Coax Cable Types

[Dockhead]

I'm facing the prospect of running quite a bit of coax cable up my mast in the next weeks and I realize that my knowledge about coax cable types amounts to diddleysquat. Maybe someone can share a bit of knowledge.

I will have on my first spreaders:

1. A VHF antenna for AIS, one tuned for the Channel 70 frequencies (156.525 and 161.125).

2. A mobile telephone antenna for my Globesurfer voice/data terminal, operating on GSM and UMTS bands (900 mhz, 1800 mhz, 1900 mhz, 2100 mhz).

These will be 8.5 meters from deck level so probably 16 or 17 meters from the nav table.

The most sensitive to the cable quality will be the mobile telephone antenna, so I will need some kind of super low loss cable for that which nonetheless can survive inside a sailboat mast.

Does anyone have any tips?

[conachair]

Have a chat with the guys at Martin Lynch..

ML&S Martin Lynch and Sons Ltd

[colemj]

Heliax will be the best, most expensive and hardest to install. LMR1200 or LDF will be excellent and suitable for all of those frequencies. These too will be expensive and difficult to install, but less so than heliax.

Or don't overly fret it and put in RG213 for all - simplest and I bet the losses will be within performance expectations.

Pay the most attention to the connectors - that is where most problems and losses occur.

Mark

[Dockhead]

Thanks very much for the good advice!

[Dockhead]

I found this:



here: Coaxial Cable Attenuation Chart

It shows the different attentuation characteristics of different cable at different frequencies. For extremely high frequencies of mobile phone service, it looks disastrous. At 2.4 ghz, RG-214 cable will eat up 13.7 dB (!) per 100 feet, or 6.8 dB in my case, which is disastrous. Wow. The lowest loss cable this company has, LMR-400, will eat up 6.6 dB per 100 feet, or about 3.3dB in my case, which means it will eat up the whole gain of my antenna It's late to be realizing this, but maybe it's not feasible to put the mobile phone antenna on the mast! Argh!

[Dockhead]

I guess there's this stuff, supposedly optimized for high frequencies:

Ecoflex 15

If I can somehow stuff another 1/2" cable up my mast. Expensive, too! But looks like it might do the job.

[gettinthere]

also pay attention to diameter. LMR400 is thicker and stiffer than LMR240.

I ran my antennas to the first spreader to shorten the run. Get decent height with less loss. Verdict is still out on the cell phone booster, I think they are voodoo science!

[Dockhead]

Originally Posted by gettinthere

also pay attention to diameter. LMR400 is thicker and stiffer than LMR240.

I ran my antennas to the first spreader to shorten the run. Get decent height with less loss. Verdict is still out on the cell phone booster, I think they are voodoo science!

Are you using an actual booster, as well as a remote antenna? What type?

[Wotname]

What frequency is your phone service in your part of the world?

I like this calculator from Times
Welcome to Times Microwave | Coaxial Cable - Attenuation & Power Handling Calculator

FWIW, for the phone I suggest you just stick with LMR 400 or if you prefer LMR 400 ultraflex. As it name implies, quite a bit more flexible than LMR 400 but a bit more lossy (but not much more). But LMR 400 will work OK in the mast.

What is important is that braid outers should not be used at frequencies above 1 GHz - see the note on the above link or partially repeated here:
"The attenuation of cables with Bare Copper and Tinned Copper outer conductors can vary substantially from the theoretical value due to oxidation and therefore we recommend they not be used above 1 GHz."

For the marine VHF, either keep with the LMR 400 (preferred) or go to the good old RG213/RG214 or a bit better RG393

[Wotname]

Originally Posted by Dockhead

........., or about 3.3dB in my case, which means it will eat up the whole gain of my antenna It's late to be realizing this, but maybe it's not feasible to put the mobile phone antenna on the mast! Argh!

IMHO, height trumps loss and 3.3 dB ain't too bad.
Watch out for hi-gain antennas, they don't work so well when heeled over - OK while mast remains vertical. The higher the gain, the bigger the problem with heel.

[Dockhead]

Thanks. That LMR-400 cable is 1/2" thick! That's definitely not what I have up the mast at the moment, yet my VHF works excellently. For the AIS antenna, I think I'll go with a smaller diameter cable; anyway the attenuation is small at those frequencies.

For the phone, I guess I'm going to have to try
to pull one of those thick cables.

I was doing a little cost-benefit analysis on this today.

I realized that in 90%+ of all situations, not having an external antenna has not been a problem. The Globesurfer has a more powerful radio and more sensitive antenna than a regular mobile handset, so just sitting on the bulkhead with no external antenna it has done a great job even miles offshore.

So all this expensive and trouble is just to gain a marginal improvement in the few percentages of cases where the signal is too weak for my present setup yet there is enough signal for a setup like this.

Yet 90% of all data comms, and 97% of all voice comms, are done on my boat using the mobile phone system. I am not retired and being unreachable is dangerous and can be harmful to my business. If I'm out of touch for a whole day I might easily miss a call or email which will lead to losing a lot of money, sums which will dwarf all these expenses. So I guess all this is worth it, although it's kind of funny when you think about how much trouble it is just to increase your "in range" time from say 90% to 94%.

I use WiFi fairly rarely on board. That's because marina WiFi is generally carp, worse than mobile phone data in terms of speed and quality, and besides that you usually have to spend time signing up, paying, etc., etc. Mobile data is instant and hassle-free and in most places in France and the UK you get real throughput of nearly 1 mb/s, which is much better than what you get out of a carpy marina wifi system.

I have a Ubiquiti Bullet M2 HP which I bought years ago, intending to put it up the mast. I'm only just now getting around to that. I use it from time to time by hauling it up on a halyard. It's very kludgy to use -- change your computer's IP settings to access the menu every time you just want to change connections -- ick. But with practice you stop noticeing the kludginess so much, and the thing sure can pull in a signal. It was brilliant last summer in Jersey -- we were anchored far out in the bay, a couple of miles from land. We ate in a restaurant on shore (out of sight of the boat) and received a password for their WiFi system. Back on the boat, got an excellent signal from this out of sight restaurant and could even use Skype. We went back to that restaurant to eat several times during our stay, and thanked the owner for letting us use his connection on our boat.

HF radio is an even higher cost per marginal % of availability proposition. What percentage of the year are even circumnavigators out of range of mobile phone coverage? But, you know, during those couple of weeks you're crossing an ocean, even if that doesn't happen very often, it's hard to tell yourself that you're out of touch for only 2% or 3% of the year, so just relax. A couple of weeks is a long time!

[Wotname]

Originally Posted by Dockhead

Thanks. That LMR-400 cable is 1/2" thick!

Gim'me a break it's only a bit over 3/8" (0.4" or 10.3mm)

That's definitely not what I have up the mast at the moment, yet my VHF works excellently.

Yep, height trumps loss again

..........
For the phone, I guess I'm going to have to try
to pull one of those thick cables.

I see you can get a waterproof LMR400 and the foil outer is a good thing at phone freqs. See http://www.timesmicrowave.com/products/lmr/downloads/22-25.pdf

I was doing a little cost-benefit analysis on this today.

I realized that in 90%+ of all situations, not having an external antenna has not been a problem. The Globesurfer has a more powerful radio and more sensitive antenna than a regular mobile handset, so just sitting on the bulkhead with no external antenna it has done a great job even miles offshore.

So all this expensive and trouble is just to gain a marginal improvement in the few percentages of cases where the signal is too weak for my present setup yet there is enough signal for a setup like this.

Yet 90% of all data comms, and 97% of all voice comms, are done on my boat using the mobile phone system. I am not retired and being unreachable is dangerous and can be harmful to my business. If I'm out of touch for a whole day I might easily miss a call or email which will lead to losing a lot of money, sums which will dwarf all these expenses. So I guess all this is worth it, although it's kind of funny when you think about how much trouble it is just to increase your "in range" time from say 90% to 94%.

Yep, double (or more) the effort cost for 10% increase in performance is normal when you are getting close to best practice.

I use WiFi fairly rarely on board. That's because marina WiFi is generally carp, worse than mobile phone data in terms of speed and quality, and besides that you usually have to spend time signing up, paying, etc., etc. Mobile data is instant and hassle-free and in most places in France and the UK you get real throughput of nearly 1 mb/s, which is much better than what you get out of a carpy marina wifi system.

I have a Ubiquiti Bullet M2 HP which I bought years ago, intending to put it up the mast. I'm only just now getting around to that. I use it from time to time by hauling it up on a halyard. It's very kludgy to use -- change your computer's IP settings to access the menu every time you just want to change connections -- ick. But with practice you stop noticeing the kludginess so much, and the thing sure can pull in a signal. It was brilliant last summer in Jersey -- we were anchored far out in the bay, a couple of miles from land. We ate in a restaurant on shore (out of sight of the boat) and received a password for their WiFi system. Back on the boat, got an excellent signal from this out of sight restaurant and could even use Skype. We went back to that restaurant to eat several times during our stay, and thanked the owner for letting us use his connection on our boat.

HF radio is an even higher cost per marginal % of availability proposition. What percentage of the year are even circumnavigators out of range of mobile phone coverage? But, you know, during those couple of weeks you're crossing an ocean, even if that doesn't happen very often, it's hard to tell yourself that you're out of touch for only 2% or 3% of the year, so just relax. A couple of weeks is a long time!

Good points!

FWIW, our guys where hauling up 1" coax (and some 1.5") for 20+ antennas on a 25 M ground mast recently - now that was a bit difficult.

[Dockhead]

You're right, my bad -- the LMR-400 cable is 0.4".

It's the Ecoflex which is the problem -- 14.6mm! Yikes, that's a snake!

I guess LMR-400 is the way to go, 3.3 dB or not. Is that stuff ok for marine/outdoor use, do you think?

[Dockhead]

Rrrrr, my antenna gain may be 6dB at 800-900mhz, but it's only 3dB at 1900-2100! So 3.3dB of loss will more than eat up my antenna gain at those frequencies.

LMR 600 is 15mm thick. Over 50 feet of cable run, however, the attenuation is only 2dB. It has "multi-ply bonded foil outer conductor" so I guess it's good for high frequencies.

[colemj]

Originally Posted by Dockhead

Thanks. That LMR-400 cable is 1/2" thick! That's definitely not what I have up the mast at the moment, yet my VHF works excellently.

That is why I implied that you may be over-worrying this and that losses will be within performance expectations.

In other words, I bet you are losing that last 1 or 2 miles of reach with your current VHF setup, but this is not important in practice.

The same will most likely be true for your phone and SSB usage.

It is very easy to get caught up in technical specs with radio gear and spend a lot of time, effort and money believing you are squeezing out performance gains - when performance is actually relative, variable and controlled by many other factors than just the coax.

Unless you know you will always be hanging by your toenails on the very far edge of a signal, highly specialized installations will not be noticeably different than lesser ones.

If constant strong connections are that vital to your business then it would be better to plan your passages and anchorages around that fact rather than hope expensive gear and installation takes up the slack.

But this is a decision that only you can make. If it is going to eat you alive thinking about it all the time, then peace of mind is worth something.

At the very least, put most of your worry into the connectors. Most otherwise good installations are half wasted because of losses in the connectors. Pay for good ones and make sure they are installed correctly. Use quality N-connectors and not cheap PL259's - convert when needed with quality N-PL259 converters.

And since I am advocating not worrying too much about the coax cabling, I need to confess here that our SSB and Ham are wired with 3/4" Heliax! I recently removed the 1/2" Heliax connecting our VHF and replaced with LMR400 (following a lightning strike where I did not trust the coax any longer and thought the Heliax was overkill on a VHF - the LMR400 is also overkill, though). But in my defense, this was already installed on our boat when we bought it. Personally, I would have used LMR400 (and N-connectors).

As for your experience with the Bullet, I believe you do not have it configured correctly. There should be no need to monkey with your computer's IP configuration each time you want to access the software or change locations. You should always be able to simply open the software web page and choose the access point you wish to use. To change AP's, you just click on a different one.

Mark