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

[Anders Wallin]

FWIW we've played with various SMA-to-SFP converter boards in the lab for
10MHz or 100MHz distribution.

A bare-bones SFP board is e.g.
https://github.com/aewallin/SFP-Breakout-Board
That interfaces directly to the differential AC-coupled TX and RX pins of
an SFP.

If you want some buffering (and limited bandwidth at the same time) you can
put an op-amp as a buffer and a transformer to convert to/from the
differential TX/RX.
Here's a design I've used https://github.com/aewallin/SFP2SMA_2018.03
We also made a box around that board:
http://www.anderswallin.net/2020/12/sfp-board-in-a-box/

If your requirements are somewhere in 1e-14 or worse then this type of
passive frequency distribution should work fine for maybe a few km fiber
runs.

Anders


On Mon, Aug 30, 2021 at 8:13 AM Poul-Henning Kamp 
wrote:

> 
> David I. Emery writes:
> > On Sun, Aug 29, 2021 at 10:43:51AM -0400, paul swed wrote:
>
> > Not completely clear what the common
> > mode  Z of the things is at 10 MHz...
>
> Twisted pair is 135 Ohm.
>
> --
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
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[time-nuts] Re: Query about List and about 10 MHz Distro

[Poul-Henning Kamp]

David I. Emery writes:
> On Sun, Aug 29, 2021 at 10:43:51AM -0400, paul swed wrote:

> Not completely clear what the common
> mode  Z of the things is at 10 MHz...

Twisted pair is 135 Ohm.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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[time-nuts] Re: Query about List and about 10 MHz Distro

[David I. Emery]

On Sun, Aug 29, 2021 at 10:43:51AM -0400, paul swed wrote:

> We my only issue is every time we had a lightning storm it seemed to
> fry the ICs.

While they may not have ideal behavior with temperature (and
related phase/group delay changes) the old antique 10Mbs era balanced
twisted pair ethernet  transformer/filter modules did eliminate common
mode energy getting into the receivers (and transmitter) which it sounds
like was the cause of your lightning EMP problem.   For 10 MHz these
ought to work pretty well with twisted pairs as they provide galvanic
isolation breaking ground loops.   Not completely clear what the common
mode  Z of the things is at 10 MHz... but unless there is a deliberate
cap from a center tap to local ground I'd guess it would be
significantly high given just winding to winding capacitance.

I do certainly beleive that optical transmission is the 
better solution... however.



-- 
  Dave Emery N1PRE/AE, d...@dieconsulting.com  DIE Consulting, Weston, Mass 
02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in 
celebration of what could have been, but wasn't and is not to be now either."
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[time-nuts] Re: About 10 MHz Optical Distro

[Julien Goodwin]

On 30/8/21 5:24 am, Lux, Jim wrote:
> Yeah, but those are piece parts.  What would be nice is if a cheap "box"
> could be found - ideally (for 10 MHz) BNC in/out and fiber connector
> with a wall wart for power. Maybe this a good idea for a TAPR project if
> someone was willing to do the design (!)

You'd do it using an SFP cage, so the actual optics could be swapped in
for standard commercial ones, and generic 1G LR optics should be < US$10
in small quantity by now (they've been much less than that in tray
quantity for at least a decade), and drive 2km easily.

I've done a little design with SFP for a previous (work-ish) project,
and basing it on the redesigned Spectracom 8140 pods I did a few years
ago[1], I could probably knock out a prototype design in an afternoon.

(Quite if I ever will, and when is a different matter)

1: https://laptop006.livejournal.com/60862.html
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[time-nuts] Re: About 10 MHz Optical Distro

[Bob kb8tq]

Hi

Ok so what is “decent” performance? 

Is -150 dbc/ Hz “floor” good enough? it is for some stuff ….

Is -130 dbc/ Hz at 10 Hz a requirement? 

Is -100 dbc / Hz at 1 Hz the target? 

Is 1x10^-12 at 1 second “good enough” ADEV?

How about 1x10^-13 at 10 seconds …..

Keep in mind that these are system floor numbers. The real signal 
“as delivered” isn’t going to ever be as good as the system floor.

You could easily move any of those phase numbers 20 db one way or the other.
The ADEV could go up or down by at least two orders of magnitude. The numbers
would still be “decent” by some definitions. 

Bob

> On Aug 29, 2021, at 3:24 PM, Lux, Jim  wrote:
> 
> On 8/29/21 12:13 PM, CFO wrote:
>> From here
>> https://forums.xilinx.com/t5/Serial-Transceivers/Sending-10Mhz-clock-over-Fiber/td-p/1026390
>>  
>> 
>> They suggest these
>> 
>> *** SNIP ***
>> what length do you need to send over ?
>> 
>> this sort of stuff is a LOT cheaper and more rugged, and more than capable 
>> of sending 10 MHz clock
>> 
>> Cable
>> https://uk.farnell.com/broadcom-limited/hfbr-rus100z/cable-fibre-optic-1-fibre/dp/1247714
>>  
>> 
>>  
>> 
>> Drivers
>> http://www.farnell.com/datasheets/1812660.pdf?_ga=2.29282815.2110613125.1570030173-2072545025.1569659196
>>  
>> 
>>  
>> 
>> and you just drive it with TTL.
> 
> 
> Yeah, but those are piece parts.  What would be nice is if a cheap "box" 
> could be found - ideally (for 10 MHz) BNC in/out and fiber connector with a 
> wall wart for power. Maybe this a good idea for a TAPR project if someone was 
> willing to do the design (!)
> 
> There's probably plenty of applications out there in amateur radio land for a 
> inexpensive RF over optical link with "decent" performance (defined however).
> 
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[time-nuts] Re: About 10 MHz Optical Distro

[Lux, Jim]

On 8/29/21 12:13 PM, CFO wrote:

From here
https://forums.xilinx.com/t5/Serial-Transceivers/Sending-10Mhz-clock-over-Fiber/td-p/1026390 



They suggest these

*** SNIP ***
what length do you need to send over ?

this sort of stuff is a LOT cheaper and more rugged, and more than 
capable of sending 10 MHz clock


Cable
https://uk.farnell.com/broadcom-limited/hfbr-rus100z/cable-fibre-optic-1-fibre/dp/1247714 
 



Drivers
http://www.farnell.com/datasheets/1812660.pdf?_ga=2.29282815.2110613125.1570030173-2072545025.1569659196 
 



and you just drive it with TTL.



Yeah, but those are piece parts.  What would be nice is if a cheap "box" 
could be found - ideally (for 10 MHz) BNC in/out and fiber connector 
with a wall wart for power. Maybe this a good idea for a TAPR project if 
someone was willing to do the design (!)


There's probably plenty of applications out there in amateur radio land 
for a inexpensive RF over optical link with "decent" performance 
(defined however).


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[time-nuts] Re: About 10 MHz Optical Distro

[CFO]

From here
https://forums.xilinx.com/t5/Serial-Transceivers/Sending-10Mhz-clock-over-Fiber/td-p/1026390

They suggest these

*** SNIP ***
what length do you need to send over ?

this sort of stuff is a LOT cheaper and more rugged, and more than 
capable of sending 10 MHz clock


Cable
https://uk.farnell.com/broadcom-limited/hfbr-rus100z/cable-fibre-optic-1-fibre/dp/1247714 



Drivers
http://www.farnell.com/datasheets/1812660.pdf?_ga=2.29282815.2110613125.1570030173-2072545025.1569659196 



and you just drive it with TTL.

*** SNIP ***


Using cheap POF - It seems like 50m is the max for 10MHz
But i think with POF , we should be able to "do connectors at home"

Using 200 μm PCS cable , it seems you could go 120m@50Mbd


But a 100m SC connected fiber cable was "only" like $30 on Aliexpress

They seem a "bit like" the other drivers mentioned , but starts with A 
instead of H



CFO
Still timenut beginner
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[time-nuts] Re: Query about List and about 10 MHz Distro

[Joseph Gwinn]

On Sun, 29 Aug 2021 13:56:42 -0400, time-nuts-requ...@lists.febo.com 
wrote:

Re: time-nuts Digest, Vol 208, Issue 24 (messages 2, 4, and 15) 


> --2
Date: Sun, 29 Aug 2021 09:51:39 -0400
From: Bob kb8tq 
Subject: [time-nuts] Re: Query about List and about 10 MHz Distro
To: Discussion of precise time and frequency measurement


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  wrote:

What about double shielded RG-223, or Thinnet ethernet cable?
Most Thinnet has both a braided shield and a foil wrap.

Robert

> --3
Date: Sun, 29 Aug 2021 09:21:32 -0500
From: Dana Whitlow 
Subject: [time-nuts] Re: Query about List and about 10 MHz Distro
To: Discussion of precise time and frequency measurement


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.


> --15
Date: Sun, 29 Aug 2021 13:29:26 -0400
From: Robert DiRosario 
Subject: [time-nuts] Re: Query about List and about 10 MHz Distro
To: time-nuts@lists.febo.com

Andrew Sureflex (FSJ) is a lot more flexible then the LDF4 Healix, 
which 
is what you find a
lot of on ebay and at hamfests.

Here is some 1/4"  Sureflex, new:

Andrew Type N Male to Type N Male Sureflex Cable 30 feet 
F1RNA-PNMNM-30-L1 NEW!
https://www.ebay.com/itm/173863049072
US $30.00 + $13.02 Shipping.  For two pieces shipping goes to $16.33, 
for three $22.90

You can cut it with a hacksaw, do NOT use wire cutters.  Connectors 
can be
installed with just hand tools.

If you move the test equipment around it's not very practical, but if 
it's setup on
a bench or in a rack it will work.

Robert

Those large 10 MHz distribution systems typically used Heliax cable, 
which as a solid copper foil shield, with better than 100 dB/meter 
shielding effectiveness (SE).  Actually, I think that's the limit of 
their ability to measure SE. Back when we did underground nuclear 
tests, the cable connecting down-hole instruments to instruments a 
safe distance away were Heliax.

At power-line frequencies, the skin depth well exceeds the thickness 
of any reasonable shield, so the transfer impedance (between inside 
skin and outside skins) is the DC resistance of the shield.  

Power-frequency ground loops can be a problem, and common-mode chokes 
are not effective against this, but 10 MHz RF transformers intended 
for galvanic isolation are.  May also need a blocking capacitor to 
prevent transformer core saturation.

As for common-mode chokes, one can implement such things by winding 
insulated coaxial cable multiple times through a big ferrite toroid 
core.  The insulation jacket prevents the cable shields from shorting 
to one another.  This dodge also works for shielded twisted pair 
cable.  This dodge is discussed in the books on Balun Transformers, 
and is raised to a high art in the book on Coaxial AC Bridges.

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

[Lux, Jim]

On 8/29/21 10:29 AM, Robert DiRosario wrote:
Andrew Sureflex (FSJ) is a lot more flexible then the LDF4 Healix, 
which is what you find a

lot of on ebay and at hamfests.

Here is some 1/4"  Sureflex, new:

Andrew Type N Male to Type N Male Sureflex Cable 30 feet 
F1RNA-PNMNM-30-L1 NEW!

https://www.ebay.com/itm/173863049072
US $30.00 + $13.02 Shipping.  For two pieces shipping goes to $16.33, 
for three $22.90


You can cut it with a hacksaw, do NOT use wire cutters. Connectors can be
installed with just hand tools.

If you move the test equipment around it's not very practical, but if 
it's setup on

a bench or in a rack it will work.

Robert



ya know.. system cost for optical fiber is probably cheaper than 
hardline - the cable certainly is (about $15 for a 100 ft duplex single 
mode). And the analog/optical converters at either end are probably 
cheaper than hardline coax connectors. And *way* easier to install.


We just need to figure out which COTS media converter is right for 
"time-nuts" usage.



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

[Mark Spencer]

This has been an interesting thread. 

I purchased some 1/4" FSJ with BNC connectors from the usual auction site years 
ago for time nuts use but never installed it.  It does seem to be a bit of a 
hassle to use in my time lab (I do use some FSJ with N connectors in parts of 
my home amateur radio station.)

I suspect I haven't looked hard enough for troubling leakage at 10 MHz from the 
RG400 I mostly use.  I have the FSJ to fall back on if I take my time nuts 
hobby to the next level.

Some of the fiber ideas seem promising as well.




Mark Spencer
m...@alignedsolutions.com
604 762 4099

> On Aug 29, 2021, at 10:29 AM, Robert DiRosario  wrote:
> 
> Andrew Sureflex (FSJ) is a lot more flexible then the LDF4 Healix, which is 
> what you find a
> lot of on ebay and at hamfests.
> 
> Here is some 1/4"  Sureflex, new:
> 
> Andrew Type N Male to Type N Male Sureflex Cable 30 feet F1RNA-PNMNM-30-L1 
> NEW!
> https://www.ebay.com/itm/173863049072
> US $30.00 + $13.02 Shipping.  For two pieces shipping goes to $16.33, for 
> three $22.90
> 
> You can cut it with a hacksaw, do NOT use wire cutters.  Connectors can be
> installed with just hand tools.
> 
> If you move the test equipment around it's not very practical, but if it's 
> setup on
> a bench or in a rack it will work.
> 
> Robert
> 
> 
> 
>> On 08/29/2021 09:51 AM, Bob kb8tq 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  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  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 3:3
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[time-nuts] Re: Query about List and about 10 MHz Distro

[Bob kb8tq]

Hi

With *any* cable setup, proper termination is vital. An improperly terminated 
balanced line can be just as bad as a poorly terminated coax. Things like
common mode chokes are part of a *lot* of setups. 

What gets messy is that a lot of gear does not properly terminate the cable. 
It’s high-z so you can run a bunch of them with Tee connectors or some other
strange approach. >20 db of return loss is *not* what most cables get terminated
in. 

It doesn’t take a lot of coax to get a quarter wave at 10 MHz. Anything nearly
that long is going to be a radiator if you let it. 

This all gets a bit insane if you have multiple 10 MHz sources (like devices 
you are testing). Close in phase noise and ADEV both can get really strange 
as a result.

Lots of issues ….

Bob



> On Aug 29, 2021, at 10:44 AM, Dana Whitlow  wrote:
> 
> Andy,
> 
> Balanced twisted pair may be helpful, but only if adequate precautions are
> taken to
> avoid creation of common mode *currents *on the line*.*
> 
> Dana
> 
> 
> On Sun, Aug 29, 2021 at 9:34 AM Andy Talbot  wrote:
> 
>> Hence my observation that balanced twisted pair might be a better solution
>> than coax for 10MHz distribution
>> Removes all possibility of ground loops
>> 
>> Andy
>> www.g4jnt.com
>> 
>> 
>> 
>> On Sun, 29 Aug 2021 at 15:22, Dana Whitlow  wrote:
>> 
>>> 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.
>> ___
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[time-nuts] Re: Query about List and about 10 MHz Distro

[Robert DiRosario]

Andrew Sureflex (FSJ) is a lot more flexible then the LDF4 Healix, which 
is what you find a

lot of on ebay and at hamfests.

Here is some 1/4"  Sureflex, new:

Andrew Type N Male to Type N Male Sureflex Cable 30 feet 
F1RNA-PNMNM-30-L1 NEW!

https://www.ebay.com/itm/173863049072
US $30.00 + $13.02 Shipping.  For two pieces shipping goes to $16.33, 
for three $22.90


You can cut it with a hacksaw, do NOT use wire cutters.  Connectors can be
installed with just hand tools.

If you move the test equipment around it's not very practical, but if 
it's setup on

a bench or in a rack it will work.

Robert



On 08/29/2021 09:51 AM, Bob kb8tq 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  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  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  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  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) 
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

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

[Joseph Gwinn]

On Sun, 29 Aug 2021 03:30:23 -0400, time-nuts-requ...@lists.febo.com 
wrote:
Re: time-nuts Digest, Vol 208, Issue 23 (message 3)

> Date: Sat, 28 Aug 2021 18:57:08 -0500
> From: Dana Whitlow 
> Subject: [time-nuts] Re: Query about List and about 10 MHz Distro
> To: Discussion of precise time and frequency measurement
>   
> 
> 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

I've run a lot of 10 MHz distribution coaxial cable, in a tree with 
links as long as 50 meters, and planned systems where the links were 
a few hundred meters.  It's necessary to use double-shielded coax 
with machined TNC (not BNC) connectors on cables and the (passive) 
power dividers.  The cable shielding effectiveness must exceed 80 dB 
per meter.  Be sure  to torque the connectors to the "inspection 
torque" range specified by the connector manufacturer.  At 10 MHz, 
cable losses are minimal.

.

Joe Gwinn
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[time-nuts] Re: of possible interest (modulation of IRIG onto 10 MHz reference)

[Joseph Gwinn]

On Sun, 29 Aug 2021 03:30:23 -0400, time-nuts-requ...@lists.febo.com 
wrote:
Re: time-nuts Digest, Vol 208, Issue 23 (Msg 10) 

> Date: Sun, 29 Aug 2021 14:33:24 +1000
> From: Julien Goodwin 
> Subject: [time-nuts] Re: of possible interest
> To: time-nuts@lists.febo.com
> 
> On 21/3/20 6:07 am, djl wrote:
>> 
>> https://www.sv1afn.com/en/products/vhf-uhf-triplexer-1.html
>> 
>> 10 mhz and uhf/vhf on same cable.
> 
> I've pondered if IRIG modulated on 10MHz would make enough sense to
> work, or if the modulation would end up degrading the 10MHz enough to no
> longer be a good reference.

I've done similar things, and yes, it can work.

AM has the least effect, but IRIG has a 3:1 voltage amplitude range, 
so the signal power range is 9 dB, which may or may not matter in 
your application.

One can also use phase modulation and a Costas-loop demodulator.

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

[Charles Steinmetz]

Robert wrote:


What about double shielded RG-223, or Thinnet ethernet cable?
Most Thinnet has both a braided shield and a foil wrap.


IME, thinnet cable is notoriously leaky.  I have also not had success 
with double-shielded cables such as RG-223.


Unless you go all the way to hardline (some of which can be bent to some 
degree for installation), there is not much you can do with shielded 
coax.  No amount of braided and/or foil shielding will really do the job 
effectively.  A braid-and-foil shield (or double-braid + foil) over a 
twisted pair is better, but in practice (for our purposes) not usually 
enough (again, IME).


Properly specified and installed *triaxial* cables can get you there, 
but understand that you would need to change the connectors on your 
instruments to gain the full benefit.  Also understand that proper 
installation of triax cables and connectors is not trivial.


Best regards,

Charles

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[time-nuts] Leviton VTP24 Is this Time Accurate enough? - Line Frequency and TXOs

[Thomas D. Erb]

In Southern California Edison's region I know that 60Hz used as a time 
reference has been unstable in possibly the last 10+ years.  I have found that 
depending on whether in the summer clocks which use this reference tend to run 
slower, and in the winter they run faster.

Have you noticed that in some way it between running fast or slow the gain/loss 
combination averages out over the course of the year?

>
I just check our test board on once a year - haven't been paying attention to 
local variations.

Have to get my old analog master power station Warren Type "B" working - to get 
a better idea.





Don Resor
Thomas D. Erb
p:508-359-4396
f:508-359-4482
a:97 West Street, Medfield, MA 02052 USA
e: t...@electrictime.com
w:www.electrictime.com
Tower & Street Clocks Since 1928

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

[paul swed]

exactly

On Sun, Aug 29, 2021 at 10:45 AM Dana Whitlow  wrote:

> Andy,
>
> Balanced twisted pair may be helpful, but only if adequate precautions are
> taken to
> avoid creation of common mode *currents *on the line*.*
>
> Dana
>
>
> On Sun, Aug 29, 2021 at 9:34 AM Andy Talbot  wrote:
>
> > Hence my observation that balanced twisted pair might be a better
> solution
> > than coax for 10MHz distribution
> > Removes all possibility of ground loops
> >
> > Andy
> > www.g4jnt.com
> >
> >
> >
> > On Sun, 29 Aug 2021 at 15:22, Dana Whitlow 
> wrote:
> >
> > > 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.
> > ___
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> >
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[time-nuts] Re: Query about List and about 10 MHz Distro

[Dana Whitlow]

Andy,

Balanced twisted pair may be helpful, but only if adequate precautions are
taken to
avoid creation of common mode *currents *on the line*.*

Dana


On Sun, Aug 29, 2021 at 9:34 AM Andy Talbot  wrote:

> Hence my observation that balanced twisted pair might be a better solution
> than coax for 10MHz distribution
> Removes all possibility of ground loops
>
> Andy
> www.g4jnt.com
>
>
>
> On Sun, 29 Aug 2021 at 15:22, Dana Whitlow  wrote:
>
> > 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.
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[time-nuts] Re: Query about List and about 10 MHz Distro

[paul swed]

Andy
The balanced line does work and does reduce the emissions on a 160 ft run.
Used it for 1, 5, 10 MHz.
We my only issue is every time we had a lightning storm it seemed to
fry the ICs.
The line drivers and receivers were analog devices ADSL type technology.
Was a bit of a pain to deal with as they were smt devices. Tried various
suppression methods. I am sure there was a way. But I went back to coax.
I have also considered optics. HP had written a paper on using them circa
1990 approx. for frequency distribution.
Regards
Paul
WB8TSL

On Sun, Aug 29, 2021 at 10:34 AM Andy Talbot  wrote:

> Hence my observation that balanced twisted pair might be a better solution
> than coax for 10MHz distribution
> Removes all possibility of ground loops
>
> Andy
> www.g4jnt.com
>
>
>
> On Sun, 29 Aug 2021 at 15:22, Dana Whitlow  wrote:
>
> > 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.
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[time-nuts] Re: About 10 MHz Optical Distro

[Martin Flynn]

Started into white rabbit on fiber recently -  one tidbit that was 
shared with me:  White rabbit typically uses a BIDI over a single fiber 
to keep the fiber length (and respective transmit / receive times) as 
close as possible


Martin

W2RWJ


On 8/29/2021 10:03 AM, paul swed wrote:

I did see the tp link. Pretty amazing. For the group these devices are
pretty useful.
But watch out for the wavelength of the light you typically need matching
fiber. Also note the connectors and get the matching units.
I have no idea how well 1350 light would pass on multimode for 850 nm.
Regards
Paul
WB8TSL

On Sat, Aug 28, 2021 at 11:57 PM Lux, Jim  wrote:


On 8/28/21 7:13 PM, AC0XU (Jim) wrote:

Thanks to all the posters. Especially to Dana -  That is exactly what I

was looking for - suggestions for parts and/or circuits to do the job. I
was originally thinking that I would go with a digital circuit (sine to
square to sine), but maybe analog/sinewave would be simpler and perform
about as well.

Anyway, I have ordered some of the recommended optical transceivers.

We'll see how that works out.

One or two posters mentioned that phase noise and/or thermal stability

may be issues. The referenced research papers don't seem to indicate that
phase noise is a problem. I don't think that thermal effects will be a big
problem for me - I just need to check the phase calibration from time to
time. Certainly there are expensive commerical optical clock distribution
systems with excellent properties. Maybe the devil is in the details...

My specifical application at the moment is putting several SDRs at

diverse antenna locs and feeding the IF via ethernet-converted-to-optical
to my computer. I may want to transmit at some point but receiving is all I
want to do for now. Still need a way to get a stable ref clock to each
radio to provide phase coherence I only need 50-60 meters but an
optical solution with single mode fibers can go many km if I ever wanted to
scale up. Anyway, my plan is to have only power carried by copper.

I don't want to go with coax, twisted pair, or any other copper solution

because of high ambient noise levels in my area and a desire to avoid
adding to it. Stringing several 100 meters of copper about my yard,
carrying 10 MHz clock signals, no matter if the cables are well shielded,
doesn't seem like a great idea.

This is totally the thing that OVRO LWA dealt with.. Not only is fiber a
LOT cheaper than coax, it solves a lot of problems.

Ethernet to fiber is really cheap ($20 for an endpoint from TP-link )
$20 from newegg


https://www.newegg.com/tp-link-mc100cm/p/N82E16833704015?item=N82E16833704015




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[time-nuts] Re: About 10 MHz Optical Distro

[Dana Whitlow]

Paul is right, and it can be difficult to figure out which cable works well
at a given
wavelength and which connector type is which.  A phone conversation with an
applications person at the cable supplier ought to help avoid any of the
traps

At the Arecibo Observatory we had some bad experiences with fiber to
ethernet
converters.
As a class, these things seemed to have problems with UHF/microwave leakage
and often had to be put in properly-shielding enclosures of our own
design.  Of
course, being a radio observatory, we might have been a wee bit more
sensitive
to such EMI than would many garden-variety users :-)

Dana


On Sun, Aug 29, 2021 at 9:04 AM paul swed  wrote:

> I did see the tp link. Pretty amazing. For the group these devices are
> pretty useful.
> But watch out for the wavelength of the light you typically need matching
> fiber. Also note the connectors and get the matching units.
> I have no idea how well 1350 light would pass on multimode for 850 nm.
> Regards
> Paul
> WB8TSL
>
> On Sat, Aug 28, 2021 at 11:57 PM Lux, Jim  wrote:
>
> > On 8/28/21 7:13 PM, AC0XU (Jim) wrote:
> > > Thanks to all the posters. Especially to Dana -  That is exactly what I
> > was looking for - suggestions for parts and/or circuits to do the job. I
> > was originally thinking that I would go with a digital circuit (sine to
> > square to sine), but maybe analog/sinewave would be simpler and perform
> > about as well.
> > >
> > > Anyway, I have ordered some of the recommended optical transceivers.
> > We'll see how that works out.
> > >
> > > One or two posters mentioned that phase noise and/or thermal stability
> > may be issues. The referenced research papers don't seem to indicate that
> > phase noise is a problem. I don't think that thermal effects will be a
> big
> > problem for me - I just need to check the phase calibration from time to
> > time. Certainly there are expensive commerical optical clock distribution
> > systems with excellent properties. Maybe the devil is in the details...
> > >
> > > My specifical application at the moment is putting several SDRs at
> > diverse antenna locs and feeding the IF via ethernet-converted-to-optical
> > to my computer. I may want to transmit at some point but receiving is
> all I
> > want to do for now. Still need a way to get a stable ref clock to each
> > radio to provide phase coherence I only need 50-60 meters but an
> > optical solution with single mode fibers can go many km if I ever wanted
> to
> > scale up. Anyway, my plan is to have only power carried by copper.
> > >
> > > I don't want to go with coax, twisted pair, or any other copper
> solution
> > because of high ambient noise levels in my area and a desire to avoid
> > adding to it. Stringing several 100 meters of copper about my yard,
> > carrying 10 MHz clock signals, no matter if the cables are well shielded,
> > doesn't seem like a great idea.
> >
> > This is totally the thing that OVRO LWA dealt with.. Not only is fiber a
> > LOT cheaper than coax, it solves a lot of problems.
> >
> > Ethernet to fiber is really cheap ($20 for an endpoint from TP-link )
> > $20 from newegg
> >
> >
> >
> https://www.newegg.com/tp-link-mc100cm/p/N82E16833704015?item=N82E16833704015
> >
> >
> >
> >
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[time-nuts] Re: Query about List and about 10 MHz Distro

[Andy Talbot]

Hence my observation that balanced twisted pair might be a better solution
than coax for 10MHz distribution
Removes all possibility of ground loops

Andy
www.g4jnt.com



On Sun, 29 Aug 2021 at 15:22, Dana Whitlow  wrote:

> 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.
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[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  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 
> 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 
> 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  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 
> 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
> >

[time-nuts] Re: About 10 MHz Optical Distro

[paul swed]

I did see the tp link. Pretty amazing. For the group these devices are
pretty useful.
But watch out for the wavelength of the light you typically need matching
fiber. Also note the connectors and get the matching units.
I have no idea how well 1350 light would pass on multimode for 850 nm.
Regards
Paul
WB8TSL

On Sat, Aug 28, 2021 at 11:57 PM Lux, Jim  wrote:

> On 8/28/21 7:13 PM, AC0XU (Jim) wrote:
> > Thanks to all the posters. Especially to Dana -  That is exactly what I
> was looking for - suggestions for parts and/or circuits to do the job. I
> was originally thinking that I would go with a digital circuit (sine to
> square to sine), but maybe analog/sinewave would be simpler and perform
> about as well.
> >
> > Anyway, I have ordered some of the recommended optical transceivers.
> We'll see how that works out.
> >
> > One or two posters mentioned that phase noise and/or thermal stability
> may be issues. The referenced research papers don't seem to indicate that
> phase noise is a problem. I don't think that thermal effects will be a big
> problem for me - I just need to check the phase calibration from time to
> time. Certainly there are expensive commerical optical clock distribution
> systems with excellent properties. Maybe the devil is in the details...
> >
> > My specifical application at the moment is putting several SDRs at
> diverse antenna locs and feeding the IF via ethernet-converted-to-optical
> to my computer. I may want to transmit at some point but receiving is all I
> want to do for now. Still need a way to get a stable ref clock to each
> radio to provide phase coherence I only need 50-60 meters but an
> optical solution with single mode fibers can go many km if I ever wanted to
> scale up. Anyway, my plan is to have only power carried by copper.
> >
> > I don't want to go with coax, twisted pair, or any other copper solution
> because of high ambient noise levels in my area and a desire to avoid
> adding to it. Stringing several 100 meters of copper about my yard,
> carrying 10 MHz clock signals, no matter if the cables are well shielded,
> doesn't seem like a great idea.
>
> This is totally the thing that OVRO LWA dealt with.. Not only is fiber a
> LOT cheaper than coax, it solves a lot of problems.
>
> Ethernet to fiber is really cheap ($20 for an endpoint from TP-link )
> $20 from newegg
>
>
> https://www.newegg.com/tp-link-mc100cm/p/N82E16833704015?item=N82E16833704015
>
>
>
>
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[time-nuts] Re: Query about List and about 10 MHz Distro

[Bob kb8tq]

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  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  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  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  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) 
> 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
>>>

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

[Robert DiRosario]

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  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  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  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) 
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
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