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Old 14-09-2012, 23:22   #1
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LMR400 clones

Hi,

I am looking to do some new wiring, looking at LMR400 for some of the circuits. The original, genuine LMR400 Coax is made by Times etc., but there are many clones available at half price or less, almost all made in China. Don't want to start an anti-China thread, but anyone got any real, hands on experience with these clones? I am looking at Jefa Tech, a US (Maryland) based distributor, in particular, which according to their product specs, is equivalent to Times.

Lee
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Old 16-09-2012, 08:11   #2
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Re: LMR400 clones

Lee,
I don't have direct experience with cheap knock-off / "generic" / made in China "LMR-type" cables....
But, I recommend against them, (and against even LMR-400 itself) for a few reasons...

a) LMR-400 is a bit stiff....has a solid copper-clad aluminum center conductor, and a low-density-foam dialectric...and requires a bit of quality control to manufacture correctly....(as well as care upon installation, etc.)

LMR-400 is not really a good choice here....if you need an ultra low-loss flexible cable, use LMR-400UF or Davis Bury-Flex....both use stranded-copper center conductor, and are more flexible, and more feasable for use in tight spots and/or where bending is required....

Further, if you are going to be installing you own connectors on LMR-400, you're apt to nick the copper cladding and expose the alum wire, giving rise to future connection issues / corrosion / etc....




b) In my 40 years in communications, there are few constants...but one constant is:
Cheap cables and connectors always end up costing you more!!!

In addition to lots of Heliax, flexible cables I've used: Times LMR-240, LMR-400UF, Belden 9913, Davis "Bury-Flex", and many variants of mil-spec/"RG" series (213, 214, etc.), as well as non-mil-spec cables (RG-8x, etc.)....
And, I've worked on / repaired more systems with cheap cables/connectors, than I care to remember....

Bottom Line:
Spend the extra $50 on the "real thing"....and you'll be ahead of the game!!!



c) With the distances of cable runs on the average sailboat, the loss differences between "ultra low-loss" cable (LMR, etc.) vs. normal low-loss cable (Foam dialectric, etc.) vs. normal cable (mil-spec 213, etc.), are slight....so worrying about the last 1/10 of a db is only done by fanatics like myself...




d) Have a look at Davis RF, for all your cable needs....either bulk or pre-made assemblies....I've done business with them for years, great people!!!
Davis RF Co. - Coax Cables
Davis RF Co. - Amateur Products, Low-Loss Braided Coaxes
Davis RF Co. - Bury-FLEX Flexible Low-Loss Coax


Also look at Texas Towers, they have coax and assemblies as well....and I've also done business with them...great guys there as well!!!
Texas Towers, Coaxial Cable Page
Texas Towers, Coax Jumpers Page


As you see, even if choosing ultra low-loss cable, the costs aren't too high....depending on how much cable you're looking at (maybe 100'???), you're probably going to spend less than $150.....




I do hope this helps...

John
s/v Annie Laurie
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Old 17-09-2012, 22:50   #3
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I'm no expert, but I read enough horror stories about LMR-400 clones that I went for the real thing. I paid 89.99 for 75 feet of LMR-400 with silver Pl-259's soldered on each end. Ham City is a good source.
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Old 18-09-2012, 00:45   #4
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Re: LMR400 clones

Hi guys,

Thanks for your response. I have decided against the clones. Do it once, do it right.

Thanks for the technical insights John, especially regarding the suitability of LMR400. I am rethinking and doing more research, and may well move away from LMR400 in favour of Davis Bury Flex. A stranded cable has clear advantage on a boat. The Davis site is particularily helpful, with tecnical reports, etc.

One of the circuits I particularily want to get right is the cabling between my iridium phone in the nav station, and its marine antenna, to be located on a stern antenna mount.

And yes I will be doing my own connectors...easier than trying to work out cable runs exactly beforehand, and I dont want to be pulling connectors through holes in the deck, up tubes which make up the antenna mount, etc.

Lee
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Old 20-09-2012, 11:50   #5
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Re: LMR400 clones

Lee,
I had assumed you were refering to VHF antenna cabling / runs up in the mast / etc....

You didn't mention you were using this as an external Iridium antenna feed....that's an L-band microwave signal your dealing with (~ 1650mhz) and I'd caution you to either buy the Iridium spec'd cable assembliy, which are LMR-type cables (already sweep-tested) or order a pre-made assembly fro Davis, etc. specifying your application....

Please understand that a minor connection issue might never cause any problems on VHF, but that same cable/connector assembly might prove to have serious VSWR / Return Loss problems and/or just a poor RF connection resulting in high attenuation....

This is an expecially important issue for an Iridium phone's external antenna, as unlike an INMARSAT geostationary sat comm antenna (which is typically a bi-directilonal active antenna system, most Iridium external antennas are simply passive external antennas and require extreme attention to cable/connection matters....


And, Lee, I'm sorry to be so blunt, but...
But, if you can afford a sat comm system (even just an Iridium sat phone), then you CAN afford to buy the proper cable assemblies....
Microwave / Sat Comm antenna systems are not systems that lend themselves to being done "on-the-cheap"!!!


Fair winds...

John
s/v Annie Laurie
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