Topband: RX Power over Coax

[Richard (Rick) Karlquist]

On 10/7/2020 7:45 AM, Grant Saviers wrote:
> Rick,
> 
> Did you CM choke the power and signal leads?  or the whole cable?
> 
> Grant KZ1W
> 

I should clarify that the CAT-5 was only used
to drive relay coils.  It did not power up a preamp, because
I did not need a preamp.  In place of a CM choke on
the RF coax, I used a flux coupled transformer,
either a Mini-Circuits T9-1 or a homebrew one
using a binocular core.  (The transformers were
used with Beverages).  The substantial drop
in signal level when the relay was de-energized
indicating that the transformer was providing
sufficient de-coupling.

Using a separate DC feed allows the option of using
a flux coupled transformer instead of a CM choke.
There seems to be a knee jerk reaction in favor of
using CM chokes vs flux coupled transformers.
A small transformer has very little interwinding
capacitance and could provide more isolation than
a CM choke.  And with Beverages, it is needed anyway.

73
Rick N6RK