Columbia 01109 RG-8/U coax specs?

Discussion in 'General Technical Questions and Answers' started by KI6USW, Sep 21, 2016.

ad: L-HROutlet
ad: l-rl
ad: abrind-2
ad: Left-2
ad: L-MFJ
ad: Left-3
ad: HRDLLC-2
ad: L-Geochron
ad: MessiPaoloni-1
  1. KI6USW

    KI6USW Ham Member QRZ Page

    Hi y'all:

    Local op gave me a 55 ft piece of this stuff (Columbia 01109 RG-8/U).
    Wondering if it will be adequate for 2m/70cm vertical w/o too much loss.
    Jacket seems to be in perfect shape, flexible stranded core, but it does use urethane insulation.

    Does anyone have a photographic memory of the spec sheet for this?
    Like v/f, and other specs?

    Thank You . . .
     
  2. WA7DU

    WA7DU Ham Member QRZ Page

    The wording you used above makes me think you already know that the mil spec for RG-8/U is an orphan spec--the product made to the mil spec has been obsolete for 10,000 years, and no products have been "qualified" under that spec for that same period of time. Consequently, anyone can make a cable and call it RG-8.

    If any spec applies, it is the manufacturer's spec, not the mil spec. Unfortunately, Columbia and their RG-8 spec seems to have escaped the WWW. Products offered under the RG-8 designation vary significantly. RG-8, RG-8X, and RG-8 mini are some of the designations available today. The cables offered under those designations vary from an O.D. of 0.240 to one with an O.D. Of 0.405, and vary in attenuation of 6 dB per 100 feet to 2.6 dB.

    Who ya gonna believe ?

    Is it OK for your use ? Well, how long will the feed-line be in your application ? If it is a short run to an antenna used for local simplex or local repeaters, you may be satisfied. But, if your application is for meteor scatter, EME, or DX you may not be satisfied.

    Velocity factor ? Try 0.8. Real world VF's are notorious estimates anyway.

    How did you ascertain the dielectric to be urethane ? I'm dubious.
     
  3. WA7PRC

    WA7PRC Ham Member QRZ Page

    I've never seen a RG8 w/ urethane insulation. I used to have the specs but, that is a very old cable. Some things to consider...
    • Most solid polyethylene dielectric center insulation VF = 0.66.
      Most foamed PE dielectric center insulation VF = 0.80.
    • Most foamed PE dielectric coax has less loss than solid PE.
    • Coaxes w/ foamed PE dielectric will "cold flow" and allow the center conductor to migrate away from the center of the cable, especially in tight corners and horizontal runs. Solid PE is better.
    • Center conductor stranding and flexibility varies from 7x19 to 19x34. The latter is more flexible. But, at higher frequencies, solid conductors have less loss due to skin effect.
    • Percentage of shielding varies from pi$$ poor (around 50%) to very good (> 95%).
    • Outer jackets vary. Many aren't very UV-resistant. Some are porous and not suitable for wet/buried applications.
    The simplest thing to do is try it. Use it until you're not happy with it. :)

    vy 73,
    Bryan WA7PRC
     
    Last edited: Sep 21, 2016
  4. KC4YLV

    KC4YLV Ham Member QRZ Page

    Water ingress would kill it, braid sucks up water like nothing else. However, not much you can do besides hook it up and try.

    Loss-wise at 55ft and 2m, eh, db or 1.5 db maybe. Nothing to cry about. It'll sting a bit on 70cm, probably have a good 3db loss there, but that's just kind of what we live with without infinitely fat pockets for Heliax :D
     
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I think Columbia used to be an American brand, but see that today Columbia Wire and Cable is based in the Philippines and there doesn't seem to be a U.S. brand like that anymore. I have no details about what happened.

    But I do remember them and their stuff was okay. I don't recall them ever being on the QPL for MIL-C-17 so they probably did not make "real" (mil-spec) RG cables, just ones patterned after those standards without all the controls and inspections -- as many manufacturers have over the years.

    I doubt the insulation is urethane. The dielectric should be polyethylene, either solid or cellular, and the jacket material also polyethylene or PVC.

    VF of "real" RG-8/U (or RG-8A/U which replaced the original many years ago and then was dropped entirely from MIL-C-17 to be replaced by RG-213/U decades ago) is 0.66. However, the cellular (foam) dielectric versions, which have never been "mil spec" can have a VF of 0.78 to 0.84 depending on the gas content.

    Loss can be measured.

    To check it out visually, I just strip back 6"-12" from each end and look for:

    Is the dielectric either translucent (solid PE) or bright, shiny white (cellular PE)? It should be one or the other.

    Is the outer conductor (braid) shiny copper or clean tinned copper? It should be one or the other.

    When stripping the dielectric material from the stranded center conductor and revealing the center conductor (core), are those copper strands nice and shiny, copper looking? Should be.

    If the cable passes those simple visual inspections, it's likely fine unless it has a break, short or hole in it somewhere along its length. You can inspect for that, too.

    One thing a lot of "cheapie" (non mil-spec) coaxial cable manufacturers did, and may still do, is "splice" cable to make a longer run before extruding the jacket material over it. You can find the "splice" (if there is one) by running the cable through your hand, gently squeezing it as you pull it through, to see if there's a "bump" in the jacket anywhere. A physical bump often means there's a splice point right there. On HF (up to 30 MHz) this normally makes zero difference in performance. On 2m, it might make some difference. On 70cm, it can make a lot of difference. A bump can be found electrically using a TDR or similar instrument.
     
  6. W9GB

    W9GB Ham Member QRZ Page

    COLUMBIA Coax cable !
    It was an "infamous" cable brand marketed during CB craze (and metal shortages) of early 1970s.
    Some loved it (cheap), others detested it (QA, consistency issues).

    Virtually any "mom and pop" CB reseller in 1970s sold it --- due to their generous credit terms and it was cheaper than Belden, Andrew, or General Cable.

    Steve (WIK) covers the proper visual inspection steps.
    A TDR is great tool (LMR shops have), but most amateurs do not have access to one.
     
  7. KI6USW

    KI6USW Ham Member QRZ Page

    Can't seem to find the mfj-259 ATM.
    Losses at 2m will be pivotal; so I'll update when I find the mfj.

    The dielectric seems to be opaque.
    Reason I stated that it is urethane/foam was from a quick glance and the 'U' designation.
    Coax isn't lumpy, so am doubtful there is any splice in it.

    Thanks for the contributors, as I couldn't find anything on the internet about it t all.
     
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    The /U follows all RG cable part numbers. RG = radio guide. U = universal. That's all they mean. Nothing about materials or construction.
     
  9. W9GB

    W9GB Ham Member QRZ Page

    Columbia Wire and Cable Corporation ( CWCC ) is a company engaged in the manufacture of electric wire and cable products.
    http://columbiawire.ph/

    The company began in 1964 as Silicon Manufacturing Corporation in San Francisco Del Monte.
    By 1973 the company became a public corporation, Columbia Wire and Cable Corporation, with manufacturing operations in the Philippines.

    They have grown from 40 employees to over 300 (last report), and focus on the commercial power industry. Their present location is at 75 Howmart Rd., Bo. Kangkong, Quezon City, Philippines.
     
  10. AI3V

    AI3V Ham Member QRZ Page

    You cannot tell how much loss a length of coax has by looking at it.

    But your wattmeter and vswr meter can measure it.

    Stick a couple connectors on it and see.

    Unless of course you like internet guesses.

    And no insult intended, but trying to make a specific electrical length without again measuring the vf is a fools errand. This parameter in particular can and will vary in different parts of even a new line

    Rege
     
    Last edited: Sep 22, 2016

Share This Page

ad: Morse-1