Heros tiny SCR Preselector User manual

Software Controlled Radio Preselector via USB v2.0 or I2C Bus
Modular 1.8MHz to 30MHz Tunable Band Pass Filter bank.
tiny SCR Preselector. User manual.
Revision B. September 2009
© Heros Technology Ltd 2006. All rights reserved

Manual
tiny SCR PRESELECTOR
Features:
■ Five bands tuneable Band Pass Filter bank for HF Bands
covering 1.8 to 30 MHz.
■ Digital tuning.
■ Suitable for Software Define Radios thanks to its high linearity.
■ Removes the strong signals radiated back to the antenna
from quadrature mixers in SDR applications.
■ Joined to a VFO can perform tracking tuning function.
■ Its modular design lets an easy implementation on your projects.
■ I2C Bus or USB control modules optional.
■ Tin plated enclosure available.
USB control module option
■ PC controlled through graphical user interface (GUI).
■ Full speed USB v2.0 compliant.
■ Plug and Play feature.
■ Runs under Windows XP OS or Windows Vista 32 OS.
I2C Bus control module option
■ 16 bits standard I2C Bus serial bus interface.
■ Support 100Kbits/s and 400kbits/s FAST I2C Bus protocols.
■ Auxiliary Input/Output ports to implement external controls.
■ Up to eight control modules can share the same I2C Bus.
■ Compatible with most microcontrollers.
© Heros Technology Ltd 2006. All rights reserved

Manual
tiny SCR PRESELECTOR
Preselector
Output
Gas Discharge Tube
Antenna
Input
8 bits/256pf variable capacitor
1pf resolution
1.8MHz to 30MHz
Five Band Pass Filters Bank
Ld
Lc
Lb LeLa
L1
Band B Band C Band D Band EBand A
Multi-Band-Pass Filter module.
Control Bus
A five bands tuneable Band-Pass Filter bank make up the core of the tiny SCR Preselector.
On SDR applications, where high linearity is needed its passive design keeps a high IP3 factor thanks to an unique large coil wounded on a
T-200 toroidal core, ultra low ESR, C0G (NP0) RF chip capacitors, low RF resistance magnetic shielded relays for tuning and telecom
grade relays for band switching, instead of nonlinear semiconductors that cause distortion in front of strong signals and exhibit
low tolerance to transients.
The tiny SCR Preselector incorporates on antenna input a gas discharge tube as surge suppressor providing safety against static spikes.
The five telecom grade relays are connected to its corresponding section of the coil through the Band Selector control on the program software.
A network of low ESR RF capacitors of 1 pF, 2 pF, 4 pF, 8 pF, 16 pF, 32 pF, 64 pF and 128 pF are connected to the coil in serial fashion emulating
the variable capacitor needed to tune the series resonant circuit formed. Each capacitor is connected to the network by means of its associated
tuning relay. The band-pass filter formed in this way is a classic serial tuned LC circuit, offering narrow bandwidth and low attenuation on the
band-pass segment of frequencies.
The program performs the task of adding or subtracting capacitor values in binary fashion in direct relationship with the tuning control on the
program software. Increments or decrements are done in steps of 1pF.
Available bands are:
• A) 1.8 MHz to 3 MHz • B) 3 MHz to 5.5MHz • C) 5 MHz to 10 MHz • D) 10.5 MHz to 21 MHz E) • 16 MHz to 30 MHz.
A carefully PCB layout design and strong L/C decoupling prevent stages to couple in to each other improving the stop band response
and filtering noise from control lines.
Connection to the control module is done with 16 ways ribbon cable and IDC connectors on both sides, carrying control signals and power supply.
BNC connectors are used for Antenna Input and Preselector Output.
Dimensions are: 153x75mm. (6.02x2.95 inch)
© Heros Technology Ltd 2006. All rights reserved
Z Match Z Match

PIC microcontroller. USB Control module.
They are two optional control modules available: USB and I2C Bus
The tiny SCR Preselector USB is located in a separate module board to avoid introducing
noise generated by the microprocessor itself and the noisy USB bus.
A 18F2455 PIC microcontroller is used. It incorporates a full speed (v2.0) USB port periph-
eral to communicate with the PC.
A four MHz quartz crystal is connected to the oscillator pins generating via internal PLL
circuitry, the 48MHz clock for the microcontroller core and the 96 MHz clock to the USB
peripheral.
In circuit serial programming (ICSP) connector is provided to let programming the microcon-
troller firmware without remove it from the PCB.
Two power drivers ULN 2803 ICs interface the PIC microcontroller output ports with the
relays on the Band Pass Filter module.
Connection to the Multi-band pass filter module is done with 16 ways ribbon cable and IDC connectors on both sides, carrying control
signals and power supply.
To suppress ESD and other transient over voltage events on the USB signals lines, an array of Avalanche Diode Array are connected to
them.
A carefully PCB design and strong decoupling avoid introduce noise on the filters board.
Standard 2.5mm diameter power jack and type B USB connector are used.
Power supply: 12V DC/250mA max.
I2C Bus control module
The tiny SCR Preselector I2C Bus control module, located in a separate module board, lets to handle
easily the Band pass Filter board from an existing control system on your radio project due the simple
implementation of the I2C protocol on any microcontroller.
It is based on the well know PCF8575 remote 16-bit I/O expander for I2C Bus. Two power drivers ULN
2803A interface the PCF8575 output ports with the relays. I2C addresses are configured through J4, J5
and J6 pin headers and J2 and J3 headers connect pull-up resistors to the I2C line if is needed.
Three auxiliary ports are provided for optional controls and/or signalling. J7 are Input/Output ports, 5volts
level and J8 are buffered ports at 12volts level.
J11 provides an open-drain interrupt output which can be connected to the interrupt logic of the microcon-
troller.
Connection to the Multi-band pass filter module is done with 16 ways ribbon cable and IDC connectors
on both sides, carrying control signals and power supply.
A carefully PCB design and strong decoupling avoid introduce noise on the filters board.
Features of the module are:
- 16 bits standard I2C serial bus interface.
- 100Kbits/s and 400kbits/s FAST I2C Bus.
- Three auxiliary Input/Output ports for optional controls and/or signalling.
- Open-drain interrupt output.
- Sixteen latched outputs with high current drive capability.
- Programmable address by 3 hardware address pins.
- Optional I2C Bus lines pull-up resistors.
- Up to eight modules can share the same I2C Bus.
- Compatible with most microcontrollers.
- Power Supply: 12V DC/250mA max.
- Dimensions: 62x47mm. (2.44x1.85 inch)
Manual
tiny SCR PRESELECTOR
PIC 18F2455
Control module diagram
Full speed USB v2
Plug and Play
Windows2K, XP, Vista, 7 OS
Control from PC
ICSP Service Coonnector
Six ports future features
expansion connector
Power Drivers
+12V DC/400mA max
© Heros Technology Ltd 2006. All rights reserved

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.
+

Manual
tiny SCR PRESELECTOR
1- Band selection.
By default Band A. Click over any button to change band.
2- Tuning Decrement
One step frequency decrement. One step increment of capacity.
3- Status Bar
4- Tune Dial
Displays the tuning value in picoFarads.
Notice due to the response of series tuned circuits, the attenuation of the pass band filter
increases with less capacity. A good practice is to avoid smaller values .
5- Tuning knob
Performs tuning moving left or right. Also by pressing left or right arrows on the keyboard or
turning mouse wheel. Adjust to maximum signal or background noise.
The tune reference is expressed in picofarads with values between 10pF and 255pF.
Sliding right or left increases or decreases the band-pass frequency.
Notice due to the response of typical series tuned circuits, the attenuation of the pass band filter
increases with less capacity. A good practice is to avoid values smaller than 50 picofarads.
6- Tuning Increment
One step frequency increment. One step decrement of capacity.
7- Memories
There are up to five memories per band (25 in total).
Clear-Store and Recall functions for each memory position.
Store function lets write a text label.
The Software
The software program on the PC runs under Windows 2K, XP, Vista32 and Windows 7 OS.
Windows 2K users need to update Framework from Windows Update site.
The user through the Graphic User Interface commands the tiny SCR Preselector.
The program can work at the same time with any SDR software running on the PC, without interference
allowing to the user to control both simultaneously.
© HEROS technology Limited 2006. All rights reserved
Standard Graphic User Interface
1
2
345
7
6

Manual
tiny SCR PRESELECTOR
Another Graphic User Interface is included.
It incorporates the same functions that the standard GUI.
© HEROS technology Limited 2006. All rights reserved
tiny SCR Preselector working with SoftRock Lite + Xtall RX V9_0

Manual
tiny SCR PRESELECTOR
When the program starts, it attempts to connect to the tiny SCR-Preselector through the USB port.
If it is not connected or the USB Driver is not installed the Status bar indicates this condition.
Driver Installation
Windows XP OS
Insert the CD ROM labelled “tiny SCR Preselector Software”
in your drive. Copy the file included in the CD in your
computer, e.g. My Documents.
Close the program if previously was open.
Connect the power supply (12VDC/250mA) and USB cable to the tiny SCR Preselector.
A “ Welcome to the Found New Hardware Wizard ” will appear on screen.
Mark on “ No, not this time” and click Next
© HEROS technology Limited 2006. All rights reserved

Manual
tiny SCR PRESELECTOR
Mark on “ Include this location....” and click on Browse button.
Mark on “Install from a list or specific.......” and click next.
© HEROS technology Limited 2006. All rights reserved

Manual
tiny SCR PRESELECTOR
Select the file Driver located inside the file copied in your computer and click OK and Next.
Installing the USB driver
© HEROS technology Limited 2006. All rights reserved

Manual
tiny SCR PRESELECTOR
The USB driver installation resumes
Click on “Continue Anyway” button
© HEROS technology Limited 2006. All rights reserved

Manual
tiny SCR PRESELECTOR
Installation completed.
Driver Installation on Windows Vista OS
© HEROS technology Limited 2006. All rights reserved

Manual
tiny SCR PRESELECTOR
Browse for the file “Driver” located inside the file copied in your computer.
Select the file “Driver”
© HEROS technology Limited 2006. All rights reserved

Manual
tiny SCR PRESELECTOR
Installing the USB driver
Click on “Install this driver anyway”
© HEROS technology Limited 2006. All rights reserved

Manual
tiny SCR PRESELECTOR
Installation completed.
© HEROS technology Limited 2006. All rights reserved

ABCD
1
2
3
4
1
2
3
4
ABCD
CD
Date
Sheet
FCSM No
DWG No
REV
Size
Drawn
Checked
Issued
Approvals
Drawing
Scale
A4
JJ de Oñate
B
XV VIII MMVIII
tiny SCR Preselector_Rev_B Diagram
1/1
©HEROS technology Limited 2006. All rights reserved
Preselector
Output
PIC 18F2455
Control module
Full speed USB v2.0
Plug and Play
Windows 2K, XP, Vista, 7 OS
Control from PC
Service Coonnector
Power Drivers
Gas Discharge Tube
Antenna
Input
8 bits/256pf variable capacitor
1pf resolution
1.8MHz to 30MHz
Five Band Pass Filters Bank
Multi Band-Pass filter module
Ld
Lc
Lb LeLa
L1
Band B Band C Band D Band EBand A
+12V DC/250mA max
Not used six ports
aux. connector
Control Bus
Z Match Z Match

Manual
tiny SCR PRESELECTOR
In the following plot a Broadcast Band rejection filter has been connected to the input of the tiny SCR Preselector in order to remove interferences from MW stations.
(N2PK Vector Network Analyzer & My VNA program software)
© HEROS technology Limited 2006. All rights reserved

Manual
tiny SCR PRESELECTOR
© HEROS technology Limited 2006. All rights reserved
Band A plot
(N2PK Vector Network Analyzer & My VNA program software)

Manual
tiny SCR PRESELECTOR
© HEROS technology Limited 2006. All rights reserved
Band B
(N2PK Vector Network Analyzer & My VNA program software)

Manual
tiny SCR PRESELECTOR
© HEROS technology Limited 2006. All rights reserved
Band C
(N2PK Vector Network Analyzer & My VNA program software)