[time-nuts] time-nuts Digest, Vol 72, Issue 72

Ronald Held ronaldheld at gmail.com
Thu Jul 22 15:19:42 UTC 2010


Jamie:
     Does the main game play correctly?
                     Ronald

On Jul 22, 2010 8:00 AM, <time-nuts-request at febo.com> wrote:
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> Today's Topics:
>
> 1. Re: Function of cap to GND in isolation transformer circuit
> (Geoffrey Smith)
> 2. Re: Function of cap to GND in isolation transformer circuit
> (Heinzmann, Stefan (ALC NetworX GmbH))
> 3. Re: A different timenuts interest (Kasper Pedersen)
> 4. Re: A different timenuts interest (Flemming Larsen)
> 5. Re: Which Rubidium to Get? (Bob Camp)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 22 Jul 2010 14:12:41 +1000
> From: Geoffrey Smith <geoffsmithoz at tpg.com.au>
> Subject: Re: [time-nuts] Function of cap to GND in isolation
> transformer circuit
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>, Geoffrey Smith <geoffsmithoz at tpg.com.au>
> Message-ID: <1279771961.4c47c539a27b1 at postoffice.tpg.com.au>
> Content-Type: text/plain; charset=ISO-8859-1
>
> Joop,
> The cap is isolate any DC from the transformer, The manual for TADD-1 has
> this iformation at the TAPR site has this manual
> http://www.tapr.org/~n8ur/TADD-1_Manual.pdf.
>
>
> On Wed, Jul 21st, 2010 at 9:46 PM, Joop <lous at xs4all.nl> wrote:
>
>> Hi,
>>
>> I noticed in several circuits that the 10MHz isolation transformer in
>> input and output circuits have a 6.8nF or 10nF capacitor to GND. How
>> necessary is this for suppression of unwanted signals? Is the
>> transformer itself not sufficient? I would expect common mode issues to
>> be a bit worse with the cap in place.
>>
>> The circuit I refer to can be seen here:
>> http://www.uploadarchief.net/files/download/cap2gnd.png
>>
>> The first one is an output as described in the Efratom FRK manual, the
>> second one the input in the TADD-2 manual.
>>
>> Cheers,
>>
>> Joop
>>
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>
>
>
>
>
>
> ------------------------------
>
> Message: 2
> Date: Thu, 22 Jul 2010 09:43:12 +0200
> From: "Heinzmann, Stefan (ALC NetworX GmbH)"
> <Stefan.Heinzmann at alcnetworx.de>
> Subject: Re: [time-nuts] Function of cap to GND in isolation
> transformer circuit
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID:
> <D7B1B5F4F3F27A4CB073BF422331203F132FA7A477 at Exchange1.lawo.de>
> Content-Type: text/plain; charset="iso-8859-1"
>
> The way these caps are wired does not isolate DC from the transformer. The
purpose is obviously a different one. Two reasons spring to mind:
>
> 1. If the caps are wired close to the connector, and Ground means the
metal enclosure, then the caps provide RF continuity between cable shield
and enclosure. That keeps RF interference out of the circuit.
>
> 2. They reduce the common mode signal coupled into the circuit via the
parasitic capacitance between the transformer windings. This should help
isolation.
>
> Cheers
> Stefan
>
>
> -----Urspr?ngliche Nachricht-----
> Von: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] Im
Auftrag von Geoffrey Smith
> Gesendet: Donnerstag, 22. Juli 2010 06:13
> An: Discussion of precise time and frequency measurement; Geoffrey Smith
> Betreff: Re: [time-nuts] Function of cap to GND in isolation transformer
circuit
>
> Joop,
> The cap is isolate any DC from the transformer, The manual for TADD-1 has
> this iformation at the TAPR site has this manual
> http://www.tapr.org/~n8ur/TADD-1_Manual.pdf.
>
>
> On Wed, Jul 21st, 2010 at 9:46 PM, Joop <lous at xs4all.nl> wrote:
>
>> Hi,
>>
>> I noticed in several circuits that the 10MHz isolation transformer in
>> input and output circuits have a 6.8nF or 10nF capacitor to GND. How
>> necessary is this for suppression of unwanted signals? Is the
>> transformer itself not sufficient? I would expect common mode issues to
>> be a bit worse with the cap in place.
>>
>> The circuit I refer to can be seen here:
>> http://www.uploadarchief.net/files/download/cap2gnd.png
>>
>> The first one is an output as described in the Efratom FRK manual, the
>> second one the input in the TADD-2 manual.
>>
>> Cheers,
>>
>> Joop
>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at 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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> ------------------------------
>
> Message: 3
> Date: Thu, 22 Jul 2010 10:06:23 +0200
> From: Kasper Pedersen <time-nuts at kasperkp.dk>
> Subject: Re: [time-nuts] A different timenuts interest
> To: time-nuts at febo.com
> Message-ID: <4C47FBFF.9080709 at kasperkp.dk>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> On 07/22/2010 02:13 AM, Morris Odell wrote:
>>
>> The pendulum requires a sustaining system to compensate for the
inevitable
>> energy loss with each swing. The system is located in the building and
>> therefore rotates relative to the pendulum. It needs to provide an
impulse
>> which does not affect the plane of oscillation of the pendulum. I was
>> thinking of an electromagnet located below the centre of the swing which
>> would be pulsed appropriately as the bob passes over it.
>>
>
> As a kid, I did a self sustaining pendulum with no moving parts and no
> magnets:
>
> The bob was suspended by two parallel wires, lacquered together, and
> shorted at the bob end. As the bob passed over the center, a one-shot
> sent a good-sized current pulse through the wire, heating it, making it
> slightly longer, and then shrink again as it cooled at the outside of
> the swing.
>
> For a heavy pendulum, and thick wire, the time constant in the cooling
> phase will likely make this infeasible.
>
> /Kasper Pedersen
>
>
>
> ------------------------------
>
> Message: 4
> Date: Thu, 22 Jul 2010 08:47:23 +0000 (GMT)
> From: Flemming Larsen <oz6oi at yahoo.dk>
> Subject: Re: [time-nuts] A different timenuts interest
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID: <130725.36541.qm at web24809.mail.ird.yahoo.com>
> Content-Type: text/plain; charset=iso-8859-1
>
> The Exploratorium at The Palace of Fine Arts in San Francisco had one of
these, and
> may still have it. I haven't been there in a while and don't know the
details.
> ?
> Nuts & Volts had a construction project for a continuously swinging
pendulum in their
> September 2009 issue. It had a magnet at the end of the pendulum which
generated
> a current in a coil mounted in the center of the base. A simple
2-transistor circuit would
> sense the pendulum swing and would generate a pulse in the same coil to
accelerate
> the pendulum and keep it swinging in infinity, or until the battery died,
whichever came
> first.
> ?
> Have you looked for ideas?on Bryan Mumford's website?
> ?
> -- FL
>
> ?
>
> --- Den ons 21/7/10 skrev Morris Odell <vilgotch at bigpond.net.au>:
>
>
> Fra: Morris Odell <vilgotch at bigpond.net.au>
> Emne: [time-nuts] A different timenuts interest
> Til: time-nuts at febo.com
> Dato: onsdag 21. juli 2010 17.13
>
>
> Hi all,
>
> I have been asked to help with the construction of a Foucault pendulum.
This
> is a long pendulum which oscillates in a slow stately fashion in a fixed
> plane which appears to move as the earth rotates. In reality the
surrounding
> environment is really moving relative to the plane of oscillation.
>
> The pendulum requires a sustaining system to compensate for the inevitable
> energy loss with each swing. The system is located in the building and
> therefore rotates relative to the pendulum. It needs to provide an impulse
> which does not affect the plane of oscillation of the pendulum. I was
> thinking of an electromagnet located below the centre of the swing which
> would be pulsed appropriately as the bob passes over it.
>
> Has anyone here had any experience with such a system of have any
> suggestions regarding the sustaining system? This is an interesting and
> challenging project.
>
> Cheers,
>
> Morris
>
>
>
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>
> ------------------------------
>
> Message: 5
> Date: Thu, 22 Jul 2010 07:58:13 -0400
> From: Bob Camp <lists at rtty.us>
> Subject: Re: [time-nuts] Which Rubidium to Get?
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID: <366965B7-CB4A-4F90-9D15-8BE8BB098CD0 at rtty.us>
> Content-Type: text/plain; charset=us-ascii
>
> Hi
>
> Efratom and Datum are the same company. The LPRO is a staple on the
e-place. The other common alternatives are Frequency Electronics,
Symmetricom, and Tecelek (that's not the right spelling ...).
>
> I would stick with the LPRO since it's the cheapest of the bunch. They all
perform pretty well.
>
> What you will need for any of them:
>
> 1) The connector to interface with them - it's often something odd
> 2) A good heat sink - they generate a lot of heat
> 3) Regulated power - 19 volts is perfect for the LPRO.
>
> Wear out life is anywhere from 5 to 20 years depending on what you read.
Best guess is that there's at least 5 years left on the LPRO's.
>
> Programable output is cute, but only if you need it. Most time nuts are
after 10 MHz only.
>
> So many choices ....
>
> Bob
>
>
> On Jul 21, 2010, at 11:18 PM, Brent Gordon wrote:
>
>> I'm considering buying a rubidium standard, not that I really need one,
just because I'm a Time Nut. I have some questions on what to look for and
what to watch out for. I'll probably get one from either fluke.l or
flyingbest on ePay.
>>
>> I know that they wear out. Is there any model I should look for or avoid?
I see both Efratoms and Datums; some of the auctions claim more lamp life
left for the Datums.
>>
>> I know that the mating connector for the rubidiums with an RF inside the
d-sub connector are expensive. Is it really needed or is the header
connector good enough?
>>
>> Some of them come with an output board (290295929282). Does this get me
anything other than a Type-N output and a mating connector for the RF d-sub?
Why is this one cheaper than just a rubidium?
>>
>> A programmable frequency output, such as this one (eBay item
290301888238), might be useful. Is it worthwhile or more trouble than it's
worth?
>>
>> Are there any gotchas I should be aware of?
>>
>> Thanks,
>> Brent
>>
>>
>>
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> End of time-nuts Digest, Vol 72, Issue 72
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