Filters for Wideband Active Antennas to Reject Strong Input Signals from Broadcasting Stations in LW, MW and FM Bands
The AAA1 amplifier has a very good dynamic range – it is higher than the most RF preamplifiers used in the best transceivers. But it is wideband and there are no filters at the input. Placing the antenna in a very strong filed can saturate the amplifier. This might happened if there is a very strong transmitter near the antenna – e.g. 100 KW BC MW transmitter 2 – 3 km away. The only way to reduce the interference is to use a reject filter at the input for the TX frequency. This filter must be placed between the antenna and AAA-1 input.
AAA-1 active antenna has very high dynamic range and its 1 dB compression point is at +20 dBm. At the output a heavy clipped signal can reach 6 V pp. This voltage is safe for the most of the conventional receivers and transceivers. This limit is reached only when there is a nearby transmitter or nearby lightning strike. Normally the total output power from 20 KHz to 30 Mhz is below 0 dBm at the antenna output.
AAA-1 is well protected at the input and does not need any special measures even when legal power TX is used. But the output voltage might be a problem for some receivers (Rx).
These are the expected radiation patterns using active antennas AAA-1 and VDLine kits combined in dual mode (dipole/loop) 2-element phased array…
The AAA-1 amplifier is inserted in a box which is marked as IP55 protection class. According to the standard it is dust and water protected. The standard says…
This is a small loop connected to an amplifier with very low input resistance e.g.3 ohms. The small loop is injecting current into this amplifier. The loop works almost in…
The noise in dipole mode in AAA-1 active antenna is usually higher than in the loop mode. One can make the wrong conclusion that the short dipole is a very noisy antenna…
Adding an Input Balun in AAA-1 in Dipole Mode to Reduce 2nd Order IMD Distortions when Asymmetric Signal Source (antenna) is Used
When using large loops as dipole arms with AAA-1 active antenna amplifier or totally asymmetric electric antennas such as ground plane (GP), some 2-nd order IMD distortion might occur due to asymmetric signal source combined with the strong signals…
The following links are useful for additional information and understanding of the Amplifier for Small Magnetic and Electrical Wideband Receiving Antennas.
- Receiving Phased Array with Small Electric or Magnetic Active Wideband Elements. Experimental Performance Evaluation
- Experimental Comparison of Small Wideband Magnetic Loops
- Single Tone Measurements of Nonlinear Distortions in Wideband RF Amplifiers
- Wideband Active Small Magnetic Loop Antenna
- Wideband Active Small Magnetic Loop Antenna. Protection from Strong Electromagnetic Fields
- Very Weak Signal Reception with Small Magnetic Loop Antenna