New amplifier design for HF Active and Active Vee antennas

Chris Moulding

The amplifier design for both these antennas has remained the same since launch as the HF Active antenna was the reference receive antenna for the RSGB Noise Measurement project.

As that project is now completed it's allowed me to look again at the amplifier design to see what improvements could be made after receiving a lot of customer feedback and learning what customers do with our antennas.

We are now launching a new version of each antenna with a re-designed amplifier. It's a push pull design with 20 dB more output that the original version with higher common mode rejection and IP3 performance.

The base unit has two RF outputs one at full level suitable for use with long feeder runs up to 305m and the second with a 20 dB attenuator for short cable runs including the 20m cable supplied with the antenna.

The amplifier in the head unit has a voltage regulator so we recommend that with short feeder runs a 12 to 15V power supply is used and with long runs a 24V supply is used.

The improved common mode rejection is very useful when used close to other electrical equipment in an urban or suburban environment.

The prototype Vee antenna using the new amplifier is now set up as part of a WebSDR server on the 160m amateur band using a SDR-4+ Special Edition receiver. The local ADSL/VDSLnoise has been nulled out by rotating the antenna for the position of minimum noise. The capacitive coupled local noise sources have been canceled out in the amplifier. The background noise is now S6 making it usable again.

The 160m WebSDR server is at:



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