K3 and AM

[w0sz]

Hello to the group.  I hope everyone is enjoying their K3 as much as I.  I
got on AM Sunday morning for the first time.  All those on the net said that
the K3 sounded great.  I wonder if anyone else has used their K3 on AM and
have any suggestions as to power levels and carrier levels and if anyone has
used a linear amplifier on AM with the K3.  I've never operated AM and I
vaguely remember that the power levels are different on AM than SSB.  My
amplifier is a Acom 1000.  I would be interested in any suggestions.  Best
73, Steve W0SZ

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[Jim Garland]

Steve,
On AM, your carrier power should be about 25% of the peak transmitter power.
For a K3, which runs 120W output, this means that the carrier output should
be about 30W. I believe the K3 automatically sets the correct
carrier-to-peak power ratio, so that when you scale back the K3's power
output, the AM carrier is reduced proportionately.

When running a linear amplifer on AM, the same percentage applies. In other
words, for a legal limit linear amplifier whose power output is 1500 Watts,
your carrier power should be 375W.  Then, your modulation peaks will be the
full 1500W.

When tuning your linear amplifier for AM, DO NOT load it with the AM carrier
of 375W.  Instead, always load it in the CW mode at the full 1500W output.
Then when you run it on AM, the amplifier will be tuned properly for 375W of
carrier.

Just to remind you where the 25% AM carrier rule comes from, in a 100%
modulated AM signal, the RF envelope varies from zero to twice the carrier
average voltage. In other words, the modulation peaks will be twice the
voltage of the unmodulated carrier. Since power varies as the square of the
voltage, twice the voltage is four times the power. Thus, your transmitter
and amplifier has to be rated at four times the unmodulated carrier value.

73,

Jim W8ZR

> -----Original Message-----
> From: [hidden email] [mailto:elecraft-
> [hidden email]] On Behalf Of W0SZ
> Sent: Monday, July 28, 2008 11:32 AM
> To: [hidden email]
> Subject: [Elecraft] K3 and AM
>
> Hello to the group.  I hope everyone is enjoying their K3 as much as I.  I
> got on AM Sunday morning for the first time.  All those on the net said
> that
> the K3 sounded great.  I wonder if anyone else has used their K3 on AM and
> have any suggestions as to power levels and carrier levels and if anyone
> has
> used a linear amplifier on AM with the K3.  I've never operated AM and I
> vaguely remember that the power levels are different on AM than SSB.  My
> amplifier is a Acom 1000.  I would be interested in any suggestions.  Best
> 73, Steve W0SZ
>
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[Eric Swartz - WA6HHQ]

One important note - Like most ham rigs, the K3 is officially specified
at 100W. While the control turns up to 120W, and most rigs will go above
above 100w, they will not make that power level on all units on all
bands. Above 100W it is not guaranteed to meet all specifications.

73, Eric  WA6HHQ

Dr. James C. Garland wrote:
> Steve,
> On AM, your carrier power should be about 25% of the peak transmitter power.
> For a K3, which runs 120W output, this means that the carrier output should
> be about 30W. I believe the K3 automatically sets the correct
> carrier-to-peak power ratio, so that when you scale back the K3's power
> output, the AM carrier is reduced proportionately.
>
>  
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