Antenna
Input
Manual
tiny SCR PRESELECTOR
Why a large toroid core T-200 is used in the tiny SCR Preselector?
The reason is to keep a high IP3 or in other words achieve tolerance
to large signals.
On SDR radios the high linearity of quadrature mixers demands the
best linearity possible to the ancillary connected before the mixer
stage to avoid to degrading its IP3. Wide cores with large sectional
area let wind more turns on it (more inductance); these parameters are
essential to keep a low magnetic flux inside the toroidal core to
achieve so mush linearity as possible.
On the other hand, the large core offers a non-loaded Q (efficiency)
value exceeding 400, providing selectivity and high stop band stop
band characteristic, limiting the bandwidth in front of the mixer which improve signal to noise ratio, image
rejection and prevents adjacent signals from reaching the circuits on the receiver side where 2nd order IMD
and other spurs is most often created because of generalized use of nonlinear semiconductors especially on
Tiny SCR Preselector connection
12V DC/250mA max.
+
Receiver
~~
to PC USB port.
Plug and Play
or
to I2C Bus line
Output
Antenna
Generic Receiver
USB or I2C Bus
Control module
Multi-band pass filter module
16 vias Ribbon cable
(included)
~
~
central pin
© Heros Technology Ltd 2006. All rights reserved
12V DC/250mA max.
+
