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diversity antenna revisited


David Cutter
 

Chris

DUAL POLARISATION ACTIVE ANTENNA

I have one of these antennas and I want replace the whips with a pair of orthogonally placed large terminated loops, ie flags.  Do you see anything that might be a problem with bringing these together?

73 David G3UNA


Chris Moulding
 

David,

The amplifier in the Dual polarisation active antenna is the same as the HF active antenna i.e. a balanced push-pull FET input amplifier.

It should work OK with a large terminated loop element. You will have to place a suitable resistor (the same value as the termination resistor) across the inputs to correctly terminate the loop element as the input impedance of the amplifier is in the megohm range.

I would be interested to hear how it works, it sounds like an interesting project.

Regards,

Chris


David Cutter
 

Thanks for the prompt reply, Chris. 

It is usual to use a high ratio transformer to get to 50ohm from low band loops but this also transforms the signal from its already weak state.  By using your boxes I get a buffer which is resilient to common mode noise with no transformer loss.  

I don't know how much gain I will need, how much gain can I expect from the active antenna terminated with 1k?

David G3UNA

On 21 March 2019 at 13:40 Chris Moulding <chrism@...> wrote:

David,

The amplifier in the Dual polarisation active antenna is the same as the HF active antenna i.e. a balanced push-pull FET input amplifier.

It should work OK with a large terminated loop element. You will have to place a suitable resistor (the same value as the termination resistor) across the inputs to correctly terminate the loop element as the input impedance of the amplifier is in the megohm range.

I would be interested to hear how it works, it sounds like an interesting project.

Regards,

Chris