[time-nuts] PDIP package 100 MHz decade dividers

[Magnus Danielson]

Hi,

A similar approach is used in the 10811 replacement oscillator setup for
the 5065, where a 7474 is used to divide 10 MHz to 5 MHz. Signal
conditioning consists of a DC-blocking cap and a pair of resistors to
bias the mid-point. The produced noise is at least 10 dB worse than you
would expect. This impacts long term stability response as I have
reported earlier.

At least using the square-up design in TADD-2 would help, even thought
that one won't work for 100 MHz, so it needs a bit of tuning. There are
chips that solve this.

Cheers,
Magnus

On 2020-07-18 14:31, Didier Juges wrote:
> A long time ago I used a 74AC74 to prescale a 100MHz VCO down to 25, the
> 74AC74 was AC coupled to the VCO and the signal was a fraction of a volt.
> Worked quite well.
> Probably not time-nuts quality but in a pinch it did the job at the time.
> Didier
>
> On Sat, Jul 11, 2020 at 9:37 PM Alex Pummer <alex at pcscons.com> wrote:
>
>> Hi Perrier
>> https://www.y-ic.es/datasheet/3b/74F569SC.pdf   will work
>> 73
>> KJ6UHN
>> Alex
>>
>> On 7/11/2020 3:00 PM, Perry Sandeen via time-nuts wrote:
>>> Learned List,
>>> On previous posts I was looking for a PDIP package 100 MHz decade
>> divider. Reading just the front of the data sheet I thought that the
>> 74LS161 would work. Boy, was I wrong.  Several members posted that 25 Mhz
>> max was its limit.
>>> So *on the road again* (sorry Willie) I went on another search this time
>> with the correct logic family.
>>> It turns out Arrow carries the 74HC161 for less that $1.
>>> Additionally I D/L'd the Charles Wenzel Unusual Frequency Dividers PDF
>> and discovered a 100 MHz decade divider circuit using 1/2 of a 74HC74 in a
>> configuration that will decade divide up to 300 MHz.
>>> I'm attaching a copy of the circuit for anyone interested.
>>> Regards,
>>> Perrier
>>>
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