Active Antenna Amplifier (model AAA-1C)

Active Antenna Amplifier

The Kit

The amplifier kit consists of the following parts:

• Amplifier board (mounted and tested)
• Control board (mounted and tested)
• 6-pin Female connector for connection of remote control switches
• Plastic ABS IP55 protected box
• 3 mounting screws diam. 3.5 mm
• Load resistor 100 ohms / 2W
• Short service cable crimped with two RJ45 connectors
• Spare RJ45 shielded plug connector
• Spare RJ45 unshielded plug connector
• This amplifier is intended for construction of small wideband active receiving antennas from LF to upper HF bands. The mechanical construction of the particular loop/dipole antenna must be performed by the user. This amplifier can use two separate small magnetic loops. These two loops are used also as two arms of a small electrical dipole. Thus 3 different antennas can be used. The amplifier has four remotely switched modes: Loop A, Loop B, crossed parallel loops A&B and dipole. Each mode can be switched immediately and this enables us to use the best antenna for the moment.

  This kit consists of two SMD mounted PC boards – an amplifier board and a control board. The amplifier has low noise, high dynamic range and wideband properties. It has separate current and voltage amplifiers for the different antennas. It is a balanced design and uses monolithic pairs. The balanced power amplifier uses medium power BJT with very low IMD and can give approximately 75 mW of output power on a 50 ohms load in order to minimize the non-linear distortions. The small antenna frequency response in all modes is flat in a wide frequency range. Usable frequencies are from 20 KHz up to 55 MHz. The antenna gain in the current and voltage mode is set to be approximately the same to avoid striking differences in the gain when the antennas are switched. Every kit set has been tested.

  Features

  • 4 remotely switched modes (Loop A, Loop B, crossed parallel loops A&B and dipole)
  • Each mode can be switched immediately
  • Good sensitivity and a flat frequency response
  • High dynamic range
  • Protected input from strong signals
  • High immunity to local noise with balanced amplifiers and balanced feed line
  • Balun transformer coupling for common mode noise reduction
  • Extensive documentation manuals with detailed description how to build your own small antennas

Control board and cable

The amplifier is connected to the receiver via a control box and an FTP (shielded CAT5E) cable with RJ45 connectors which ensure good balance to avoid common mode noise signals. The cable length can be above 100m. There is a possibility to limit the maximal voltage applied to the receiver input which is needed for some direct sampling SDR. The amplifier has jumpers for setting it to the particular environment. It is of SMD design and is mounted and tested.

Input

The amplifier input is protected from high electromagnetic field intensities – it can be used with magnetic and electric small antenna in the immediate vicinity (20 – 30 m) of transmitting HF antennas even if the power is 1 – 2 KW. The amplifier has input filters to reject the frequencies above 55 MHz to avoid the influence of strong stations in the broadcast FM band (80-108MHz).

Power & Other

The amplifier is powered by a nominal 13.8 V (12.3 – 16 V margins) DC power supply @ 145 mA nominal current. The standard existing power supplies (PS) for the transceivers or receivers can be used. The amplifier is mounted in an ABS plastic (IP55 protected) box. It can be used with any receiver which has sufficient sensitivity and 50 ohms input impedance. This amplifier can be used as a building block for more sophisticated antennas such as phased arrays etc.

Tested parameters in production stage

• DC operating points
• Frequency response at 7 points. 0.1, 0.3, 1, 10 , 30, 50 , 100 MHz
• Output noise power
• 1 dB output compression point at 10MHz
• Second harmonic OIP2 at 3.680/7.360 MHz

This set of measurements assures that the amplifier has normal gain, frequency response, noise floor and dynamic range.

Block diagram. Two small loops act also as arms of a small vertical dipole

 

Spice simulated antenna factor K_a for loop and dipole. The circular loop is with single turn 1m diam. made with 25mm diam. alum. tube with 2.4 uH inductance. The dipole has two 1 m long arms – effective height is 1 m. .

Active Antenna MDS at 1 KHz BW – Spice Models

Spice simulated input minimal discernible signal (MDS) in [uV/m] for different antennas. The noise bandwidth is 1KHz. First two loops are 1m diam. single turn (thin and fat conductor). 2-crossed loops are loops with 1m diam. circular shape (1.56 m² total area), each with fat conductor. The dipole is with 2 arms of 1 m. See Antenna section for details. A small loop and dipole models are used which is acceptable up to 10 MHz. For higher frequencies the MDS values might be not reliable.

Price 87 euros – See More:Link

Warning: file_get_contents(https://plusone.google.com/_/+1/fastbutton?url=https%3A%2F%2Fqrznow.com%2Factive-antenna-amplifier-model-aaa-1c%2F): failed to open stream: HTTP request failed! HTTP/1.0 404 Not Found in /home/qrznow/public_html/wp-content/themes/goodnews5/framework/functions/posts_share.php on line 151