Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: Jeroen Belleman <jeroen@nospam.please>
Newsgroups: sci.electronics.design
Subject: Re: OT: sound speed depends on frequency on mars
Date: Sun, 1 Sep 2024 20:37:29 +0200
Organization: A noiseless patient Spider
Lines: 204
Message-ID: <vb2c3l$1j6t8$1@dont-email.me>
References: <vas9g2$1so9m$1@solani.org>
 <vgl3dj9uq2t9bmo6miqr8faaiuoi1d24c2@4ax.com> <vaso5i$hnfl$1@dont-email.me>
 <2uu3djptvil2j5vberhsj4otm3nbd6l557@4ax.com> <vaucih$th84$1@dont-email.me>
 <hn86djdkbkqbursfjvav0mj4bj38ie87p9@4ax.com> <vavgsg$12nmc$1@dont-email.me>
 <hsq6dj5abqj5dhoc9fseaqq4ici2l4a4sd@4ax.com> <vavvk4$154hn$1@dont-email.me>
 <0797djh7b67m0htlvush9uk6e6j33k0cd8@4ax.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Injection-Date: Sun, 01 Sep 2024 20:34:30 +0200 (CEST)
Injection-Info: dont-email.me; posting-host="1566ab80bd259a9b5ee3988cbdb647e1";
	logging-data="1678248"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX19w223CBG/Bqf7s3imzIFgz"
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.13.0
Cancel-Lock: sha1:vj/pn+aXj/uwMi03FoLjFG69QIA=
Content-Language: en-US
In-Reply-To: <0797djh7b67m0htlvush9uk6e6j33k0cd8@4ax.com>
Bytes: 10086

On 9/1/24 01:32, john larkin wrote:
> On Sat, 31 Aug 2024 22:52:08 +0200, Jeroen Belleman
> <jeroen@nospam.please> wrote:
> 
>> On 8/31/24 21:31, john larkin wrote:
>>> On Sun, 1 Sep 2024 02:37:22 +1000, Bill Sloman <bill.sloman@ieee.org>
>>> wrote:
>>>
>>>> On 1/09/2024 12:18 am, john larkin wrote:
>>>>> On Sat, 31 Aug 2024 16:17:39 +1000, Bill Sloman <bill.sloman@ieee.org>
>>>>> wrote:
>>>>>
>>>>>> On 31/08/2024 3:10 am, john larkin wrote:
>>>>>>> On Sat, 31 Aug 2024 01:23:19 +1000, Bill Sloman <bill.sloman@ieee.org>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> On 31/08/2024 12:34 am, john larkin wrote:
>>>>>>>>> On Fri, 30 Aug 2024 11:13:05 GMT, Jan Panteltje <alien@comet.invalid>
>>>>>>>>> wrote:
>>>>>>>>>
>>>>>>>>>> NASA's Mars rover Perseverance has found that sound travels much more slowly on the Red Planet than it does on Earth
>>>>>>>>>> and behaves in some unexpected ways that could have strange consequences for communication on the planet.
>>>>>>>>>> https://www.space.com/nasa-mars-rover-perseverance-speed-of-sound#main
>>>>>>>>>>       At frequencies above 240 Hertz, "the collision-activated vibrational modes of carbon dioxide molecules do not have enough time to relax, or return to their original state,"
>>>>>>>>>>       the researchers said, which results in sound waves at higher frequencies traveling more than 32 feet per second (10 m/s) faster than the low-frequency ones.
>>>>>>>>>>       That means that if you were standing on Mars, listening to distant music, you would hear higher-pitched sounds before you would hear the lower-pitched ones.
>>>>>>>>>>
>>>>>>>>>> paper:
>>>>>>>>>> https://www.hou.usra.edu/meetings/lpsc2022/pdf/1357.pdf
>>>>>>>>>>
>>>>>>>>>> So...
>>>>>>>>>> Music from far away may sound funny?
>>>>>>>>>>
>>>>>>>>>> For Mars we will need compensation headphones with distance measurement and variable delays....
>>>>>>>>>> ;-)
>>>>>>>>>>
>>>>>>>>>> Better use radio.. and earplugs/ headphones...
>>>>>>>>>
>>>>>>>>> Funny, I just delivered a lecture on transmission lines and noted that
>>>>>>>>> microstrips have dispersion from  the unbalanced dielectric constants
>>>>>>>>> and skin effect. Rising edges get sloppy at the and of a long trace.
>>>>>>>>
>>>>>>>> I hope you pointed out that buried strip-line isn't dispersive. I have
>>>>>>>> pointed this out here from time to time.
>>>>>>>
>>>>>>> Of course it's dispersive, maybe a bit less than microstrip.
>>>>>>
>>>>>> Why do you think that?
>>>>>
>>>>> Because dielectrics are imperfect, especially FR4, and because there
>>>>> are lots of papers online that analyze dispersion in stripline.
>>>>
>>>> But you can't cite any of them.
>>>
>>> Can't you google?
>>>
>>>
>>> You wouldn't use FR4 around a stripline
>>>> if you wanted a low-dispersion transmission line. There are better
>>>> substrates his frequency work.
>>>>
>>>>>>> It's hard to keep up decent impedances on stripline in a multilayer
>>>>>>> board, especially 8 or 10 layers.
>>>>>>
>>>>>> Stripline is buried between two ground planes. The only tricky part of
>>>>>> impedance control is the thickness of the dielectric in the two layers
>>>>>> above and below the strip-line. In a ten layer board this is thinner
>>>>>> than it would be in a board with fewer layers.
>>>>>
>>>>> And eventually the trace has to be skinnier than PCB houses are
>>>>> willing to etch.
>>>>
>>>> Why?
>>>
>>> Run the Saturn program. More layers make the dielectrics thinner, so
>>> to maintain a useful impedance the traces have to get narrower.
>>>
>>> 10 layers gets nasty.
>>>
>>>
>>>
>>>>
>>>>> Standard pricing seems to be around 5 or maybe 4 mils
>>>>> width these days. We do a lot of 5, to sneak between BGA balls, but
>>>>> sometimes even 5 is too big.
>>>>>
>>>>> Thin dielectrics have tolerance issues too. I'm talking about real
>>>>> PCBs here, not ideal theoretical stuff.
>>>>
>>>> Printed circuit board are always real.
>>>
>>> Exactly.
>>>
>>>>
>>>>>> Pay enough for close-tolerance substrates in the two relevant layers and
>>>>>> you should be okay.
>>>>>
>>>>> "Pay enough" can get crazy fast. I don't want to pay hundreds of
>>>>> dollars for a smallish PCB.
>>>>
>>>> An eight or ten layer PCB isn't going to be small. You only need lots of
>>>> layers when you have to connect lots of stuff.
>>>>>>>> https://www.wevolver.com/article/stripline-vs-microstrip
>>>>>>>>
>>>>>>>>> I wonder if anyone has added surface-mount Heaviside loading coils to
>>>>>>>>> a PCB trace.
>>>>>>>>>
>>>>>>>>> https://en.wikipedia.org/wiki/Loading_coil
>>>>>>>>
>>>>>>>> It would be a bit silly.
>>>>
>>>> John snipped the rest of that senstence, without marking the snip.
>>>>
>>>>>>>> You can make lumped constant transmission lines by linking a
>>>> series >>>> of capacitors with discrete inductors, if you want a high
>>>> impedance >>>> transmission line - people sold them as thick film hybrid
>>>>>>>> assemblies, and I even used a few, a very long time ago.
>>>>>>>
>>>>>>> Most ideas seem silly to people who are by nature hostile to ideas.
>>>>>>
>>>>>> Not a problem I've got.
>>>>>>
>>>>>>> Dismissing is easier than thinking.
>>>>>>
>>>>>> Thinking about what a loading coil might be doing to the impedance of a
>>>>>> PCB trace isn't something that you seem to have managed to do.
>>>>>
>>>>> I certainly had the idea.
>>>>
>>>> In a remarkably half-baked way.
>>>
>>> Ideas start out fuzzy, or at least they should. I tell my kids, stay
>>> confused for a while.
>>>
>>>>
>>>>> I might Spice a bunch of ltlines with
>>>>> inductors between, just for fun. It's unlikely that I'd use such an
>>>>> arrangement in real life, but it's just possible, especially if analog
>>>>> quality of a fast edge matters, like in a laser modulator maybe. It's
>>>>> preferable to just keep all the traces very short, but that's not
>>>>> always possible.
>>>>
>>>> You seem to be intent on re-inventing the lumped constant delay line,
>>>> without being aware that they were commercially available some thirty
>>>> years ago, back when I used them. They may still be available.
>>>
>>> The Tek 545 30 MHz scope had a gigantic, lumped, tunable, differential
>>> delay line up to the CRT, so you could see the edge that you triggered
>>> on.
>>>
>>> https://w140.com/tekwiki/images/thumb/1/10/Tek_545a_delay_close.jpg/231px-Tek_545a_delay_close.jpg
>>>
>>> A lossy pcb trace with periodic loading coils is not a lumped-constant
>>> tx line. In fact, lumped lines are nasty. The number of sections goes
>>> as Td/Tr squared, which can get awkward fast.
>>>
>>> Meander-line sections connected by loading coils could be interesting.
>>> One product that I'm considering now is a programmable delay line, and
>>> that idea might help.
>>>
>>>
>>>
>>
>> In the 1980's we had NIM-format boxes with binary-weighted-length cables
>> and cheap slide switches, and CAMAC modules with basically the same
>> cables, but with fancy miniature DPDT relays in metal TO-8 style
>> packages. Physicists would invariably mess up the relay contacts.
>>
>> Jeroen Belleman
> 
> I was thinking of using the cute little $1 Fujitsu telecom relays,
> which are good up to about 3 GHz.
> 
========== REMAINDER OF ARTICLE TRUNCATED ==========