[time-nuts] HP 105B Modification

francesco messineo francesco.messineo at gmail.com
Wed Dec 9 19:59:05 UTC 2009


Hi all,

indeed this is very interesting, can this buffer amplifier be used as
a building block for a distribution amplifier for the 10 MHz signal of
a thunderbolt? I remember having seen on the list a similar version
but with european transistors (like the ubiquitous bc548/bc558?) that
are very common here, but I can't remember when it was to surf the
list archives in the right time-period. Anyone?
best regards

Francesco IZ8DWF

On 12/9/09, Ed Palmer <ed_palmer at sasktel.net> wrote:
> I was thinking that I might be reinventing the wheel by designing a buffer
> amp.  You guys have almost built the entire car!  Thanks again for the
> ideas.  It'll take me a while to get it built and tested.
>
>  Ed
>
>  Bruce Griffiths wrote:
>
> > John Miles wrote:
> >
> > >
> > >
> > > >
> > > > > 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.
> > > >
> > > >
> > > See http://www.ke5fx.com/norton.htm for measurements
> and connection details
> > > of the copy of Bruce's amp that I added to my 5061A.
> > >
> > > -- john, KE5FX
> > >
> > >
> > >
> > Note the LED I used in the schematic was merely for simulation purposes
> (ie LTSpice had a model for it).
> > A standard red or amber LED is just fine.
> >
> > Another point is the LTSpice LED model isn't particularly accurate for
> simulating the effects of temperature variations.
> > Does anyone knows of more accurate LTSpice compatible LED models?
> >
> > The LED model voltage drop increases with temperature even at low current,
> whilst the voltage drop across a real LED at low currents decreases with
> temperature.
> > In practice the variation in the LED forward drop tracks the variation in
> the pnp Vbe quite well.
> >
> > Bruce
> >
> >
>
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