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Author Topic: Proper way to tie trick line  (Read 8009 times)

Lyle Williams

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Re: Proper way to tie trick line
« Reply #20 on: January 03, 2017, 04:01:50 pm »

The stuff that matters is vastly different between 100MHz and 10GHz.
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Jonathan Johnson

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Re: Proper way to tie trick line
« Reply #21 on: January 03, 2017, 04:27:44 pm »

The stuff that matters is vastly different between 100MHz and 10GHz.

And remember that is radio frequency, not audio frequency (as in old-school modem or RS232 connections). Radio frequency is much more susceptible to one-time capacitance changes in the cabling than audio frequencies are. ("one-time" meaning the capacitance has changed from A to B; not that the capacitance is in the process of change). So a crushed Ethernet cable that stays crushed will exhibit problems where a crushed microphone cable that stays crushed will work just fine.

100 Mbit circuits are much more tolerant of out-of-spec capacitance than 10 GBit circuits are. So while a kink in a cable won't make much difference in a 100 Mbit connection, it can kill a 10 GBit connection.
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Tim McCulloch

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Re: Proper way to tie trick line
« Reply #22 on: January 03, 2017, 06:48:50 pm »


Citing success in the face of doing the wrong thing is tempting fate, not engineering as it was taught to me.

^THIS^

That's how Genie lift roofs are perpetuated.  If there hasn't been a catastrophic failure (meaning people die) recently the client would rather have the low price that comes with such a construct.  If it doesn't fail on their gig, they'll presume it to be safe (until it fails).
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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

Scott Holtzman

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Re: Proper way to tie trick line
« Reply #23 on: January 03, 2017, 07:28:37 pm »

And remember that is radio frequency, not audio frequency (as in old-school modem or RS232 connections). Radio frequency is much more susceptible to one-time capacitance changes in the cabling than audio frequencies are. ("one-time" meaning the capacitance has changed from A to B; not that the capacitance is in the process of change). So a crushed Ethernet cable that stays crushed will exhibit problems where a crushed microphone cable that stays crushed will work just fine.

100 Mbit circuits are much more tolerant of out-of-spec capacitance than 10 GBit circuits are. So while a kink in a cable won't make much difference in a 100 Mbit connection, it can kill a 10 GBit connection.

RS-232 is alternating DC voltage not FSK or other type of audio modulation
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Scott AKA "Skyking" Holtzman

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Jonathan Johnson

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Re: Proper way to tie trick line
« Reply #24 on: January 03, 2017, 08:49:06 pm »

RS-232 is alternating DC voltage not FSK or other type of audio modulation
Yes, well, I guess you could call it square wave with a DC bias, though not entirely correctly. :-) The "frequency" or rate at which the DC switches on and off could be considered to be in the "audio" spectrum. Certainly not audio modulated (as the phone line of a POTS analog modem connected to that RS-232 line). And if you connected a speaker to an RS-232 line, you'd probably hear something.
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Scott Holtzman

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Re: Proper way to tie trick line
« Reply #25 on: January 03, 2017, 09:01:01 pm »

I think we are talking semantics.  Sure the pulses would move a speaker cone and produce an audible output.

The key is that an analog MODEM (MODulator/DEModulator) converts the RS-232C signals to an analog waveform capable of being transmitted within the bandwidth of a telephone circuit.

RS232-C voltages while the standard specifies a wide range for cable loss the typical UART chip used to covert TTL levels (0 and +5) to the 0 biased RS-232C voltages used +/- 12V rails.  Modern UARTS have DC to DC converters and built in clocking circuits.

As an aside one of the first circuits I designed was for my bulletin board system in the early 80's.  I upgraded to 1200baud with a telco grade 212A UDS modem that has a light when it trained on 1200baud.  I turned on a gate with that light that selected the right clock multiplier for 1200 baud on the UART ending the stupid press return until you can read the software baud rate clock routines common at the time.  It was fast and slick and I was damn proud of myself.
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Scott AKA "Skyking" Holtzman

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brian maddox

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Re: Proper way to tie trick line
« Reply #26 on: January 04, 2017, 12:00:19 pm »

I think we are talking semantics.  Sure the pulses would move a speaker cone and produce an audible output.

The key is that an analog MODEM (MODulator/DEModulator) converts the RS-232C signals to an analog waveform capable of being transmitted within the bandwidth of a telephone circuit.

RS232-C voltages while the standard specifies a wide range for cable loss the typical UART chip used to covert TTL levels (0 and +5) to the 0 biased RS-232C voltages used +/- 12V rails.  Modern UARTS have DC to DC converters and built in clocking circuits.

As an aside one of the first circuits I designed was for my bulletin board system in the early 80's.  I upgraded to 1200baud with a telco grade 212A UDS modem that has a light when it trained on 1200baud.  I turned on a gate with that light that selected the right clock multiplier for 1200 baud on the UART ending the stupid press return until you can read the software baud rate clock routines common at the time.  It was fast and slick and I was damn proud of myself.

I love how a thread that started with "how do i tie a knot?" has veered to ^^this....

Seriously.  Only on this forum.  It's kinda what i love about it....  :)
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Re: Proper way to tie trick line
« Reply #26 on: January 04, 2017, 12:00:19 pm »


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