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Re: Mode-S Antennas

> Then we get to  the hard part,  the oscillator!
> Converters are easy, its the LO that is difficult.  There are some
> advantages to using a conventional crystal LO as opposed to a
> PLL.   For one thing, phase noise will be lower.  Also no PIC is 
> required.  Keep in mind that there are many of us that are not
> programers and most likely never will me.  Ordering a xtal from
> ICM is trivial, getting a PIC programed is not (at least for me).
> The idea of placing the LO (or at least the low frequency portion
> of it) in the shack and piping the signal up to the converter is a good
> one.  I considered it long ago and made that idea part of my plans.


I am just developing a PLL. Check http://symek.com and follow 
'English Language' then 'RF-assemblies'.

In spring, this PLL oscillator assembly (100 to 1200 MHz) will be
available. Using a simple frequency doubler would be all you need
to generate the programmable LO of 2.5 GHz for the 13cm S-Band RX.

The PLL will be very stable, due to temperature compensation and
is ideal for satellite applications (e.g. AFC input for doppler
compensation etc.).

I agree: the PLL as the 'Kernel' of a receiver is not an easy thing,
it requires RF and programming knowledge. Problems as spurious signals,
temperature drift, phase noise etc. are lurking....

73! Ulf, DK9SJ

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