How to use Boost.Unit with ratios in the same unit

I have a very simple use case for using Boost.Unit, but not sure if there is a better/easier way to get the same done.

I want to convert between the same units, but different ratios. For example, hertz to kilohertz to megahertz.

From my understanding, I first must define units with my specific ratios:

typedef boost::units::make_scaled_unit<si::frequency, scale<10, static_rational<0> > >::type  Hertz_unit;
typedef boost::units::make_scaled_unit<si::frequency, scale<10, static_rational<3> > >::type  KilloHertz_unit;
typedef boost::units::make_scaled_unit<si::frequency, scale<10, static_rational<6> > >::type  MegaHertz_unit;

Then create quantities that represent the units:

typedef boost::units::quantity<Hertz_unit     , double> Hertz;
typedef boost::units::quantity<KilloHertz_unit, double> KilloHertz;
typedef boost::units::quantity<MegaHertz_unit , double> MegaHertz;

Finally some constants and literals:

BOOST_UNITS_STATIC_CONSTANT( Hz, Hertz_unit     );
BOOST_UNITS_STATIC_CONSTANT(KHz, KilloHertz_unit);
BOOST_UNITS_STATIC_CONSTANT(MHz, MegaHertz_unit );

Hertz      operator"" _Hz  (long double val) { return Hertz     (val *  Hz); }
KilloHertz operator"" _KHz (long double val) { return KilloHertz(val * KHz); }
MegaHertz  operator"" _MHz (long double val) { return MegaHertz (val * MHz); }

Now I can use the quantities:

Hertz      freq_1 = (10 *  Hz);
KilloHertz freq_2 = (10 * KHz);
MegaHertz  freq_3 = (10 * MHz);
// OR
Hertz      freq_4 = 10.0_Hz;
KilloHertz freq_5 = 10.0_KHz;
MegaHertz  freq_6 = 10.0_MHz;
// Convert between units
Hertz freq_7 = static_cast<Hertz>(10 * KHz);

Is this how Boost.Unit should be used or am I missing something that might make it easier to use?

Are there not already defined units/quantities that I can use somewhere hidden in a header? Or should this be done for all my units that I use?

Do I need to know/remember that Kilo is `scale<10, static_rational<3>' or is this already defined and available?