[TowerTalk] Marine Grade Coax -- NOT!

[Jim Brown]

Several years ago, I did a friend a favor by providing guidance about 
suppressing RFI to the HF installation on her sailboat. As you might 
guess, I gave her a bunch of ferrite cores. In appreciation, she gave me 
a short length (turned out to be 28 ft) of a so-called "Marine Grade" 
coax with an Ankor brand. It had laid on a shelf outside the shack until 
I picked it up a few days ago, put a connector on one end, hooked it up 
to my VNWA, did a TDR sweep, made 5 MHz to 100 MHz shorted and open 
impedance sweeps, and fed them to ZPlots to compute Zo, VF, and 
attenuation.

Results were unimpressive, but unsurprising given a physical examination 
of the cable. It's labeled RG213, has a flimsy outer jacket that is 
easily nicked, a tinned copper braid that's also easily nicked, and what 
appears to be a stranded copper-clad steel center! Loss was 0.77dB/100 
ft at 10 MHz, VF was 0.669. The outer jacket came to me nicked in one 
place (a slice about 0.5 in long), and there was obvious staining from 
corrosion of shield that lay beneath it.

The Ankor website describes their RG213 as having a "premium tinned 
copper center conductor as well as a tinned copper outer braid for 
corrosion resistance and easy soldering. It features signal loss ratios 
of up to 50 percent less than other coaxial cables. 96 percent braid 
provides best signal strength and least interference with UV inhibited 
white jacket for longest life." The website contains no specs.

In fact, loss is significantly greater than ordinary good quality RG8 
and RG213 from companies like Belden, Times, and Davis RF, and physical 
properties are significantly worse. Amazon sells a 100 ft length for 
$95. And they'll sell you Shakespeare-branded gold PL259-knockoffs for 
$12.87 EACH!  A gold plated barrel (also a knock-off) will set you back 
$11.74. Compare with great coax like Buryflex with AWG 9.5 stranded 
copper shield, foil plus tinned copper braid shield, and really nice 
UV-resistant PE jacket. 100 ft costs you $0.89/ft.

This marine stuff is on the level of the ultra-expensive but useless 
stuff sold to high-futility folks!

73, Jim K9YC