Db Loss notwithstanding (LMR wins here), what would be a preference between these two types of coax cable for bending abilities/flexibility and weight for installation on a 33Ft sailboat, mast height = 43ft, plus about 35 inside the cabin? Also, any installation experiences out there including connectors and crimping?
RG213 or LMR400UF?
- Thread starter SVTatia
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Foam dielectric can be damaged very easily by bending too tightly. Which you choose should be a function of how difficult the installation will be which varies from boat to boat. All else beng equal, either is a good choice.
I'd vote for the LMR400. It isn't delicate or easily kinked, but is a bit more flexible than 213. A lot of people argue with me about this, but I often recommend LMR240 because of the similar loss characteristics to 213, but only 1/4 inch in diameter. The difference in performance between any of these cables is minimal at the lengths you are considering. I would also recommend crimp on connectors over solder - not those push-on types either. There are no common connectors that are truly weatherproof so seal up any exposed connectors.
For the best durability, I put three concentric layers of heat shrink tubing on the coax up to the base of a crimped on connector. The glue filled type works well here, but isn't required. You should be able to put the third layer over the entire connector after it's installed. If no heat shrink, you can wrap in electrical tape, but that only lasts a couple of months in this area. They make silicone tape, self amalgamating butyl, or regular butyl tape. After connecting, I usually wrap with electrical tape, then with one of the sealing tapes above, then another wrap of electrical tape. This is a common method professionals use that really lasts a long time in the Louisiana heat and sun.
For the best durability, I put three concentric layers of heat shrink tubing on the coax up to the base of a crimped on connector. The glue filled type works well here, but isn't required. You should be able to put the third layer over the entire connector after it's installed. If no heat shrink, you can wrap in electrical tape, but that only lasts a couple of months in this area. They make silicone tape, self amalgamating butyl, or regular butyl tape. After connecting, I usually wrap with electrical tape, then with one of the sealing tapes above, then another wrap of electrical tape. This is a common method professionals use that really lasts a long time in the Louisiana heat and sun.
Thank you for the responses, and the choice is becoming harder...
Forrest thank you for the pointers. I would like to know a bit more about the LMR240 - same flexibility and construction as the 400? Mind telling the reasoning for the arguments?
240 is small-.240 inch in diameter while 400 is .4 inch. It's not a whole lot cheaper than LMR400, but if space is a concern, it's good quality low loss cable for its size and is very flexible. One of the primary ratings on all coaxial cable is loss. Loss increases with cable length and higher frequency. That's important to remember when choosing cable, but some of the differences are very small and make no real difference in the real world.
For example, let's round up your installation to requiring 100' of cable, because 100' is a common specification given by manufacturers and 150MHz is a common frequency posted also. That's close enough for an accurate estimate. At 150MHz, 100' of lmr400 has 1.5dB of loss, RG213- 2.8dB, LMR240 - 3.0dB. 3dB here is a useful rule of thumb measurement too. it basically represents 1/2 of power. 6dB would halve it again. If your VHF radio puts out 25watts at the connector on the back of the transceiver, with 3dB loss, the power input to the antenna would be 1/2, or 12.5 watts. The LMR400 @1.5dB would measure 17.7 watts at the antenna, and the 213 @ 2.8dB would be 13.1 watts.
This is where the argument comes in. I claim the 1.5 dB difference in loss is too small to noticeably affect actual radio performance. 1/2 power seems like a lot, but what we're actually looking at is 1/5 power difference between cables. There has to be a significant increase in signal to be noticed by a distant receiving station. It's more like 2-3dB. In other words, it would require twice the power to make a noticeable change at the distant receiver. This is true comparing 17 watts to 12 or 1700 watts to 1200 watts. The person on the other end will not be able to tell the difference. Some folks get hung up on 3dB meaning 1/2 power, but ignore the real difference here of 1.5dB when comparing cables. Connectors add to the loss also, but are so minimal at VHF and are roughly the same no matter the cable.
We all want the most efficiently operating system, but this can be like splitting hairs and can add up in expenses- little or no bang for the buck.
I think there are too many tight angles in a boat for either cable. I would recommend finding a dual shielded cable that can somewhat match the attenuation but will be a little more flexible on the bend radius. Just look at the bend radius between the mast base and the coach roof. Unless you plan on running all the way to the keel but then the bend is still extreme.
These cables are great for outside installation where there is freedom for greater radius bends. I just don't like the fact that boats have too tight of compartments.
If this is just for VHF, you don't really need that cable. A good quality RG-8X would be a better choice, or LMR-240 (-3dB @ 150MHz @ 100 ft).
These cables are great for outside installation where there is freedom for greater radius bends. I just don't like the fact that boats have too tight of compartments.
If this is just for VHF, you don't really need that cable. A good quality RG-8X would be a better choice, or LMR-240 (-3dB @ 150MHz @ 100 ft).
Forrest, now I understand that the counter argument is about the difference of Db loss between the cables. Good explanation.
Brian, according to the Times Microwave specifications, the LMR240-UF has a bend radius of 3/4 inch and the LMR400 UF 1 inch. These are pretty good for routing either cable inside my boat and my mast is deck stepped. The 240 is half the diameter and half the weight up the mast, easier to clamp it up there, and so far it is my choice. The challenge now is to find a good supplier of cable and connectors. Once again, thank you for the help.
Brian, according to the Times Microwave specifications, the LMR240-UF has a bend radius of 3/4 inch and the LMR400 UF 1 inch. These are pretty good for routing either cable inside my boat and my mast is deck stepped. The 240 is half the diameter and half the weight up the mast, easier to clamp it up there, and so far it is my choice. The challenge now is to find a good supplier of cable and connectors. Once again, thank you for the help.
I posted a similar question a few years back:
http://forums.catalina.sailboatowners.com/showthread.php?t=126879&highlight=LMR400
I used the LMR400UF but if I was to do it again I would use the 240. The 400 is Ø7/16 and shares the same space as my radar cable of the same size. It didn't leave much room.
http://forums.catalina.sailboatowners.com/showthread.php?t=126879&highlight=LMR400
I used the LMR400UF but if I was to do it again I would use the 240. The 400 is Ø7/16 and shares the same space as my radar cable of the same size. It didn't leave much room.
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You might try texastowers.com for cable and connectors.
Besides low loss a big plus for the LMR cables is the won't wick moisture between the shield and dielectric, causing loss, I have several hundred feet of 213 type that the dieletric is soaked after a year or two, it makes a good dummy load.
Fred Villiard
Besides low loss a big plus for the LMR cables is the won't wick moisture between the shield and dielectric, causing loss, I have several hundred feet of 213 type that the dieletric is soaked after a year or two, it makes a good dummy load.
Fred Villiard