HF Preselector

3 types of HF Preselector

HF Preselector operates from 2-30MHz. It is typically constructed with switches and band pass filters. AWG Tech produces three types of HF Preselector.

  • Passive HF Preselector
  • Fixed gain active HF preselector
  • Adjustable gain active HF preselector

Passive HF Preselector

This is the most basic configuration of our HF preselector series. It is constructed using only switches and bandpass filters. It is modular and can be like a regular RF component. Available configurations are  4 channels, 6 channels and 8 channels.

Fixed Gain Active HF Preselector

The fixed gain active HF pre-selector provides gain to the overall system by adding a low noise amplifier after the preselection filters. Typical gains are 20 dB, 30 dB and 40 dB. This is available in modular form.

Adjustable Gain Active HF Preselector

The adjustable gain active HF preselector allows the user to set the gain by adding digital step attenuators to the fixed gain active HF preselector. This gives the user 30dB of gain control. The maximum gain at 0 dB attenuation are available in 20, 30 and 40 dB. The adjustable gain active HF preselector is available in modular form as well as in 19″rack mountable chassis.

Customised models

Customers can request for customization based on:

  • Number of channels
  • Maximum gain
  • Gain control range

Click here to request for datasheets.

Other related products

Phase matched UHF preselector in 19″rack mountable chassis

Typical Specifications of a 19"rack mountable HF Preselector
Operating frequency2 – 30 MHz
Gain30 dB typ at maximum gain setting
Passband flatness+/- 1 dB
Number of channels8
Noise Figure8 dB typ, 10 dB max
Gain control30 dB in 1 dB step
OIP3+35 dBm
CH 1Passband: 2 – 4 MHz
50 dB attenuation: dc- 1 MHz, 8-50 MHz
CH 2Passband: 4 – 8 MHz
50 dB attenuation: dc- 2 MHz, 16-50 MHz
CH 3Passband: 8 – 12 MHz
50 dB attenuation: dc- 4 MHz, 22-50 MHz
CH 4Passband: 12 – 16 MHz
50 dB attenuation: dc- 6 MHz, 28-50 MHz
CH 5Passband: 16 – 20 MHz
50 dB attenuation: dc- 8 MHz, 36-50 MHz
CH 6Passband: 20 – 25 MHz
50 dB attenuation: dc- 10 MHz, 42 – 50 MHz
CH 7Passband: 25 – 30 MHz
50 dB attenuation: dc- 12 MHz, 50 MHz
CH 8Passband: 2 – 30 MHz
40 dB attenuation: dc- 1 MHz, 50 MHz
InterfaceSMA-F: RF in & RF out
DB9-F: Controls
Power Supply110 – 220 Vac 50 Hz
Weight7 kg max
Dimensions19″1U rack mountable chassis

Need more information? Click on the blue button to the right!

Exploring the Important Basics of the Switched Filter HF Preselector

A switched capacitor is an electronic circuit element that is utilized for discrete time signal processing. It functions by moving charges into and out of capacitors when switches are either opened or closed. Generally, non-overlapping frequency signals are utilized to control the switches, thus not every switches are simultaneously closed.

In addition, filters that are implemented with these elements are referred to as “switched filters”, and they depend only on the ratios that lie between capacitances. These make them suitable for utilization within integrated circuits, where accurately specified resistors and capacitors are not economical to construct. Also, there are other switched capacitors integrated in other RF components, such as the switched filter HF preselector.

Looking into the Fundamentals of Preselectors

As mentioned above, there are switched filters that are integrated with other RF components as well. Let’s look at some of the fundamentals of the preselector.

A preselector is the name given to an electronic device that links together a radio antenna and a radio receiver. In addition, the preselector impedes troubling out-of-tune frequency signals that may pass through from the antenna into the radio receiver (also referred to as the preamplifier) that otherwise would be directly linked to the radio antenna.

A preselector’s function is to enhance the functionality of nearly any form of receiver; however, it’s especially helpful to receivers with broadband front-ends that are susceptible to overloading, such as scanners and the regular consumer-market receivers.

Usually, a preselector is tuned to have a bandwidth that is narrow, placed in the core of the receiver’s operating frequency. The preselector passes through the signal it’s tuned to, only being slightly reduced, but it attenuates other signals and eliminating unnecessary interference.

A preselector can be manufactured so that in addition to attenuating interferences from other signals, it’ll also protect a sensitive receiver from damaged caused by static input, voltage spikes and signal overloading from other transmitters in nearby areas. However, a preselector will not eliminate interference that came from the same frequency that both it and the receiver are tuned with.

Understanding the HF-band Frequency

Aside from the switched filter and the preselector, a frequency band is also used in this RF component, the HF-band frequency. Some information of such is detailed below.

The HF-band frequency (or the high frequency band) is the classification of electromagnetic wave on the electromagnetic spectrum that has a frequency range that falls from 3 to 30MHz. This frequency band is also referred to as the decameter wave due to its wavelength that ranges from one to ten decameters.

In addition, the HF-band frequency is one important part of the shortwave frequency bands, thus communications initiated with the use of this frequency band is often referred to as shortwave radio. Also, due to the radio waves in this band can be reflected back to the Earth with the help of the ionosphere layer, these frequencies are suited for long-distance communications across intercontinental distances.

In order for one to understand the functionalities of the switched filter HF preselector, one must first comprehend some of the fundamentals of the different bits and pieces of the component. Each and every one of them has a role to play in every circuitry.