[time-nuts] homebrew 13 dBm distribution amplifier based on NIST design 5 to 100 MHz

[Bruce Griffiths]

Tom Clark, K3IO wrote:
>    Gerhard -- the discussion between you and Bruce has been very
>    interesting. I asked a VLBI colleague to look over your design and he
>    had this comment.
>    In VLBI,  H-Maser frequency standards used to generate local
>    oscillators at microwave frequencies. We have problems with amplitude
>    modulation being converted to phase modulation when hum is present.  I
>    notice that Bruce also uses transformers. Comments from both of you
>    will be eagerly awaited!
>
>          Thanks Tom. I notice the Gerhard Hoffmann circuit has a
>      transformer on the outputs. Wenzell also uses transformers and we
>      have found them to be a problem if there is any stray AC mag. field
>      around. We have added some magnetic shielding to the UpDown
>      converters to reduce the 60/120 Hz modulation which results if the
>      UpDown is close to a another piece of electronics with a AC fan or
>      AC transformer. I don't think 60/120 Hz is a problem for VLBI2010
>      but it can be a problem for mmvlbi.
>
>   
Tom

Another problem with ferromagnetic materials such as transformer cores 
and magnetic shields is magnetostriction.
The resultant vibration can modulate component parameters.

Bruce