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
significant.
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
www.DavisRF.com
Commscope SFX-500:
.................................................... atten dB/100
ft...............................
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 <k2xx@swva.net>
> Subject: [TowerTalk] 1/2" Commscope 50 ohm hardline (SFX-500)
> To: towertalk@contesting.com
> Message-ID: <4A2ABA08.1030905@swva.net>
> 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
>
>
> ------------------------------
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
>
> End of TowerTalk Digest, Vol 78, Issue 23
> *****************************************
>
>
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|