date:20151219


Tim,

There is two major strategies as you build a system and needs to figure 
out how your ground bonding network (often just referred to bonding 
network or grounding) should operate.


The isolation strategy says that the various equipments should only be 
power grounded, as required for personal safety, and then have all other 
grounding paths "galvanically separated" (thus, DC and power frequencies 
separated in common mode).


The mesh strategy says that you extend the grounding of the power ground 
with additional grounding with every cable and additional grounding 
cables. This strategy strengthen with every cable you pull, as the 
conductance increases. Any potential difference produce a current that 
is current shared by the shunted conductors. It is common to explicitly 
add main grounding conductors to take the main current and reduce the 
current on other cables.


The difficulty with the isolation strategy is that if you happens to 
make contact with ground, you can now be the source of a large current 
to average out the potential, and that may not be what you want to see 
on your coax cable for instance. We have pointed out that it may not be 
so nice that we have sparks jumping the connectors on broadcast 
equipment, as we saw once.


Another difficulty with the isolation strategy is that it makes the EMC 
aspect harder to do, as you want the shield of your cable to extend the 
shield of your box, and not become a source of energy emitting out on 
the cable and thus be a conducted source of RF emission (and reception).
The RF choke with associated capacitance (or conductance, the important 
being low-impedance path) on both sides is the way to go to achieve good 
common mode RF rejection.


In the mesh strategy, you can skip transformers most of the time and 
only use RF chokes, and then mostly to decouple the chassi and PCB 
RF-wise on common mode.


Measurement instruments is most of the times built for the mesh 
strategy, with BNC/SMA/N connectors hard-tied to the chassi. There is 
the braindead idea to cut the chassi to ground connection, which do make 
some measurements easier, but kills the safety. If you follow the mesh 
strategy, you have the star-ground of the power-system complemented with 
additional grounding wires of the racks etc.
So, you wire your instruments together, and then provide multiple ground 
connections to your DUT. You need to figure out how to avoid common mode 
to differential mode conversions, but that is not unique to the mesh BN 
strategy, it's even more important in the isolation BN strategy as you 
have higher potentials to isolate.


Even when having the majority of the rig being mesh BN style, for some 
measurement connections it can be beneficial to do DC separation of 
common mode, in which case transformers or capacitors can provide 
isolation. I prefer to use differential amps when possible, and for some 
reason the 1 GHz differential probe is often used in the lab.


As a reference, Ethernet is designed to work in an isolation BN setup, 
because the Ethernet connections often span over an office building, 
between different branches of the power distribution for which the 
grounding wires can have quite different potential and hence there being 
a potential difference that can produce a sizeable current. It also runs 
in environments where typical does not understand grounding issues, and 
where by local code and design of equipment, they have a star grounding 
network and no concept of interconnection between consumers (think of 
lamps, radiators, kitchen stoves and ovens and similar "simple" devices).


Also recall that the first rule of thumb for electrical safety is that 
the first connection you make to a box is ground, and the last 
connection you remove is to ground. Thus, a box shall at least be 
grounded for safety, and only when grounded it will receive power, from 
anywhere.


There is more war-stories to be told.

Cheers,
Magnus

On 12/19/2015 03:23 PM, Tim Shoppa wrote:

I think there is a valid heritage in transformer isolation in time and
frequency distribution, and it goes back to when telephone wiring was
used to distribute audio-type IRIG signals around a campus or other
facility. Even if a bunch of 60Hz or a local AM station was leaking
through the IRIG signaling was quite impervious to it. (Heh, the
aircraft VHF radio getting into Spinal Tap's lead guitar was hardly
noticeable at that air force base, for that matter!!!)

But something feels "off" with lifting grounds on coax if the
environment is just a test lab.

CAT 5/6 and Ethernet transformers work great at 10MHz but most all test
equipment is expecting coax and a BNC.

Tim N3QE

On Sat, Dec 19, 2015 at 8:29 AM, Magnus Danielson
> wrote:

Transformer isolation isn't helping much at RF, as you will
capacitively couple through the transformer. I've been bitten by
that in real life, as I was called in

Re: [time-nuts] Anybody who can record last Loran-C transmissions ?

2015-12-19 Thread Jörg Logemann

I could make a raw capture with a 14bit Perseus or 16bit Elad FDM-S2 and
a good active receiving antenna, but the station I can receive very
strong is Sylt here in Germany. As far as I know this station will not
shut down...

73 Joerg, DL2NI

Am 19.12.2015 um 12:25 schrieb Magnus Danielson:
> Hi Poul-Henning,
>
> On 12/19/2015 11:35 AM, Poul-Henning Kamp wrote:
>> It doesn't seem like my old hack to record VLF spectrum works anymore.
>>
>> Are there anybody in Europe who can do a raw capture of the VLF spectrum
>> over new years eve to capture the last LORAN-C transmissions as a
>> historical document ?
>>
>> Ideally a 1 MSPS ADC directly on a good antenna, but failing that just
>> a water-fall would be nice...
>>
>
> Nice idea. An SDR with the HF mod would probably be the simplest way
> to do it. As the Loran-C stations lay on top of each other, using a
> multi-station Loran-C receiver in parallel would be nice. The 8000
> chain should suddenly be quite alone.
>
> Cheers,
> Magnus
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-- 
Dipl.Ing.(FH) Jörg Logemann 
Veilchenstraße 3 
D-89150 Laichingen 
Germany 
Tel. +49 7333 922506 
Mobil  +49 171 2814359
Fax. +49 7333 922507 
mail: joerg.logem...@t-online.de

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Re: [time-nuts] SMD TADD-1 distribution amplifier - seeking comments and suggestions?


Poul-Henning,

On 12/19/2015 03:58 PM, Poul-Henning Kamp wrote:


In message <56755ba1.7000...@rubidium.dyndns.org>, Magnus Danielson writes:


There is an over believe in isolation, as it only takes one mistake to
break the system. Another approach is to ground everything, cross-ground
etc. and bring the DC/power-spurs down through conduction.


Tony Waldron argued similar for audio systems:

http://www.fragrantsword.com/twaudio/



Haven't seen those, but it looks like a nice reading.
He uses the mesh-BN terminology.

One document to read is the ITU-T K.27 which is for free download here:
https://www.itu.int/rec/T-REC-K.27/en

The ISO/IEC/CENELEC standards often referred to is something you have to 
pay for, but the ITU-T stuff is for free, so it's a good starting point.


Cheers,
Magnus
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Re: [time-nuts] FE-5680A Breakout board

2015-12-19 Thread John Ackermann N8UR


Hi Ian --

Happy holidays!

A few years ago I got some of the breakout board kits you did for the 
FE-5680A.  They've finally risen to the top of my "to assemble pile." :-)


Looking for the schematic and any assembly info you might have available 
-- I only have the boards and parts but can't find the docs.


Thanks and 73,
John

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Re: [time-nuts] SMD TADD-1 distribution amplifier - seeking comments and suggestions?


Poul-Henning,

On 12/19/2015 10:11 PM, Poul-Henning Kamp wrote:


In message <56757344.2020...@rubidium.se>, Magnus Danielson writes:


The isolation strategy says that the various equipments should only be
power grounded, as required for personal safety, and then have all other
grounding paths "galvanically separated" (thus, DC and power frequencies
separated in common mode).

The mesh strategy says that you extend the grounding of the power ground
with additional grounding with every cable and additional grounding
cables.


Please bear in mind that there is a *huge* difference between
single-ended (as in: RF-Coax-BNC) and balanced (as in: Audio-Twinax-XLR)
for both of these scenarios.

While you can get away with the isolation strategy with balanced,
because you have high CMRR inputs, there is nothing to "take care
of" the ground potentials in the single-ended mode.


Oh yes, indeed. I've worked both fields.


As a reference, Ethernet is designed to work in an isolation BN setup,
[...]


That is actually a new thing, the original Ethernet was 1/2" coax
and ground-loops and lightning damage was the order of the day.


Well, it's been a long time since that was Ethernet.


The main reason Ethernet went balanced was actually for fault
isolation (star-topology vs. bus) and signal quality (IT people
were horrible at "sharking" and crimping coax.)


The way they destroyed yellow cable with their attempts to drill for 
their vampire... yes. I've seen that too.


Cheers,
Magnus
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Re: [time-nuts] End of Loran-C in Europe confirmed.

Hi

Each navigation chain requires 4 stations for navigation (one master to supply 
timing and three slaves to triangulate against). For reasonable navigation 
solutions
you are limited to an area much smaller than the entire US. You can get a bit 
more
distance over an “all water” path (it’s more predictable / easier to correct). 
Even so,
it will take a half dozen or so chains to cover the US.



The real issue here is not the death of Loran providers, but the death of Loran 
users.
When they go out and ask “how much do you need Loran?” and the answers mostly 
come
back “what’s Loran? I use GPS all the time…”. That’s the root of the problem. 
The active GPS “user 
group” is probably 99.xxx% of the population. The “aware I use GPS” user group 
is probably 
>75% of the population. The active Loran users (pre shutdown) … probably < 
>0.25%.

Bob

> On Dec 19, 2015, at 1:17 PM, paul swed  wrote:
> 
> It is very sorry to hear that this is happening.
> This was the same lame excuse they used in the US. Save 2 cents then find
> out you don't have launch vehicles to get replacement GPS satellites in
> orbit. Nor the funds to build the satellites.
> I am actually happy I did not build the large loop for European reception.
> As it would have just started working and then stopped.
> eLORAN  for at least frequency and timing needs 1 station. So if thats the
> application then with whats left there can be a very good distribution of
> these two components as we see here in the US with 1 station doing eLORAN
> testing and thats not even a full power station.
> Oddly the US may be coming around to eLORAN. It seems promissing.
> Rightly stated for navigation you need more stations. I think in teh past
> it was 24. But appears that 4 will cover the US and thats a lot of area.
> All of the Westcoast stations are intact. The East coast has been gutted
> and many antennas are down. But enough exist for eLORAN.
> Long strange trip we are on. My fingers are crossed for eLORAN.
> Regards
> Paul
> WB8TSL
> 
> On Fri, Dec 18, 2015 at 10:13 AM, Poul-Henning Kamp 
> wrote:
> 
>> 
>> In message <5673c1bd.6070...@rubidium.dyndns.org>, Magnus Danielson
>> writes:
>> 
>>> It seems like the biggest problem for Loran-C is that they have not been
>>> able to build an economical model to support it. That it complements the
>>> GPS and GLONASS systems, as well as GALILEO in a somewhat different mode
>>> disturbance is a technical detail which doesn't ripple though the reports.
>> 
>> No, it's really very simple, in Europe it is all about saving face.
>> 
>> The political bluff which should have moved GPS control to NATO
>> rather than DoD failed, and forced the EU to follow through.
>> 
>> Finding the claimed eager private investors failed predictably and in
>> the end EU had to fund Galileo with tax money, precisely like pretty
>> much every had predicted.
>> 
>> Then the draft European Radio Navigation Plan said that at few
>> millions on LORAN produced 40% of the benefit while all the billions
>> for Galileo hardly produced any[1].
>> 
>> In other words:  Some almost-pensioners with 50 year old cold-war
>> tech were about 100 times more cost-efficient than the biggest
>> political prestige project of EU's history.
>> 
>> No wonder all copies of that draft has vanished from the surface
>> of the planet.
>> 
>> Poul-Henning
>> 
>> [1] The two lost/marooned Galileo sats have cost about the same as
>> updating and running Loran-C for 10-15 years would have.
>> 
>> --
>> 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.
>> ___
>> 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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Re: [time-nuts] SMD TADD-1 distribution amplifier - seeking comments and suggestions?

Hi

There is a very significant difference between coax and twisted pair when it 
comes
to magnetic induction. The twist “cancels out” the signal on the pair. The 
shield has
the signal induced on it’s outer surface. Transformers work better on twisted 
pair than
on coax. If you look at a “normal” ethernet twisted pair interface (magnetics) 
you will 
likely see both a transformer and a common mode choke inside. That of course 
assumes
that the schematic is showing you what really is in there. Even with twisted 
pair the 
choke helps.

Bob


> On Dec 19, 2015, at 9:23 AM, Tim Shoppa  wrote:
> 
> I think there is a valid heritage in transformer isolation in time and
> frequency distribution, and it goes back to when telephone wiring was used
> to distribute audio-type IRIG signals around a campus or other facility.
> Even if a bunch of 60Hz or a local AM station was leaking through the IRIG
> signaling was quite impervious to it. (Heh, the aircraft VHF radio getting
> into Spinal Tap's lead guitar was hardly noticeable at that air force base,
> for that matter!!!)
> 
> But something feels "off" with lifting grounds on coax if the environment
> is just a test lab.
> 
> CAT 5/6 and Ethernet transformers work great at 10MHz but most all test
> equipment is expecting coax and a BNC.
> 
> Tim N3QE
> 
> On Sat, Dec 19, 2015 at 8:29 AM, Magnus Danielson <
> mag...@rubidium.dyndns.org> wrote:
> 
>> Transformer isolation isn't helping much at RF, as you will capacitively
>> couple through the transformer. I've been bitten by that in real life, as I
>> was called in to solve issues in someone elses design. It was only when I
>> introduced an RF choke that we got conducted noise battled. It's also not
>> enough, as the RF choke needs an RF path to ground in order to start
>> rejecting effectively, which was the issue another time, so you want an RF
>> choke with caps to ground on the inside.
>> 
>> The galvanic isolation can be done using transformer or capacitors after
>> that.
>> 
>> There is an over believe in isolation, as it only takes one mistake to
>> break the system. Another approach is to ground everything, cross-ground
>> etc. and bring the DC/power-spurs down through conduction. It have proven
>> itself easier to ensure RF properties when shield and chassi is tied hard
>> to each other, as it provides good RF conduction and the cable does not act
>> like an antenna against the shield for the RF power being unbalanced. The
>> RF choke then acts to separate the chassi RF from that of the board,
>> assisting in the balance.
>> 
>> Transformers can provide RF shielding, if they have double shields between
>> the coils, and where the shield of each side is connected to it's ground.
>> That way each coil will capacitively terminate in it's own shield, and the
>> remaining capacitive coupling will mainly be between the shields and hence
>> grounds. I rarely see people doing this.
>> 
>> I've been bitten multiple times by the capacitive coupling in
>> transformers, and only when I found a way to handle it things have started
>> to work. It's not all magnetics.
>> 
>> Cheers,
>> Magnus
>> 
>> 
>> On 12/19/2015 12:33 AM, Tim Shoppa wrote:
>> 
>>> All the inputs and outputs were deliberately transformer isolated. Why
>>> break the isolation by using capacitor from coax shield to chassis ground?
>>> 
>>> I do realize that some isolation transformers have "extra floating turns"
>>> to give transformer action that cancels stray capacitive coupling. I don't
>>> think the capacitors tying coax shield to chassis ground can serve that
>>> purpose.
>>> 
>>> Tim N3QE
>>> 
>>> On Mon, Nov 30, 2015 at 3:02 PM, Anders Wallin <
>>> anders.e.e.wal...@gmail.com>
>>> wrote:
>>> 
>>> HI all,
 I need to build a few distribution amplifiers (>90% for 10MHz, sometimes
 maybe 5MHz) and instead of reinventing the wheel I decided to try to
 modernize the TADD-1 into an all (almost) SMD design. Here are some draft
 sketches:
 
 
 http://www.anderswallin.net/2015/11/frequency-distribution-amplifier-plans-a-k-a-smd-tadd-1/
 
 Does this sound/look reasonable or crazy?
 Any suggestions for op-amps to try and/or compare to the AD8055?
 What causes the extra phase-noise below 1 Hz offset in John A's result:
 
 https://www.febo.com/pages/amplifier_phase_noise/amplifier_phase_noise.png
 
 Suggestions for a low noise DC-regulator circuit? The 12-24VDC supplied
 to
 this board will most likely come from a switched-mode PSU, so filtering
 of
 common-mode noise is mandatory.
 I found the TI LP38798 shown in the schematic by googling - if someone
 has
 a proven a measured design that would be a safer choice. In any case more
 filtering (e.g. ferriites) is probably a good idea.
 
 This design will be available on my blog or on github when it is done -
 if
 anyone is interested.
 
 Thanks,
 Anders

Re: [time-nuts] Anybody who can record last Loran-C transmissions ?


In message <56758aa9.6000...@lai.de>, =?UTF-8?Q?J=c3=b6rg_Logemann?= writes:

>I could make a raw capture with a 14bit Perseus or 16bit Elad FDM-S2 and
>a good active receiving antenna, but the station I can receive very
>strong is Sylt here in Germany. As far as I know this station will not
>shut down...

I have not been able to find any announcements about Sylt either, but
it would be truly strange if that single station continues running...


-- 
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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Re: [time-nuts] Anybody who can record last Loran-C transmissions ?

2015-12-19 Thread Rob Sherwood .

The Perseus has a higher dynamic range than the Elad, if that matters.  Rob, 
NC0B

Sent from my iPad

> On Dec 19, 2015, at 1:30 PM, "Jörg Logemann"  wrote:
> 
> 
> 
> I could make a raw capture with a 14bit Perseus or 16bit Elad FDM-S2 and
> a good active receiving antenna, but the station I can receive very
> strong is Sylt here in Germany. As far as I know this station will not
> shut down...
> 
> 73 Joerg, DL2NI
> 
>> Am 19.12.2015 um 12:25 schrieb Magnus Danielson:
>> Hi Poul-Henning,
>> 
>>> On 12/19/2015 11:35 AM, Poul-Henning Kamp wrote:
>>> It doesn't seem like my old hack to record VLF spectrum works anymore.
>>> 
>>> Are there anybody in Europe who can do a raw capture of the VLF spectrum
>>> over new years eve to capture the last LORAN-C transmissions as a
>>> historical document ?
>>> 
>>> Ideally a 1 MSPS ADC directly on a good antenna, but failing that just
>>> a water-fall would be nice...
>> 
>> Nice idea. An SDR with the HF mod would probably be the simplest way
>> to do it. As the Loran-C stations lay on top of each other, using a
>> multi-station Loran-C receiver in parallel would be nice. The 8000
>> chain should suddenly be quite alone.
>> 
>> Cheers,
>> Magnus
>> ___
>> 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.
> 
> -- 
> Dipl.Ing.(FH) Jörg Logemann 
> Veilchenstraße 3 
> D-89150 Laichingen 
> Germany 
> Tel. +49 7333 922506 
> Mobil  +49 171 2814359
> Fax. +49 7333 922507 
> mail: joerg.logem...@t-online.de
> 
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Re: [time-nuts] End of Loran-C in Europe confirmed.

2015-12-19 Thread paul swed

It is very sorry to hear that this is happening.
This was the same lame excuse they used in the US. Save 2 cents then find
out you don't have launch vehicles to get replacement GPS satellites in
orbit. Nor the funds to build the satellites.
I am actually happy I did not build the large loop for European reception.
As it would have just started working and then stopped.
eLORAN  for at least frequency and timing needs 1 station. So if thats the
application then with whats left there can be a very good distribution of
these two components as we see here in the US with 1 station doing eLORAN
testing and thats not even a full power station.
Oddly the US may be coming around to eLORAN. It seems promissing.
Rightly stated for navigation you need more stations. I think in teh past
it was 24. But appears that 4 will cover the US and thats a lot of area.
All of the Westcoast stations are intact. The East coast has been gutted
and many antennas are down. But enough exist for eLORAN.
Long strange trip we are on. My fingers are crossed for eLORAN.
Regards
Paul
WB8TSL

On Fri, Dec 18, 2015 at 10:13 AM, Poul-Henning Kamp 
wrote:

> 
> In message <5673c1bd.6070...@rubidium.dyndns.org>, Magnus Danielson
> writes:
>
> >It seems like the biggest problem for Loran-C is that they have not been
> >able to build an economical model to support it. That it complements the
> >GPS and GLONASS systems, as well as GALILEO in a somewhat different mode
> >disturbance is a technical detail which doesn't ripple though the reports.
>
> No, it's really very simple, in Europe it is all about saving face.
>
> The political bluff which should have moved GPS control to NATO
> rather than DoD failed, and forced the EU to follow through.
>
> Finding the claimed eager private investors failed predictably and in
> the end EU had to fund Galileo with tax money, precisely like pretty
> much every had predicted.
>
> Then the draft European Radio Navigation Plan said that at few
> millions on LORAN produced 40% of the benefit while all the billions
> for Galileo hardly produced any[1].
>
> In other words:  Some almost-pensioners with 50 year old cold-war
> tech were about 100 times more cost-efficient than the biggest
> political prestige project of EU's history.
>
> No wonder all copies of that draft has vanished from the surface
> of the planet.
>
> Poul-Henning
>
> [1] The two lost/marooned Galileo sats have cost about the same as
> updating and running Loran-C for 10-15 years would have.
>
> --
> 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.
> ___
> 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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Re: [time-nuts] Anybody who can record last Loran-C transmissions ?

2015-12-19 Thread Graham

Would you be able to record what you want via the online web SDR at the 
Twente University?


http://websdr.ewi.utwente.nl:8901/

cheers, Graham ve3gtc


On 2015-12-19 10:35, Poul-Henning Kamp wrote:

It doesn't seem like my old hack to record VLF spectrum works anymore.

Are there anybody in Europe who can do a raw capture of the VLF spectrum
over new years eve to capture the last LORAN-C transmissions as a
historical document ?

Ideally a 1 MSPS ADC directly on a good antenna, but failing that just
a water-fall would be nice...



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Re: [time-nuts] FE-5680A Breakout board

2015-12-19 Thread John Ackermann N8UR

Apologies, all -- this wasn't meant for the list.  Thanks to another 
time-nut, though, I now have the info!


Best,
John


On 12/19/2015 12:53 PM, John Ackermann N8UR wrote:

Hi Ian --

Happy holidays!

A few years ago I got some of the breakout board kits you did for the
FE-5680A.  They've finally risen to the top of my "to assemble pile." :-)

Looking for the schematic and any assembly info you might have available
-- I only have the boards and parts but can't find the docs.

Thanks and 73,
John

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Re: [time-nuts] SMD TADD-1 distribution amplifier - seeking comments and suggestions?

In message <56757344.2020...@rubidium.se>, Magnus Danielson writes:

>The isolation strategy says that the various equipments should only be 
>power grounded, as required for personal safety, and then have all other 
>grounding paths "galvanically separated" (thus, DC and power frequencies 
>separated in common mode).
>
>The mesh strategy says that you extend the grounding of the power ground 
>with additional grounding with every cable and additional grounding 
>cables.

Please bear in mind that there is a *huge* difference between
single-ended (as in: RF-Coax-BNC) and balanced (as in: Audio-Twinax-XLR)
for both of these scenarios.

While you can get away with the isolation strategy with balanced,
because you have high CMRR inputs, there is nothing to "take care
of" the ground potentials in the single-ended mode.

>As a reference, Ethernet is designed to work in an isolation BN setup, 
>[...]

That is actually a new thing, the original Ethernet was 1/2" coax
and ground-loops and lightning damage was the order of the day.

The main reason Ethernet went balanced was actually for fault
isolation (star-topology vs. bus) and signal quality (IT people
were horrible at "sharking" and crimping coax.)

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
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Re: [time-nuts] SMD TADD-1 distribution amplifier

2015-12-19 Thread Charles Steinmetz


Li Ang wrote:


Hi Charles,
I'm making a 1-to-4 distribution amplifier for 10MHz.  Can you give 
any suggestion

The opamps I'm considering are LMH6609 LMH6624 LMH6702.
Does the piezoelectric effect of capacitors need to be considered here?


I'm working on a response to your questions.  In the meantime, since 
I do not know what you plan to do with your distribution amplifier 
(feed a reference oscillator to several instruments and/or radios to 
keep them on frequency?  feed an oscillator as an input signal to a 
phase noise analyzer or DMTD system to characterize its frequency 
stability?), I'm repeating something I posted in November 2014 for 
you to think about:


This brings up the distinction between *isolation* amplifiers and 
*distribution* amplifiers.  Most of us need a [number of] feeds for 
various test equipment, radios, etc.  These feeds should have 50 ohm 
output impedance, moderate isolation (35dB or more), and should not 
noticeably degrade the noise, PN, distortion, or xDEV of the 
source.  That is the job of a distribution amp.


I would generally [use] some version of a two- or three-transistor 
Class A buffer amplifier [or an IC-based circuit for this].  There 
are lots of circuits to choose from.  Many are transformer (or 
autoformer) coupled, some are not (the JPL circuits come to mind) 
and can also be used to distribute lower frequencies.  You can get 
[fanout] the NIST way ([high] buffer amp input impedance so you 
parallel a bunch of them at the input connector), or by using one 
stage with low output impedance to drive a number of output 
amplifiers in parallel, or by using an amplifier with very low 
output impedance (perhaps a high-current monolithic amplifier) to 
drive a number of 50 ohm build-out resistors, or by fanning out with 
CMOS logic and following each CMOS final buffer with a Tee network 
to [re]generate sine waves.


Then there are the times when you are making measurements of 
oscillators and must absolutely ensure that there is no interaction 
between them.  That is the job of an isolation amp[, with isolation 
of 80dB or more].  Rarely will you need more than two or three feeds 
per oscillator, so what you need are several, one-to-three iso amps 
(one for each oscillator).  Here, something like the NIST amplifiers 
makes sense.


I uploaded a basic tutorial on various distribution amplifier 
topologies to Didier's site, but it is still in the "recent uploads" 
section and not yet available for download.  I'll post again when it 
can be searched and downloaded.


Best regards,

Charles


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Re: [time-nuts] Anybody who can record last Loran-C transmissions ?

2015-12-19 Thread Lizeth Norman

That's what I said. 61.44MS/s. This thing is a fire hose.
Saturate a usb 3.1 without much problem.
Gotta love computing!

On Sat, Dec 19, 2015 at 5:01 PM, Poul-Henning Kamp  wrote:
> 
> In message <5675ac3c.8020...@aei.ca>, Graham writes:
>
>>Would you be able to record what you want via the online web SDR at the
>>Twente University?
>
> Not really.  That would only give a water-fall.
>
> What I think should be preserved is the actual raw, unadultered signal on air.
>
>
> --
> 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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Re: [time-nuts] End of Loran-C in Europe confirmed.

2015-12-19 Thread paul swed

I was of the impression 3 would do and the master can be one of the points.
However for LORAN C after the new year it won't matter.

eLORAN has some useful properties in the data channel. I suppose with luck
we will all learn more about that. At least at the moment my old LORAN C
gear is very happy with the eLORAN out of NJ and so far my house hasn't
moved an inch or meter.
I hope that there may be further testing and development of eLORAN in
Europe.
Though I think you were way ahead of us on that front.
Regards
Paul.

On Sat, Dec 19, 2015 at 5:16 PM, Poul-Henning Kamp 
wrote:

> 
> In message <678a5344-8039-4145-89a9-223106955...@n1k.org>, Bob Camp
> writes:
>
> >Each navigation chain requires 4 stations for navigation (one master to
> supply
> >timing and three slaves to triangulate against).
>
> All the european LORSTAs are absolutely timed, that improved precision
> dramatically.
>
> You really only need 3 stations to navigate, but for typical layouts
> the fourth station gives many more nautical square miles per buck
> than the first three.
>
> --
> 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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>
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Re: [time-nuts] Anybody who can record last Loran-C transmissions ?

2015-12-19 Thread Bill Byrom

The Tektronix RSA306 9 kHz - 6.2 GHz RF signal analyzer samples the IF
at 112 MS/s (14 bit A/D), so it streams data over USB 3 at 224 MB/sec. A
PC with an I7 (or even a good I5) and a modern solid state hard drive
can keep up with this streaming data and store hundreds of GB of
contiguous streaming samples. These can be read back with the SignalVu-
PC application (base version is free, but option is required for
playback) and analyzed as I/Q data (contiguous spectrograms over up to 1
second, export to Matlab, etc.).

Unfortunately, I'm in Texas so I can't receive these transmissions from
Europe. ;)
--
Bill Byrom N5BB

On Sat, Dec 19, 2015, at 05:10 PM, Lizeth Norman wrote:
> That's what I said. 61.44MS/s. This thing is a fire hose.
> Saturate a usb 3.1 without much problem.
> Gotta love computing!
>  
> On Sat, Dec 19, 2015 at 5:01 PM, Poul-Henning Kamp 
> wrote:
>> 
>> In message <5675ac3c.8020...@aei.ca>, Graham writes:
>>  
>>> Would you be able to record what you want via the online web SDR at the
>>> Twente University?
>>  
>> Not really.  That would only give a water-fall.
>>  
>> What I think should be preserved is the actual raw, unadultered signal on 
>> air.
>>  
>>  
>> --
>> 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.
>> _
>> time-nuts mailing list -- time-nuts@febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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> _
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Re: [time-nuts] SMD TADD-1 distribution amplifier - seeking comments and suggestions?

2015-12-19 Thread Hal Murray


p...@phk.freebsd.dk said:
> The main reason Ethernet went balanced was actually for fault isolation
> (star-topology vs. bus) and signal quality (IT people were horrible at
> "sharking" and crimping coax.) 

The reason Ethernet switched to a star topology was to take advantage of the 
wires that were already installed in most buildings.

The electronics at each end were cheap compared to the cost of installing a 
new wire in the ceiling.


-- 
These are my opinions.  I hate spam.



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[time-nuts] Anybody who can record last Loran-C transmissions ?

It doesn't seem like my old hack to record VLF spectrum works anymore.

Are there anybody in Europe who can do a raw capture of the VLF spectrum
over new years eve to capture the last LORAN-C transmissions as a
historical document ?

Ideally a 1 MSPS ADC directly on a good antenna, but failing that just
a water-fall would be nice...

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
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Re: [time-nuts] Anybody who can record last Loran-C transmissions ?


Hi Poul-Henning,

On 12/19/2015 11:35 AM, Poul-Henning Kamp wrote:

It doesn't seem like my old hack to record VLF spectrum works anymore.

Are there anybody in Europe who can do a raw capture of the VLF spectrum
over new years eve to capture the last LORAN-C transmissions as a
historical document ?

Ideally a 1 MSPS ADC directly on a good antenna, but failing that just
a water-fall would be nice...



Nice idea. An SDR with the HF mod would probably be the simplest way to 
do it. As the Loran-C stations lay on top of each other, using a 
multi-station Loran-C receiver in parallel would be nice. The 8000 chain 
should suddenly be quite alone.


Cheers,
Magnus
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Re: [time-nuts] SMD TADD-1 distribution amplifier

2015-12-19 Thread Bruce Griffiths

The LMH6624 has too much distortion to be particularly useful for 10MHz with 
outputs of 3dBm or more. 

Bruce

On Saturday, 19 December 2015 10:01 PM, Li Ang <379...@qq.com> wrote:

 Hi Charles,
  I'm making a 1-to-4 distribution amplifier for 10MHz.  Can you give any 
suggestion? The schematic is attached. The opamps I'm considering are LMH6609 
LMH6624 LMH6702. 
  Does the piezoelectric effect of capacitors need to be considered here?

Thanks
BI7LNQ

-- Original --
From:  "Charles Steinmetz";;
Date:  Sat, Dec 19, 2015 09:18 AM
To:  "Discussion of precise time and frequency 
measurement"; 

Subject:  Re: [time-nuts] SMD TADD-1 distribution amplifier

Anders wrote:

>Far-out PN/AM is still 7dB short of the 6502!
>Looks like an SNR issue to me, rather than some issue with the linear
>regulator noise feeding through?!
>AD8055 in non-inverting circuit with 1+2k7/2k7 gain has 9.6 nV/sqrt(Hz)
>input-referred voltage noise PSD (if I calculated correctly..)
>With an ADA4899-1 and lower value resistors I get about -4.5 dB improvement
>to 3.4 nV/sqrt(Hz) input-referred

You're the victim of a very unfortunate choice of op-amp.

The op-amp that the TADD-1 was designed around (MAX477) is specified 
with 5 nV/sqrtHz (typical) of input voltage noise at 10MHz.  No 
details are given about its noise performance at lower frequencies, 
but the fact that the noise is specified at 10MHz suggests that the 
1/f corner frequency is probably high, very likely 10kHz or 
higher.  This further implies that its 10Hz input voltage noise is 
more than 1,000 nV/sqrt/Hz.

The AD8055 is specified at 6 nV/sqrtHz at 10kHz, rising to ~150 
nV/sqrtHz at 100Hz below a corner frequency of ~1kHz.  Extrapolating 
the curve suggests that the 10Hz voltage input noise is > 1,000 nV/sqrtHz.

The AM and PM noise you are measuring is caused primarily by noise at 
baseband, *not* by the in-band noise of the op-amp.  Baseband noise 
AM modulates the signal, and it is also converted to PN because the 
fluctuating voltage modulates the bandwidth of the op-amp (by 
modulating the locations of the second and subsequent amplifier poles 
with signal-dependent bias changes).  So these egregiously noisy (at 
baseband) op-amps cause high AM and PM noise.

Compare those with the following op-amp specs (like the specs above, 
these are all "typical"):

ADA4899:      1nV/sqrtHz at 100kHz      10nV/sqrtHz at 10Hz
AD8010:          2nV/sqrtHz at 10kHz    ~12nv/sqrtHz at 10hz  [note 
specific bypassing instructions]
LME49713:      1.9nV/sqrtHz at 10kHz      11.5nV/sqrtHz at 10Hz

So, at 10Hz, each these three possible choices is more than 100x 
quieter than the MAX477 or AD8055.  (They are also quieter in the 
signal band, but not by as much.)

Best regards.

Charles

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[time-nuts] TAC32 not behaving properly

2015-12-19 Thread Morris Odell

Hi all,

I have what I hope is a minor problem with TAC32 software. I'm running it on
a Windows 7 machine and using it to monitor a Motorola VP Oncore receiver in
my master clock. The seems to work OK but when I turn on the sound effects
it only sounds the second ticks when it's synchronizing i.e. when the time
display is red. Once it's locked on to the receiver and the display turns
black the ticks stop but it still beeps at the head of each minute. In the
past it's worked properly but since I had the machine down while my study
was being renovated it's started doing this.

Has anyone else had this problem or know of a solution?

Thanks,

Morris


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Re: [time-nuts] SMD TADD-1 distribution amplifier

In message <20151219095948.xmkoo...@smtp17.mail.yandex.net>, Charles Steinmetz 
writes:

>There is a reason why some power transformers cost $385 and others 
>with similar basic specs (voltage, current) cost $22.

For sensitive stuff I usually pick power supplies (of all kind)
which are certified for medical use, they usually have wastly
superior specs on all these "secondary" paramters, but only
twice the cost.

-- 
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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Re: [time-nuts] SMD TADD-1 distribution amplifier

2015-12-19 Thread Charles Steinmetz


Chris wrote:


You are going to get at least a little circulating ground current because
of power supply parasitics


There is a reason why some power transformers cost $385 and others 
with similar basic specs (voltage, current) cost $22.  Properly 
designed instruments, radios, medical and other equipment (even 
quality audio and video gear) that must interoperate in adverse 
circumstances use the expensive ones, for good reason.



I agree that for the typical test equipment case where all the gear is
running from the same power feed it likely should not be necessary.  But
putting the connectors on opposite sides of the PCB is still just asking
for trouble.


I think those are two different things (ground currents and RF 
currents).  If the shields of all of the incoming and outgoing signal 
connectors are bonded firmly to a small area of the metal enclosure, 
and the enclosure is an effective shield at the RF frequencies of 
interest, there will be very little to no RF current on the shields 
to be drawn across the PCB.  If the internal power supplies are 
single-point grounded there, as well, and the parasitics are kept low 
and balanced (you used the $385 transformer, and best design 
practices), no mains power-related current will be originated on the 
shields by the device.


Even a moderately complex instrument has signals coming and going not 
just to different areas of one PCB, but to several (or even dozens) 
of different PCBs that may use different power supplies.  I'm not 
saying it's a bad idea to put each PCB's IOs in one small area of the 
card, but that is just one way to get where you need to be.


To maximize the probability that the conditions above are met (in 
particular, to maximize the effectiveness of the enclosure as a 
shield), you can add ferrite common-mode chokes to both the internal 
and external coax cables feeding the IO connectors.  Use lots of 
fasteners to assemble the enclosure, make sure each one provides good 
metal-to-metal bonding (use masks when the various enclosure parts 
are painted), and use RFI gaskets, spring fingers, wire mesh shaft 
seals, etc. as needed.  Look critically at every hole you are forced 
to make in the enclosure, and use whatever means are necessary to 
make them RF-tight at all frequencies at which your circuitry might 
be vulnerable.


Best regards,

Charles


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Re: [time-nuts] TAC32 not behaving properly

2015-12-19 Thread William Beam

Review  your operating system sound settings (on taskbar or in
control panel/sounds).
The one second ticks are quite low level compared to the top of minute
tone.

- Original Message -
From: "Discussion of precise time and frequency measurement" 
To:
Cc:
Sent:Sat, 19 Dec 2015 17:41:09 +1100
Subject:[time-nuts] TAC32 not behaving properly

 Hi all,

 I have what I hope is a minor problem with TAC32 software. I'm
running it on
 a Windows 7 machine and using it to monitor a Motorola VP Oncore
receiver in
 my master clock. The seems to work OK but when I turn on the sound
effects
 it only sounds the second ticks when it's synchronizing i.e. when the
time
 display is red. Once it's locked on to the receiver and the display
turns
 black the ticks stop but it still beeps at the head of each minute.
In the
 past it's worked properly but since I had the machine down while my
study
 was being renovated it's started doing this.

 Has anyone else had this problem or know of a solution?

 Thanks,

 Morris

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Re: [time-nuts] Anybody who can record last Loran-C transmissions ?


In message <5675ac3c.8020...@aei.ca>, Graham writes:

>Would you be able to record what you want via the online web SDR at the 
>Twente University?

Not really.  That would only give a water-fall.

What I think should be preserved is the actual raw, unadultered signal on air.


-- 
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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Re: [time-nuts] End of Loran-C in Europe confirmed.

In message <678a5344-8039-4145-89a9-223106955...@n1k.org>, Bob Camp writes:

>Each navigation chain requires 4 stations for navigation (one master to supply 
>timing and three slaves to triangulate against).

All the european LORSTAs are absolutely timed, that improved precision
dramatically.

You really only need 3 stations to navigate, but for typical layouts
the fourth station gives many more nautical square miles per buck
than the first three.

-- 
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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Re: [time-nuts] SMD TADD-1 distribution amplifier

Hi

The medical wall warts (at least the US ones) are a nice option. If you get
them from the importer, the cost adder is in the 20 to 30% range. The great
thing they do is to break the ground connection between the AC supply line and 
the output
negative. It’s not a prefect solution, but it’s a start.

Bob

> On Dec 19, 2015, at 3:12 AM, Poul-Henning Kamp  wrote:
> 
> 
> In message <20151219095948.xmkoo...@smtp17.mail.yandex.net>, Charles 
> Steinmetz writes:
> 
>> There is a reason why some power transformers cost $385 and others 
>> with similar basic specs (voltage, current) cost $22.
> 
> For sensitive stuff I usually pick power supplies (of all kind)
> which are certified for medical use, they usually have wastly
> superior specs on all these "secondary" paramters, but only
> twice the cost.
> 
> -- 
> 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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Re: [time-nuts] SMD TADD-1 distribution amplifier - seeking comments and suggestions?

Transformer isolation isn't helping much at RF, as you will capacitively
couple through the transformer. I've been bitten by that in real life,
as I was called in to solve issues in someone elses design. It was only
when I introduced an RF choke that we got conducted noise battled. It's
also not enough, as the RF choke needs an RF path to ground in order to
start rejecting effectively, which was the issue another time, so you
want an RF choke with caps to ground on the inside.

The galvanic isolation can be done using transformer or capacitors after
that.

There is an over believe in isolation, as it only takes one mistake to
break the system. Another approach is to ground everything, cross-ground
etc. and bring the DC/power-spurs down through conduction. It have
proven itself easier to ensure RF properties when shield and chassi is
tied hard to each other, as it provides good RF conduction and the cable
does not act like an antenna against the shield for the RF power being
unbalanced. The RF choke then acts to separate the chassi RF from that
of the board, assisting in the balance.

Transformers can provide RF shielding, if they have double shields
between the coils, and where the shield of each side is connected to
it's ground. That way each coil will capacitively terminate in it's own
shield, and the remaining capacitive coupling will mainly be between the
shields and hence grounds. I rarely see people doing this.

I've been bitten multiple times by the capacitive coupling in
transformers, and only when I found a way to handle it things have
started to work. It's not all magnetics.

Cheers,
Magnus

On 12/19/2015 12:33 AM, Tim Shoppa wrote:

All the inputs and outputs were deliberately transformer isolated. Why
break the isolation by using capacitor from coax shield to chassis ground?

I do realize that some isolation transformers have "extra floating turns"
to give transformer action that cancels stray capacitive coupling. I don't
think the capacitors tying coax shield to chassis ground can serve that
purpose.

Tim N3QE

On Mon, Nov 30, 2015 at 3:02 PM, Anders Wallin
wrote:

HI all,
I need to build a few distribution amplifiers (>90% for 10MHz, sometimes
maybe 5MHz) and instead of reinventing the wheel I decided to try to
modernize the TADD-1 into an all (almost) SMD design. Here are some draft
sketches:

http://www.anderswallin.net/2015/11/frequency-distribution-amplifier-plans-a-k-a-smd-tadd-1/

Does this sound/look reasonable or crazy?
Any suggestions for op-amps to try and/or compare to the AD8055?
What causes the extra phase-noise below 1 Hz offset in John A's result:
https://www.febo.com/pages/amplifier_phase_noise/amplifier_phase_noise.png

Suggestions for a low noise DC-regulator circuit? The 12-24VDC supplied to
this board will most likely come from a switched-mode PSU, so filtering of
common-mode noise is mandatory.
I found the TI LP38798 shown in the schematic by googling - if someone has
a proven a measured design that would be a safer choice. In any case more
filtering (e.g. ferriites) is probably a good idea.

This design will be available on my blog or on github when it is done - if
anyone is interested.

Thanks,
Anders
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Re: [time-nuts] SMD TADD-1 distribution amplifier

Hi

A biassed CMOS gate (NC7SZ125 is one) is quieter than anything you will feed 
through the 
amplifier below about 10 KHz. Above that it’s as quiet as all but a very few 
sources. At less
than 10 cents each, they are hard to beat.

Bob

> On Dec 18, 2015, at 9:46 PM, Li Ang <379...@qq.com> wrote:
> 
> Hi Charles,
>   I'm making a 1-to-4 distribution amplifier for 10MHz.  Can you give any 
> suggestion? The schematic is attached. The opamps I'm considering are LMH6609 
> LMH6624 LMH6702. 
>   Does the piezoelectric effect of capacitors need to be considered here?
> 
> 
> 
> 
> 
> 
> Thanks
> BI7LNQ
> 
> 
> -- Original --
> From:  "Charles Steinmetz";;
> Date:  Sat, Dec 19, 2015 09:18 AM
> To:  "Discussion of precise time and frequency 
> measurement"; 
> 
> Subject:  Re: [time-nuts] SMD TADD-1 distribution amplifier
> 
> 
> 
> Anders wrote:
> 
>> Far-out PN/AM is still 7dB short of the 6502!
>> Looks like an SNR issue to me, rather than some issue with the linear
>> regulator noise feeding through?!
>> AD8055 in non-inverting circuit with 1+2k7/2k7 gain has 9.6 nV/sqrt(Hz)
>> input-referred voltage noise PSD (if I calculated correctly..)
>> With an ADA4899-1 and lower value resistors I get about -4.5 dB improvement
>> to 3.4 nV/sqrt(Hz) input-referred
> 
> You're the victim of a very unfortunate choice of op-amp.
> 
> The op-amp that the TADD-1 was designed around (MAX477) is specified 
> with 5 nV/sqrtHz (typical) of input voltage noise at 10MHz.  No 
> details are given about its noise performance at lower frequencies, 
> but the fact that the noise is specified at 10MHz suggests that the 
> 1/f corner frequency is probably high, very likely 10kHz or 
> higher.  This further implies that its 10Hz input voltage noise is 
> more than 1,000 nV/sqrt/Hz.
> 
> The AD8055 is specified at 6 nV/sqrtHz at 10kHz, rising to ~150 
> nV/sqrtHz at 100Hz below a corner frequency of ~1kHz.  Extrapolating 
> the curve suggests that the 10Hz voltage input noise is > 1,000 nV/sqrtHz.
> 
> The AM and PM noise you are measuring is caused primarily by noise at 
> baseband, *not* by the in-band noise of the op-amp.  Baseband noise 
> AM modulates the signal, and it is also converted to PN because the 
> fluctuating voltage modulates the bandwidth of the op-amp (by 
> modulating the locations of the second and subsequent amplifier poles 
> with signal-dependent bias changes).  So these egregiously noisy (at 
> baseband) op-amps cause high AM and PM noise.
> 
> Compare those with the following op-amp specs (like the specs above, 
> these are all "typical"):
> 
> ADA4899:   1nV/sqrtHz at 100kHz   10nV/sqrtHz at 10Hz
> AD8010:  2nV/sqrtHz at 10kHz ~12nv/sqrtHz at 10hz  [note 
> specific bypassing instructions]
> LME49713:  1.9nV/sqrtHz at 10kHz  11.5nV/sqrtHz at 10Hz
> 
> So, at 10Hz, each these three possible choices is more than 100x 
> quieter than the MAX477 or AD8055.  (They are also quieter in the 
> signal band, but not by as much.)
> 
> Best regards.
> 
> Charles
> 
> 
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Re: [time-nuts] Anybody who can record last Loran-C transmissions ?


In message <56753e8d.8090...@rubidium.dyndns.org>, Magnus Danielson writes:

>Nice idea. An SDR with the HF mod would probably be the simplest way to 
>do it. As the Loran-C stations lay on top of each other, using a 
>multi-station Loran-C receiver in parallel would be nice. The 8000 chain 
>should suddenly be quite alone.

Yes.  It will be interesting to see if that makes it usable.


-- 
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Re: [time-nuts] SMD TADD-1 distribution amplifier - seeking comments and suggestions?


In message <56755ba1.7000...@rubidium.dyndns.org>, Magnus Danielson writes:

>There is an over believe in isolation, as it only takes one mistake to 
>break the system. Another approach is to ground everything, cross-ground 
>etc. and bring the DC/power-spurs down through conduction. 

Tony Waldron argued similar for audio systems:

http://www.fragrantsword.com/twaudio/

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Re: [time-nuts] SMD TADD-1 distribution amplifier - seeking comments and suggestions?

2015-12-19 Thread Tim Shoppa

I think there is a valid heritage in transformer isolation in time and
frequency distribution, and it goes back to when telephone wiring was used
to distribute audio-type IRIG signals around a campus or other facility.
Even if a bunch of 60Hz or a local AM station was leaking through the IRIG
signaling was quite impervious to it. (Heh, the aircraft VHF radio getting
into Spinal Tap's lead guitar was hardly noticeable at that air force base,
for that matter!!!)

But something feels "off" with lifting grounds on coax if the environment
is just a test lab.

CAT 5/6 and Ethernet transformers work great at 10MHz but most all test
equipment is expecting coax and a BNC.

Tim N3QE

On Sat, Dec 19, 2015 at 8:29 AM, Magnus Danielson <
mag...@rubidium.dyndns.org> wrote:

> Transformer isolation isn't helping much at RF, as you will capacitively
> couple through the transformer. I've been bitten by that in real life, as I
> was called in to solve issues in someone elses design. It was only when I
> introduced an RF choke that we got conducted noise battled. It's also not
> enough, as the RF choke needs an RF path to ground in order to start
> rejecting effectively, which was the issue another time, so you want an RF
> choke with caps to ground on the inside.
>
> The galvanic isolation can be done using transformer or capacitors after
> that.
>
> There is an over believe in isolation, as it only takes one mistake to
> break the system. Another approach is to ground everything, cross-ground
> etc. and bring the DC/power-spurs down through conduction. It have proven
> itself easier to ensure RF properties when shield and chassi is tied hard
> to each other, as it provides good RF conduction and the cable does not act
> like an antenna against the shield for the RF power being unbalanced. The
> RF choke then acts to separate the chassi RF from that of the board,
> assisting in the balance.
>
> Transformers can provide RF shielding, if they have double shields between
> the coils, and where the shield of each side is connected to it's ground.
> That way each coil will capacitively terminate in it's own shield, and the
> remaining capacitive coupling will mainly be between the shields and hence
> grounds. I rarely see people doing this.
>
> I've been bitten multiple times by the capacitive coupling in
> transformers, and only when I found a way to handle it things have started
> to work. It's not all magnetics.
>
> Cheers,
> Magnus
>
>
> On 12/19/2015 12:33 AM, Tim Shoppa wrote:
>
>> All the inputs and outputs were deliberately transformer isolated. Why
>> break the isolation by using capacitor from coax shield to chassis ground?
>>
>> I do realize that some isolation transformers have "extra floating turns"
>> to give transformer action that cancels stray capacitive coupling. I don't
>> think the capacitors tying coax shield to chassis ground can serve that
>> purpose.
>>
>> Tim N3QE
>>
>> On Mon, Nov 30, 2015 at 3:02 PM, Anders Wallin <
>> anders.e.e.wal...@gmail.com>
>> wrote:
>>
>> HI all,
>>> I need to build a few distribution amplifiers (>90% for 10MHz, sometimes
>>> maybe 5MHz) and instead of reinventing the wheel I decided to try to
>>> modernize the TADD-1 into an all (almost) SMD design. Here are some draft
>>> sketches:
>>>
>>>
>>> http://www.anderswallin.net/2015/11/frequency-distribution-amplifier-plans-a-k-a-smd-tadd-1/
>>>
>>> Does this sound/look reasonable or crazy?
>>> Any suggestions for op-amps to try and/or compare to the AD8055?
>>> What causes the extra phase-noise below 1 Hz offset in John A's result:
>>>
>>> https://www.febo.com/pages/amplifier_phase_noise/amplifier_phase_noise.png
>>>
>>> Suggestions for a low noise DC-regulator circuit? The 12-24VDC supplied
>>> to
>>> this board will most likely come from a switched-mode PSU, so filtering
>>> of
>>> common-mode noise is mandatory.
>>> I found the TI LP38798 shown in the schematic by googling - if someone
>>> has
>>> a proven a measured design that would be a safer choice. In any case more
>>> filtering (e.g. ferriites) is probably a good idea.
>>>
>>> This design will be available on my blog or on github when it is done -
>>> if
>>> anyone is interested.
>>>
>>> Thanks,
>>> Anders
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To

Re: [time-nuts] Anybody who can record last Loran-C transmissions ?

2015-12-19 Thread Lizeth Norman

Too bad my vacation takes me south of the border for satellite operations..
Bought an Ettus B210 to play with.
mix, filter and sample!

On Sat, Dec 19, 2015 at 7:30 AM, Poul-Henning Kamp  wrote:
> 
> In message <56753e8d.8090...@rubidium.dyndns.org>, Magnus Danielson writes:
>
>>Nice idea. An SDR with the HF mod would probably be the simplest way to
>>do it. As the Loran-C stations lay on top of each other, using a
>>multi-station Loran-C receiver in parallel would be nice. The 8000 chain
>>should suddenly be quite alone.
>
> Yes.  It will be interesting to see if that makes it usable.
>
>
> --
> 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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Re: [time-nuts] SMD TADD-1 distribution amplifier - seeking comments and suggestions?