Topband: Probably-dumb question re current mode chokes on RXantennas

[Richard (Rick) Karlquist]

Lee K7TJR wrote:
>
>      Interestingly enough, one of the claims on the 
> Rauch/DXEngineering patent on the active antenna 4-square
>  receiving system is that resonating the DC carrying chokes
>  across the output common mode isolation transformer in an 
> active antenna amplifier increases the common mode 
> rejection. I would like to see how that works with an amplifier 
> that covers many octaves of bandwidth and a resonance being
>  usually fairly narrow band. Anybody know how that works at 
> more than one narrow band of frequencies?

I haven't read the patent, but I did purchase a couple of
these for evaluation and trace out the schematic.  The INPUT
has a resonating system using jumpers to select the frequency.
This is a shunt tank that will do nothing to prevent feedline
pickup.

I don't remember seeing any resonating capacitors across the
DC chokes, but as you say, it would be a narrow band solution.

I tried to make a dipole from two of the DXE units and found
that the feedline pickup made it unusable.  In my homebrew
receiving dipoles, I only use transformers to decouple the
feedline.  Of course I can do that because I don't have to convey DC, 
since I don't use preamps at the antenna.

Rick N6RK