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Old 23-07-2015, 18:05   #1
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Coax: - solid, untinned center conductor?

I want to upgrade my old, decrepit RG58, but as soon as I go beyond RG8X it seems even the big names like Times Microwave use untinned wire for the center conductor. Is this not a problem as long as I use good installation practices?
Also, Joel at the RFC Connection is recommending solid center wire, claiming it has 15% better attenuation than stranded.
So, I am looking at LMR240 or LMR400, both with untinned, solid center conductor.
Is there a good brand out there that offer a stranded and tinned center conductor? (most have tinned shield)

What say you, O wise ones?


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Old 24-07-2015, 01:10   #2
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Re: Coax: - solid, untinned center conductor?

I would not worry about tinned vs untinned. Good practice will keep moisture out. If it does get in, you will have problems with either one.

You may find LMR400 difficult to route due to its stiffness. Stranded center conductor coax will be a bit more flexible. If that isn't an obstacle, LMR400 is good stuff.

Chip


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Old 24-07-2015, 04:11   #3
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Re: Coax: - solid, untinned center conductor?

I use RG214 tinned inner & outer double braid (not RG213)
Multi wire centre conductor.
Would not advise single wire centre conductor except in static situations as it
is more prone to hardening & fracture if repeated movement or vibration occurs.
Have 20+yrs as a communications rigger/installer.
A big issue is adequate sealing of connectors!!!!!!!!!
Use 3 wraps of rubber amalgamating tape with 50% overlap being well stretched
as wound on.
Then then 3 wraps of 3m super33+ over the top to protect against UV.
If this is done correctly the connection will be 100% waterproof even if immersed
in water.
The connection will remain protected for 10+ yrs.

How do I know this ???????
Have been doing it for 20+ yrs.
With revisit (inspections) over this time
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Old 06-08-2015, 21:31   #4
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Re: Coax: - solid, untinned center conductor?

As far as connector sealing goes, we use type-N connectors whenever possible (yes they are expensive compared to standard PL259 connectors, but much more waterproof) and then wrap them with Vapor Wrap https://www.tessco.com/products/disp...o.do?sku=53051

and then PVC Tape
3M 51 Scotchwrapâ„¢ Corrosion Protection Tape - 4" x 100' S-20339 - Uline

When we have sealed Type-N connectors in this manner wer have yet to have one fail due to moisture.
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Old 07-08-2015, 07:31   #5
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Re: Coax: - solid, untinned center conductor?

Type N connectors are superior, but PL259 connectors can easily be sealed too. Never had a water intrusion with mine sealed with 3M 2228 with an over-wrap of 3M Super 33+ Vinyl tape.

Chip


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Old 08-08-2015, 10:08   #6
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Re: Coax: - solid, untinned center conductor?

Thanks to all for the input - I went with Belden 9913 cable from rfc.


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Old 10-08-2015, 12:45   #7
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Re: Coax: - solid, untinned center conductor?

Nitpik,
With an online name like that, I assume you won't mind me "nitpiking"...

1) First off, I hope you didn't already buy this Belden 9913?? As this is one of the worst choices for your application!!
Quote:
Originally Posted by nitpik View Post
Thanks to all for the input - I went with Belden 9913 cable from rfc.
Belden 9913F7 is useable/acceptable....BUT....
But, actual Belden 9913 is NOT a good choice at all!!!

Please note that 9913 is a air-dielectric / semi-solid-air-dielectric, cable with a solid copper center-conductor....
And, as such, it is EXTREMELY susceptible to being rendered completely useless if any moisture at all seeps into the cable!!! (FYI, I used Belden 9913 starting back in the early 1980's....for a single, straight run up a tower for UHF ham radio....and until a lightning strike about 9 years ago, was still working fine....BUT, but I know exactly what this cable can do, can't do, and how to properly install it...and I would NEVER use this cable on-board!!!)

http://belden.com/techdatas/english/9913.pdf

http://www.belden.com/techdatas/english/9913F7.pdf


2) Secondarily, while a larger solid center conductor DOES reduce cable losses, this type of cable is a REAL pain in the a** to work with, and extremely difficult to install in tight spaces!!!



3) Thirdly, you will most likely notice a difference in reduced cable loss going from your old cable to any new cable (even to a new run of the same RG-58!).....and WILL notice a difference in reduced cable loss by going from your old RG-58 to even RG-8x (reduction in loss of 1.5db), and an even larger difference going to RG-213, or LMR-240 (a reduction in loss of 3db)....
Although, the actual differences you see, in real world use, (if you actually see any), will most likely be due to the "new" cable and connectors, rather than because of the specified "loss" of the cable...


And, please understand that while reducing cable losses is a good thing, there is a point where you go way over-board into the area of "overkill"....and this is especially true with vhf FM systems, and absolutely true with 99.9% of our Marine VHF-FM systems, where most of our comms are using "line-of-sight"....



4) So, there is really little need to obsess over squeezing out every last 1/10 of a db from your system....
Quote:
Originally Posted by nitpik View Post
I want to upgrade my old, decrepit RG58, but as soon as I go beyond RG8X it seems even the big names like Times Microwave use untinned wire for the center conductor. Is this not a problem as long as I use good installation practices?
Also, Joel at the RFC Connection is recommending solid center wire, claiming it has 15% better attenuation than stranded.
So, I am looking at LMR240 or LMR400, both with untinned, solid center conductor.
Is there a good brand out there that offer a stranded and tinned center conductor? (most have tinned shield)

What say you, O wise ones?
I do not know Joel.....but if I can politely write that while he is telling you the truth that a larger center conductor, combined with a higher velocity-factor dielectric, does reduce the cable's loss (compared to other similarly-sized cables), but his recommendation of a solid-center conductor cable for your application is seriously flawed (bad advice)...and his recommendation of an "semi-air-spaced dielectric" cable is VERY BAD advice for you!!!

Please do NOT use regular Belden 9913....this is a VERY bad choice!!
(although Belden 9913F7, is a good cable....and will work well, it is overkill...)



5) Chip (SoonerSailor) and BraiF, both gave you good advice / recommendations....and that's why I didn't post earlier....(not much to add to their recommendations...)
But, now that I see you are ordering 9913, I thought I better post some helpful, expert advice....

a) Use a name brand RG-213, or if you have limited space to run the larger cable use LMR-240UF (note the "UF"....it means "Ultra Flexible"..)
And, if you really want overkill, then use LMR-400UF....(again, note the "UF"...)


b) Read over these recent threads, where you'll get all the info you'll need to understand what cable to use and why...

AIS Antenna on Spreaders

VHF and AIS Radiowave Propagation and VHF and AIS Radio Range

Connecting VHF, AIS, GPS - NMEA0183 and NMEA2000

Top of mast, or RG213.... cant do both!




I hope this helps....and if "Joel" wishes to discuss this with me directly, I would be more than happy to give him a phone call and explain your application / needs, and try to explain to him why vhf FM line-of-sight comms, with elevated verticals, etc. there is little need to go to extremes trying to reduce cable losses....

Fair winds...

John
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Old 10-08-2015, 18:10   #8
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Re: Coax: - solid, untinned center conductor?

John, thank you for the very helpful reply!
Mia culpa! - when I posted that I was going with the Belden 9913, I did not realize that cable is different from the 9913F7, and I got lazy, and left off the F7.
While I realize it is over-kill, and I may not realize any benefits over the cheaper RG 8X, I did in fact purchase the 9913F7.
(Joel did suggest this was more cable than I needed - he recommended LMR 240 UF)
The 9913 F7 High Flex is double shielded, with a high density foam dielectric, which apparently resists water intrusion. It also has a 7/19, 10 AWG stranded center conductor, which is, unfortunately, not tinned.
I will have to rely on good installation practice to avoid moisture problems.

I must say, however, that the original wires feeding the masthead anchor light and the steaming light, are plain copper, and show absolutely no signs of corrosion at all! (They were installed in 1983)

Thanks again for all input!


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Old 11-08-2015, 07:09   #9
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Re: Coax: - solid, untinned center conductor?

Any opinions on using anti-oxidizer or dielectric grease on the internals before screwing the coupler on?


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Old 11-08-2015, 10:24   #10
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Re: Coax: - solid, untinned center conductor?

You might put a tiny bit on the threads, but be careful not to get it on surfaces you want the sealing tape to adhere to. It really isnt necessary for moisture-proofing if the connector is properly wrapped up.


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Old 11-08-2015, 11:57   #11
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Re: Coax: - solid, untinned center conductor?

Actually, I wasn't thinking of it as moisture sealing, but rather as an anti oxidant on the contacts to inhibit corrosion, and maintain good electrical contact.
I have had success filling trailer hitch sockets with dielectric grease. They are notorious for corroding to pieces in a very short time, due to road salt.

The coax to antenna connection, 'though properly weather sealed, might sit up at the mast head, unattended, for a number of years. A bit of protection inside the coupling might not be a bad idea.
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