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Mistake: frontend LO frequency stability
Hi Peter and All,
In a previous posting I wrote:
> The low noise local oscillators in the WSE high level converters that I
> currently work with are stable enough if they are kept at
> constant temperature.
> An FFT that spans 40 seconds with a bin bandwidth of about 0.05Hz
> (50% interleaved transforms with a sine squared window) will have
> a bandwidth
> below 0.1Hz most of the times when averaged over 2 minutes. It may go up
> to 0.15 Hz occasionally but as I have them, lying on a table
> indoors, there is nothing to gain with a better LO for 144 MHz QRSS
> except for absolute frequency accuracy.
The above is NOT correct. My brains slipped, the scale was in Hz and not
in 0.1Hz per division. I was just careless......
When I discovered this mistake I decided to have a closer look.
The conclusion is that the WSE converters have to locked to a
frequency reference if bin widths below about 0.5 Hz are used.
Provision is made to allow this, all LO frequencies are multiples
of 100kHz. It is nothing I will give priority, but may be some day....
Leif / SM5BSZ