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

Bob kb8tq kb8tq at n1k.org
Mon Jun 4 08:52:04 EDT 2018


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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