The Achilles heal of active whip receive antennas is the
inability to do filtering ahead of the amplifier.
I have spent many hours
brainstorming this problem, and have yet to devise a
solution. Especially one with 40 dB rejection.
I am thinking that if there was any way to
do this, DXE would be selling it as an option.
If anyone reading this has a solution, I would love
to hear about it.
As an alternative, see this URL for a passive receive
4 square design:
http://www.n6rk.com/RX4sqr.gif
There are no amplifiers to overload. You can put a
rejection filter at the receiver.
73
Rick N6RK
On 9/11/2017 7:25 AM, Grant Saviers wrote:
I was asked by a DXpedition leader if it was practical to bandpass
filter the input (antenna side) of the DX Engineering 4 sq's they plan
A deeper question is what impedances are possible for a 20' whip and the
input of the amplifier for a filter design? Sacrificing noise
performance, some gain, and frequency range are all reasonable to solve
the problem. Probably more than 40db of rejection is needed. Switching
a pair of filters with an outboard box on each whip looks to be the easy
part.
Grant KZ1W
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