[time-nuts] Distribution amp - Use a video amp unit ?

[Bruce Griffiths]

Bruce Griffiths wrote:
> cfo wrote:
>> I need a distribution amp for my Tbolt , with 6..8+ outputs
>>
>> The TAPR-1 is NA , and the successor status is ???.
>>
>> I need it for distributing 10Mhz ref-clock to Counters
>> (HP,Racal,Phillips), a Rigol Sig-gen&  maybe Oscilloscopes etc.
>>
>> It's for "better than ocxo/hobby use" , and not Tnut (ps accuracy).
>>
>> I have seen suggestions for using a video distributiution unit.
>> But in my part of the world (EU) , there isn't a lot on "eby".
>> I have seen some RGB amps , and was wondering if i could use those ?
>>
>> Could i use a 1:6 RGB unit for : Tbolt on R , FEI-5680A on G  - and 
>> ?? on
>> B ?
>>
>> I'm not experienced (yet) in the analog domain.
>>
>> If i go (simple diy) Would this one work  (also wo. the trafo's) ?
>> http://www.oz9fw.dk/PDF%20files/rubidium.pdf
>>
>> I do have some trafo's on an old 10Mhz 8-chan Hub , that i might be able
>> to salvage if needed.
>>
>> Thanx for any input/hints
>>
>> CFo - T-Nut beginner Denmark.
>>
>>
>>
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> Winding your own transformers isnt particularly difficult if you have 
> suitable (binocular) cores.
> The discrete amplifier shown has a class AB output stage, lower 
> distortion is possible if a class A output stage is used (requires an 
> extra resistor between the output stage emitters and an additional 
> diode in series with the LED).
> With a Class A output stage the 39 ohm resistors should be replaced by 
> a a pair of 100 ohm resistors to match the load.
> Significantly lower distortion is possible if feedback from the output 
> to the input stage is used.
> If the feedback gain is unity (or less) at dc higher AC gains won't 
> significantly degrade the close in phase noise.
> A different amplifier topology using the same number of transistors 
> will allow a higher reverse isolation to be achieved.
>
> One problem with video distribution units (aside from the relatively 
> high phase noise floor) is the limited output drive available. For 
> some purposes 16-20dBm outputs are desirable.
>
> Bruce
A circuit schematic for a current feedback triple with reasonably low 
noise and distortion is attached.

Bruce
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