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What is traditionally best coax for 800mhz scanning

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JamesO

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#21
RG6 is what I would suggest in the thread linked and use, ALONG with a quality LNA, not a "Pre-amp"!!

Others here also mentioned RG6 as well.

Take the money that you would spend on low loss coax and connectors and spend it on an LNA, the end result will likely be superior, probably cheaper and a far easier install.

Additionally if you plan on feeding multiple scanners, the LNA route is a far better solution.

Some understand, some don't.
 
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#22
AND not all "LMR400" is good stuff. lots of knock off cable out there.

My take is genuine Times LMR400 with genuine Times type N connectors. The new Cent cables may be a good choice, I have NOT worked with them.

zz0468 writes: " 4. I have seen your pissing match with prcguy in the other thread. Truth be told, I'd back his technical comments over just about anyone else on here. The guy is pretty damned sharp. "
And I agree PRCGuy IS very knowledgeable. Probably lots of 'time in grade'.
 

bobsav21

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#24
Solid copper

AND not all "LMR400" is good stuff. lots of knock off cable out there.

My take is genuine Times LMR400 with genuine Times type N connectors. The new Cent cables may be a good choice, I have NOT worked with them.

zz0468 writes: " 4. I have seen your pissing match with prcguy in the other thread. Truth be told, I'd back his technical comments over just about anyone else on here. The guy is pretty damned sharp. "
And I agree PRCGuy IS very knowledgeable. Probably lots of 'time in grade'.
I've been looking to buy some decent Coax and heard everyone talking about Times LMR400 and how great it was. We'll I can buy it locally for 89 cents a foot which isn't too bad. Someone else mentioned good quality RG6 which is somewhat cheaper.
The weird thing is when I went to the Times web site and looked at their spec;s I found out that Times LMR400 has a copper coated aluminum center core.

Inner Conductor Solid BCCAI 0.108 (2.74)
Dielectric Foam PE 0.285 (7.24)
Outer Conductor Aluminum Tape 0.291 (7.39)
Overall Braid Tinned Copper 0.320 (8.13

I always thought that Copper clad aluminum was the cheap stuff like you get from China.
Real RG6 or RG8 has a solid Copper core which should be better and last longer.

Confused

Bob
 
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#25
Due to the RF skin effect, the outer layer of the conductor is the only portion that has current flow, so solid copper is unnecessary. There is nothing wrong with using copper-coated aluminum for this application.
 
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#26
Even some of the mid sized Andrew/Commscope Heliax coax has copper clad aluminum center conductor due to the skin effect as jonwienke mentioned. The larger Heliax has a hollow copper tube for the center conductor because the middle is not necessary for most RF frequencies.

You will find most RG-6 is copper clad steel center conductor, however DirecTV and other satellite providers specify solid copper center because they are powering distant equipment up the coax with DC and steel core would have too much voltage drop on long runs.
prcguy

I've been looking to buy some decent Coax and heard everyone talking about Times LMR400 and how great it was. We'll I can buy it locally for 89 cents a foot which isn't too bad. Someone else mentioned good quality RG6 which is somewhat cheaper.
The weird thing is when I went to the Times web site and looked at their spec;s I found out that Times LMR400 has a copper coated aluminum center core.

Inner Conductor Solid BCCAI 0.108 (2.74)
Dielectric Foam PE 0.285 (7.24)
Outer Conductor Aluminum Tape 0.291 (7.39)
Overall Braid Tinned Copper 0.320 (8.13

I always thought that Copper clad aluminum was the cheap stuff like you get from China.
Real RG6 or RG8 has a solid Copper core which should be better and last longer.

Confused

Bob
 

bobsav21

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#27
Well

Well all I know is that way back in the old days :) there was never anything like CCAL.

The first time I ever heard of CCAL was when I bought a couple hundred feet of Coax from E-bay to rewire
the TV drops in a house remodel and found out it was not copper on the inside. That's my first experience with what everybody ( at that time ) was calling " Cheap Chinese Coax.".
Now all of a sudden it seems to permeate the market.. No name and Brand name...whatever .

I sure the reason behind this is they discovered that they could "get away " with it in most applications and make more profit at the same time.

So if I read you correctly your saying that 2 lengths of coax, one solid copper, one CCAL will perform the same and there is no performance reason to use solid copper. ?

Bob
 
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#28
So if I read you correctly your saying that 2 lengths of coax, one solid copper, one CCAL will perform the same and there is no performance reason to use solid copper. ?
That is correct, unless you are feeding DC power through the coax to run an amplifier or something. In that case solid copper will have less DC voltage drop.

But for RF, especially 800MHz, there is no measurable difference, because the RF current is only flowing in the outer surface of the inner conductor, which is copper either way. No current is flowing in the aluminum core.

The reason it has become popular is because getting copper to stick to the aluminum requires some clever metallurgy that is a fairly recent development.
 
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#30
If you had two identical coax cables except one had solid copper center conductor and the other had copper clad steel, you could probably find two frequency ranges like 100KHz and 30MHz where the steel core cable would show more loss at 100KHz than the solid copper. This would be due to the lower 100Khz frequencies penetrating deeper into the lossy steel compared to the higher 30Mhz frequency riding on mostly the surface.
prcguy

That's very interesting, first time I've heard that explanation.
Well that helps and make me think at the same time..
Thanks
Bob
 
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#31
Ladder Line

What about Ladder line or twin lead , I know it is very low loss at HF frequencies. I wonder how it would work for receive only scanner antennas?
 
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#33
About the aluminum center conductor with copper clad/plating: Make sure you do not mess up the copper plating when installing connectors.

Same problem with the steal center on RG6 cables.

On ladder line, we have very low loss coaxial cables today that we did not back in the 'days'. And there was some loss in the Balun, matching transformers.
 
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#34
About the aluminum center conductor with copper clad/plating: Make sure you do not mess up the copper plating when installing connectors.

Same problem with the steal center on RG6 cables.

On ladder line, we have very low loss coaxial cables today that we did not back in the 'days'. And there was some loss in the Balun, matching transformers.
I am sure there are better options today , but what is the cost compared to Ladder Line / Twin Lead
 
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#36
Twin lead is balanced, and unlike coax, is susceptible to loss and interference when it is routed near metal objects (the metal is significantly closer to one conductor than the other). You'd need a transformer to adapt from the balanced 300-ohm twin lead to unbalanced 50-ohm BNC/SMA.
 
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#38
Twinlead, ladder line and open wire line will usually have much less loss than most coax you will encounter. For example, at 450MHz where 100ft of LMR400 has about 2.68dB loss a common 450 ohm ladder line has only .68dB loss for the same length. For super long runs at HF ladder line or open wire line is king. At 28Mhz, 1,000ft of LMR400 has about 6.4dB loss where 600 ohm open wire line has about 1dB. That's not much for 1,000ft of feedline!

One problem with twinlead or ladder line is it needs to be used in a balanced system, meaning neither side will connect direct to ground. It will usually be fed from a transmitter through an antenna tuner that provides a balanced output by design or by use of a transformer and to an antenna that is balanced like a 1/2 wave dipole.

Another problem is the impedance is not 50 ohms and an antenna tuner or matching transformer is usually required. One good thing is once you match the ladder line at the radio end you can feed a 50 ohm antenna with ladder line and the mismatch between 450 ohm feedline and the antenna can almost be ignored due to the very low loss of the balanced line.

For use with a scanner and a typical scanner antenna like a Discone you would use a broad band transformer at each end like a TV transformer that will (sort of) match the low impedance of the scanner and antenna to the higher impedance feedline. You can get very low loss VHF/UHF transformers that are a lot better than the typical and lossy TV transformer.
prcguy

How would you hook twin lead to a scanner?
1 lead to center of connector the other lead to outside of connector ?

That doesn't sound right

Bob
 

iMONITOR

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#39
I have been using R6 for scanning 800mhz, roughly about 50 feet of coax line. Since I'm gonna be taking down my antenna before winter hits and move it to a different location, I thought I would ask the fellow RRs what are thoughts for coax if RG6 is the best quality for loss and such. I'm gonna be having a 50-75 foot run of cable and the antennas will be off the ground about 30 feet.


 

rs989

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#40
My setup will be 3 Wilson Yagi Beams and a L-Com Globel Omi
I use kind of the same setup. A Wilson 800MHz yagi fed by 35 feet or RG-6 quad pointed spot on to a distant site about 20 miles. This setup works well and I have my Scantenna using RG-6 quad as well which also works great. I can see if it's a very long run at the higher frequencies then the hardline would be the best route. Some of those cables are so stuff it seems like fighting a snake, they have a mind of their own. The other lower loss cables are nice but can be expensive.
 
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