[mccoady]

I have a CM 3671 antenna on a 20' tower with a CM7777 preamp and Beldon 1694A coax ran to the preamp power supply in my attic. From the power supply I have a splitter with one run of Beldon 1694A ran to my tv and the other run from the splitter is old cheap flatlead antenna wire going to my son's room. I use the CM 3671 to bring in my local digital channels from about 55 -60 miles away to my HDTV.


I want to replace the flat antenna wire with RG6 and was looking on ebay for 500 to 1000 feet of RG6 since it's cheaper to buy alot verse buying 100' at a time. The run to replace the flatlead is maybe 75' but I will also use this cable for various smaller runs as needed in the future.


I ordered some standard shield RG6 that was copper clad steel, 100% aluminum foil, 60% aluminum braid and rated 3GHz but now I'm having second thoughts about whether I should have ordered some with pure copper center conductors.


After ordering the above coax I read that one should use pure copper if DC is involved such as the CM 7777 provides.


So even though it will cost me to send the copper clad back (or sell on Craig's List)) do I really need to use pure copper as I don't want to lose any signal strength running from the CM 7777's power supply to my son's bedroom? (A side note, I just found out I can buy some from Monoprice for about $15 more with pure copper center conductors)

 

[nybbler]

The only run to be concerned about DC about is the run between the power supply and the pre-amp. Since you're not replacing that run you'll be fine with the copper-clad stuff.

 

[mccoady]

Thanks it sounds like any cable runs that I might make within the house will be fine using the copper clad steel coax without loosing anything when compared to a pure copper conductor coax.


Now if I decide to ever make any new satellite cable runs from the multi-switch will the copper clad still be fine or would I need to use pure copper conductor coax for this?

 

[olyteddy]

Look up 'Skin Effect' and you'll see that copper is generally a waste on any RF cable. Also at the power consumption (1 watt or less) of most preamps and switches the higer 'loop resistance' of steel and aluminum -vs- pure copper doesn't matter either...

 

[nybbler]

Copper clad is cheaper, more commonly available, works just as well for RF, and the center conductor is mechanically stronger as well. It does mess up cutting tools made for copper, though.

 

[mccoady]

Actually I didn't realize all RG6 didn't have solid copper conductors until after I had already placed my ebay order then realized it said Copper Clad steel so then I did some researching. When I ran (maybe 4 years ago) all the Beldon 1694A from the OTA antenna down into my attic and into my home theater room I specifically used a really good quality coax so I suppose it only makes sense to do that now whether it's necessary or not.


I ordered a 1000' box of solid copper from monoprice which is probably overkill in my situation whereas some of you see the copper clad steel as working fine. It will allow me the option of running more satellite runs if needed (or replace any bad Beldon runs), but maybe more than anything it will give me piece of mind.


Now I just need to sell the ebay RG6 probably at a discount before my wife finds out I have 2000' of coax laying around.(lol)

 

[petern]



Quote:
Originally Posted by Rick0725 /forum/post/15420532


You will need solid copper to pass voltage without issues. you therefore will need solid copper to the preamp and for satellite signal distribution.

.

What issues?

 

[dr1394]



Quote:
Originally Posted by petern /forum/post/15435944


What issues?

None. Let's do the math. Typical ohms per hundred feet for solid copper 18 gauge wire is 0.64 ohms. Typical ohms per hundred feet for copper clad steel 18 gauge wire is 2.8 ohms.


A CM7777 preamp draws about 125 milliamps. From Ohm's law, E = IR.


0.125 * 0.64 = 0.08 volts


0.125 * 2.8 = 0.35 volts


The CM7777 power supply outputs 18 volts. I'll guess it will work fine down to around 12 volts or even less. The voltage drop difference between a solid copper and copper clad center conductor of 0.27 volts (over 100 feet of coax) is so small, it just doesn't matter.


Ron

 

[AntAltMike]

With voltage switched satellite LNBs, the receiver sends out 18 volts when calling for even transponders and 13 volts when calling for odds. If the "evens" voltage measured at the LNB drops below about 15.5 volts, the LNB will source the wrong transponders. LNBs typically draw about twice the current of a Channel Master Preamp,but the switching voltage never drops below 15.5 volts with less than 300 feet of copper clad center conductor RG-6.


Residential off-air antenna installations commonly used RG-59 for downleads for about two decades before RG-6 became prevalent they rarely suffered from voltage drop problems even though the RG-59 DC resistance might over double the copper clad RG6 resistance.

 

[olyteddy]



Quote:
Originally Posted by Rick0725 /forum/post/15420532


You will need solid copper to pass voltage without issues. you therefore will need solid copper to the preamp and for satellite signal distribution.


Why even bother with copper clad for the rest of your wiring. I would not even consider clad RG6 and refuse to use it. It is not worth the aggrevation for a couple bucks.

Sell your copper clad RG 6 to olyteddy.

Rick, now that's a cheap shot. There are numerous other reasons solid copper is not used for TV RF. Consider if you will the standard 'F' connector. The center conductor is part of the connector and copper isn't durable enough to use as such. The recomended termination for solid copper is BNC, because the center pin for BNC fittings is crimped onto the center conductor.

Quote:
Originally Posted by http://www.bluejeanscable.com/pages/technicaldocs/1694tech.htm /forum/post/0


SUGGESTED CONNECTORS: AMP 221185-1 DUAL CRIMP GOLD PIN


BNC (75 OHMS)


AMPHENOL 31-70000 DUAL CRIMP GOLD


PIN BNC (75 OHMS)


KINGS 2065-10-9 DUAL CRIMP GOLD


PIN (75 OHMS)


TROMPETER UPL220-20 DUAL CRIMP


GOLD PIN BNC (75 OHMS)


ADC BNC-1694D DUAL CRIMP GOLD


PIN BNC (75 OHMS)

There is also the dielectric used. Most TV (RF) coax has a higher Propagation Velocity and hence lower loss. This is largely a factor of dielectric material and construction (Foam Injected, Teflon based, etc.). If you wish to use a video specced cable, with a kludged connection system for RF, then more 'power' to you. I assure you that the loop resistance, at the power levels required, is not an issue. The distribution cable used in CATV systems is a solid aluminum shield with a copper clad aluminum center conductor and it carries 90 Volts at up to 20 Amps (1800 Watts!) to power the line gear and that doesn't generally cause a problem...


PS: I already have an adequate supply of Coax, both video and RF, thank you.

 

[videobruce]

There was already a thread on this topic;
http://www.avsforum.com/avs-vb/showt...757&highlight=

 

[olyteddy]



Quote:
Originally Posted by videobruce /forum/post/15462678


There was already a thread on this topic;
http://www.avsforum.com/avs-vb/showt...757&highlight=

That thread seems to be mostly about RG 11 type cables, but does contain a lot of pertinent info. One interesting thing about RG 11 size cable is that most 'F' connectors for it have a a seizure clamp and a stinger, making solid copper center conductors as usable as CC Steel.

 

[videobruce]

Doesn't matter, the electrical principles still apply.

 

[nybbler]



Quote:
Originally Posted by dr1394 /forum/post/15436449


The CM7777 power supply outputs 18 volts. I'll guess it will work fine down to around 12 volts or even less. The voltage drop difference between a solid copper and copper clad center conductor of 0.27 volts (over 100 feet of coax) is so small, it just doesn't matter.


Ron

It's not quite that simple. Adding resistance between the supply and the pre-amp means that the voltage at the pre-amp fluctuates more with varied load, which can cause increased distortion of the signal from the pre-amp.


That effect is also probably too small to worry about at 100 feet, though.

 

[olyteddy]



Quote:
Originally Posted by nybbler /forum/post/15473714


It's not quite that simple. Adding resistance between the supply and the pre-amp means that the voltage at the pre-amp fluctuates more with varied load, which can cause increased distortion of the signal from the pre-amp.


That effect is also probably too small to worry about at 100 feet, though.

And why would the load vary? Also, wouldn't there be some kind of regulator in a well designed preamp? I mean one thing that defines an Op Amp is immunity to power supply variations...

 

[cpcat]

What about with temperature variation?


I thought that with very cold temperatures there could be issues with wire guage/voltage. I think this is an issue with rotator control wires. Does this impact copper vs. copper-clad or does temperature effect both the same?

 

[Speedskater]



Quote:
Originally Posted by cpcat /forum/post/15499442


What about with temperature variation?


I thought that with very cold temperatures there could be issues with wire guage/voltage. I think this is an issue with rotator control wires. Does this impact copper vs. copper-clad or does temperature effect both the same?

Resistance increases with increasing temperature!

Not that conductor resistance has anything to do with signal levels (at reasonable cable lengths)

 

[cpcat]

We're not talking about signal levels, but rather DC voltage.


I thought I read somewhere around the time I installed my rotator wire that larger gauge was important especially for longer runs and cold weather. Maybe I'm remembering wrong.

 

[Speedskater]

Still - Resistance increases with increasing temperature!

It's the rotators bearing that don't like the cold. So the motor use's more power in cold weather.

 

[olyteddy]



Quote:
Originally Posted by Rick0725 /forum/post/15505536


In my years doing this stuff, .... I went with a common practice of using solid copper and moved on.

And what do you use for connectors?