Tiny. HF Tunable Preselector.

1.8MHz to 30MHz 5 bands tunable Band-Pass Filter bank. Digital tuning system.

Intended to complement radio projects due its modular design.

USB or I2C bus control options.

Compatible with any Analogue and Software Define Radios.

Control software runs under Windows 7, Windows 8, Windows 10, Windows 11




Tiny HF tunable preselector is connected in line between the antenna and your receiver or transceiver providing filtering of R.F.spectrum to reduce broadband signal energy into the receiver.

If the preselector is connected to a transceiver take precautions to prevent transmitting through it. An Input/Output by-pass dual power relay accessory is available to by-pass the preselector in transmission. FlexRadio user do not need external by-pass relay; see Owners Manual, Primary antenna ports configuration.

Suitable to work with any SDR or analogue radio.Tiny-CAT Digital preselector is remotely operated from a personal computer via USB over VCP by means of the USB control module option or from a radio or digital system supporting I2C bus data communication by means of the I2C bus control module option.

Operating modes:

Using the USB control module option: It works connected to a PC via USB over Virtual COM Port under Windows OS. Tuning and Band selection can be performed from:

- Its own Graphic User Interface (GUI) on PC.
- CAT protocol over Virtual Com Port (VCP), Kenwood TS-2000 protocol.
- Over the Internet or Local Network. (TCP/IP protocol).
See below Tiny-CAT Digital Preselector user manual for more details.

Using the I2C bus control module option:

From a radio or digital system supporting I2C bus remote control. On PowerSDR It works connecting the hardware to FlexWire socket on FlexRadio rear panel. Tuning and Band selection is done by means of an embedded control slider on PowerSDR under label "Heros". See below Tiny-CAT Digital Preselector user manual for more details.

Tiny HF Tunable Preselector. Filter module.
Input side
(SKU: HS-2008-Filter)
Tiny HF Tunable Preselector. Filter module.
Output side
(SKU: HS-2008-Filter)

Tiny HF Tunable Preselector. USB control module.
Tiny HF Tunable Preselector. I2C bus control module.

Technical features:

■ Compatible with any Analogue and SDR radios.
■Control software runs under Windows 7, Windows 8, Windows 10, Windows 11
■ Signed USB driver.
■ Tunable Band Pass Filter bank for HF Bands covering 1.8 to 30 MHz.
■ Five selectable bands.
■ Passive Band Pass Filters.
■ Removes strong signals radiated back to the antenna from SDR quadrature mixers.
■ No active switching or amplifier devices in the signal path, therefore it does not contribute to (IMD (Intermodulation Distortion).
■ High linearity (IP3). Suitable for Software Define Radios and analogue receivers.
■ Five Band Pass Filters: Tapped mono coil wound on large toroidal T-200 iron core avoiding saturation in front of large signals.
■ Digital tuning. Eight bits variable digital capacitor emulator.
■ 16 way IDC connector input for control signals and power supply.
■ Size: 157mm x 75mm. (6.181 x 2.953in).
■ USB or I2C bus control modules option.
■ Suitable aluminum enclosure option available.

Scalar Network response plots
Band A plot Band B plot
Band A Band B
Band C plot Band D plot
Band C Band D
Band E plot FM band rejection plot
Band E FM broadcast band rejection.

Operating modes


- Remote control. USB version control module.


GUI console context menu.

Tiny HF Tunable Preselector. Graphic User Interface (GUI) console on PC.


- Graphic User Interface (GUI). Remote control console.

The control console application provides manual remote tuning control from PC and a set of options.
It runs on PC under Windows OS including the last Windows 11. It is an executable file does not need to be installed.


- CAT remote control. Tracking feature using USB control module.

Popular CAT (Computer Aided Transceiver), serial data communication protocol over Virtual Com Port (VCP) enables the Tiny HF Tunable Preselector to provide the user with a way to interface with several radios using third party software applications. The microcontroller on USB control module board decodes valid CAT commands into specific instructions to be executed. The user can remote operate the preselector from remote control applications running on PC.


- Internet/Local network remote control.

The Tiny-CAT Tunable preselector supports connections via the Internet and Local network.To make use of this feature execute the application on your computer and on a remote one.The protocol only uses TCP/IP; UDP which by definition is unreliable is not used.



Remote Server console (Preselector side)

Remote client console (Remote side)


  Remote control. I2C Bus version

Using the I2C Bus control module

The Tiny HF Tunable preselector I2C Bus remote control module version lets to handle it easily from any FlexRadio/PowerSDR.

Also from a custom made digital control system or radio project due the simple implementation of the I2C protocol on any microcontroller.


I2C remote control console on PowerSDR

  The Preselector control window includes band switch and tune slider.



Tiny HF Tunable Preselector boxed option available.

The Tiny HF Tunable preselector should be enclosed in a RF tight box due the antenna effect of its large coil that easily gathers nearby signals or noise.

The following pictures show the Tiny HF Tunable preselector assembled in hardy aluminum enclosure from Hammond model 1455T1601.

Dimensions are: 160mm X 160mm X 51mm. (6.29 x 6.29 x 2 inch)

The USB or I2C bus boxed versions, ready to use contains:

- The Tiny HF Tunable preselector. Band Pass Filter bank module and control module.
- USB or I2C control module option.
- USB cable. (USB control module option)
- CD ROM including user manual, software and USB driver for Windows Operate Systems.
- BNC-BNC coaxial cable tails.


USB or I2C Boxed versions front view
(SKU: HS-2008I2C-BOX)

USB version rear view

I2C bus version rear view
(SKU: HS-2008I2C-BOX)

USB version.
((SKU: HS-2008USB-BOX))

I2C version.
((SKU: HS-2008I2C-BOX))


Optional Accessories


General purpose LF-HF-VHF-UHF, Dual Port, by-Pass relay

100 Watts RF power rating

DC - 1300MHz

It is designed to by-pass the Input and Output RF ports of any device in line with your transceiver or transmitter
A typical application includes inserting between antenna and a transceiver or transmitter a preselector, preamplifier or filter device.

On transmission switchover, via PTT or Keying line, the Input and Output RF ports of the device are by-passed avoiding being overloaded


USB Galvanic Digital Isolator

For SDR radios is designed to break the galvanic connection between USB host PC and the attached SDR radio peripheral avoiding that whatever power and ground noise from the PC side do not influence the sensible radio on the other side.

The resultant galvanic isolation improves common-mode voltage, prevents ground loops, a common cause of interference and data distortion issues, improves reception, as the noise floor in the receiver is lowered, and removes spikes and birdies on the PC panoramic Digitaleen.

In addition provides isolation of 1000V AC between the host PC and the radio peripheral that guard against surges that may come from the antenna connected to the receiver.




10KHz to 60MHz Antenna Galvanic Isolator.

Removes local pick-up noise by the antenna feedline.

Specifically recommended to work with SDR radios.
Suitable for analogue radios.
Indoor mount.


  Pedal Swich  


PTT foot switch

Robust momentary action foot operated switch with non slip base.

• 1.8m cable length.
• Standard 3.5mm jack plug. Other connectors available, Please ask.
• Dimensions 74 x 75 x 32mm
• Rated 3A 250V AC







Tiny HF Tunable Preselector options

  Plug and Play boxed version USB ; SKU: HS-2008USB-Boxed version £ 295.00 SCR Preselector-CAT  
  Plug and Play boxed version I2C ; SKU: HS-2008I2C-Boxed version £ 295.00 SCR Preselector-CAT  
  Modular version USB including filter bank board and USB control module board; SKU: HS-2008USB-MOD £ 190.00 SCR Preselector-CAT  
  Modular version I2C including filter bank board and control module board; SKU: HS-2008I2C-MOD £ 190.00 SCR Preselector-CAT  
  Filter Bank module board only; SKU: HS-2008-Filter £ 132.00 SCR Preselector-CAT  
  USB control module only; SKU: HS-2008CNT-USB £ 55.00 SCR Preselector-CAT  
  I2C control module only; SKU: HS-2008CNT-I2C £ 55.00 SCR Preselector-CAT  
  Flexwire I2C bus interconnection cable (Shielded, EMI protection); SKU: HS-2008Flex £ 35.00 SCR Preselector-CAT  
  All models include documentation in CDROM format.
In addition boxed models include:
Tiny-CAT HF Tunable preselector, user manual in CDROM format, two BNC-BNC coaxial cable tails, power supply cable with EMI filter and auxiliary connectors. USB version includes USB cable.