RG-6 vs RG-58

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by N4JWA, Jan 8, 2011.

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  1. W0BTU

    W0BTU Ham Member QRZ Page

    Copper-Clad Steel RG-6?

    I ought to check what I have. If I have some, I would be happy to mail you a little for your tests. How much would you need?
     
  2. VK1OD

    VK1OD Ham Member QRZ Page

    Thanks Mike, but it will cost you more to mail it than for me to buy a bit locally.

    I will see what I pull out of here, I threw lots out, but if the last piece which will be 10-15m is CCS, I will measure it.

    If not, I should buy a little. I have a roll of quad shield for the TV, it may well have CCS in it. I will check when (if) the rain stops.

    Owen
     
  3. KM1H

    KM1H Ham Member QRZ Page

    AFIK its all Copperweld. An extensive test I did personally or directed the tests in the late 80's showed straight line loss from 600MHz right down to 1MHZ for RG-6 and RG-59 CATV cable and which was the low frequency limit I used. The loss at 2 MHz is .34dB per 100'.

    I was managing a R&D group at Wang Labs that was developing the Wangnet CATV style based RF data network and extensive testing was done from RG-59 to 1" "Fused Disc".

    A 20 cable graph (later 22 cables)from 1-1000MHz was published that also included popular 50 Ohm cables from RG-58 to 7/8" Andrew Heliax. It also appeared in the Radiokit Catalogs of 1987-91

    All the cable tested was high end name brands such as CommScope, Times, General Cable, Trilogy for 75 Ohms and only Belden for the flexible 50 Ohm cables.

    I would have to "assume" that the specs have not degraded over the years from US production companies. I cant speak for China sourced.

    Carl
    KM1H
     
  4. VK1OD

    VK1OD Ham Member QRZ Page

    Carl,

    It is not all Copperweld (CCS). I just pulled some out of the roof, it has copper centre conductor. The roll I use for my ham stuff also has copper centre conductor.

    I am looking at the specs for Belden 1189A. It has a CCS centre conductor of 0.04" diameter, and DC resistance of 28 ohms per 1000'.

    It is fairly simple calculation to show that the copper thickness is about 4% of diameter, or 40┬Ám. At frequencies below about 17MHz, it will show a departure from copper like conductivity.

    Not all RG6 will be the same. Some do have copper conductor, and some have CCS, and no doubt, the CCS cladding thicknesses may vary.

    Owen
     
  5. KM1H

    KM1H Ham Member QRZ Page

    Actually the straight line attenuation starts at around 600MHz and the gradual added attenuation is quite visible. This is for the 1980's cable when it wasnt rated any higher in frequency. I never disputed the loss factor, just that it only affects some magical lower frequency.

    You can graph the latest and greatest from the data here

    http://awapps.commscope.com/catalog/systimax/product_details.aspx?id=25197

    Carl
     
  6. VK1OD

    VK1OD Ham Member QRZ Page

    The data shows loss/100' of 2dB at 100Mhz. If the conductor was copper, you would expect that loss at 10Mhz to be 0.63dB and at1MHz to be 0.2dB, but it is quoted at 0.70dB and 0.38dB. These figures show a departure from copper performance just noticeable at 10MHz, and nearly double copper attenuation at 1MHz.

    Owen
     
  7. W0BTU

    W0BTU Ham Member QRZ Page

    The Commscope quad-shield flooded RG-6 I have is CCS.
     
  8. KM1H

    KM1H Ham Member QRZ Page


    And?? You are just repeating the same thing over that is already known, CCS has a bit more loss than pure copper but the FACT is that its a straight line if you graph it.

    If you look at RG8X the loss of 100' at 150 MHz is 4.5dB versus 2.2dB for RG-6. As the frequency goes down the losses almost converge at 2MHz with 8X still a bit higher at .4dB.

    Mike, Ive never seen RG-6 that isnt CCS. It was developed for CATV drop cable and the steel core is for strength in drops from the utility pole to a building. If some other version has all copper it should have a different designation such as RG-6A.

    Now all this worry over a tiny bit of loss is pure nitpicking as it would take several hundred feet to be of any consequence even at 160M. Im sure not losing any sleep over 200-400' of it on several Beverages used on 30-160M that feed a relay box with another 100' back to the house. Its certainly cheaper than 8X and the quad shielded and flooded benefit cant be duplicated with any 50 Ohm cable.

    Off to the woods to run the last Beverage before Wednesdays snow storm.

    Carl
     
  9. VK1OD

    VK1OD Ham Member QRZ Page

    The three points I gave in my post about your Commscope product prove that it is not a straight line, yet you continue to insist that it is a straight line. This questions whether you have actually plotted this data.

    [​IMG]

    I have plotted Belden's data for 8262 (RG58CU type), see blue points above, they do not fall on a straight line, but are a very good fit to a smooth curve (red) that loss=k1*f^0.5+k2*f.

    I have also plotted Belden's data for 1189A (RG6 type), it is a smooth curve which is not a very good fit to the loss model that loss=k1*f^0.5+k2*f, although the points above 100MHz are a good fit to such a model.


    Owen
     
  10. W0BTU

    W0BTU Ham Member QRZ Page

    Sure, but that doesn't mean that this subject isn't interesting. :)
    Time spent doing something you enjoy is not wasted time.

    This is somewhat of an extension of another post about antennas (VERY interesting), where the paramagnetic properties of galvanized steel wire and copperweld were being discussed.
     
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