Using a broadband active antenna

Equipment Antennas
1

I’d like to use a broadband active antenna on my SunSDR2 Pro in the second HF port, with a standard antenna such as my Super Antenna MP1 in the first HF antenna port. The transceiver has a bandscope that covers 160m to 6m and it would be useful to have a picture of other bands to hand, and be able to listen to them without re-configuring the main antenna. For example if I am working 20m and want to see what activity there is on 60m this would allow me to do it without having to add a loading coil to the antenna and extra counterpoises first.

I contacted the manufacture of the antenna (the COMPACT COIL ACTIVE HF AERIAL from Spectrum Communications) and they told me that the antenna input must be grounded when transmitting to stop the circuit being damaged.

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I’m presuming I may need to build a remote control circuit to achieve this? Has anyone completed this sort of task?

Many thanks, Mark.

2

Unless you are running an LOT of power then provided you can get the active antenna outside the near field of the TX antenna I would be surprised if there was a problem (and would be seriously unimpressed with the preamp design!). If you really want belt and braces, or the antennas have be be in close proximity then yes, a simple changeover relay driven by your TX line could be used to ground the input to the preamp. As there is no power switching involved, a small, cheap reed relay would be perfect.

3

Hi,
You may do OK with just a 3 m wire and no preamp. Or you could use a simple source follower buffer to connect a short antenna to a coax line. That will accept lots of volts. If you really do need a sensitive preamp then you should heed the makers advice.

73
Ron
VK3AFW