So I guess the question is this: is it expected to see such a large
variance in power consumption for the same output power based on the
values of C and L for the KAT3A?
Is the KAT3/KAT3A *tuned correctly*?
Any solid state amplifier will draw more current if it is driving a
low impedance load than it draws driving a high impedance load. If
the KAT3/3A is transforming the antenna impedance to a low value,
you will see higher current than you would for a proper 50 Ohm load.
The only valid measurement is with a 50 Ohm dummy load attached to
the antenna jack and the KAT3/3A tuned for the 50 Ohm load (or
bypassed). You should *never* be operating with the tuner adjusted
for other than 50 Ohms to the PA.
> min C/max L max C/min L bypass not-inst
> 40m, 12w 3.55A 2.23A 3.4A 3.3A
> 20m, 12w 3.70A 1.99A 3.1A 3.0A
>
>
> 40m, 13w 11.5A 4.65A 7.3A 7.2A
> 20m, 13w 15A 5.63A 6.9A 6.8A
You are comparing apples and oranges here. At 12W the 100 W amplifier
is bypassed. At 13W the 100W amplifier is engaged. The differene you
see is due to the 100W amplifier.
73,
... Joe, W4TV
On 2020-05-12 2:31 PM, Nicklas Johnson wrote:
I've had a few exchanges with support on this, but as Covid-19 is imposing
some new burdens on the shop, I thought I might ask the larger community
for input as well.
I've been troubleshooting seemingly anomalous power consumption when
transmitting. My K3S pulls way more current on 20m than on 40m for the same
input signal and output power.
After some experimentation, I found that the input current is related to
whether the KAT3A is engaged, and which values of C and L are selected.
The lowest power consumption comes from the highest value for C and the
lowest value for L, and the highest power consumption comes from the lowest
C and highest L. Here's a chart of what I found going into a dummy load,
manually setting C and L values:
min C/max L max C/min L bypass not-inst
40m, 12w 3.55A 2.23A 3.4A 3.3A
20m, 12w 3.70A 1.99A 3.1A 3.0A
40m, 13w 11.5A 4.65A 7.3A 7.2A
20m, 13w 15A 5.63A 6.9A 6.8A
If that chart doesn't render well on the list, here's a screen shot of it:
https://imgur.com/GF4IUIy
(This was transmitting a 1500Hz tone, SSB at almost 100% modulation with
14v supplied, and is the value reported by the K3s, though my ammeter
reports a similar value. I get similar results with FT8 going into an
actual antenna instead of a dummy load.)
So I guess the question is this: is it expected to see such a large
variance in power consumption for the same output power based on the values
of C and L for the KAT3A?
Nick
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