[TowerTalk] BURY FLEX and PE outer Jackets (also used on our ROTOR CABLE). ROPE Re: LMR 400 UF issue and Low Loss cables in general Re: TowerTalk Digest, Vol 203, Issue 15

Wed Nov 13 13:31:35 EST 2019

  Dick,  Thanks for the comments ref. Bury-Flex Tm vs. LMR-400 UF.  I think that answers Bob 's  question.

Just to add, when I designed Bury-Flex Tm I used a medium  density PE (polyethylene).  PE is highly resistive to rot, mildew, UF, various oils, chem's and gasoline.   It has a higher durometer than PVC (PVC can be had in various formulas and is most often used for flexibility and relative low cost.  Only certain formulas of PVC are UV and plasticizer migration resistant. 
DAVIS RF only uses the UV compounds of PVC for any type of cable that will be used outdoors. But again, PE has even more qualities )  

   I have Bury- Flex Tm  Buried directly in the ground, and laying on the surface in my woods to my tower.  It has been out there over 15 years.   The jacket is as shiny as new, really.   I have all the critters here in MA and they do not bother the PE outer jacket of Bury-Flex Tm.  

  We also have our various rotor cables that we sell extruded with a PE outer jacket.   We are only one of two dealers that I can find who uses PE.   The most common mfr. Of rotor cable is JSC Wire, they use a PVC outer jacket.

  So, bottom line,  PE is an excellent outer jacket material for resistance to the above noted elements.      I have not tested shelf life, or outdoor or buried life, because it has been around 15 years so far that we have had Bury-Flex Tm out there, and less years for our rotor cables, since we converted to PE.  But clearly, based on my experience and insight as a cable design engineer, I'd depend on PE jacketing to be "out there" or on the shelf for at least 30 years.

Our rotor cable with PE, as well as Bury-Flex Tm, and others, are available from many ham dealers including HRO, Universal Radio,  Texas Towers and others.

   Any questions, feel free.    Need ROPE of all types / sizes , at LOW prices, made in USA??   DavisRopeAndCable.com  (this is a totally separate company, staff and location than DAVIS RF... please contact me for either company)

73, Steve, K1PEK       Steve Davis,  DAVIS RF Co.  and  DavisRopeAndCable.com

On 11/13/19, 12:50 PM, "Dick Green RLG Analytics" <dick at rlganalytics.com> wrote:

    I've had long outdoor runs of Buryflex, both direct-buried and in the air, for more than 15 years -- probably close to 20 years -- with no degradation problems.

    Before going with Buryflex I used LMR400UF. I didn't use it long enough to comment on degradation, but I did have significant problems with critters chewing the cables, sometimes all the way through. I must have replaced the 100-foot run to my 4-square half a dozen times before replacing the LMR400UF with BuryFlex. I haven't had any problems with critters since.

    The other issue I had with LMR400UF was flexibility. I had a run going up my 72' U.S. Tower rotating tubular tower, an application that requires flexibility. I had a near-disaster where the coax migrated around the tower and got hung up on the motor control cabinet, and determined that lack of flexibility in the cable was partly responsible. I replaced the run with RG213, which is pretty flexible but higher loss. A couple of years later I did some tests with Buryflex and found that it's as flexible or more flexible than RG213. Since the loss is considerably lower, I replaced the RG213 with Buryflex and have had no problems in the 15-20 years since.

    73, Dick WC1M

    -----Original Message-----
    From: Bob Shohet, KQ2M <kq2m at kq2m.com> 
    Sent: Tuesday, November 12, 2019 2:50 PM
    To: Steve Davis | Davis RF <sdavis at davisrf.com>; towertalk at contesting.com
    Subject: Re: [TowerTalk] LMR 400 UF issue and Low Loss cables in general Re: TowerTalk Digest, Vol 203, Issue 15

    Hi Steve,

    Regarding Buryflex, what is the anticipated lifespan of Buryflex under “normal” use cndx?   How long can it be stored inside (prior to use) without significant degradation?

    Tnx & 73

    Bob  KQ2M

    From: Steve Davis | Davis RF 
    Sent: Tuesday, November 12, 2019 1:20 PM
    To: towertalk at contesting.com 
    Cc: wa6tla at icloud.com ; W4EF at dellroy.com 
    Subject: [TowerTalk] LMR 400 UF issue and Low Loss cables in general Re: TowerTalk Digest, Vol 203, Issue 15

    Hi Elliot

    Mike, W4EF, hits it on the head ref. potential degradation of LMR 400 UF, in outdoor environments vs. UV impact.

    My firm, DAVIS RF Co., sells various RF cables, as well as control cables, and provides government, military and numerous industries, with cable design and solutions, not only in the RF spectrum.  We are not just wholesalers, we are cable design engineers fulfilling many custom needs.     One cable I designed, which many hams recognize, is Bury-Flex Tm, used also by Lockhead Northrup and NASA ground stations.

    In the past on T Talk, I have pointed out the issue with LMR-400 UF, and suggested alternatives. 

    We sell a lot of Times LMR sizes, and in fairness to them, their cables in general are superb.  However, in order to max out flexibility of UF's, they chose to use a TPE jacket (Thermoplastic elastomer).
    This outer jacket material does not hold up well to UV, over the longer term (depending on where  in the world it is used). Times latest specs have deleted ref. to the potential life of the cable.  And W4EF'S experience, as noted, confirms the problem. 

    So, what is the alternative??:  Belden 9913F7, which has excellent flexibility, and same attenuation specs (only slightly different at and over 2 GHz).   And, 9913F7  is LESS expensive than 400 UF.  
    Why is it better vs. UV??  Because they use their own formulated "Belflex" Tm outer jacket material.  It is a highly flexible hybrid PVC.   NOTE: do not mix this cable up with Belden 9913, which at least in the ham market has had a bad reputation.   9913F7 is a totally different build. And I highly recommend it.

    I will just add also that many customers come to me thinking they need to run their entire length of a cable using a UF type, where there are alternatives to that which results in our sale being less, but that also means saving the customer his $$, which is what we want to do for our fellow hams , without sacrificing performance and application sense. 

    Lastly,  we have very low prices on Low Loss cables, hardline, Andrew Heliax and RFS Cablewave Heliax Tm equivalent.  And we do the assemblies using mfr. Certified installers.  We provide our fellow hams with the same low wholesale pricing as we do  all other commercial customers.  And we provide free application consulting, unlike any other commercial or ham dealer that I am aware of. 

    Contact me anytime with any questions.  73,  Steve Davis,   DAVIS RF Co.  

    On 11/12/19, 12:01 PM, "TowerTalk on behalf of towertalk-request at contesting.com" <towertalk-bounces at contesting.com on behalf of towertalk-request at contesting.com> wrote:

        Today's Topics:

           1. Re: Times Microwave LMR-400 UltraFlex Cable (Michael Tope)

        ----------------------------------------------------------------------

        Message: 1
        Date: Mon, 11 Nov 2019 20:56:47 -0800
        From: Michael Tope <W4EF at dellroy.com>
        To: towertalk at contesting.com
        Subject: Re: [TowerTalk] Times Microwave LMR-400 UltraFlex Cable
        Message-ID: <3199f5a5-9526-3649-f146-36c4a06d8d64 at dellroy.com>
        Content-Type: text/plain; charset=utf-8; format=flowed

        Are you planning on using the TM cable outdoors, Elliot? I had really 
        bad luck using LMR400UF in an outdoor application. While it was indeed 
        very flexible, the jacket essentially disintegrated in the Southern 
        California sun. Regular LMR400 by contrast holds up extremely well in 
        the SoCal sun. Apparently the UF variety uses a TPE (thermoplastic 
        elastomer) jacket whereas the regular LMR400 uses a PE (polyethylene) 
        jacket.

        Unless Times improved the formulation of the UF jacket material, I would 
        be cautious about using it outdoors without some additional protection 
        for the jacket (for a short rotor loop, a layer of 3M tape might do the 
        trick). For indoor service, it should be fine.

        73, Mike W4EF

        On 11/10/2019 12:28 PM, Elliott Lawrence via TowerTalk wrote:
        > I?m looking for a source of Times Microwave LMR-400 UltraFlex cable assemblies.  I have found one company, Field Components in Florida, that specifically states that they use this cable.  Other suppliers,  ABR, DX Engineering etc have preassembled cables but do not specific Times Microwave.  Based on the pricing by those suppliers I doubt that the TM cable is used.
        >
        > Recommendations, suggestions etc would be appreciated.
        >
        > 73
        > Elliott WA6TLA
        >
        >
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