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[NE7AM]

Hi I would like to hear opinions about using RG316, for an 2m/70cm mobile antenna, that, might be mount by the front hood of a toyota 4runner

[K0BG]

Why? In the lengths we deal with, RG58B or C is adequate in both attenuation and temperature specs. I'd avoid RG58A (foam insulated) because of its lower temperature rating.

RG316 isn't a good one in any case. Although it is Teflon, it is some what smaller in size thus difficult to attach a connector to, the wire is copper coated steel, and its attenuation is triple that of RG58.

If you know where to go, you can buy RG58 "sized" coax that is silver plated real copper wire, and full Teflon construction. It isn't for the feint of heart, however, as it costs almost $5 a foot!

Alan, KØBG
www.k0bg.com

[WB2WIK]

RG58-sized Teflon coax is expensive retail for sure, but it's cheap surplus.  I use RG400/U, which is double-shielded, silver plated and Teflon dielectric coax with a silver-plated stranded center conductor (same loss as RG58/U, but much higher power and temperature ratings), all over the place and get it surplus from Apex Electronics in Sun Valley, CA for about $0.50/foot (spools).  I think they'll sell it for $1/foot in smaller quantities.

Great stuff if you're working under extreme conditions.

WB2WIK/6

[K7VO]

The advantage of the tiny coax (RG-174 or RG-316) is that it can get through small places without being crunched.  I've had larger coax get to the point where the insulation between the center and the braid broke down and the coax became a dead short.  I find that happens less with the miniature stuff.

The disadvantage of RG-174 and RG-316 is that it's really hard to put on connectors properly and it is quite lossy.  RG-316 has less loss than RG-174 but it still isn't better than RG-58.  Alan is quite correct that in a very short run in a mobile environment any of these will work just fine.

I use a Diamond K-400 mount with their 13' run of RG-174 made especially for that mount.  It's lasted for years.  Comet and Diamond go to RG-316 only for their N-connector mounts which are generally used at UHF and above.  They sell it as "low loss" to convince you to buy it for something like a 1.2GHz antenna.  

My take on all this:  I wouldn't spend much extra for RG-316.  If, OTOH, you have some and are comfortable putting on the correct connectors or have your run already made up from the manufacturer then there is certainly nothing wrong with it.  Up to 70cm (450MHz) I've had no issues using RG-174.

73,
Caity
K7VO