[time-nuts] Noise and non-linear behaviour of ferrite transformers

Tim Shoppa tshoppa at gmail.com
Fri Jul 25 09:56:59 EDT 2014

General Radio used to have some common values of capacitances available in
"terminator" type configuration and "passthru"/"bulkhead" type
configuration.  These were moderately useful doing some bridge-type
measurements. I remember blowing one up once, and taking it apart being
pretty impressed the capacitor was a concentric design. I haven't seen
examples of these newer than the type 874 hermaphoditic connectors.

I swear a couple decades ago I saw BNC terminator-type capacitors in the
Pasternack catalogs that filled my mailboxes, but I never saw any of these
in the flesh.

I do know that "DC blocking capacitor" series-capacitor BNC's are widely
available from Pasternack and others.

Tim N3QE

Tim N3QE

On Fri, Jul 25, 2014 at 7:31 AM, Stefan Heinzmann <stefan_heinzmann at gmx.de>

> On 24.07.2014 18:00, Ackermann, John R wrote:
>> Just FWIW, the TADD-1 uses transformers to provide DC isolation, but the
>> shield side of the coax goes to ground through a 0.1uF cap.  The hope is
>> that this reduces the issue that John's referring to (and which I've
>> seen plenty of times using baluns).
> For optimum results with respect to high RF frequencies, I'd expect that
> you would need this cap to be annular, so that the cable can pass through
> the middle, and the outside connects to the chassis hole all around. This
> is like a feedthrough capacitor, except that the wire that goes through the
> center actually is a coaxial cable.
> While feedthrough caps for single wires are common, I haven't seen any for
> coaxial cables (rigid or semi-rigid cables come to mind). Do they really
> not exist, and if so why? Or have I failed to look in the right places?
> Cheers
> Stefan
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