Unfortunately, the IMD can be unacceptable even with the supply set to the high
side.
I will confess to not having measured IMD v. supply voltage. For my manual
method, that entails another layer of data. I have however, characterized my
old K3 and my new K3S with three different LPAs and four HPAs, with frequency
and output power as variables. I suspect that most would be surprised to know
that there is significant variation over frequency; more than with respect to
power.
My K3s in its latest reincarnation KLPA3A Rev B3, KPA3A Rev C9, has exceptional
IMD of -42 dBc at 40 meters and unacceptable IMD of -22 dBc at 10 meters and 10
W output. Same radio, power supply and measurement system. The only variable:
frequency.
Wes N7WS
On 4/17/2018 6:31 PM, Bob wrote:
I think the original question has morphed. It is really two questions. The
operational range of the K3 as one. The second is really the optimum range of
the K3. In dealing with the drops between the K3 and power supply how much is
excessive? My Astron is set for 14 volt and drops at the K3 under XMIT. How
much drop would be necessary for the IMD to rise to an unacceptable level? Or
put another way what is a reasonable goal for the drop in the power cable or
power distribution to the K3?
Zero millivolts would be ideal but not obtainable. I'll admit to not having
the knowledge or test gear to measure the IMD. If instead of getting 100 watts
I could only get 95 watts to me that would be insignificant. But I don't want
to XMIT a "dirty" signal either.
73,
Bob
K2TK ex KN2TKR (1956) & K2TKR
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