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 Post subject: Mpx cable maximum length
PostPosted: Fri Oct 17, 2014 4:25 am 

Joined: Fri Oct 17, 2014 2:45 am
Posts: 8
hello, I have a distance of 50 meters from the pc to the transmitter. have unbalanced input and output mpx. I have to use a special cable or it will not work?

Thanks!!


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PostPosted: Fri Oct 17, 2014 4:42 am 

Joined: Sun Feb 10, 2013 6:58 am
Posts: 152
Location: Sydney, Australia
That is a long cable run to be running a low level baseband signal through. I would think you need to find another solution to get your PC closer to the exciter.

RG-62 is about 30 pF/m so after 5 metres you're in trouble and forget RG58 after about 2 metres. You could try RG-114 but I think the real solution is move the exciter closer to the PC or PC closer to the exciter.

C.


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PostPosted: Fri Oct 17, 2014 4:55 am 

Joined: Fri Oct 17, 2014 2:45 am
Posts: 8
I can make it closer to 30 meters. And I can not bring more because I think using the same pc studio I have no other. it can work?


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PostPosted: Fri Oct 17, 2014 6:06 am 

Joined: Mon Aug 25, 2014 3:22 pm
Posts: 282
Work? Yes. Be flat? Unlikely. That's the problem with baseband, it's extremely delicate. Any small amount of nonlinearity (phase or amplitude) you introduce will result in overshoots. Be warned that you may need to undermodulate a few percent so that your peaks don't put you over the line. But yes, you'll get audio, and even stereo.


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PostPosted: Fri Oct 17, 2014 6:20 am 

Joined: Fri Oct 17, 2014 2:45 am
Posts: 8
I found that my transmitter has balanced mpx input , so could do with a balanced cable 30 meters of mpx signal without problem?


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PostPosted: Fri Oct 17, 2014 11:54 am 
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Joined: Tue Mar 17, 2009 2:56 pm
Posts: 4165
Quote:
I found that my transmitter has balanced mpx input , so could do with a balanced cable 30 meters of mpx signal without problem?
First make sure that inside transmitter all 3 wires are used. Sometimes they put balanced and it's just not.

_________________
control point
control point2


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PostPosted: Fri Oct 17, 2014 12:34 pm 

Joined: Tue Nov 05, 2013 10:24 pm
Posts: 77
Shortest possible


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PostPosted: Sat Oct 18, 2014 5:40 am 

Joined: Fri Oct 17, 2014 2:45 am
Posts: 8
yes i have 10kw elenos whit mpx+ and mpx- input for balanced mpx...i try this and i tell you.


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PostPosted: Sat Oct 18, 2014 6:08 am 
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Joined: Mon Mar 17, 2008 1:40 am
Posts: 11211
You might be able to correct a lot of issues with the calibration settings. But it's always better to not need those (although, if you have enough headroom on your sound card, there will be no difference to your listeners).

Without calibration I have noticed a clear difference in stereo separation (this was years ago, before I had measurement equipment, but it must also have caused overshoots and tilt) when I added just 5 meters of cable.


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PostPosted: Sat Oct 18, 2014 6:20 am 

Joined: Sun Feb 10, 2013 6:58 am
Posts: 152
Location: Sydney, Australia
Another alternative could be to move your exciter close to your PC and use a run of heliax from the exciter to the power amplifier.


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