RG213U- a practical alternative?

[rognvald]

This year I am completely reconditioning/rewiring my mast. In attempting to provide the best possible installation/reception/transmission, I read that RG213U would be the best antenna wire for my VHF. However, when I read the specs, the cable is 3/8" in diameter which is quite sizeable next to the RG8U Foam core and would not only be considerable weight aloft, but could be a real "bellringer" inside the mast. Which will provide the best all around performance based upon these practical considerations? Are there any other considerations I have overlooked? Also, is there a premium brand for terminal connections at the radio/antenna ends? All "techy" responses will be greatly appreciated.

[btrayfors]

My favorites, in descending order of preference for VHF on a boat:

LMR-400
9913F7
RG-214
RG-213/U
RG8X

The first four are the same diameter, .405"

RG8X is .242" in diameter

Note: DO NOT USE REGULAR RG8 or RG58.

Here's a good listing of available coax:
RF Connection Coaxial Cable

This is also an excellent source of supply.

They also carry good PL-259 connectors for these types of coax.

Bill

[colemj]

I would agree with Bill, except that I would add Heliax as the top performer to the list.

However, for your boat, I assume the run will be 50' or less. Any additional cost in cabling above that for RG8X is probably not going to make any practical difference. You would get more bang for your buck putting that extra money into high quality connectors and even paying someone with expertise to install them.

If your run is much longer than 50', then considering higher grade coax may be worth it.

Good attention to properly installing and sealing the connectors and providing strain relief and drip loops will provide an installation with as good of practical performance as possible (and should be done regardless of the cable chosen).

Mark

[transmitterdan]

RG-142 is a good choice. It's low loss and 1/2 the size of RG-8.

[Dockhead]

I thought LMR400 was foam dielectric, with untinned conductors, and prone to moisture problems - not really suitable for marine use? Or am I misinformed?

[Rhapsody-NS27]

Not sure about how well it is around the marine environment, but at one point, I had a house with a ham radio tower in the back yard and ran all the RF lines with LMR-400. It's a good cable that I would get again if I were to ever install another tower somewhere, just not planning to anytime soon.

[Pacey16]

I am also looking at saving wieght of the co ax in the mast, I see that RG8X is only 3.5lb/100ft where as RG213U is 10lb/100ft.
Practicaly how less a range should i expect from the RG8X with a 70ft run all else being equall?

[Wotname]

Originally Posted by Dockhead

I thought LMR400 was foam dielectric, with untinned conductors, and prone to moisture problems - not really suitable for marine use? Or am I misinformed?

There is a waterproof LMR400; don't have the exact part number in front of me and IIRC, it also has a low halogen (smokeless?) outer cover.

We use it a bit of off-shore oil/gas platforms.

[GordMay]

Originally Posted by Wotname

There is a waterproof LMR400 ...

LMR-400-DB ?
➥ http://www.emc-rflabs.com/Rflabs/med...LMR-400-DB.pdf

[transmitterdan]

Originally Posted by Pacey16

I am also looking at saving wieght of the co ax in the mast, I see that RG8X is only 3.5lb/100ft where as RG213U is 10lb/100ft.
Practicaly how less a range should i expect from the RG8X with a 70ft run all else being equall?

At 160MHz the difference for your length of coax is about about 1.8dB. That means about a 33% reduction in radiated signal level for RG8X compared to RG213U. Range is a function of power and height. At low height power isn't as important because range is limited by line of sight. As antenna height increases then power becomes the limiting factor. So I would say if your antenna is 20' off the water or less then the coax doesn't matter. If your antenna is 50' or more off the water then the power reduction will reduce the range especially when communicating with equally high antennas. Exact numbers are not easy to verify.

[Paul Elliott]

Originally Posted by transmitterdan

At 160MHz the difference for your length of coax is about about 1.8dB. That means about a 33% reduction in radiated signal level for RG8X compared to RG213U. Range is a function of power and height. At low height power isn't as important because range is limited by line of sight. As antenna height increases then power becomes the limiting factor. So I would say if your antenna is 20' off the water or less then the coax doesn't matter. If your antenna is 50' or more off the water then the power reduction will reduce the range especially when communicating with equally high antennas. Exact numbers are not easy to verify.

While I think that an extra 1.8dB isn't going to be a deal-breaker, remember that even with a low antenna height, you may be trying to talk to a Coast Guard shore station. These often have tall hilltop antennas (in northern California, some are at 2000 and 3000 ft), so with a good signal you can communicate with them for fairly long distances.

My advice: Unless you're a hard-core racer or performance-junkie, with a 70-ft cable run go with the better (heavier) cable and ignore the extra few pounds.

[transmitterdan]

If we assume no earth obstruction for the case of a tall shore station then range will be reduced by about 20% in distance all else being perfect. This is for RG8X compared to RG213.

[Pacey16]

Thanks for the excellent explanations, I will probably go with the lighter stuff as I have HF also.

[Shipraiser]

I have seen so many mast cables totally destroyed by moisture and oxidation. Therefor I recommend RG214 which have both shield and center silver plated, no bare copper at all. Inside the boat it's not so critical and you can step down to a Belden or Bedea 6mm low-loss (half the loss as RG58 but only 0,5mm thicker).

Connections at the top should be protected with vulcanizing tape + outer layer of good quality electrical tape. Connectors for de-masting should be placed inside the boat, so if you have a deck-stepped mast use a Cableport or "swan's neck" to get the mast cables inside with connectors on.

I have 5 runs of RG214 in my mast + wind instr + 5 cables for lights. Mast has 2 conduits for cables.

/Marcus

[Dockhead]

Originally Posted by Shipraiser

I have seen so many mast cables totally destroyed by moisture and oxidation. Therefor I recommend RG214 which have both shield and center silver plated, no bare copper at all. Inside the boat it's not so critical and you can step down to a Belden or Bedea 6mm low-loss (half the loss as RG58 but only 0,5mm thicker).

Connections at the top should be protected with vulcanizing tape + outer layer of good quality electrical tape. Connectors for de-masting should be placed inside the boat, so if you have a deck-stepped mast use a Cableport or "swan's neck" to get the mast cables inside with connectors on.

I have 5 runs of RG214 in my mast + wind instr + 5 cables for lights. Mast has 2 conduits for cables.

/Marcus

Wow, what kind of antennae do you have to need FIVE runs of RG214?!