That's good info, if you understand how to interpret it. It's not clear
what u' amd u" are. And the info on their site doesn't tell you just how
good (low losses and reactance across a wide bandwidth, among other
things)
a matching transformer is made from a 73 material binocular core. They
only
offer it as RFI suppression.
Mike,
You might want to go to this page
http://www.fair-rite.com/newfair/index.htm
and hover the link button [technical]>[Use of Ferrites in Broadband
Transformers]
For receiving or low power transmitting, where voltage across a winding is
minimal, you can use a core that presents a resistive impedance. That shunt
impedance parallels the windings, so it has to be high compared to the
operating impedance or the transformer will be lossy. Receiving or low power
applications are very forgiving.
For high power, we get into trouble quickly. Since voltage across a winding
can be fairly high, the parallel resistance has to be very high. Even then
we can get into trouble. If a core dissipates just a few watts of heat it
can go into thermal runaway, where it quickly reaches Curie temperature and
no longer acts like a magnetic core.
Think about choke baluns where they have 10,000 ohms impedance, dominantly
resistive. If you applied a 500 ohm load and 1000 watts you would have 2000
V/2 =1000 volts in an ideal balance condition, which is 100 watts in the
cores. This is why core selection generally has to shift to a dominantly
reactive impedance, rather than resistive, at high power.
With a 100 watt lower voltage PA we might be able to use a 52 material. If
it is higher voltage across the winding, the shunting resistance might kill
it with heat. With high voltages across windings we might have to drop from
a 52 material to 61, just to stop long term heating while maintaining the
high end response.
What is simple and unimportant for low winding voltages really becomes a
much more complex series of compromises at higher voltages across windings.
That parallel resistance caused by the core is more problematic for heat
than it is for loss.
73 Tom
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