The spur also changes with bandwidth. In my K3 it happens to fall at 50.279.00 with FC=1.50, BW=2.80 in DATA_A when the rig is at 50.276.00. When going to FC=2.20, BW=4.00 the "spur" moves to ~50.285.5 and in USB "NORM" it falls at 50.275.71 (zero beat). Again, this is fortunate in that the spur is equivalent to a -96 dBm signal as measured on the P3 and would be a killer if it fell "in band".
I see additional (bothersome) spurs at 50.047.57 (-100 dBm), 50,082.72 (-116 dBm), 50.095.32 (-119 dBm), 50.102.04 (-116 dBm), 50.110.52 (-118 dBm), 50.111.65 (-120 dBm), 50.112.78 (-120 dBm), 50.150.26 (-110 dBm), 50.193.57 (-103 dBm), 50.222.56 (-119 dBm), 50.351.35 (-119 dBm), 50.390.82 (-119 dBm), 50.393.90 (-110 dBm), 50.435.85 (-119 dBm), 50.465.09 (-120 dBm), and 50.486.11 (-120 dBm) - frequencies are zero beat in USB with DSP = norm. Measurements were made with dummy load and PRE_1 in K3 s/n 1450 with 2x KSYN3A and KXV3B. "Bothersome" to me is > 6 dB above the receiver noise floor under the measurement conditions described. I have not attempted to catalog spurs on the other bands. 73, ... Joe, W4TV On 2015-06-25 9:14 AM, Ken_ke2n via Elecraft wrote:
My K3 with the new synth (and upgraded DSP board) has an unfortunate "birdy" on 50.276 (unfortunate because this is the JT65 calling frequency in the US). I know it is a DSP-type artifact because the pitch of the birdy changes with the IF Shift control. The IF shift control does not change the frequency of the signal, just the birdy. This phenomenon is actually useful. By shifting the center frequency to 1.35 kHz I can move the spur down to zero beat. And, like all spurs, the pitch of the spur changes a lot faster than the tuning rate of the radio. The pitch of the spur also varies with the setting of the crystal filter offset (mine is set at 200 Hz). ----- 73 Ken -- View this message in context: http://elecraft.365791.n2.nabble.com/6m-birdies-and-K3S-and-or-new-synth-boards-tp7604211p7604287.html Sent from the Elecraft mailing list archive at Nabble.com. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
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