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Discussion Starter · #1 ·
Does RG-11 make a difference in a UHF-HDTV pre-amplified run of 100-150ft?
 

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Murray,


RG-11 does exhibit less signal loss than RG-6. But your biggest problem is that you're in digital hell out there in Calabasas. If a pre-amp hasn't solved your signal problem, adding RG-11 isn't likely to make a profound difference either.
 

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According to a recent Belden Cable master catalog, RG-6/U has about 5.3 dB attenuation per 100' run, while RG-11/U has 3.5 dB loss per 100' run.


Common RG-59/U attenuates 6.5 dB of signal @700 MHz in a 100' run.


700 MHz is right around UHF DTV channel 53.


KC
 

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Discussion Starter · #4 ·
Is Quad Sheilded RG-6 any better than RG-6?
 

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Quote:
According to a recent Belden Cable master catalog, RG-6/U has about 5.3 dB attenuation per 100' run, while RG-11/U has 3.5 dB loss per 100' run.
...and extended to 167 feet, RG6 provides half the signal that RG11 does.



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Quote:
Originally posted by mkerdman:
Is Quad Sheilded RG-6 any better than RG-6?
Murray,


The center conductor diameter sets the signal loss perameter. The larger that conductor, the less signal loss. RG-6 and RG-6Q have the same center conductor diameter. Where the quad shielding would make a difference is in situations where the cable is routed in physically close proximity to RF interference sources - unshielded motors, generators, or closely parallel to to AC lines, and the like.

 

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Discussion Starter · #7 ·
Thanks for the tips.


Murray Kerdman
 

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RG-11 would be better if you can't use a pre-amp due to a strong overload from a close proximity transmitter.


The 2-3db that you would gain with RG-11 versus RG-6 makes a difference.


In the UHF analog world, you can attenuate a strong local signal with a

variable uhf trap before the pre-amp, but you destroy the picture of that channel(sync & ghost) in order to get clean distant channels.


I wonder what would happen to a digital signal going through an attenuation trap before a pre-amp.


Anybody want to shed some light on that?

 

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Quote:
Originally posted by Ray H:
The center conductor diameter sets the signal loss perameter
At high frequencies, you have to model the coax cable as a transmission line, with series inductance and resistance, and shunt capacitance and conductance. The loss per unit length is going to be determined by the geometry of the cable (the radius of the outer conductor is a term in the formula), and the conductance of the dielectric.


That's what I remember from my course in applied electromagnetics when I was getting my EE degree.


-Jonathan
 

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One needs to be careful when selecting cables. Belden makes a wide range of RG-11/U cables. Some only have performance specified to 50 MHz, others 500MHz and others are up to 1 GHz. The loss is dramatically different. The RG-11/U comes with many different shields, dielectrics, and coverings. All are 75 ohm but whether they have braid, braid +foil or ??? is depends on which you buy. Another item to be careful of is connectors. At frequencies of 700 MHz there are a lot of poor connectors and trying to get from your F-Connector on your STB to your RG-11 connector can cost you dB. BNCs are popular because of their ease of use in video but above 350 MHz there performance is not so stellar. Connections in lines cause discontinuities that result in reflections and loss. UHF is very unforgiving in how it is handled.

..Doyle
 

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Murray,

To answer your question,RG-11 will not make any difference if you use a preamp.

I done some experimenting a while back mixing several pieces of RG-59,RG-6 and RG-11 spliced with barrel connectors(about 250ft.total length),using a stable digital channel, and there was no degredation on the signal meter whatsoever(DTC-100).


It does make a big difference on long runs without a preamp.


BTW,does anyone know a source for RG-11-Stark said they don't carry it anymore.



 
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