[time-nuts] 10MHz Square to Sine Wave Conversion

[Bob Camp]

Hi

If you run a filter with a shunt capacitor input (as opposed to the series L proposed by Charles, the current in the driving gate goes 
way up. It’s driving a short at the harmonic frequencies and it does not like this. If you want more power with a simple T, just run the 
T. No resistor at the input or output. You can get > 18 dbm this way. A single gate providing 18 dbm probably will not last very long. A
gate in a “3.3V only” family may not be happy with the ringing on the filter input. This of course begs the question - do you *need* more
than 18 dbm?

Bob

> On Jul 16, 2015, at 11:10 PM, D W <watsondaniel3 at gmail.com> wrote:
> 
> Hi,
> 
> A while back I ordered an item of equipment from a very excellent eBay seller, johnkw40. He may be a member of the list, I'm not sure. He included a schematic for a low pass filter circuit to filter a 10 MHz square wave to a sine wave.
> 
> A quick analysis shows that it is a 5th order chebyshev filter with a cutoff frequency of about 14MHz. You could do better, but this filter can be built with only five standard value passives, which is quite convenient.
> 
> I made a little SMT version of it and ordered the boards on OshPark. It seems to work pretty well. The circuit schematic and a screen shot of the response is attached. Any comments from the list on how that looks would be welcome.
> 
> Dan
> 
> <image2.png>
> 
>> On Jul 16, 2015, at 10:49 AM, skipp Isaham via time-nuts <time-nuts at febo.com> wrote:
>> 
>> re: 10MHz Square to Sine Wave Conversion  
>> 
>> The GPSDO I recently acquired outputs a 10 MHz square wave. I'd like 
>> to convert it to a sine wave and I am looking for suggestions and info re 
>> any reasonable pre-made circuits and/or boards. No sense reinventing the 
>> wheel if I can avoid it. 
>> 
>> Otherwise I will start Sent from my iPhone
>> 
>> Thank you in advance for your replies. 
>> 
>> Regards, 
>> 
>> skipp 
>> 
>> skipp025 at yahoo dot com 
>> 
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