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Old 01-01-2008, 07:57   #1
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Help with coax identity

I am replacing the VHF coax onboard having discovered several intrusions (tears) in the casing down to the sheild.
The existing coax is marked 52 ohm saxton 8317,l have not been able to cross reference this with beldon or find any information on the web.
Could someone offer assistance with finding info on this cable?
Dave
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Old 01-01-2008, 08:06   #2
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If it's for a mast head antenna. I'd use RG8x
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Old 01-01-2008, 10:36   #3
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or RG213 or it's equivalent will yield lower loss at VHF
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Old 01-01-2008, 11:36   #4
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Never Monday and Illusion are both right, but I'd go with the lower loss stuff.
The PO on my boat used the skinny stuff (RG58) all the way up the mast.
The range is pathetic compared to my old boat in which I'd installed RG213.
I've just gotta pull the mast one of these days!

Steve B.
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Old 01-01-2008, 11:39   #5
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You can search BELDEN Marine VHF Antenna Cables at:
Belden Catalog

In order of my preference (bigger is better, if you can fit it):

RG-8U - Belden #9913F7
10 AWG stranded (7x19) .108" bare copper conductor, gas-injected foam HDPE insulation, Duobond II + tinned copper braid shield (95% coverage), Belflex jacket.
http://bwccat.belden.com/ecat/pdf/9913F7.pdf

RG213/U - Belden #8267:
13 AWG stranded (7x21) .089" bare copper conductor, polyethylene insulation, bare copper braid shield (96% coverage), non-contaminating PVC jacket.
http://bwccat.belden.com/ecat/pdf/8267.pdf

RG-8X - Belden #7808R:
15 AWG solid .057" bare copper conductor, gas-injected foam HDPE insulation, Duobond II + tinned copper braid shield (95% coverage), PVC jacket.
http://bwccat.belden.com/ecat/pdf/7808R.pdf

Cable Attenuation (dB loss) should be compared at the Marine VHF Radio nominal frequency of 157 Mhz (150 MHz).
U.S. VHF Channels - USCG Navigation Center

There's a basic tutorial at:
What you need to know to get the most out of your Marine VHF Radio installation
VHF Radio
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Old 01-01-2008, 11:44   #6
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9913 would be the cat's meow.
If you could find some small dia LMR400 that would be an even further step up.

Here I found Andrews Heliax in 1/4" dia. 1db loss per 100'
HS2RP-50 - Product Details
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Old 01-01-2008, 15:41   #7
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I would go with RG-213/U every time due to its very consistent quality between manufacturers, its stranded centre conductor, its solid dielectric (insulation) and its low loss (when compared to smaller cables). It is also easy to buy due to its popularity.

I would steer away from RG-8X for in mast use because of its inconsistent quality, its foam dielectric and often solid centre conductor as well.

Foam dielectrics are generally less resistant to moisture contamination and in my view they also mean that the cable is less robust (especially in small cable diameters) and there is the risk of the centre conductor migrating through the dielectric on bends as the cable ages. So for in mast applications I would steer away from cables using them.

In my view solid centre conductor cables have no place in a mast as for proper installation they should be supported along their length to prevent the possibility of fatigue failure of the centre conductor. So I would steer away from cables using them.

In my view, if you have to pay much of a premium for cable with tinned braid then it is not worth using. Coaxial cable is toast from the time it gets wet as that is when transmission line losses increase, not just from the time it starts corroding after it has got wet. From that point of view tinning really serves not much purpose.

We have done the calculations for VHF masthead antenna to hill top shore station comparing a lossy small diameter cable such as RG-58 with a less lossy cable such as RG-213. It was along time ago so I do not have the actual figures anymore (the result was so conclusively in favour of the better cable we have never investigated it again) but was of order of getting around 1/3 greater range with the better cable due to the smaller power loss in it.
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Old 02-01-2008, 04:53   #8
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From Topband: Connecting radial systens together- thanks!!!! de W0AH you could try contacting the ham who mentioned that after an hour searching, he couldn't find a web site for Saxon but he was going to use some of their cable.

There are some tradeoffs to be made in VHF cabling that is going to run up the mast and be used on a boat. If you select thin cable, it has higher loss. If you select thick cable, it puts weight aloft and is harder to run. If you select cable with a foam (inner) insulation, it has lower less--but tends to absorb water and collapse more than cable with solid insulation would. Then there's a choice of solid or braided inner conductor--either should work on a boat as long as the ends are sealed, I would think.

The actual loss figures for cables are posted on many web sites, every large manufacturer posts them. At marine VHF frequencies (160MHz) fortunately it is not TOO expensive to pick a cable with low losses from a prime manufacturer. Sometimes you can pick up a 100' spool very reasonably, and if it wasn't your first choice, it may be close enough.
If you are not familiar with these things, loss is usually posted as "db per 100 feet" (thousand feet, whatever) and a 3db loss represents losing a full HALF of the power going to your antenna. So if a choice between two cables, for the hundred (?) feet that you will need, shows one has 3db less loss than the other--go for it. If the difference is only 1db or 1.5db...most folks wouldn't worry about it if there were other reasons to chose the cable.
Coax cable is also often rated (or unrated) for the percent of the shielding braid. A 100% shield braid would be unusually good, 80% shield more typical, and some of the cheap stuff runs down to a 40% shield. Given that cable on a boat is usually a short run in an RFI-quiet environment, don't let the last few percent on the shield braid worry you too much either. But "we don't know" and "50%" are unacceptable at any price.
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Old 02-01-2008, 05:44   #9
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As MidLandOne suggests, moisture intrusion (into dielectric insulation) will quickly and severely degrade your antenna cable performance (which is why he avoids RG8 cables /w Foamed dielectrics, & recommends RG-213/U).

Since the prime source of moisture intrusion is at the terminations, it makes sense to apply a weather-seal to the fittings. Sealing and taping the coax connector will help eliminate moisture from entering the coax (the outer PVC jacket is fairly impervious).

I usually use Linerless Rubber Splicing Tape (3M #130C) with Lined Heat Shrink tubing over all, to seal PL-259s etc.
Others sometimes recommend a Mastic Tape (“Coax-Seal”, or 3M #2229) or Silicone (3M #70) tapes, all of which are also self-fusing (self-amalgamating).

Tips:

I like to cut off a foot or 2 of new coax cable, prior to installation. This insures that you are starting out with a dry cable.

Any time you wrap tape on a threaded component, make sure you wrap it in the direction that tends to tighten the screw threads, not the other way. That means if you are taping a splice, for example two PL-259's screwed into a double barrel female (PL-258/83-1J) you must tape each connector from the cable end to the barrel center.

Always run the tape "uphill", and from the smaller diameter to the larger diameter.

Start at the smallest end, make several tight turns of one-quarter lap for a good seal, then run the tape in one-half laps to the center, with moderate stretch so the diameter of the tape is reduced to about 1/2 of it's original width.
On the last few turns reduce the stretch tension until it is zero at the last turn, to prevent flagging. Use a scissors to cut the tape end square, as a knife or ripping will add stretch to the last lap and cause it to come loose. Repeat the same strategy from the other side, and meet in the center (if it is a splice), overlap the left hand side tape with the right hand side tape.
Finally install an adhesive lined heat shrink tube, and/or spray the entire assembly with clear coat enamel or other dielectric spray (Krylon Crystal Clear).
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Old 02-01-2008, 08:53   #10
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This is all good information but my original question was concerning the specifics on the Saxton cable so l might cross reference it to something in production.
Reason being that l have reports of an excellent signal strength and range and do not wish to reduce those qualities. Mast height is 53 feet BTW.
Dave
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Old 02-01-2008, 10:23   #11
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Quote:
Originally Posted by wind rose ll View Post
This is all good information but my original question was concerning the specifics on the Saxton cable so l might cross reference it to something in production.
Reason being that l have reports of an excellent signal strength and range and do not wish to reduce those qualities. Mast height is 53 feet BTW.
Dave

The problem is this brand is apparently some knock-off label so it's not a straight-forward cross-reference. You signal quality is more related to the quality, condition and type of coax, not the "saxton" label on it and the suggestions provided are all sound advice in replacement and will yield the same or better result.
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Old 02-01-2008, 11:30   #12
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Dave, it is hard to cross-reference a blank, and that's pretty much what you have unless you can find someone who can contact Saxton--who could literally be anywhere on the globe.

If you look for a cable of the same diameter (or larger) and then look for the lowest loss in a suitable cable, you will meet or exceed the performance of the Saxton cable. That's the best you are going to get, until you track that company down. And in this day and age, if they have no web site and no web presence, I doubt their cable is anything special.

Does the cable itself give you any hit? Say "Made in USA" or "Made in Armenia" or anything like that on it? Unless it is total junk, it will have the cable type, name, and some other information printed every couple of inches on it. If it just says Saxton with a number, you're out of luck. Get something from Belden or LMR, you can call them both up directly here in the US and ask them "What's your finest cable for this application?" and they'll tell you. They are both top-tier makers, buy the best cable you can afford for the purpose--because there's a limit to both performance and budget for most of us, and you stop at whichever one comes first. (I'm sure BETTER performance wouldn't bother you.<G>)
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Old 02-01-2008, 15:10   #13
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Quote:
Originally Posted by wind rose ll View Post
This is all good information but my original question was concerning the specifics on the Saxton cable so l might cross reference it to something in production.
Reason being that l have reports of an excellent signal strength and range and do not wish to reduce those qualities. Mast height is 53 feet BTW.
Dave
Saxton could be anything - anyone can get cable run off with their name and product number on it. For example much of the bigger cable in my own boat has the boatbuilder's name printed on it and if you buy coaxial cable from some discount house it will likely have their name on it. If you pick up a leftover offcut from a telecommunications company it may have their name on it (any telecommunications companies by the name of "Saxton" - in Saxton PA, perhaps?). I have coaxial cable here from a reputable cable wholesaler and it has his name on it, not the manufacturers.

If you tell us its outside diameter, the nature of the dielectric and of the inner conductor we could take a guess as to what you have. But that is all really just a waste of time because without going to something really exotic but inappropriate for on a sail boat you really will not do better than RG-213/U - it is a robust, low loss cable and almost no matter who you buy it off it will be good quality because it is made in big quantities targeted at the professional market.

If you cannot fit RG-213 up inside your mast conduit with the other cables then that is another matter and you may have to go for a smaller cable that is not so good. In my own boat's case that would have been so except that the builder realised it was important enough to add another conduit.
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Old 02-01-2008, 15:40   #14
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I pack all my terminations with silicon grease after soldering them. It displaces any water that might get in otherwise. I then use self-amalgamating tape meant for electricians from 3-M over the outside. It's never failed me.
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