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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => Wireless and Communications => Topic started by: Keith Broughton on September 10, 2015, 03:15:56 pm

Title: com over CAT5... update
Post by: Keith Broughton on September 10, 2015, 03:15:56 pm
So I made an interface box to connect Clearcom to FOH using the CAT5 cable config as discussed a few months back.
Worked in the shop but once the cable was laid out on a show, there was noise picked up.
As it turns out, the CAT5 is not STP... :(
Replaced the CAT with mic cables and com was quiet so I can only associate the noise with the lack of shield on the CAT.
Title: Re: com over CAT5... update
Post by: Tim McCulloch on September 10, 2015, 04:22:33 pm
So I made an interface box to connect Clearcom to FOH using the CAT5 cable config as discussed a few months back.
Worked in the shop but once the cable was laid out on a show, there was noise picked up.
As it turns out, the CAT5 is not STP... :(
Replaced the CAT with mic cables and com was quiet so I can only associate the noise with the lack of shield on the CAT.

Clear-Com is also unbalanced - no CMR.

Perhaps Pete or Mac can comment on use of CATx cables and party line intercoms.
Title: Re: com over CAT5... update
Post by: Keith Broughton on September 10, 2015, 06:05:51 pm
Clear-Com is also unbalanced - no CMR.

Perhaps Pete or Mac can comment on use of CATx cables and party line intercoms.
Yep... no CMR.
 Knew that from the start and suspected it might be a problem but gave it a try anyway.
Fail  :-[
Title: Re: com over CAT5... update
Post by: brian maddox on September 10, 2015, 11:00:05 pm
Yep... no CMR.
 Knew that from the start and suspected it might be a problem but gave it a try anyway.
Fail  :-[

Yeah, clearcom will buzz when everything is perfect. Good luck with no shield...  😀

The old Telex balanced Comms would work over Cat5. But that's largely a dead forrmat at this point.

You could of course convert to four wire and then cat5 is not only acceptable, it's a viable option.  But I digress.
Title: Re: com over CAT5... update
Post by: Mac Kerr on September 10, 2015, 11:57:42 pm
Yeah, cclearcom will buzz when everything is perfect. Good luck with no shield...  😀

The old Telex balanced Comms would work over Cat5. But that's largely a dead forrmat at this point.

You could of course convert to four wore and then cat5 is not on.y acceptable, it's optional. But I digress.

You could also put dry out boxes at each end of the run, but you would have to power each end separately.

Here's a LINK (http://static1.squarespace.com/static/53062f8de4b09e63a23ce552/t/5327a47de4b09aa77d06f2f9/1395106941863/Audio_only_adapter.pdf) to Pete Erskine's download page of a dry out box. Connect the balanced sides together with a Cat5 cable, making sure pins 2&3 are on the same pair, and you're good to go. As I said, this does require power at both ends.

Mac

Title: Re: com over CAT5... update
Post by: Keith Broughton on September 11, 2015, 06:42:11 am
You could also put dry out boxes at each end of the run, but you would have to power each end separately.

Here's a LINK (http://static1.squarespace.com/static/53062f8de4b09e63a23ce552/t/5327a47de4b09aa77d06f2f9/1395106941863/Audio_only_adapter.pdf) to Pete Erskine's download page of a dry out box. Connect the balanced sides together with a Cat5 cable, making sure pins 2&3 are on the same pair, and you're good to go. As I said, this does require power at both ends.

Mac
I had considered this option but wasn't sure if the call light would still function.
Thanks for the link.
Title: Re: com over CAT5... update
Post by: Pete Erskine on September 11, 2015, 11:25:39 am
I had considered this option but wasn't sure if the call light would still function.
Thanks for the link.

CC Call light is done with DC so it won't work.

Title: Re: com over CAT5... update
Post by: Mac Kerr on September 11, 2015, 11:26:02 am
I had considered this option but wasn't sure if the call light would still function.
Thanks for the link.

The call light will not work with Clear Com for sure, they use a DC voltage for signaling. RTS might work, they use a 20k tone for signaling.

Mac
Title: Re: com over CAT5... update
Post by: Pete Erskine on September 11, 2015, 11:45:18 am
Replaced the CAT with mic cables and com was quiet so I can only associate the noise with the lack of shield on the CAT.

I have used twisted pair successfully.  The gig was handed to me after the venue (a river in Tennessee) had already been wired with 25 pair telco cable up one side and down the other with punch blocks at each gate on both sides of the river, all paralleled.  I was using RTS so was saddled with unbalanced comm.

At each Gate on each side of the river of the White water rafting event the judges needed to talk to each other and to the main judge.  There were 10 Gates spanning 200 yards at least.

I started by assigning to each twisted pair a ground and a comm channel.  A second pair was the Ground only so each RTS beltpack got the common ground pair on pin 1, the hot of the ch 1 twisted pair on pin 3 and the hot of the ch 2 twisted pair on pin 2.  Pin 2 was unique to each gate and pin 3 was common among all the beltpacks.

I was hoping that the unbalanced comm would be shielded by the twist with a ground wire.  These ground wires were only grounded at the base.

Worked OK but still had a medium level of buzz, OK for communication but not ideal.  I had used 12 Pairs so far, 1 for each gate private, 1 for global channel 1 and 1 for common ground.  On a lark I grounded the remaining 13 pairs and all the buzz went away. 

With Plain Cat5 you don't have the advantage of all those unused pairs as a ground/shield.  Shielded Cat6 might have a chance but if you need to run a cable anyway run shielded twisted pair like Belden 8451 at least.
Title: Re: com over CAT5... update
Post by: David Buckley on September 11, 2015, 04:59:06 pm
I'd give pro intercom a call.  They have a couple of boxes, the AD903 being the one I'm familiar with, that converts party line to four wire audio, and also the AD920 that convert party line unbalanced to four wire intercom.  The AD920 can convert signalling as well to match four wire comms, but what I don't know is if you can just use a pair of AD920s back to back.

Not a cheap solution, but an off-the-shelf solution.
Its a pity the designers and manufacturers  of the AD903 did not include a call signal passthrough using audio signalling.
Title: Re: com over CAT5... update
Post by: Mac Kerr on September 11, 2015, 06:21:11 pm
I'd give pro intercom a call.  They have a couple of boxes, the AD903 being the one I'm familiar with, that converts party line to four wire audio, and also the AD920 that convert party line unbalanced to four wire intercom.  The AD920 can convert signalling as well to match four wire comms, but what I don't know is if you can just use a pair of AD920s back to back.

Not a cheap solution, but an off-the-shelf solution.
Its a pity the designers and manufacturers  of the AD903 did not include a call signal passthrough using audio signalling.

Yes, you can run two 4W converters back to back, that is what they are meant for. You will however have to remotely power each end or be limited to the small number of stations that can be powered by the converter, assuming it can provide power, most can.

Mac
Title: Re: com over CAT5... update
Post by: Keith Broughton on September 11, 2015, 06:44:07 pm
Yes, you can run two 4W converters back to back, that is what they are meant for. You will however have to remotely power each end or be limited to the small number of stations that can be powered by the converter, assuming it can provide power, most can.

Mac
In this case, a run of mic cable will be cheaper but I will try the cct you linked to for interest sake.
It would be fine for cameras as they don't signal but for festival use, I need to have the call function.
Title: Re: com over CAT5... update
Post by: Pete Erskine on September 11, 2015, 08:27:34 pm
Yes, you can run two 4W converters back to back, that is what they are meant for. You will however have to remotely power each end or be limited to the small number of stations that can be powered by the converter, assuming it can provide power, most can.

Mac


Here (http://static1.squarespace.com/static/53062f8de4b09e63a23ce552/t/53269ff2e4b0f07b1f05dc9e/1395040242831/Intercom_interface_01.pdf) is an example of what Mac is describing - it shows interconnect with 4 wire converters (or satellite)