[time-nuts] Source for DC-blocking 50-ohm terminators? (Spectracom 8140)

paul swed paulswedb at gmail.com
Mon Jun 4 10:56:34 EDT 2018


Yes I would say you have to build it.
The only reason make such a requirement is if the amplifier is not using a
split power supply. But instead is a single supply with the output at 50%
of the supply voltage. It could be very reasonable if what I suggest is
true to open the amp and install the caps within it.
Just a thought.
Regards
Paul
wb8tsl

On Mon, Jun 4, 2018 at 10:06 AM, Julien Goodwin <time-nuts at studio442.com.au>
wrote:

> Making my own that fits in either the mini Pomona boxes (which has
> BNCs)[1] or the nice really tiny Crystek SMA housings[2] with a BNC to
> SMA looks like it's probably the sensible option.
>
> 1: https://www.pomonaelectronics.com/products/boxes/boxes-with-connectors
>
> 2: http://www.crystek.com/microwave/spec-sheets/
> enclosure/SMA-KIT-1.3MF.pdf
>
> On 04/06/18 22:52, Bob kb8tq wrote:
> > Hi
> >
> > DC blocked 50 ohm terminations are indeed a bit odd. One answer is to
> simply use the
> > 75 ohm version and move on. The gotcha there is that they may / may not
> have a block
> > that works well at 10 MHz ( = the cap is to small ). The one thing *not*
> to do is to run the
> > device with no termination on the cable. The gizmo will be perfectly
> happy. Your lab will
> > be a mess. The coax will normally be long enough to make a great antenna
> at 10 MHz.
> > Leaving the end un-terminated puts it in “antenna mode”. You will have
> RF all over everything.
> > I have a lot of experience with this specific problem …..
> >
> > Bob
> >
> >> On Jun 4, 2018, at 12:09 AM, Julien Goodwin <time-nuts at studio442.com.au>
> wrote:
> >>
> >> I'm looking at using a Spectracom 8140 for 10Mhz distribution, and they
> >> specify using a DC-blocking 50-ohm terminator on each run.
> >>
> >> These seem to be odd enough that none of my usual sources have them
> >> (75-ohm DC-blocking terminators yes, 50-ohm, no).
> >>
> >> While it's easy enough to chain a DC block and a terminator, I'd prefer
> >> a single module I can more obviously label as the line termination.
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