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Coax Choices

posted Jan 6, 2014, 3:43 PM by Charles Boling
Coaxial cable is one area where money invested can potentially pay off big over time compared to e.g. spending the amount saved with cheap coax on a nicer radio.  Cable losses increase as you go up in frequency, and the same cable that does okay on HF can turn your 50W UHF rig into a cheap HT.  As with all things, there is a point of diminishing returns, where a particular level of performance improvement is not cost-effective for your application.  Sure, gold-plated silver cable may give your signal a boost, but...

A friend is shopping for coax to replace some old weathered RG-58, and asked for some advice.  Here's my email to him, showing some approximate loss & price characteristics of different cables.



Coax attenuation/price chart
(Oops, that should say 2014, not 2013...)

Attached is a chart I made showing some different types of coax, from
high loss to low (I didn't bother pricing hardline, which is great, but hard to work with and expensive!). Beldin 9913 used to be a "poor man's" alternative to LMR-400, but competition at the high end seems to have driven prices down so that you can get LMR-400 cheaper than real 9913! For Jacket materials, PVC is usually indoor-only, whereas PE is for outdoor. The F7 variant (which I have) of 9913 has a foam-type jacket that, while it's not as slick as hard PE, is also for outdoor, and claims better UV resistance. Not that we get that much UV here compared to lower latitudes; standard PE should last quite a while if it's not flexed a lot. The F7 is also more flexible, but (skin effect notwithstanding) has slightly higher loss than the standard. As you can see, making the jump in size from the RG-58 to the RG-8 size (which the rest of the cables are) makes a big difference, and going to the "low loss" cables yields another significant, though not quite as big, improvement. VHF isn't as dramatic as UHF, but even on 2m you're still losing most of your power with the small stuff. I paid $1.38 for the -F7 (now $1.49) in 2008, and IIRC I couldn't touch LMR for under $2. That off-brand LMR (EMR-400) for $67/ft would be mighty tempting!

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