On Monday 11 September 2017 19:23:37 Chris Albertson wrote: > Why not SPI speeds over a long cable? Gigabit Ether net is a good > example. It is built into almost all computers and can be 1GHz over > 100 meters of cheap unshielded wire. > > They use only a few basic tricks, none of which add much to the cost > > 10/8 encoding to guarantee a minimum number of bit transitions even if > the data is a long string of zeroes. > Clock mixed with data so the receiver clock can be cheap non-precision > Differential to resister common mode noise > galvanic isolation to prevent ground loops > > There is also 10GHz Ethernet but it is not built into common consumer > equipment but even 10G data rates are easy to pushover 100 feet using > just RJ45 jacks > > The trick is to NOT think about how hard it is to push 10Gbps over a > wire. But to think how easy it is to build a microwave data link when > you can use wire in place of a clear air path. No need for antennas > and you can use way ultra-low power. > > even for the case of SPI, think in terms is radio transmission lines > and the job becomes easier. > > On Mon, Sep 11, 2017 at 9:54 AM, Nicklas Karlsson < > > [email protected]> wrote: > > > On Monday 11 September 2017 07:16:00 theman whosoldtheworld wrote: > > > > why not powerlink ie? > > > > > > Wikipedia description shows some promise. SPI speeds over a longer > > > cable, maybe. > > > > No SPI over long cable. For long cable RS422 will work, there is a > > tradeoff between cable length and speed. > > Or for mind boggling distances, how about a g-line? Virtually zero losses over a mile or 3 using common steel wire, single strand? No real reason it cannot be bidi by using 2 non-harmonically related carrier frequencies.
2 secrets to both low loss and low cost since the wire's ohmic losses aren't a major concern, its nothing but a waveguide with no external walls. The other is that when it goes past a supporting pole, it must be tight so the the included angle where its attached to the supporting insulator is less than 5 degrees, as a certain amount of the waveform energy will be radiated and lost as it continues in a straight line, leaving the confines of the field established by the central wire. This central wire exits from the center of a flat conductive panel that is 1 or more wavelengths in radius. And re-enters the rx end in a similar structure. Or with small dishes and "gunn" diodes, which are innately bidirectional, the wire can be dispensed with. We have a remote broadcast linkage lashup running at 23 gigahertz, using 12" dishes on both ends, that has, when our satellite truck is on location up to several miles, I think 22 is the record, which has saved the station its cost in satellite time not rented many times over. If we can clear line of site see the studio's 255 foot STL towers top beacon we fire it up and cancel the satellite time. Our unit isn't bidirectional, but thats a matter of changing out its video circuitry on both ends. Power output is 60 milliwatts. If the sheckles can be found, distance vs bandwidth is a solveable problem. In this case the g-lines initial construction costs for planting all the support poles, and the cost of the gunn diode assemblies, both up front costs, are at best, still discouraging. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
