[time-nuts] RFTG-m-XO disassembly photos

Dr Bruce Griffiths bruce.griffiths at xtra.co.nz
Wed Dec 27 06:27:55 EST 2006


Dr Bruce Griffiths wrote:
> Rex wrote:
>   
>> On Tue, 26 Dec 2006 22:06:28 -0600, "Bill Hawkins" <bill at iaxs.net>
>> wrote:
>>
>>   
>>     
>>> What's all this about 15 MHz out?
>>>
>>> Bill Hawkins
>>>     
>>>       
>> I have an FRS-C rubidium (10 MHz) that I bought a couple years ago. It
>> came in a metal box that also contained a circuit board that provided 3
>> TNC output connectors. Two of those had 10 MHz square wave output. One
>> provided a strong (24.3 dBm into 50 ohms) 15 MHz sine wave output.
>>
>> The board somehow used the 10 MHz from the rubidium to generate a 15 MHz
>> sine. I never figured out exactly how they were doing this; the board
>> had an an Altera EP610PC-25T PLD doing most of the interesting stuff. I
>> now suspect my box must have been for a similar setup to the Lucent
>> application.
>>
>> In the FRS box I noticed a 15 MHz filter on the board. If you look at
>> John's picture rftg-m-xo-7.jpg, the metal can in the top-center (not the
>> Efratom oscillator) is a 15 MHz filter.
>>
>>
>>
>> _______________________________________________
>> time-nuts mailing list
>> time-nuts at febo.com
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>
>>   
>>     
> Rex, Bill
>
> The simplest way of generating a 15MHz output signal from a 10MHz input 
> signal, is to divide the 10MHz by 2 using a flipflop and then extract 
> the 15MHz 3rd harmonic component of the 5MHz square wave output of the 
> flipflop with an analog bandpass filter.
>
> Bruce
>
> _______________________________________________
> time-nuts mailing list
> time-nuts at febo.com
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>
>   

Rex, Bill

A low added phase noise technique for generating 15MHz from a 10MHz input is to use a regenerative divider comprising a low noise Schottky diode mixer, a pair of amplifies, a couple of low pass filters and a 15MHz bandpass filter.
A regenerative divider with an input signal of frequency f Hz can produce 2 signals outputs with frequencies of f/2 and 3f/2 respectively.

Bruce




More information about the time-nuts mailing list