Don't use cheap cables -- a cautionary tale
I was measuring two OCXO and was getting some quite unusual results -- a
symmetrical frequency cycling of several more than 1e11 p-p, with a
period of around 15 seconds.
I removed an RG-58 3 foot jumper cable that fed 5 MHz from the rear
panel of another OCXO to a patch panel (where it was terminated in 50
ohms), and the noise quieted right down. See the attached frequency plot.
The other OXCO had a similar jumper cable in the path, and although the
two cables were not parallel to each other for any significant distance,
there was still enough signal radiation and pickup to cause a nasty problem.
Lesson learned -- use only double-shielded cable in the oscillator rack
(and in any RF measurement path) from now on.
John
Hi
By any chance is the connector a BNC? They have been known to create similar looking issues.
Bob
On Mar 3, 2013, at 9:59 AM, John Ackermann jra@febo.com wrote:
I was measuring two OCXO and was getting some quite unusual results -- a symmetrical frequency cycling of several more than 1e11 p-p, with a period of around 15 seconds.
I removed an RG-58 3 foot jumper cable that fed 5 MHz from the rear panel of another OCXO to a patch panel (where it was terminated in 50 ohms), and the noise quieted right down. See the attached frequency plot.
The other OXCO had a similar jumper cable in the path, and although the two cables were not parallel to each other for any significant distance, there was still enough signal radiation and pickup to cause a nasty problem.
Lesson learned -- use only double-shielded cable in the oscillator rack (and in any RF measurement path) from now on.
John
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Yup, they are BNC (by necessity). I'm still experimenting but it may be
an ill-fitting connector on the cheap patch cable. Switching to a
better quality cable seems to have solved the problem, one way or the other.
John
Bob Camp said the following on 03/03/2013 10:10 AM:
Hi
By any chance is the connector a BNC? They have been known to create similar looking issues.
Bob
On Mar 3, 2013, at 9:59 AM, John Ackermann jra@febo.com wrote:
I was measuring two OCXO and was getting some quite unusual results -- a symmetrical frequency cycling of several more than 1e11 p-p, with a period of around 15 seconds.
I removed an RG-58 3 foot jumper cable that fed 5 MHz from the rear panel of another OCXO to a patch panel (where it was terminated in 50 ohms), and the noise quieted right down. See the attached frequency plot.
The other OXCO had a similar jumper cable in the path, and although the two cables were not parallel to each other for any significant distance, there was still enough signal radiation and pickup to cause a nasty problem.
Lesson learned -- use only double-shielded cable in the oscillator rack (and in any RF measurement path) from now on.
John
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On Mar 3, 2013, at 7:59 AM, John Ackermann jra@febo.com wrote:
Lesson learned -- use only double-shielded cable in the oscillator rack (and in any RF measurement path) from now on.
I've learned that lesson as well. John Miles said that RG-58 is occasionally referred to as 'soaker hose'.
Kevin
Hi
BNC's suffer from shield separation issues and from basic wear out on the connector it's self. Cheap coax = shield seperation. On the connector its self it's either plating or loss of spring in the fingers. The best solution is to cut the connector off the cable. That way at least it doesn't mess you up a second time. Once you get a big enough pile of single ended cables, it's time to get out the crimp tool….
Bob
On Mar 3, 2013, at 10:46 AM, John Ackermann jra@febo.com wrote:
Yup, they are BNC (by necessity). I'm still experimenting but it may be an ill-fitting connector on the cheap patch cable. Switching to a better quality cable seems to have solved the problem, one way or the other.
John
Bob Camp said the following on 03/03/2013 10:10 AM:
Hi
By any chance is the connector a BNC? They have been known to create similar looking issues.
Bob
On Mar 3, 2013, at 9:59 AM, John Ackermann jra@febo.com wrote:
I was measuring two OCXO and was getting some quite unusual results -- a symmetrical frequency cycling of several more than 1e11 p-p, with a period of around 15 seconds.
I removed an RG-58 3 foot jumper cable that fed 5 MHz from the rear panel of another OCXO to a patch panel (where it was terminated in 50 ohms), and the noise quieted right down. See the attached frequency plot.
The other OXCO had a similar jumper cable in the path, and although the two cables were not parallel to each other for any significant distance, there was still enough signal radiation and pickup to cause a nasty problem.
Lesson learned -- use only double-shielded cable in the oscillator rack (and in any RF measurement path) from now on.
John
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On 3/3/13 8:00 AM, Kevin Rosenberg wrote:
On Mar 3, 2013, at 7:59 AM, John Ackermann jra@febo.com wrote:
Lesson learned -- use only double-shielded cable in the oscillator rack (and in any RF measurement path) from now on.
I've learned that lesson as well. John Miles said that RG-58 is occasionally referred to as 'soaker hose'.
RG-58 (which by the way, is a spec that officially no longer exists as
part of MIL-C17-28, ditto for RG-8, RG-213, etc. The military apparently
doesn't use PVC insulated wire any more.) comes in myriad forms all of
which bear a passing resemblance to each other. (leaving aside the
RG-58A, RG-58, RG-58C differences).
The term seems to be used for any 50 ohm single shield coax that's about
0.20 inch in diameter with solid polyethylene insulation. You really
need to look at the specific model number to know what the shielding
looks like. It could be anything from a very loose weave of thin copper
strands to something nice and dense.
Yes, we all have to learn that lesson...
At the time I use bedea RG-223 and Belden H155 with soldered and crimped
Telegaertner BNC connectors as general purpose cable (up to 2 GHz).
Above that frequency I wouldn't use BNC. If you simply connect your
tracking generator with the spectrum analyzer by using such a BNC cable
there's not one that is absolutely stable when stressing the connector.
I tried several manufacturers, HP, Suhner, Radiall, Rosenberger, it's
always the same.
To make precise measurements I prefer screwed connectors like N or SMA.
Volker
Am 03.03.2013 17:30, schrieb Jim Lux:
On 3/3/13 8:00 AM, Kevin Rosenberg wrote:
On Mar 3, 2013, at 7:59 AM, John Ackermann jra@febo.com wrote:
Lesson learned -- use only double-shielded cable in the oscillator
rack (and in any RF measurement path) from now on.
I've learned that lesson as well. John Miles said that RG-58 is
occasionally referred to as 'soaker hose'.
RG-58 (which by the way, is a spec that officially no longer exists as
part of MIL-C17-28, ditto for RG-8, RG-213, etc. The military
apparently doesn't use PVC insulated wire any more.) comes in myriad
forms all of which bear a passing resemblance to each other. (leaving
aside the RG-58A, RG-58, RG-58C differences).
The term seems to be used for any 50 ohm single shield coax that's
about 0.20 inch in diameter with solid polyethylene insulation. You
really need to look at the specific model number to know what the
shielding looks like. It could be anything from a very loose weave of
thin copper strands to something nice and dense.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Hi,
The use of double shielded cables does raise the question to what type of connectors to use?
Regards,
Henk
Op 3 mrt. 2013 om 17:30 heeft Jim Lux jimlux@earthlink.net het volgende geschreven:
On 3/3/13 8:00 AM, Kevin Rosenberg wrote:
On Mar 3, 2013, at 7:59 AM, John Ackermann jra@febo.com wrote:
Lesson learned -- use only double-shielded cable in the oscillator rack (and in any RF measurement path) from now on.
I've learned that lesson as well. John Miles said that RG-58 is occasionally referred to as 'soaker hose'.
RG-58 (which by the way, is a spec that officially no longer exists as part of MIL-C17-28, ditto for RG-8, RG-213, etc. The military apparently doesn't use PVC insulated wire any more.) comes in myriad forms all of which bear a passing resemblance to each other. (leaving aside the RG-58A, RG-58, RG-58C differences).
The term seems to be used for any 50 ohm single shield coax that's about 0.20 inch in diameter with solid polyethylene insulation. You really need to look at the specific model number to know what the shielding looks like. It could be anything from a very loose weave of thin copper strands to something nice and dense.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Alligator clips, of course.
-Bob
On Sun, Mar 3, 2013 at 11:50 AM, Henk ten Pierick henk@deriesp.demon.nlwrote:
Hi,
The use of double shielded cables does raise the question to what type of
connectors to use?
Regards,
Henk
Op 3 mrt. 2013 om 17:30 heeft Jim Lux jimlux@earthlink.net het volgende
geschreven:
On 3/3/13 8:00 AM, Kevin Rosenberg wrote:
On Mar 3, 2013, at 7:59 AM, John Ackermann jra@febo.com wrote:
Lesson learned -- use only double-shielded cable in the oscillator
rack (and in any RF measurement path) from now on.
I've learned that lesson as well. John Miles said that RG-58 is
occasionally referred to as 'soaker hose'.
RG-58 (which by the way, is a spec that officially no longer exists as
part of MIL-C17-28, ditto for RG-8, RG-213, etc. The military apparently
doesn't use PVC insulated wire any more.) comes in myriad forms all of
which bear a passing resemblance to each other. (leaving aside the RG-58A,
RG-58, RG-58C differences).
The term seems to be used for any 50 ohm single shield coax that's about
0.20 inch in diameter with solid polyethylene insulation. You really need
to look at the specific model number to know what the shielding looks like.
It could be anything from a very loose weave of thin copper strands to
something nice and dense.
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Some of the older synchronised signal generators (2-box systems) e.g
Marconi, used TNC connectors with solid coax where signal leakage was likely
to be a problem.
Alan G3NYK
----- Original Message -----
From: "Volker Esper" ailer2@t-online.de
To: time-nuts@febo.com
Sent: Sunday, March 03, 2013 6:49 PM
Subject: Re: [time-nuts] Don't use cheap cables -- a cautionary tale
Yes, we all have to learn that lesson...
At the time I use bedea RG-223 and Belden H155 with soldered and crimped
Telegaertner BNC connectors as general purpose cable (up to 2 GHz). Above
that frequency I wouldn't use BNC. If you simply connect your tracking
generator with the spectrum analyzer by using such a BNC cable there's not
one that is absolutely stable when stressing the connector. I tried
several manufacturers, HP, Suhner, Radiall, Rosenberger, it's always the
same.
To make precise measurements I prefer screwed connectors like N or SMA.
Volker
I've previously encountered noise from mechanical movement of BNCs. You
can definitely see noise bursts when you move a BNC cable around.
Replacing TNC-BNC adapters and BNC-BNC cables at the analyzer with real
TNC to SMA cables, and SMA to BNC adapters on the far end when
necessary, solved a lot of those problems.
But this was the first time I've seen a continuous beat-note type of
interference that I could trace to the cabling.
As a follow-on topic -- I wonder if the leakage problem would also be
significant in a PPS distribution/measurement system (vs 5 or 10 MHz
RF). I'd think that working with pulses and using a defined trigger
level might mitigate that, but as I contemplate my rat's nest of PPS
cabling I wonder if there could still be problems.
John
Alan Melia said the following on 03/03/2013 03:36 PM:
Some of the older synchronised signal generators (2-box systems) e.g
Marconi, used TNC connectors with solid coax where signal leakage was
likely to be a problem.
Alan G3NYK
----- Original Message ----- From: "Volker Esper" ailer2@t-online.de
To: time-nuts@febo.com
Sent: Sunday, March 03, 2013 6:49 PM
Subject: Re: [time-nuts] Don't use cheap cables -- a cautionary tale
Yes, we all have to learn that lesson...
At the time I use bedea RG-223 and Belden H155 with soldered and
crimped Telegaertner BNC connectors as general purpose cable (up to 2
GHz). Above that frequency I wouldn't use BNC. If you simply connect
your tracking generator with the spectrum analyzer by using such a BNC
cable there's not one that is absolutely stable when stressing the
connector. I tried several manufacturers, HP, Suhner, Radiall,
Rosenberger, it's always the same.
To make precise measurements I prefer screwed connectors like N or SMA.
Volker
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
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and follow the instructions there.
Fahnestock clips?
-----Original Message-----
From: time-nuts-bounces@febo.com
[mailto:time-nuts-bounces@febo.com] On Behalf Of Robert Darlington
Sent: Sunday, March 03, 2013 11:04
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Don't use cheap cables -- a cautionary tale
Alligator clips, of course.
-Bob
On Sun, Mar 3, 2013 at 11:50 AM, Henk ten Pierick
henk@deriesp.demon.nlwrote:
Hi,
The use of double shielded cables does raise the question
to what type of
connectors to use?
Regards,
Henk
Op 3 mrt. 2013 om 17:30 heeft Jim Lux
jimlux@earthlink.net het volgende
geschreven:
On 3/3/13 8:00 AM, Kevin Rosenberg wrote:
On Mar 3, 2013, at 7:59 AM, John Ackermann jra@febo.com wrote:
Lesson learned -- use only double-shielded cable in the
oscillator
rack (and in any RF measurement path) from now on.
I've learned that lesson as well. John Miles said that RG-58 is
occasionally referred to as 'soaker hose'.
RG-58 (which by the way, is a spec that officially no
longer exists as
part of MIL-C17-28, ditto for RG-8, RG-213, etc. The
military apparently
doesn't use PVC insulated wire any more.) comes in myriad
forms all of
which bear a passing resemblance to each other. (leaving
aside the RG-58A,
RG-58, RG-58C differences).
The term seems to be used for any 50 ohm single shield
coax that's about
0.20 inch in diameter with solid polyethylene insulation.
You really need
to look at the specific model number to know what the
shielding looks like.
It could be anything from a very loose weave of thin
copper strands to
something nice and dense.
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
On 3/3/13 1:41 PM, DaveH wrote:
Fahnestock clips?
Alligator clips, of course.
But, I looked through the connector catalogs and I didn't see any double
shielded Fahnestock OR Alligator clips..
More seriously, you hook both shields to the shield of the connector.
Unless you want to get Triax connectors or use Tip/Ring/Sleeve 1/4" or
1/8" phone plugs. They're used for shielded twisted pair kinds of
applications as well (MIL-STD-1553B, for instance) and for audio
applications.
RG-223 fits with Telegaertner J01000B0608 (Solder), Buerklin 78F201
or Rosenberger 51S107-108N4 (Crimp)
(straight plugs BNC)
H155 fits with Telegaertner T00100B3300 N Crimp)
...
Am 03.03.2013 19:50, schrieb Henk ten Pierick:
Hi,
The use of double shielded cables does raise the question to what type of connectors to use?
Regards,
Henk
Op 3 mrt. 2013 om 17:30 heeft Jim Luxjimlux@earthlink.net het volgende geschreven:
On 3/3/13 8:00 AM, Kevin Rosenberg wrote:
On Mar 3, 2013, at 7:59 AM, John Ackermannjra@febo.com wrote:
Lesson learned -- use only double-shielded cable in the oscillator rack (and in any RF measurement path) from now on.
I've learned that lesson as well. John Miles said that RG-58 is occasionally referred to as 'soaker hose'.
RG-58 (which by the way, is a spec that officially no longer exists as part of MIL-C17-28, ditto for RG-8, RG-213, etc. The military apparently doesn't use PVC insulated wire any more.) comes in myriad forms all of which bear a passing resemblance to each other. (leaving aside the RG-58A, RG-58, RG-58C differences).
The term seems to be used for any 50 ohm single shield coax that's about 0.20 inch in diameter with solid polyethylene insulation. You really need to look at the specific model number to know what the shielding looks like. It could be anything from a very loose weave of thin copper strands to something nice and dense.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
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and follow the instructions there.
Noise bursts come from the rubbing of the shield on the dielectric. Try
putting some rg58 on the input of a guitar amp :-)
Even "low-noise" rg58 type coax is noisy; it has some graphite on the
dielectric supposedly to suppress the triboelectric (rubbing) noise. You
might think Teflon would be quiet, but not so.
Don
John Ackermann
I've previously encountered noise from mechanical movement of BNCs. You
can definitely see noise bursts when you move a BNC cable around.
Replacing TNC-BNC adapters and BNC-BNC cables at the analyzer with real
TNC to SMA cables, and SMA to BNC adapters on the far end when
necessary, solved a lot of those problems.
But this was the first time I've seen a continuous beat-note type of
interference that I could trace to the cabling.
As a follow-on topic -- I wonder if the leakage problem would also be
significant in a PPS distribution/measurement system (vs 5 or 10 MHz
RF). I'd think that working with pulses and using a defined trigger
level might mitigate that, but as I contemplate my rat's nest of PPS
cabling I wonder if there could still be problems.
John
Alan Melia said the following on 03/03/2013 03:36 PM:
Some of the older synchronised signal generators (2-box systems) e.g
Marconi, used TNC connectors with solid coax where signal leakage was
likely to be a problem.
Alan G3NYK
----- Original Message ----- From: "Volker Esper" ailer2@t-online.de
To: time-nuts@febo.com
Sent: Sunday, March 03, 2013 6:49 PM
Subject: Re: [time-nuts] Don't use cheap cables -- a cautionary tale
Yes, we all have to learn that lesson...
At the time I use bedea RG-223 and Belden H155 with soldered and
crimped Telegaertner BNC connectors as general purpose cable (up to 2
GHz). Above that frequency I wouldn't use BNC. If you simply connect
your tracking generator with the spectrum analyzer by using such a
BNC
cable there's not one that is absolutely stable when stressing the
connector. I tried several manufacturers, HP, Suhner, Radiall,
Rosenberger, it's always the same.
To make precise measurements I prefer screwed connectors like N or
SMA.
Volker
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--
"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
De Erroribus Medicorum, R. Bacon, 13th century.
"If you don't know what it is, don't poke it."
Ghost in the Shell
Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
www.lightningforensics.com
www.sixmilesystems.com