[time-nuts] RFG-RB Crystal Filter

Bob Camp lists at cq.nu
Sat Jan 16 18:37:29 UTC 2010


Hi

It looks like they are doing something in an Altera part and a 14 stage ripple counter. The RF out of the LPRO appears to go into the Altera part. It looks like a "one shot" fuse link part. I doubt I'll get any use out of it. I'm not desperate enough for 4000 series CMOS dividers to make pulling it off of the board....

Bob


On Jan 16, 2010, at 1:15 PM, John Ackermann N8UR wrote:

> IIRC, the 15 MHz was derived from a divide-by-2 to get a 5 MHz square wave, then selecting the 3rd harmonic via the filter.
> 
> John
> ----
> 
> Bob Camp said the following on 01/16/2010 12:40 PM:
>> Hi U3 looks like it's at the output of the filter. U4A seems to be the power stage that then drives the output through a Minicircuits 11 to 18 MHz L-C filter. The output of U4A also looks like it goes to the one-shots in the monitor circuitry. Both amps are driven through some big coils and a set of 4 1/4W resistors in parallel. Looks like they both are pulling significant current.
>> There's some magic on the other side of the filter to do the 10 to 15 MHz conversion. None of it appears to be very exciting. Everything else looks like it does the alarm functions. Half the area on the board monitors and reports on what the other half is doing....
>> Bob
>> On Jan 16, 2010, at 10:46 AM, paul swed wrote:
>>> As I recall there are 2 amps. Both of the 4 pin type transistor. Small as a
>>> gain stage and the large as a power stage. Considering a 7 port splitter and
>>> the need for 0 dbm or more for each terminated port thats a fair amount of
>>> power neatly wrapped up in a small package.
>>> 
>>> On Fri, Jan 15, 2010 at 10:49 PM, Bob Camp <lists at cq.nu> wrote:
>>> 
>>>> Hi
>>>> 
>>>> My guess would be that the crystal filter strips the phase noise off of the
>>>> multiplied 15 MHz and then the little amps boost it back up. If that is
>>>> indeed what they are doing, the amps should be pretty quiet when running
>>>> fairly high power signals.
>>>> 
>>>> Bob
>>>> 
>>>> 
>>>> On Jan 15, 2010, at 10:43 PM, paul swed wrote:
>>>> 
>>>>> Actually the little rf amps pretty nice. It will take any signal in and
>>>>> amplify it so that you can use a 7 way passive splitter for frequency
>>>>> distribution. At least thats how mine worked.
>>>>> Its pretty efficient. Can't speak to the noise quality.
>>>>> 
>>>>> On Fri, Jan 15, 2010 at 10:32 PM, Bob Camp <lists at cq.nu> wrote:
>>>>> 
>>>>>> Hi
>>>>>> 
>>>>>> I'm sitting here stripping LPRO-101's out of RFG-RB's and kind of
>>>> wondering
>>>>>> about the other "fine stuff" on the PC board. About the only thing that
>>>>>> looks useful appears to be a 15 MHz crystal filter made by either PDI or
>>>>>> Netcom. Has anybody gone to the trouble of pulling one off the board and
>>>>>> seeing what a network analyzer says about it?
>>>>>> 
>>>>>> The RFG-RB's were cheap enough that I have no real need to get anything
>>>> off
>>>>>> of the pc board. I just hate to throw away anything that might be
>>>>>> useful.....
>>>>>> 
>>>>>> Bob
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