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Author Topic: com over CAT5... update  (Read 5834 times)

Keith Broughton

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com over CAT5... update
« 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.
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Tim McCulloch

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Re: com over CAT5... update
« Reply #1 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.
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Keith Broughton

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Re: com over CAT5... update
« Reply #2 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  :-[
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brian maddox

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Re: com over CAT5... update
« Reply #3 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.
« Last Edit: September 13, 2015, 11:24:43 pm by brian maddox »
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Mac Kerr

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Re: com over CAT5... update
« Reply #4 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 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

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Keith Broughton

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Re: com over CAT5... update
« Reply #5 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 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.
« Last Edit: September 11, 2015, 06:44:14 am by Keith Broughton »
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Pete Erskine

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Re: com over CAT5... update
« Reply #6 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.

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Mac Kerr

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Re: com over CAT5... update
« Reply #7 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
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Pete Erskine

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Re: com over CAT5... update
« Reply #8 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.
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David Buckley

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Re: com over CAT5... update
« Reply #9 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.
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Re: com over CAT5... update
« Reply #9 on: September 11, 2015, 04:59:06 pm »


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