D & RIO Terminating Resistors

Hi,


I'm just making some notes about the resistors for DH & RIO networks.


I know the advice is for 150ohm for 57 - 115k, and 82 Ohms for 230k. I also read that it's 82 ohm for RIO


My understanding is that the resistors match the characteristic impedance of the cable, in the case of Blue Hose that's 78Ohms, so I can see the sense in 2x 150Ohm resistors being 75 Ohm in parallel, which make the signal think its an infinite run of cable to stop any reflections.


Am I right in thinking that the 230k network uses the lower resistance terminators because the increase in frequency drops the characteristic impedance of the cable down? I guess to circa 40 Ohms?


Moving onto RIO cables (with SLC PLCs in mind), I found info suggesting 82 Ohms for these? but wouldn't that be dependant on the network speed again? Not done a lot with setting up RIO on these really.






Another question - whilst I'm here!


Does mixing drop-line (with station connectors) and daisy chain seriously effect performance, or is it only marginal? I know the official idea is that you should not mix them. I'm trying to work out why that is?




Thanks


Andy

Hi Andy,

I would think that Ken will chime in but... I have used 150 ohm on all mine and I have mixed drop line with daisy chain, like you im sure its not the best practice, I also found that you really need to have something messed up bad for the DH+ not to work, I remember Ken stating they did a test with barbed wire in place of the blue hose and it worked.

I have not used the RIO very much so not sure on it.

No difference between DH+ and RIO. The protocol doesn't make a difference.


57.6kb uses 150 ohm 1/4 watt
230.4kb uses 82 ohm 1/4 watt


115.2kb can use either, just make sure it is the same on both ends. There is some conflicting data in their manuals for 115.2kb where they list just 150 ohm and others were they list both. Also I am assuming you are daisy chaining the connections. If you happen to be using the old style station connectors (hope not!) they recommend 1/2 watt resistors.


OG

Thanks for the info so far guys.


Regarding station connectors; we do use a lot of these across our various sites. Are we saying these are a bad idea these days? and that the daisy chain method is more reliable - and maybe a bit less prone to trouble?


Andy

Not necessarily. They are just an older method. They had their good points, but for the most part they really became an unnecessary added cost. The Trunk/Drop method can save you some cabling distance, but I personally haven't seen anyone using them in years.

OG