Re: Octagon LNB

Andy G4JNT

The ADF4113 is specified for Fmin of 200MHz.   How have you made it work with 27MHz input.

I'm guessing by using a square wave and the internal dividers are static logic, so if clocked properly will go down to DC

Even the lowest frequency variant of that family, the ADF4110, only goes down to 800MHz officially.  
May have missed a trick here;  I've quite recently been bemoaning the fact modern synth chips can't go particularly low in frequency

On Fri, 1 Feb 2019 at 16:49, brian.flynn via Groups.Io <> wrote:
Hi Mike,
I have taken the 27 MHz xtal out of my octagon and made an external input using the second F-tyle socke as described by Bernie 'HJW.
I have a waterproof box externally which contains a 27 MHz VCXO based on a varactor tuned Colpitts osc which I have locked to 12.8 MHz ex-cellphone
TCXO.  The PLL uses an ADF4113 with a band width of about 10 Hz. I feed about +10 dbm into the  LNB.  The water proof box with the PLL conrtains a Bias Tee to draw the DC off the LNB feed to power the PLL  I am powering the LNB/dish from a cheapo freesat box which allows Polarisation switching and Hi/Lo band switching.
A byproduct of it is I now get Sat TV as the 60 CM dish I am using is wide enought to pick Astra as well!! The 10706 MHz beacon is about 25 db out of the noise.  There is still a slow drift with temperature but it is only a couple of kHz and I can live with that until I find a better TCXO.

Brian GM8BJF

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