AS-RXFEP HF, VHF, RX Front End
Protectors
HF, VHF, and UHF Receiver protectors’ limits input
RF signal threshold from 1 to 150MHz to less than 0.3Vrms to
protect receiver front end from damage due to nearby transmitted fields.
Receiver still acts normally and measured signal strength is not
affected. Typically used for Receive only low band DXing antennas to
prevent damage to preamps and front ends of receivers from nearby
transmitting antennas.
Circuit uses a multi-stage design of transformer
saturation coupling and current limiters. They also incorporate a low
voltage GDT to protect from lightning events. These are receive only you
cannot transmit through them without damaging the
unit.
The model AS-RXFEP RF limiter consists of a high
voltage blocking capacitor input, two impedance converting
broadband transformers and low-capacitance limiter diodes. The circuit
is constructed to transform the 50 or 75 ohm input impedance in a
broadband configuration where the diodes limit the applied signal to
about .5 volt. The signal is then transformed back to 50 ohms to the
output of the device.
When large signals are presented to the unit the
input transformer saturates instantly, an increase in input VSWR occurs,
and the balance of input signal is reflected back toward the source. For
this reason power handling capacity is mostly irrelevant, but the
components used can handle 10 watts ICAS. Impedance of other signals at
lower levels are undisturbed. Insertion loss 1. MHz to 150 MHz is
typically .3dB. Limiting begins and holds at approximately .3 volts
constant.
The limit specification of .3V RMS is 0 dBm into 50
ohms.
The transformers used also provide circuit
isolation which prevents extraneous diode detection effects.
Circuit components and chassis easily handle the noted environmental
conditions.
Use these devices for all receivers, especially the
new broadband super-sensitive solid state units.
SO239 connectors ONLY. Use adapters of
to prevent accidental hooking unit to a transceiver output.
