[time-nuts] Re: Query about List and about 10 MHz Distro

[Dana Whitlow]

I believe that a significant problem in my case was not leakage through the
shield, but
rather common-mode currents on the cable.  My experiences were with RG-6
style cable,
namely a cable that mostly went around the outside of the house for TV
distribution.
I get all the TV I want with an indoor dipole, and I had had plans of using
that TV
cable for ham purposes.  One thing I have noted is that adding ferrite
common mode
chokes near the ends of the cable did help quite a  bit, just not enough.

Those who are conversant with RF shielding concepts will recognize that
this puts most
of the blame squarely on my own shoulders, for not putting my kluges in
proper enclosures.
But I'm retired, old, shaky, tired, etc, and am not too ambitious any
more.  But I take
some solace in the observation that I'm not the only one; much of the
commercially-built
equipment I own has similar (and quite obvious) flaws.

I worked in the Tektronix spectrum analyzer group some years back, and one
of my side
tasks was taking instruments over to the EMI lab for compliance tests.  On
more than
one occasion those people told me that they were always delighted to test
stuff designed
by our group, because it was designed and built well enough that it almost
always passed
FCC specs on the first round.

Dana


On Sun, Aug 29, 2021 at 8:52 AM Bob kb8tq <kb8tq at n1k.org> wrote:

> Hi
>
> Skin depth is what gets you with most coax at 10 MHz, even with the
> “double
> shield” stuff. Hardline with a nice heavy outer would do better. It’s not
> terribly
> practical around the typical lab. Might not be a bad choice for a “burry
> in the yard”
> setup though. With normal cable, the losses from the soil at normal burial
> depths make a good shield, that makes dealing with it questionable even
> there ….
>
> Bob
>
> > On Aug 29, 2021, at 9:36 AM, Robert DiRosario <ka3zyx at comcast.net>
> wrote:
> >
> > What about double shielded RG-223, or Thinnet ethernet cable?
> > Most Thinnet has both a braided shield and a foil wrap.
> >
> > Robert
> >
> > On 08/28/2021 08:26 PM, Bob kb8tq wrote:
> >> Hi
> >>
> >> Anything you do that has a bunch of 10 MHz cables running out from here
> or there
> >> will impact your ability to listen to WWV at 10 MHz :)  Other than
> killing all the sources,
> >> there is no silver bullet.
> >>
> >> Bob
> >>
> >>> On Aug 28, 2021, at 7:57 PM, Dana Whitlow <k8yumdoober at gmail.com>
> wrote:
> >>>
> >>> Bob, my own motivation  for going to fiber was entirely different.  I
> >>> simply wanted to
> >>> run 10 MHz all over the place from reference sources in disparate
> >>> locations in the
> >>> house, and I quickly discovered that cable leakage was embarrassingly
> >>> severe.  So
> >>> I shut down and began contemplating a fiber link.  But then reality
> set in
> >>> and I realized
> >>> that running fiber across the house had its own big problems, so I set
> the
> >>> project aside.
> >>>
> >>> Dana
> >>>
> >>>
> >>> On Sat, Aug 28, 2021 at 3:32 PM Bob kb8tq <kb8tq at n1k.org> wrote:
> >>>
> >>>> Hi
> >>>>
> >>>> With a whole variety of pretty good OCXO’s going for cheap money
> >>>> on eBay, it’s likely less expensive to do cleanup oscillators on the
> link
> >>>> compared to going crazy with low noise optical this or that. Yes, you
> >>>> will be getting something in the high 150’s for noise, but still
> pretty
> >>>> good
> >>>> for $10.
> >>>>
> >>>> If you need better, spend $50 or so on a 10811. Still less money than
> >>>> some of the crazy fiber stuff.
> >>>>
> >>>> With either one, send over a high enough frequency that the loop isn’t
> >>>> dealing with reference spurs in any significant way. Given the clock
> rates
> >>>> Ethernet runs at these days, that part should be fairly
> straightforward.
> >>>>
> >>>> This *assumes* that there is a crossover somewhere practical between
> >>>> the fiber noise and the noise on the optical gear. You should be able
> to
> >>>> work out what it is with some fairly normal phase noise or ADEV
> testing.
> >>>>
> >>>> Bob
> >>>>
> >>>>> On Aug 28, 2021, at 3:03 PM, Dana Whitlow <k8yumdoober at gmail.com>
> wrote:
> >>>>>
> >>>>> I was looking for something similar about 18 months or so ago.
> Although
> >>>> I
> >>>>> haven't taken any
> >>>>> action yet, I concluded that one could do a nice job for under $200
> per
> >>>>> segment, including the
> >>>>> transmitter and receiver modules and lots of connectorized multimode
> >>>>> fiber.  What I *don't* know
> >>>>> is what the phase noise performance would be, except that I do know
> that
> >>>>> the fiber's VF *is*
> >>>>> materially influenced by temperature.
> >>>>>
> >>>>> I was looking primarily at the HFBR-2416 for the fiber receiver, and
> the
> >>>>> HFBR-1412 (standard
> >>>>> power) or the HFBR-1414 (high power option) for the transmitter
>  Unlike
> >>>>> most of the available
> >>>>> models, these are fundamentally analog devices, meaning that you can
> >>>>> transmit sinewave
> >>>>> 10 MHz through them.  At the time I was looking, Mouser was selling
> these
> >>>>> for about $20 each.
> >>>>>
> >>>>> See the datasheet at
> >>>>>
> >>>>
> https://www.mouser.com/datasheet/2/678/AV02-0176EN_2019-02-15-1827546.pdf
> >>>>> with particular attention to page 21 regarding the HFBR-2416
> receiver.
> >>>>>
> >>>>> I was also looking at Fiber Instrument Sales for patch cords.  We
> bought
> >>>> a
> >>>>> lot of fiber stuff from
> >>>>> them at Arecibo, and I was always happy with them.  See:
> >>>>>
> >>>>
> https://www.fiberinstrumentsales.com/catalog-cable-assemblies?gclid=Cj0KCQjwvaeJBhCvARIsABgTDM7eNTkP2nQbyFzhcwDE38VnSEP879MBKV1ZyDq2YrnEtOn7_VfzjbkaAtpfEALw_wcB
> >>>>> Somebody had pointed out yet another source of connectorized fibers
> >>>> ("patch
> >>>>> cords") to me, but I cannot find the name
> >>>>> at the moment.
> >>>>>
> >>>>> Dana   K8YUM
> >>>>>
> >>>>>
> >>>>> On Sat, Aug 28, 2021 at 11:52 AM AC0XU (Jim) <
> James.Schatzman at ac0xu.com>
> >>>>> wrote:
> >>>>>
> >>>>>> I am hoping that you can help me about a couple of things:
> >>>>>>
> >>>>>> 1) My time-nuts summaries sometimes appear unformatted and
> unreadable.
> >>>> All
> >>>>>> the text from all the postings is crammed together without spacing.
> How
> >>>> can
> >>>>>> I fix it?
> >>>>>>
> >>>>>> 2) I want to distribute 10 MHz references by fiber. There are
> >>>>>> RF-over-Fiber products available, but too expensive for me
> (thousands of
> >>>>>> $$$ per xmit/rcv set).  I am thinking that it should be possible to
> use
> >>>>>> fiber Ethernet components to do this. I don't mean IEEE 1588 but a
> much
> >>>>>> simpler, no-computer-required, solution. Possibly just converting
> sine
> >>>> wave
> >>>>>> (coax) to square wave (fiber) to sine wave (coax). I am looking for
> a
> >>>> low
> >>>>>> cost solution. Any thoughts or recommendations??
> >>>>>>
> >>>>>> Thanks!
> >>>>>>
> >>>>>> Jim
> >>>>>> _______________________________________________
> >>>>>> time-nuts mailing list -- time-nuts at lists.febo.com -- To
> unsubscribe
> >>>> send
> >>>>>> an email to time-nuts-leave at lists.febo.com
> >>>>>> To unsubscribe, go to and follow the instructions there.
> >>>>>>
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