Phase noise in oscillators is a subject much discussed amongst
microwave hams and eme'rs who are trying to obtain optimum reception.
It is not totally agreed but much thought is that MDS is lowered by
having low phase-noise (even in a completely quiet band (no adjacent
signals). Thinking is that phase noise *somehow* combines with
antenna noise and internal amplifier noise (NF) to limit MDS. W1GHZ
has recently been *playing* with VCXO's in place of PLL's and states
that he is seeing a 2-dB reduction in MDS level as a result. The
voltage-controlled xtal oscillator takes advantage of the better
phase noise of the xtal osc. Many PLL use a VCO which is wide
frequency in range which is much harder to design for low phase noise
(Wayne and co. can probably tell us a whole bunch about that).
This is probably of no concern on LF/MW/HF/6m due to the much higher
sky noise being the limit on MDS from new equipment (K3 MDS -140 to
-145 dBm on 6m). My 2m-eme station MDS is about -155 dBm without
adding antenna gain (21.3 dBi). MDS does not add in the effect of
antenna gain or sky noise. It is also referred to as Trx (receiving
system noise temperature). This stuff is not in the normal HFers
vocabulary...my apologies.
But I am excited to learn of the improved Synth for the K3s and upgrade for K3.
73, Ed - KL7UW
http://www.kl7uw.com
"Kits made by KL7UW"
Dubus Mag business:
dubus...@gmail.com
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