[time-nuts] HP 105B Modification

Ed Palmer ed_palmer at sasktel.net
Tue Dec 8 03:52:35 UTC 2009


I was wondering about that transformer.  Thanks for the cross-reference.

Ed

John Miles wrote:
>> Ed
>>
>> If it helps I can send you some LTSpice schematics so that you can
>> simulate the circuit for yourself.
>> The breadboards behave as predicted by the simulations at 10MHz.
>>
>> John Miles has done some preliminary phase noise measurements on his
>> version.
>>
>> The transformers are wound on binocular ferrite cores.
>> I used some 14mm (long) cores intended for 40MHz to 220MHz (I had some)
>> operation in my breadboard which works well at 5MHz and 10Mhz.
>>     
>
> You can also use an off-the-shelf Mini-Circuits transformer for low-power
> applications.  The T13-1 was the one I tried.  I'll stick some of the plots
> up on the web later tonight if possible.
>
> Residual PN is very good with this circuit, with a broadband floor near -170
> dBc/Hz at 10 MHz, and no excess 1/f noise relative to a passive mixer.
>
> -- john, KE5FX
>
>   



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