output power is not stabel. When set to 50 watt the power goes from 50 to 100 and back, wich causes to much drive for my Amp. Other then that the K2 works fine with 100watts, barefood.
> Any one knows this problem? And more important, how do is solve it.
> My K2 is serial nr 4072. It's build in sprng 2004. Rev B  KPA100
>
> Have the K3 on order, have to wait a few more months
>
>  
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[AC7AC]

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[Kurt Cramer-2]

Dick, I think you're getting RF back in to the K2 for it to change that much. Since it works OK bearfoot.
 
Kurt



> From: [hidden email]> To: [hidden email]> Date: Thu, 10 Apr 2008 21:32:01 +0200> Subject: [Elecraft] Output power on K2 not stabel> > Hi All> > I'm using my K2/100 to drive my Amp with 50 watts. But the output power is not stabel. When set to 50 watt the power goes from 50 to 100 and back, wich causes to much drive for my Amp. Other then that the K2 works fine with 100watts, barefood. > Any one knows this problem? And more important, how do is solve it.> My K2 is serial nr 4072. It's build in sprng 2004. Rev B KPA100> > Have the K3 on order, have to wait a few more months> > 73 de Dick PA3FQA> _______________________________________________> Elecraft mailing list> Post to: [hidden email]> You must be a subscriber to post to the list.> Subscriber Info (Addr. Change, sub, unsub etc.):> http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm> Elecraft web page: http://www.elecraft.com_______________________________________________
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[AC7AC]

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[Dick Grolleman]

Hi gentelmen

More info

I have been testing my K2 on the power issue.
I have the following findings
It is stabel on low power. I set it to 5 watt, press tune and it is stabel.
turn the power up to 50 watt, and it goes from 42 to 50. stop the tuning,
press tune again and the power is 28 watts and going down to 20. Turn it op
to 50 again, and stop tuning. press tune again after a few seconds and again
is 28 watt and goes down to 20. turn it up again, and it repeats again, so i
keep increasing the power. but if it is on 50 watt is is quit stabel. Then
start transmiting, and the power varies from 40 to 70watt.
never noticed this before as it is the first time I use the radio witn an
amp. But I does not matter if the amp is on or not. works fine on 100 watt

Maybe this helps.

many thanks 73 de Dick


----- Original Message -----
From: "Ron D'Eau Claire" <[hidden email]>
To: "'Dick Grolleman'" <[hidden email]>; <[hidden email]>
Sent: Friday, April 11, 2008 4:17 AM
Subject: RE: [Elecraft] Output power on K2 not stabel

> Excellent suggestion. Hopefully you have a dummy load you can use with the
> amp to see if you're getting more stable results without your antenna.
>
> The issue that involves tweaking the resistor is one that might cause the
> output power to vary a few watts - maybe run between 48 and 53 watts  when
> set to 50 watts output. That's enough to bother some ops and the resistor
> tweaking can immunize that. This sounds like something quite different.
>
> Ron AC7AC
>
> -----Original Message-----
>
>
> Dick, I think you're getting RF back in to the K2 for it to change that
> much. Since it works OK bearfoot.
>
> Kurt
>
>

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[Don Wilhelm-4]

Dick,

Sorry, but that does not help a lot - the operation in TUNE that you
describe in normal.  TUNE (with the KPA100) normally controls power at
20 watts.  If you enter TUNE and then turn the power control, it will
try to produce the power that is set on the power control knob.

The gain of the power control loop is increased (over the base K2 gain)
when the KPA100 is present and the power control set for greater than 11
watts - so the fact that this problem does not show up at low power is a
not unusual.  If the gain of your KPA100 is greater than the average,
you may notice this power control loop oscillation problem.

Try increasing RF Board R98 to see if the power control oscillation
settles down.

73,
Don W3FPR

Dick Grolleman wrote:

> Hi gentelmen
>
> More info
>
> I have been testing my K2 on the power issue.
> I have the following findings
> It is stabel on low power. I set it to 5 watt, press tune and it is
> stabel. turn the power up to 50 watt, and it goes from 42 to 50. stop
> the tuning, press tune again and the power is 28 watts and going down
> to 20. Turn it op to 50 again, and stop tuning. press tune again after
> a few seconds and again is 28 watt and goes down to 20. turn it up
> again, and it repeats again, so i keep increasing the power. but if it
> is on 50 watt is is quit stabel. Then start transmiting, and the power
> varies from 40 to 70watt.
> never noticed this before as it is the first time I use the radio witn
> an amp. But I does not matter if the amp is on or not. works fine on
> 100 watt
>
> Maybe this helps.
>
> many thanks 73 de Dick
>

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