mast antenna install

Fred Villiard · Apr 16, 2015

I can't help on the conduit, but have a suggestion on the coax, use LMR 400 UF, it is much more flexable and easer to handle.

seadaddler · Apr 16, 2015

Chase Line

How about running a chase line down first and than pull the coax
up to the top of mast.
I have a chase line left over on the bottom to top of my mast to top
for pulling any wires or coax.
Nick

Forrest15112 · Apr 17, 2015

How about ditching the LMR400 and going with LMR240? It's only 1/4 inch in diameter, super flexible, and low loss. Assuming this is for your VHF or FM stereo, the difference in attenuation on say 50' is negligible. At 150MHz, LMR400 has 1.5db loss per 100'. LMR240 is 3.0dB. In comparison, 50' of LMR400 will have .75dB loss and the LMR240 will have1.5dB. Trust me, the difference in performance will not be detectible without test equipment. In other words, side by side, you would not be able to tell the difference of .75dB and neither would whoever is receiving your signal. Get crimp on connectors and seal any that are exposed. Buy a cheap crimping tool on ebay ( $30) and sell it afterwards if you want. If you have a thru-deck fitting or other splice in the line, use N type connectors if possible. They're more durable than the UHF type that is on the radio and antenna. Wherever it connects to the antenna and the radio, put 3 concentric layers of adhesive lined heatshrink over the cable and connector ferrule. This will help make the connector more durable.

Don S/V ILLusion · Apr 17, 2015

To add to what Forrest described
LMR240. For 100ft @ 1:1 SWR AT 50 watts power input
Loss equates to 25 w at antenna

For same conditions with LMR400
Loss equates to 35 w at antenna

The extra 10 w loss represents 20% of your signal. I won't tell you my opinion of crimp coax connectors...

The Garbone · Apr 18, 2015

Depending on what areas you frequent transmission power may not be a big issue as the horizon it set and once you can hit it with decent power so be it. I installed Lmr400 on our boat more for reception. I think that I want to hear someone on a handheld weather they are ashore getting groceries and have a question or on the water a few miles out in a dink. That loss of receive sensitivity can then come back to get you.

Forrest15112 · Apr 23, 2015

Assuming similar lengths/losses, the tx or rx range wouldn't be noticeable. LMR400 is ideal for longer runs and higher frequency devices like cell phone or wifi amps, gps, etc. At UHF frequencies and above, these losses increase and LMR400 is a significant improvement over the smaller cables. At 160MHz it isn't enough to make a difference even when trying to copy a very distant weak station.

A lot of people will look at Don's calculations and say that since they're losing a significant amount of power, that must relate directly to the same percentage of range, ie: a 25% power loss=25% range loss. It doesn't work like that. Also, Don's calculation was based on 100' of coax and 50W output. At 50' length and 25W output of a VHF transceiver, The LMR240 would have roughly 17.5W feeding the antenna. The LMR400 would allow 21W. 3.5W is not enough to make a noticeable difference when at the current power levels. On receive, if you’re LMR400 fed xcver is receiving a signal at the bottom of its specification, -119dBm, that same signal would be -119.75dBm on the LMR240 setup. The difference is insignificant. There are many other things to consider as well, such as noise and interference that is always present and makes copying a -119dBm signal nearly impossible most of the time anyway.

You might say, like many do, “yeah, but my life may depend on it”. Well, if you feel that strongly about it, why not squeeze every milliwatt out of it by running LMR600, or 7/8 inch heliax, which is a greater improvement, but still insignificant. The reasons are the same, size, and with those cables, cost is a significant factor. But…your life may depend on it, right? My point here is to show that it isn’t a detriment to performance at reasonable lengths. Cost is only about $0.20 per foot difference between basic LMR240 & LMR400. Not much of an expense difference either way, but if size is an issue, like it is in this case, the LMR240 isn’t a bad choice and isn’t a compromise in performance.

Chief RA · Apr 23, 2015

Harlan: Bring the coax you decide on and pull it out the top of the conduit, roll it back down to a drilled hole 6" down outside of the conduit. If you only had 5 watts at that height you would still hit horizon+. Reception coax attenuation is more critical.
Chief, EE

Don S/V ILLusion · Apr 23, 2015

Forrest

These aren't my calculations but rather the inherent characteristics of the cable. There is no denying a 20% reduction in effective radiated power.

While it may be argued what difference that loss means in terms of effective communications, better is still better.

My intent wasn't to trade opinions but to provide real data on which someone can make their own decision.

The Garbone · Apr 24, 2015

Just FYI. 2 runs of LMR400 and 6 power wires for lights and such can fit into a 1" conduit but will require a sweeping 90 as it will not pull thru a squared 90.

As for choice of coax, when we discuss receive db let's remember it actually volt p to p we are developing across the front of the receiver. On its own not a deal killer but if the same approach is persists throughout our component choices with .75 here an .3 there all the sudden your looking at 1 or 2 db.

This leads to, " hey, you here the guy call the coasties on 16 about the lost diver this morning?" " no. I heard them asking questions but not his half". "Once it started I dropped my squelch and he was down there in the dirt, diver showed up. ". " oh, I tried but did not get it."

Chief RA · Apr 24, 2015

Garbone: You got it! Receive is the critical part. Chief

Forrest15112 · Apr 24, 2015

Don S/V ILLusion said:
Forrest

These aren't my calculations but rather the inherent characteristics of the cable. There is no denying a 20% reduction in effective radiated power.

While it may be argued what difference that loss means in terms of effective communications, better is still better.

My intent wasn't to trade opinions but to provide real data on which someone can make their own decision.

I understood what you meant and didn't mean to imply anything wrong with your calculations.

Forrest15112 · Apr 24, 2015

The Garbone said:
Just FYI. 2 runs of LMR400 and 6 power wires for lights and such can fit into a 1" conduit but will require a sweeping 90 as it will not pull thru a squared 90.

As for choice of coax, when we discuss receive db let's remember it actually volt p to p we are developing across the front of the receiver. On its own not a deal killer but if the same approach is persists throughout our component choices with .75 here an .3 there all the sudden your looking at 1 or 2 db.

This leads to, " hey, you here the guy call the coasties on 16 about the lost diver this morning?" " no. I heard them asking questions but not his half". "Once it started I dropped my squelch and he was down there in the dirt, diver showed up. ". " oh, I tried but did not get it."

I didn't suggest cutting corners, I suggested an alternative, high quality, low loss cable that will be easier to fit in the designated space. I described the minimal loss associated with the choice and how little it affects real communications. Your scenario isn't accurate and assumes extra losses here and there.

jibes138 · Apr 25, 2015

I rewired my mast last spring and had the same issue. The OEM wiring in the mast wasn't tinned, my lights were all shot and after reading Maine Sail's advice on antenna cable I attempted to use the LMR400 and ran into the same problem. After contemplating it I decided to just replace the mast wiring with the same wire that was in it but used the LMR400 for the run from the mast to the radio to reduce some of the losses. I never had a problem with the OEM wiring in terms of communicating so while it might not be optimal it works for my needs. I can't think of how you can do what you want without some surgery on the mast hardware. While you are in there replace all your other wiring and light fixtures. Beware the Aqua Signal steaming light, my new fixture had a cold solder joint that immediately failed. I used a sealed LED anchor light at the masthead.