Re: SI5351 quadrature VFO

Ashhar Farhan

My question wasn't clear enough. I was asking if the library worked to 290 MHz. Above 150 Mhz, integeral divider is needed. There was some overflow with jerry's code. 
That apart, i see some sidebands about -40dbc on both sides of the signal, a few hundred kilohertz on either sides. They appear only on specific frequencies. 
I am really interested in using the Si5351 on 435 MHz. I pushed a 150 Mhz signal out of the Si5351 into a 450 Mhz band pass filter (doubly tuned, promixally coupled). It gave about -4dbm out of the band pass filter, A MMIC raises it to the obligatory +7dbm. 

- f

On Sat, Jun 16, 2018 at 12:00 AM, Hans Summers <hans.summers@...> wrote:
Hi Farhan

> Are you sure these work upto 290 mhz? 

According to the datasheet specification the top frequency is 200MHz. 

However if you ignore this and just configure it for higher and higher frequencies, in my test it really did seem to work fine up until 290MHz. After that the output just gives up. Other QRP Labs kit owners also verified similar maximum frequency around 300MHz.

Of course I have no idea what performance specification may be violated, or no longer guaranteed under all specified conditions, at 290MHz. The wisdom of using the chip up so far outside its specification is debatable, particularly in anything other than a one-off homebrew project. 

73 Hans G0UPL 

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