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Mobile scanner coaxial cable

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#1
New to this form so will try to give as much pertinent information as I can, retired Volunteer fighter, 74 yrs old.
Ford F150 Super Crew, UWS low profile aluminum tool box, current scanner Uniden 760 (hope to go to a Uniden BCD536 digital scnner), freq. of interest 150MHz, 700MHz, 800MHz. I have a Yaesu 8800 HAM radio w/ Larsen NMO2/70B antenna roof mounted ( back edge of roof due to moon roof)
I plan to mount a scanner antenna and a CB antenna on a 2"X3"X40" aluminum angle bolted to the rear face of the tool box. Cable run will be around 20', currently planning to use a Fire Stik MSM4-B antenna BUT will try others (maybe Austin Spectra or a Laird WPD136C). Since I'll be running the cable thru holes in the tool box and bed I need a cable that isn't too large a diameter, prefer .300" of less, fairly flexible, accept common coax connectors.
I want to stay with 50 ohm cable in case I decide to use that antenna mount for a HAM or CB antenna. In the past I've used the standard RG58, but have become aware that there are much better choices, especially for the higher frequencies (700, 800). I am open to suggestion on the best cable for my application. Cussin' and discussin' please. Thanks for all your help.
 

chief21

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#2
LMR-240 (an upgraded, low-loss version of RG8x) should do nicely for your situation. Much better than RG58 and smaller and easier to work with than full-sized LMR400. Crimp or solder connectors of various types are readily available. Be sure to use grommets where you have to run the coax through metal.
 
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#3
I'm also a fan of LMR-240 for mobile use. I would not consider the Firestick and if you don't need VHF-lo the Spectra would be a waste. For 150-450-800 bands the Laird WPD136C or Larsen tri-band or Maxrad BMAXSCAN1000 or a few others would work fine.
 
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#4
Cable run will be around 20', currently planning to use a Fire Stik MSM4-B antenna BUT will try others (maybe Austin Spectra or a Laird WPD136C).
You can order NMO mounts with longer cable assemblies, which might make life easier for you.
You can also order NMO mounts with FME or N connectors on the base, that way you can just build a custom cable as long as you need.

However, consider that putting the antenna down on the tool box below the cab will have some impact on performance.
 

DJ11DLN

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#5
Another vote for LMR-240. It's a little on the stiff side but the extra performance at high frequencies over RG-8 is worth the trouble, at least in my opinion.

+1 on don't put it on the toolbox.
 
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Boston/Mansfield, MA
#6
Just chiming in to say make sure you specify LMR-240-UF "Ultraflex". It has a stranded center conductor and more flexible jacket. It will be more expensive than standard LMR-240 but has a smaller bend radius and will fare better with the vibration from a mobile installation.

LMR-240 and LMR-240-UF are nominally the same size as RG-8X and will fit most connectors designed for that size cable.
 
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3,668
#7
There's always the small heliax (https://www.commscope.com/catalog/cables/product_details.aspx?id=94823 or the slightly smaller https://www.commscope.com/catalog/cables/product_details.aspx?id=88831) that would have even lower loss and better shielding than the LMR-240 (less than half the loss over 100'). If you check their catalog, they make various versions of the heliax that may fit your project best (some are stiffer, others are more flexible, some are fire resistant, others have the typical specs, etc.).

The point may be, what are you trying to accomplish using special coax for your mobile run(s)? The loss difference over twenty feet or so might be measurable, but in real use won't be noticed. For the most part, you'll find more difference between brands of the same type of coax (cheap junk brands vs. quality brands like Belden, Comscope, etc.) over the 20' run than using high cost specialty coax. For longer runs, especially on higher frequencies, the better coax will make a difference (at times even a huge difference), but for short runs, not so much.

Let's say you have a very very very noisy signal you're trying to pick up, nearly all static but you can make out words most of the time while using the standard Belden RG-58A/U. You switch to some LMR-240 and expect some difference due to the extra work and cost. The signal is now very very very noisy and nearly all static but you can make out words most of the time. Next you upgrade to the more expensive Heliax and expect lots of difference due to the much larger cost. The signal is now very very very noisy and nearly all static but you can make out words most of the time.
 
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