[Elecraft] Happy But Very Sad
Wayne Burdick
n6kr at elecraft.com
Fri Jun 22 18:42:10 EDT 2012
Adrian wrote:
> K3 a superior transmitter in imd product results?....
Adrian,
The K3 is a 12-volt-powered transceiver. When running at 100 W and
from a typical DC supply, its transmit 3rd-order IMD is very similar
to that of other 12-V radios, as confirmed by multiple test labs.
A transceiver with a class-A final or running from much higher supply
voltages (15 V is OK, as you mentioned) will have better IMD. But
radios with built-in supplies are not suited for portability -- a
major design goal of the K3, which is used by more DXpeditions than
any other rig.
Also, I suspect most "splatter" comments derive from improper
adjustment of the K3 when used with an external amplifier.
Some amplifier manufacturers still insist on instructing users to
crank up their radio's power output to maximum when driving the amp,
forcing the use of wideband ALC at the radio, and that can indeed
result in splatter. But if you adjust the K3's power output as
described in the owner's manual (with no more drive than required for
full amp power), and do not depend on aggressive ALC action, its
signal will be very clean. This allows all of the K3's fast ALC to be
achieved *ahead* of the crystal filter, avoiding the wideband ALC
splatter characteristic of transceivers designed for "crank-it-all-the-
way-up" mode.
Also note that the K3 typically runs at 20-50 W when driving the
KPA500 or other amp with similar gain, resulting in excellent third-
order IMD.
If anyone had a K3 exhibiting IMD worse than specified, we would
certainly repair it at no charge.
73,
Wayne
N6KR
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