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Hi all,
One of the first things I noticed with the K3 was that the preamplifier seemed quite noisy compared to my old IC-718. With the IC-718 connected to a dummy load, the noise level rose an estimated 3dB or so but with the K3 I estimated at least twice that. Recent measurements using the Elecraft XG1 signal generator module bears this out. Using the recommended procedure in the XG1 manual, I measure an MDS at 500Hz BW at -133dBm without preamp and -136dBm with preamp. Without the preamp this is very good, but an improvement of a mere 3dB switching in 11dB's worth of gain is disappointing. Even if the XG1 is not perfectly in calibration, the relative performance with and without the preamp is not in doubt. Sensitivity is often poo-pooed these days, but on 10m (and 6m which I have no experience with), the band is really quiet. The -136dBm meets the K3's spec, but only barely and is a little short of ARRL and Sherwood's measurements.
Anybody else with a similar experience? Anything I should be looking for affecting the preamp's performance?
Knut - AB2TC
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