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[TowerTalk] DAVIS RF response: Alternatives & Comscope SFX-500 data vs.

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Subject: [TowerTalk] DAVIS RF response: Alternatives & Comscope SFX-500 data vs. LMR & LDF4
From: "Steve Davis -Davis RF Co." <>
Date: Sun, 7 Jun 2009 11:43:48 -0400
List-post: <">>
Hi Joe and others,

Here is your loss data (below).  Not sure how this will reproduce on TT, so, 
for ref.,  the .5 MHz = .065,   the 10 MHz = .293;      30  = .512, etc.

 Although Commscope is a well built cable, Andrew and LMR are also very well 
built as likely you know.  Often, for various reasons, Heliax (LDF, etc) is 
overkill for hams and more costly.  By overkill, I am not referring to 
attenuation, as often the alternative choices are very close to same 
attenua.  Overkill is as to the extra strength (and cost vs. comparable LMR) 
of Heliax (for hauling up very high commercial towers) and crush resistance 
(if you plan to drive your car over it day in day out... HI).

 Bend radius is larger ("worse" depending on the installation issues) for 
Heliax vs. similar size LMR (and the bend rad will be same or close to for 
the other Heliax similar constructions like RFS and Eupen, etc).   The bend 
radius on this Commscope is  1.25",  LDF4 is  5 ", and LMR-400 is 1" (but I 
always recommend adding about 1" to these bend radius's to be safe).

  Thus, this Commscope is the same build as LMR  ; i.e., not the more 
expensive "corrugated" build of Heliax (or RFS, Eupen, etc).

   Attenuation wise,  comparing the .5" Heliax is not a good comparison 
because LMR-400 is a .405" OD which increases the attenuation (given that 
the dielectrics and ctr. conductor is fairly equal).  Thus LMR 400 at 30 MHz 
is .7 dB per 100 ft  and .512 for this Commscope   vs. .357 for LDF4   .

  Obvious conclusion:  It appears that your "below 150 MHz"  data interest 
indicates usage at HF, as most readers here are involved with.  At HF, a 
choice between LMR and Commscope is almost a non-consideration...they are so 
close in attenuation that I highly doubt you would ever make or break that 
last contact for DXCC.   The cost differential of these two vs. LDF4 would 
be significant.
The cost of connectors, and bend radius install issues of Heliax, also 

  Lastly,  a better comparison to LMR-400 or Commscope SFX-500, attenuation 
wise, is LMR-600:    .4  dB/c ft  at  30 MHz and 1.5 " Bend rad (add 1" for 
safety) .

10 MHz  attenua:   Commscope SFX-500:  .52
                                 LMR 400:                      .43  prox 
(from Times graph, not from formula
    $ .79/ ft  from DAVIS RF Co.
                                 LMR 600:                       .27 prox   $ 
1.56/ft   DAVIS RF Co.
                                 LDF4-50A:                    .205 
$  2.21/ft       DAVIS RF Co.

Bottom line:  Commscope vs. LMR:  Davis RF sells quality and reputation. 
LMR is made in CT, to high quality stds. It's been around some 30 or more 
years.   Many knock offs of LMR are out there and I know some of the 
factories.  We won't sell them.  Yes, you can
save money on the knock offs, and you are welcome too as long as you test 
them to the same degree that would support comparison to LMR.  Installing 
cable is only a real pain when you have to trouble shoot it, go up that 
tower, or hire a guy to futz with it in the middle of CQ World Wide, or dead 
of winter.  Then there is the little addage, that some of us take sincerely 
to heart, "By American".  Yes, I know the reports on here of having success 
with the knock offs, but who has really tested them completely, and who has 
had that cable up for 5 or 10 + years???.  With LMR PE jacketed, or DAVIS RF 
Bury-Flex Tm,  I'll give you a good 30 + years of life.   And also, I will 
take the time to give you complete info (as above) before, during and after 
your purchase ... do you see Commscope,  Tessco, etc. on here, or do you 
have somebody there to consult??  (Sorry, that's another subject:  What RF 
qualified ham engineers (vendors) are supporting you, and are you 
"supporting "  them ???  )  Note:  Joe, not directed at you .....HI

If I can answer any further questions for you or anybody on TT, just ask.
73,   Steve ,  K1PEK,

DAVIS RF Co.,  Div. of Orion Wire Co., Inc.

Wire, Cable, RF Connectors and wire aerial parts.   LMR, Heliax, Eupen

Commercial / Military / & Custom Cable Design

tel:  978-369-1738     Fax:  978-369-3484

Commscope SFX-500:
.................................................... atten dB/100 
      0.5 0.213 0.065 15.60
      1 0.302 0.092 15.60
      1.5 0.37 0.113 15.60
      2 0.428 0.13 15.60
      10 0.962 0.293 8.97
      20 1.367 0.417 6.32
      30 1.68 0.512 5.14
      50 2.18 0.664 3.96
      88 2.913 0.888 2.96
      100 3.112 0.948 2.77
      108 3.238 0.987 2.67
      150 3.838 1.17 2.25

    73,  Steve  K1PEK

> Message: 6
> Date: Sat, 06 Jun 2009 14:48:40 -0400
> From: Joe Giacobello <>
> Subject: [TowerTalk] 1/2" Commscope 50 ohm hardline (SFX-500)
> To:
> Message-ID: <>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> Anyone have experience with this hardline?  Its attenuation at 150 MHz
> is 1.2 dB vs about 0.9 db for LDF4-50a and 1.5 for LMR-400.  There are
> no data available for frequencies below 150 MHz.
> 73, Joe
> K2XX
> ------------------------------
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> End of TowerTalk Digest, Vol 78, Issue 23
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