K3: Adjusting SSB modulation for proper PEP rating

[Edward R Cole]

Since the K3 operates so differently (than traditional radios) for
proper modulation I thought I'd ask this:
In olden days amplifiers were rated in PEP typically as 2x average
(or CW) power, so for AM one had to set carrier at 1/4 full carrier
output to stay linear. (1/2 carrier  for SSB).

But now I am setting up a 600w linear amp to run at P1 which is about
0.9 of P3 (saturated power) and wondering what level of carrier power
to run in SSB to stay linear and also not to overdrive and stress the
expensive LDMOS device in the amplifier.

I'm running the K3 in transverter mode on 28-MHz so max output is
1.5mw.  I can view this with a scope.  The amplifier is running at
1296-MHz which is too high a freq to monitor with my scope.  I can
only observe average RF power from a directional coupler and diode
detector (like a Bird meter).

Normally, I just set power on the K3 to drive my amp to nominal full
power and select SSB mode.  Modulation level is set by observing ALC
meter.  I is ALC showing five bars when saying the word "five" loudly
and six bars with compression.  So does this mean the K3
automatically adjusts RF power in SSB to stay linear with proper
modulation audio setting?

My reason is when running 1296 SSB to avoid overdriving the amplifier
into P3 possibly causing harm, as much as not wanting to produce
non-linear products.

73, Ed - KL7UW
   http://www.kl7uw.com
Dubus-NA Business mail:
   [hidden email]

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[Don Wilhelm]

Ed,

The power you request with the power knob is the PEP level that the K3
will control.  That is regardless of mode.
The K3 compensates for the mode automatically.

The same should be true of the transverter output.

73,
Don W3FPR

On 4/23/2018 4:56 AM, Edward R Cole wrote:

> Since the K3 operates so differently (than traditional radios) for
> proper modulation I thought I'd ask this:
> In olden days amplifiers were rated in PEP typically as 2x average (or
> CW) power, so for AM one had to set carrier at 1/4 full carrier output
> to stay linear. (1/2 carrier  for SSB).
>
> But now I am setting up a 600w linear amp to run at P1 which is about
> 0.9 of P3 (saturated power) and wondering what level of carrier power to
> run in SSB to stay linear and also not to overdrive and stress the
> expensive LDMOS device in the amplifier.
>
> I'm running the K3 in transverter mode on 28-MHz so max output is
> 1.5mw.  I can view this with a scope.  The amplifier is running at
> 1296-MHz which is too high a freq to monitor with my scope.  I can only
> observe average RF power from a directional coupler and diode detector
> (like a Bird meter).
>
> Normally, I just set power on the K3 to drive my amp to nominal full
> power and select SSB mode.  Modulation level is set by observing ALC
> meter.  I is ALC showing five bars when saying the word "five" loudly
> and six bars with compression.  So does this mean the K3 automatically
> adjusts RF power in SSB to stay linear with proper modulation audio
> setting?
>
> My reason is when running 1296 SSB to avoid overdriving the amplifier
> into P3 possibly causing harm, as much as not wanting to produce
> non-linear products.

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[Edward R Cole]

Thanks, Don, as I suspected (kind of).

Of course in CW PEP=carrier power and makes
sense.  I never really *asked* this question
before as I always had nice reports on my
SSB.  Gives me confidence running my new
*expensive* LDMOS kilowatt amps on 144 and 1296
plus my old-school 16 NLA transistor Harris on
50-MHz when running SSB.  Mostly run them "full
bore" with either CW or digital on eme, where PEP
is approx equal to carrier power.

The 144 and 1296 amps are new and not yet QRV
(but soon).  I will sell my 2m W6PO-8877 with
HVPS when this is accomplished.  Passing of an
era to "no-tube" operation which started 60 years ago with a DX-35 (6146).

73, Ed - KL7UW

At 02:52 AM 4/23/2018, Don Wilhelm wrote:

>Ed,
>
>The power you request with the power knob is the
>PEP level that the K3 will control.  That is regardless of mode.
>The K3 compensates for the mode automatically.
>
>The same should be true of the transverter output.
>
>73,
>Don W3FPR
>
>On 4/23/2018 4:56 AM, Edward R Cole wrote:
>>Since the K3 operates so differently (than
>>traditional radios) for proper modulation I thought I'd ask this:
>>In olden days amplifiers were rated in PEP
>>typically as 2x average (or CW) power, so for
>>AM one had to set carrier at 1/4 full carrier
>>output to stay linear. (1/2 carrier  for SSB).
>>But now I am setting up a 600w linear amp to
>>run at P1 which is about 0.9 of P3 (saturated
>>power) and wondering what level of carrier
>>power to run in SSB to stay linear and also not
>>to overdrive and stress the expensive LDMOS device in the amplifier.
>>I'm running the K3 in transverter mode on
>>28-MHz so max output is 1.5mw.  I can view
>>this with a scope.  The amplifier is running
>>at 1296-MHz which is too high a freq to monitor
>>with my scope.  I can only observe average RF
>>power from a directional coupler and diode detector (like a Bird meter).
>>Normally, I just set power on the K3 to drive
>>my amp to nominal full power and select SSB
>>mode.  Modulation level is set by observing
>>ALC meter.  I is ALC showing five bars when
>>saying the word "five" loudly and six bars with
>>compression.  So does this mean the K3
>>automatically adjusts RF power in SSB to stay
>>linear with proper modulation audio setting?
>>My reason is when running 1296 SSB to avoid
>>overdriving the amplifier into P3 possibly
>>causing harm, as much as not wanting to produce non-linear products.

73, Ed - KL7UW
   http://www.kl7uw.com
Dubus-NA Business mail:
   [hidden email]

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