Discussion in 'General Technical Questions and Answers' started by N6DCN, Sep 5, 2008.
What it the difference and benefits of one vs the other.
RG8X is "mini-8." It's commercial-hobbyist cable with no mil spec to guide it, so it varies a lot in construction and quality. But it's supposed to be .242" diameter with a #16 AWG stranded center conductor and a "foam" dielectric. It's usually very flexible.
RG8/U is a very old military specification for 52 Ohm coax. It's .405" in diameter with a #13 AWG center conductor and a solid polyethylene dielectric. As a "mil spec" product, it was discontinued 20 years ago; however as a "commercial" product, anybody can make and sell it and it doesn't have to meet any particular specification. RG8/U was replaced by RG213/U decades ago. There isn't a lot of difference, except RG213/U always has a stranded #13 AWG center conductor, at least 95% outer conductor (braid) coverage, and a Type IIA outer jacket material which is more UV-radiation tolerant than the old RG8/U product which was Type I and could degrade with exposure to the sun.
The "larger diameter" cable (RG8/U types) can handle more power and have somewhat less loss than RG8X.
Alright so the RG213/U is actually a better product with the stranded #13 center conductor.
Thank you for your help. Great explanation.
I have rg-8x now but will change to rg-213 shortly. I wished I would have gone with 213 to begin with. I need a buriable coax and 8x will not last long buried. Steve is absolutely 100% correct with everything he said. I respect his opinion more than most. He knows!!! I highly respect his opinions. Good Luck!
Another note is that 8x is not very useful above 50 mHz due to losses.
I like 8x for portable use, it's better for RF than RG-58 [but is a little bit thicker and heaver] but a great deal easier to handle than RG-213.
8x is also useful for in-shack jumpers due to it's lighter weight and greater flexability.
Sometimes it's hard to hold 213 up with a dipole - if it is a long run, you can use 8x to the ground then 213 the rest of the way if you want.
Personally, I have used RG-8x for all my HF antennas, but I don't use an amp either - when I get an amp, I'm going to have to upgrade some or all of my coax.
I don't think classifying rg-8x as an inferior product as compared to rg213 is not exactly what 'WIK was trying to portray. First, there are good and bad products in both classes of cable. Second, as an engineer, I recognize that each type of cable may be more appropriate in given situations. For things like jumpers below 30 mHz and probably higher, a good brand of rg-8x is entirely appropriate. As pointed out, it is appropriate to use for hf dipoles if the center isn't supported.
I guess my point is don't say rg-8x is inferior just recognize it has different design criteria and is more appropriate for certain applications.
Unfortunately, many sources of RG-8X, RG-8-mini, etc. ARE inferior. Since there's no standard for such a cable, there's no level of quality that can be guaranteed. About the ONLY standard for RG-8x cable is the outside diameter; internal construction, braid coverage, outer insulation material is up to the individual MANUFACTURER, not even the dealer or distributer.
On the other hand, RG-213/U cable is expected to be constructed to at LEAST the mil-spec as to insulation (solid polyethylene) conductor type and size, shield/braid coverage, and outer jacket material. It will also have to have the appropraite power handling capability.
"RG-8 type" cables have a meaningless definition now. The "RG-8" mil-spec was dropped years ago, as WIK said. So now, any manufacturer can make a 'RG-8 type" cable with NO real semblance to the original RG-8/U spec, and no guarantee of quality.
On the other hand, reputable manufacturers can and DO produce high quality "RG-8 type" cables, often of higher quality and lower loss than the original RG-8/U spec. Typical examples are Belden 9913, 9914, and 9913F, as well as original LMR-400 and the newer LMR-400 Ultra-flex and other variations.
I have runs of RG8x into the woods for HF loops and dipoles behind my house, as long as 250 ft, with no problems on 160-30 M bands.
If I had a reason to put up antennas for higher bands with long runs I would use a better variety of coax.
For my 10 M yagi and a few VHF/uhf antennas I use Belden 9913 coax, that is similar to RG213 but has a bit less loss on VHF/UHF bands. I only have about 50 ft runs of that line to the antennas.
At HF, good quality 8x from a reputable manufacturer is acceptable, if you realize the loss associated with a 250' run. THAT is pretty long, and personally, if I had a run that long, I'd use something a bit lower in loss than 8x, probably something like LMR-400. There's always a trade off of loss vs. cost for feedline. 9913 (despite complaints of some) if properly installed, is a good choice for the VHF and UHF antennas, unless hardline or HELIAX were economically available. With only a 50' run, it wouldn't show much improvement. It may be a luxury for only a 50' run at 10 Meters, but certainly doesn't hurt.
Correct coax feedline selection depends on a number of factors. Frequency of use? Length of coax run? Power level? Special conditions like direct burial?
For HF use, Most any coax cable will function just fine. The "top" choice is Belden RG-213, Which can be run over with a truck, And will handle high power levels. But any RG-8 type, Or RG 8X, (Or even RG-6 CATV coax) can be used for 160 meters up through 10 meters ........
VHF and UHF however are a very different story. For any length longer than 15 or so feet, Nothing but the best Times LMR-400 type coax will do.
(A good cable to AVOID is Belden 9913. Belden has produced many "versions" of 9913, Several of which are just junk.) They claim that the latest version is now OK. It may very well be. After failures of THREE different versions, We gave up on 9913.
LMR-400 is good for up to 75 or so feet of length at VHF/UHF for normal use, To go longer, Get some good used Andrew Heliax, Now available at most all swapfests for reasonable prices, Complete with connectors.