On 02/04/2014 16:19, Wayne Burdick wrote:
The K3 and KX3 both have very low phase noise. It can vary a bit from band to
band and from one unit to the next. Sherwood measured one example of each, but
typically both measure right around -140 dBc/Hz at 20 kHz.
When we designed the K3, we were trying to improve on the phase noise numbers
usually found in transceivers with synthesized local oscillators. Typical
values were -110 to -120 dBc/Hz, and this definitely impacted stations within
close proximity of each other. By using a very high C/L ratio in the K3's VCO,
we achieved numbers in the -140 range, and our field testers in close proximity
could no longer hear each other at all.
This result was corroborated by the Ducie Island DXpedition, the first to use
K3s. They told us that they had a 30-m CW station and a 30-m RTTY station both
running at the same time within 1 kHz of each other.
The KX3 uses a different type of synthesizer, but the result is the same. In
this case an on-chip VCO runs at a very high frequency and is then divided down
to get to the HF range.
73,
Wayne
N6KR
Wayne
My understanding is that the KX3 is worse than the K3 on TX
phase noise sidebands. Is that what you would expect?
This can be quite critical when choosing between the K(X)3s as
a transverter driver in a dense VHF/UHF environment (5 to 10Km
separation at 400W to high gain beams) such as you find in the
SE of UK.
Stewart/G3YSX
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