[time-nuts] 10MHz to 25MHz

[Neil Smith G4DBN]

That is exactly what I have just done, using an HMC1031 to lock a good 100MHz OCXO to my GPSDO, using a very narrow filter bandwidth with decent 22uF ceramic caps in the loop filter. I’ve also made a second version using an XOR gate and an MC12080 prescaler and flipflops and fast comparators, but the HMC1031 version is way simpler and has a wider lock-in range. Hard to measure the performance as the noise appears lower than my E4406A can resolve, but with one 100MHz OCXO locked to the GPSDO and the other to my 10MHz Rb standard, and monitoring the relative phases using an AD8302, I see none of the (slight) glitchiness of the GPSDO reflected in the 100MHz locked output.

Neil 

> On 19 Jan 2017, at 02:08, Bob Camp <kb8tq at n1k.org> wrote:
> 
> Hi
> 
> What are you going to use the 25 MHz for? Will it drive any sort of radio? If so, cleaning up the phase
> noise of the GPSDO is a *very* good idea. With a PLL, you can *subtract* noise. With a multiplier you 
> can only *add* noise. The narrow bandwidth PLL combined with a low nose VCXO is your friend in this case. 
> 
> I would take the process one step further. I’d lock up a 100 MHz VCXO to the 10 MHz. Then you can get
> 100, 50, 25, and 20 MHz outputs. The 100 MHz is the key if you want to head up into the microwave 
> region. 
> 
> Bob
> 
>> On Jan 18, 2017, at 8:40 PM, Loren Moline WA7SKT <lmoline at hotmail.com> wrote:
>> 
>> Are you talking about locking the 50MHz VCXO to my 10 MH. Standard? I want the 25MHz to be from my 10MHz OCXO which is my station standard which will locked to GPS eventually.
>> 
>> Loren WA7SKT
>> 
>> 
>> 
>> 
>> On Wed, Jan 18, 2017 at 4:01 PM -0800, "Richard (Rick) Karlquist" <richard at karlquist.com<mailto:richard at karlquist.com>> wrote:
>> 
>> 
>> A better and easier way is to phase lock a crystal oscillator.
>> I would use a 50 MHz VCXO and divide the output by 2 to get a
>> 25 MHz square wave.
>> 
>> Rick N6RK
>> 
>> On 1/18/2017 10:28 AM, Loren Moline WA7SKT wrote:
>>> Hello,
>>> 
>>> I am looking for a good X5 multiplier to use to generate a 25MHz signal from my 10MHz OCXO. I want to divide by 2 and multiply by 5 with a bandpass filter in the output and then a 3.3 volt 25MHz signal out.
>>> 
>>> 
>>> Maybe someone has better ways?
>>> 
>>> 
>>> Loren Moline  WA7SKT
>>> 
>>> Member: Pacific Northwest VHF Society and ARRL
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