[TowerTalk] Misrepresentation of LMR-400 vs. 400 UF

[Steve Davis | Davis RF]

I have seen some ham suppliers indicating that LMR-400 is good for up to 20 years of life, on average (correct per Times, the mfr).  Then below it they give the spec on LMR-400 UF without rating life of the UF version.

These suppliers do point out that 400 is a PE jacket, and that the 400 UF is a TPR jacket.

As an RF cable design engineer, I am aware that TPR is used on the 400 UF to provide extra flexibility to the build, vs. using PE which has a higher durometer (related to density), thus
PE would reduce the flexibility of a stranded center conductor (stranding  aids the flexibility) of the UF vision. The 400 has a solid center conductor, less flexible than a 7 strand center conductor  as is the UF version.

   TPR used on the UF version has nowhere near the life of 20 years that the PE version does.  Times describes the UF version as having an outdoor life "in excess of 10 years". Of course any life expectancy is dependent on ambient conditions, particularly temp and UV.

  I have never recommended that UF will last up to 10 years in UV.  A great,  less expensive and longer lasting alternative is Belden 9913F7  (not to be confused with the totally different construction of 9913).  It is an equivalent, mechanically and electrically to LMR 400 UF, but the key aspect is that  Belden uses a patented "Bell Flex" jacket, a PVC concoction, that has excellent flexibility, UV resistance and will last a lot longer.

Lastly, Customers often want to run a flexible cable  from the shack out and up the tower, but that expense is not really necessary.  LMR 400, 400 UF and DRF-400 all have 1" bend radius's (2" is safer),  and Bury-Flex Tm (2" b.rad.).

So, think why you really need a full shack to antenna run of 400 UF or 9913F7 or Bury-Flex Tm.
Use a lower cost low loss cable to the tower top (such as DRF-400 Tm.)  Then use the flexible cable for the rotor loop.  Wait:  add connectors in the cable !?!:

High quality commercial connectors, such as what I carry, only interject .002 dB at their MUF, so two males and a barrel connector amounts to only .006 dB at the MUF of that type of connector.
MUF for a quality  UHF  connector is 300 MHz.   At 30 MHz the insertion loss of each connector and barrel is only 10 % of .002 , or  .0002 dB for each  !!  MUF for N types is much higher.

  So, if you bought 300 ft of an expensive UF, and now feel like hanging yourself, I also have plenty of rope:  Davis Rope and Cable Assembly Co., totally separate from DAVIS RF.  HI    DavisRopeAndCable.com
We appreciate your continued business and support.  73,  de K1PEK    Steve   DavisRF.com
    DRF-400 and Bury-Flex are trademarked by DAVIS RF.  LMR is a registered Tm of Times Microwave Systems

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