2 Jan
2022
2 Jan
'22
9:12 a.m.
Hi all,
I'm thinking about building a GPS-disciplined 10 MHz reference
oscillator. Of course, I'd like to add some networking features to it :-)
NTP server is the most obvious, and is well documented.
But I'd like to be able to carry 10 MHz reference signal to various
locations in the shack over network cabling. My first idea is about
using existing converters for TV/SAT :
- RF to Ethernet passive couplers (a F connector tied to pins 1-2 of a
RJ45 connector, $1 on Chinese warehouses). Will it work at 10 MHz ?
Anyway, I do not have any idea about whether it will work or not while
maintaining the reference/stability purpose of the 10 MHz signal.
Any suggestions ?
HNY & 73 de TK1BI
2 Jan
2 Jan
9:50 a.m.
Interesting idea... So I see three potential issues:Impedance, cat3-> cat6 cabling
Impedance is 100 ohmsUnbalanced to balanced, coax is unbalanced, twisted pair is balanced.
If you can convert from unbalanced to balanced it could work. If it is out of balance
you'll have that reference signal radiating from the line.Topology, twisted pair is
normally run in a star configuration, but that requires a Impedance matching hub in the
middle. You'll need to design and add that to drive multiple devices.I've never
seen a cheap cat45 to f converter that actually had the right circuits to be clean. I used
some for extending cctv signals and there was always ringing on the signal showing the 75
to 100 ohm and back mismatch. I worry that ringing might affect your oscillator lock
accuracy. However, I bet if you built a active signal hub using op amps to drive the
differential signal down the twisted pair you could get away with the single Impedance
bump at the client device end. If you went with a more careful balun at the client devices
that did a 2:1 Impedance adjustment it would be perfect.Good luck, it sounds like a fun
project...73Bill Buhler - AF7SJSent from my Galaxy
-------- Original message --------From: Toussaint OTTAVI via 44Net
<44net(a)mailman.ampr.org> Date: 1/2/22 7:12 AM (GMT-07:00) To: AMPRNet working
group <44net(a)mailman.ampr.org> Cc: Toussaint OTTAVI <t.ottavi(a)bc-109.com>
Subject: [44net] Carrying 10 MHz reference clock over network ? Hi all,I'm thinking
about building a GPS-disciplined 10 MHz reference oscillator. Of course, I'd like to
add some networking features to it :-)NTP server is the most obvious, and is well
documented.But I'd like to be able to carry 10 MHz reference signal to various
locations in the shack over network cabling. My first idea is about using existing
converters for TV/SAT :- RF to Ethernet passive couplers (a F connector tied to pins 1-2
of a RJ45 connector, $1 on Chinese warehouses). Will it work at 10 MHz ?Anyway, I do not
have any idea about whether it will work or not while maintaining the reference/stability
purpose of the 10 MHz signal.Any suggestions ?HNY & 73 de
TK1BI_________________________________________44Net mailing
list44Net@mailman.ampr.orghttps://mailman.ampr.org/mailman/listinfo/44net
10:27 a.m.
Le 02/01/2022 à 15:50, Bill Buhler a écrit :
Impedance, cat3-> cat6 cabling Impedance is 100 ohms
$1 Chinese adapters seem to be direct-connect of the coax connector to
pins 1-2 of RJ45, HI :-) Anyway, it's just a matter of 2:1 balun, so it
should be doable easily.
Topology, twisted pair is normally run in a star configuration, but
that requires a Impedance matching hub in the middle. You'll need to
design and add that to drive multiple devices.
Some existing GPSDO already have several outputs, that should not be a
problem. I won't redesign the GPSDO from scratch, I'll probably
integrate some existing modules around a RPi or ESP8266 for management.
I've never seen a cheap cat45 to f converter that actually had the
right circuits to be clean.
I saw adapters called "baluns" for satellite distribution over RJ45 on
electrical equipment catalogs. But if they really contain a balun, it
would be for 75 Ohms, so not usable directly.
The other (maybe promising) idea would be to use fiber adapters, that
would in the meantime avoid RFI, QRM and ligntning...
Good luck, it sounds like a fun project...
My interest is mostly in digital modes, computing, SDR, satellite,
etc... Most of those things require frequency stability, so having a 10
MHz signal available everywhere in the shack seems to be something
future-proof :-)
Moreover, "HF over fiber" is also something I am interested in for the
future. If the lightning strikes, I'd prefer it to stay outside of the
shack :-) Carrying 10 MHz over fiber may be a good start point.
73 de TK1BI
11:18 a.m.
Are you distributing square waves or sine waves?
Not sure why use cat5 for the distribution?
RG58 and BNC is inexpensive, and conventional. And was up to date for networking in 1990
;)
I bet RG6 and F connectors would work, caveat being stay away from lengths that would
transform 50 ohm impedance.
Does that really matter? I looked at my sources through a long RG59 lab cable; no
discernable difference vs RG58
I use DEMI distribution amplifiers. 1 in, 4 out (star), MAR-1 MMIC amps and good
filtering really cleans up the input. For example, several of my OCXOs have measurable 2x
and 3x harmonics, the DEMI really cleans up the signal.
This is a fascinating area. If you haven't already, subscribe to the "time
nuts" email list.
Cliff K6CLS CM87
On January 2, 2022 7:27:50 AM PST, Toussaint OTTAVI via 44Net
<44net(a)mailman.ampr.org> wrote:
Le 02/01/2022 à 15:50, Bill Buhler a écrit :
Impedance, cat3-> cat6 cabling Impedance is 100 ohms
$1 Chinese adapters seem to be direct-connect of the coax connector to
pins 1-2 of RJ45, HI :-) Anyway, it's just a matter of 2:1 balun, so it
should be doable easily.
Topology, twisted pair is normally run in a star configuration, but
that requires a Impedance matching hub in the middle. You'll need to
design and add that to drive multiple devices.
Some existing GPSDO already have several outputs, that should not be a
problem. I won't redesign the GPSDO from scratch, I'll probably
integrate some existing modules around a RPi or ESP8266 for management.
I've never seen a cheap cat45 to f converter that actually had the
right circuits to be clean.
I saw adapters called "baluns" for satellite distribution over RJ45 on
electrical equipment catalogs. But if they really contain a balun, it
would be for 75 Ohms, so not usable directly.
The other (maybe promising) idea would be to use fiber adapters, that
would in the meantime avoid RFI, QRM and ligntning...
Good luck, it sounds like a fun project...
My interest is mostly in digital modes, computing, SDR, satellite,
etc... Most of those things require frequency stability, so having a 10
MHz signal available everywhere in the shack seems to be something
future-proof :-)
Moreover, "HF over fiber" is also something I am interested in for the
future. If the lightning strikes, I'd prefer it to stay outside of the
shack :-) Carrying 10 MHz over fiber may be a good start point.
73 de TK1BI
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44Net mailing list
44Net(a)mailman.ampr.org
https://mailman.ampr.org/mailman/listinfo/44net 
12:25 p.m.
On Sun, 2 Jan 2022, Toussaint OTTAVI via 44Net wrote:
Hi all,
I'm thinking about building a GPS-disciplined 10 MHz reference
oscillator. Of course, I'd like to add some networking features to it
:-)
NTP server is the most obvious, and is well documented.
But I'd like to be able to carry 10 MHz reference signal to various
locations in the shack over network cabling. My first idea is about
using existing converters for TV/SAT : - RF to Ethernet passive
couplers (a F connector tied to pins 1-2 of a RJ45 connector, $1 on
Chinese warehouses). Will it work at 10 MHz ?
Anyway, I do not have any idea about whether it will work or not while
maintaining the reference/stability purpose of the 10 MHz signal.
You need to be lookng at PTP if you're using a high stability clock and
distributing it to PTP consumers:
https://sourceforge.net/p/ptpd/wiki/Home/
PTP daemons tend to support NTP as a fall-back protocol.
73,
--
Kris Kirby, KE4AHR
Disinformation Architect, Systems Mangler, & Network Mismanager
868
days inactive
868
days old
4 comments
4 participants
participants (4)
-
Bill Buhler -
Cliff Sojourner -
Kris Kirby -
Toussaint OTTAVI