On 7/25/2014 12:32 PM, Brian Mullaney wrote:
Maybe wideband noise.. but the IMD numbers in both the ARRL test and
reported elsewhere were pretty bad.
That depends on how the radio is run. Lab testing is done full power
barefoot. Don't know the DC power supply voltage. IMD is significantly
reduced by operating the radio from higher DC voltage (13.8V rather than
12V), and at the reduced power levels required to drive most power amps
(my Titans get to full power between 40 and 50W). And sideband trash
matters a lot more when you're running 1.5kW (or more) than when you're
at 100W.
BTW -- early K3s shipped with firmware allowing them to be cranked to
120W out, but IMD got pretty bad, and firmware was subsequently modified
to limit output power to 110W.
Further, phase noise is particularly bad when it extends very far from
the carrier, and that's where the K3 shines on both TX and RX.
See the slides from K6XX's Clean Signals talk, on my website.
k9yc.com/publish.htm
73, Jim K9YC
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