David Cole <[email protected]> writes: > It occurs to me that the the the RX VFO phase noise would be less > influencing, (on phase noise sidebands), than the transmit VFO phase > noise... Is that correct? > > If so, then that would explain why the largest change occurred when > K7OLN got his new synthesizer, as opposed to me getting my new > synthesizer, as shown in the difference between photos 2 and 3. > > Is my understanding correct?
In an ideal system, the receiver sees the convolution of the transmit signal, as conveyed by the antennas and progagation and the receiver's LO. So for the most part, I think TX and RX phase noise hurt equally (when viewed in dBc/Hz at some separation). Of course, RX phase noise is under one's control, and TX is imposed on others, so from that viewpoint TX phase noise is more like crossing the yellow line than hitting a tree yourself. >From the measurements I've seen, I don't think it's a fair assumption that transmit and receive phase noise in a given rig is the same. The K3 (with original synth) has a transmitter which is relatively cleaner than RX reciprocal mixing, according to: http://www.sm5bsz.com/dynrange/dubus313.pdf But in many radios (including the KX3), that article says that the transmitter is worse than the receiver. Also see: http://k9yc.com/TXNoise.pdf which focuses on lab measurements of transmitters, disconnected from receiver issues. Presumably the spectrum analyzers are good enough that they're not an issue, but I wonder if that's really true given the levels we're talking about. I think QST reviews should give some measurement of joint TX/RX noise. Perhaps the isolation required so that with one instance of a transceiver at 100W, the 2nd instance receiving at 100 kHz separations (perhaps for 2/10/50/100/200 kHz) ees some particular absolute level of noise, picking some level that is about 10 dBo worse than typical MDS. This is trying to capture "what happens when you have two of Rig X at Field Day in the same band", or the 300m neighbor situation. 73 de n1dam ______________________________________________________________ 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]
