[Elecraft] Interpretation of P3 display

[David Gilbert]

Anything that represents a transmit non-linearity can cause splatter, 
and a very quick change in gain represents a non-linearity.

My ICOM 756Pro was one of those offenders that used an internal ALC to 
set the power level.  The internal delay in the ALC caused nasty power 
spikes at the beginning of transmissions that kept tripping the 
overdrive protection on my TenTec ALS-500 solid state amp.  It was a 
stupid system and I don't know if ICOM ever addressed it with their 
later rigs.  Amplifiers that use screen grid tubes like the GU-74B also 
do not those fast leading edge power spikes, making me grateful for the 
way the K3 handles things.

73,
Dave   AB7E


On 6/9/2012 7:03 AM, Jim Brown wrote:
> On 6/9/2012 5:14 AM, Geoffrey Mackenzie-Kennedy wrote:
>> the reason why a typical ALC can be responsible for splatter is because
>> these ALC systems sample the output of an amplifier and/or exciter, and due
>> to time delays cannot "throttle back" the drive power immediately.
> The ONLY proper ways to set power output are 1) to turn down the
> transceiver's output power by turning down the power control on the
> transceiver; or 2) using a resistive attenuator (voltage divider)
> between the transceiver and the amplifier.  W8JI, who has designed a lot
> of power amps, and, as part of that design work, has studied the
> behaviour of lots of ham transceivers, has written an excellent and
> detailed tutorial on this matter, and on how some ham transceiver ALC
> systems badly misbehave, and NEED to use option 2.  The K3 (and the
> FT1000MP)  do not have this problem, and work fine with option 1.
>
>
> 73, Jim K9YC
>