[Elecraft] Why is KX3 phase noise so much less than the K3 ?

[Edward R Cole]

Larry,

Not knowing much about the R390A, but Sherwood ranks it very low in 
phase noise.  Xtal oscillators are easier to design with low phase 
noise than synthesizers.  This is primarily why later radios have a 
problem with noise as most use synthesized LO's, and why the old 
radios with xtal oscillators hear so well.

As to why it would matter, phase noise will limit the sensitivity of 
a receiver.  HF sky noise masks most receiver noise issues, but if 
you are pursuing weak-signal contacts is matters a lot.  HF receivers 
used with transverters on VHF/UHF/mw frequencies are way more 
sensitive if they have low phase noise, especially due the fact that 
sky noise drops of very quickly above 6m.

Phase noise was one of the prime reasons I chose the K3 for my eme 
station which detects signals in the -180 dBm level.

73, Ed
-----------------------------
I'm wondering why the KX3 Lo noise is so much better than the K3.
The R390A value strange since the first local oscillator is a quartz
crystal.

I've owned a Icom 720A and own a FT-1000D.
Ive never owned a K3, KX3 or a R390A.

Larry


73, Ed - KL7UW
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