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Old 26-03-2013, 14:20   #1
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VHF *and* WiFi antennas on masthead

The mast is down for a number of other reasons, so I though I'd re-wire the mast and that led to what else would I want up there while I have it down. I've already bought a Lopolight Tricolor/Anchor to replace the crazed ancient Aquasignal. The VHF antenna plan at this point is a Shakespeare Galaxy 5400 per the recommendation of S/V Jedi in another thread. The plan for the WiFi is for a RogueWave pro setup. There will also be a Shakespeare disk type TV antenna, the windex, and the wind instrument senders. I don's anticipate any issues except maybe a possible problem with the WiFi and VHF antennas being so close.
A couple of questions:
1)Am I justified in my concern, or is this a common installation? Is there a minimum distance they should be from each other (VHF and WiFi)? My concern is not with them operating at the same time (unlikely) but more with one antenna's close presence compromising the other.
2)Is there a best/common mount that permits mounting the antennas to the sides of the top of the mast. The old mount for the old VHF antenna was a light weight (read cheap) 'L" bracket. Is there a good version of this for this type of antenna? I like the flange mount S/V Jedi has, but I don't think I'll have room for two of these on the top of the mast head. If there was a right angle version, that would be good, but I have not found one.
3) I don't want the shield of the coax to be (DC) connected to the Mast. Is the mounting ferule on the antennas isolated from the shield? (I will AC couple the mast to DC ground, I just don't want a DC path there)
4) Same question for the WiFi. Is the Case and mount of the Bullet DC isolated from all signals/and gnd?

-Tom
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Old 27-03-2013, 09:10   #2
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Re: VHF *and* WiFi antennas on masthead

VHF is in the neighborhood of 150-160 Mhz. Wifi is either 2.4 or 5 Ghz. Huge separation in the frequencies. Hence, no need to worry about RF interference between them.
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Old 27-03-2013, 09:28   #3
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Re: VHF *and* WiFi antennas on masthead

The huge advantage of the Bullet is that there is zero attenuation of the signal -- the radio is attached directly to the antenna. So you can mount it wherever you want, within effective Ethernet range, as long as you're willing to pull that much cable. I wish someone would make a mobile phone terminal like that, and with a remote SIM card reader -- that would be tats.

However, I don't know if I would mount it all the way up at the masthead. I am installing my Bullet and wifi antenna on the first spreader. It will be much easier to get to the unit, and there's less cable involved, less crowding at the masthead, etc. My first spreader is 30 feet about the water which is plenty of height for my purposes.

The Bullets do sometimes require fiddling, and they sometimes require replacement. There is a new model (forgot what it's called) which is more weatherproof; the previous ones, like mine, are not known to be completely impervious to weather. Another reason for it to be mounted in a reasonably accessible place.
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Old 27-03-2013, 09:49   #4
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Re: VHF *and* WiFi antennas on masthead

Tom: I posted a picture of a suitable L-bracket in that other thread. It comes with extra hardware to attach to a railing that you just don't use.

Also, the stainless steel base of the antenna is isolated from the antenna. There is a length of RG58 with connector attached to the antenna, that comes out the side at the bottom. Inside the fiberglass rode, it goes up to halfway the rod where it connects to a vertical dipole which is nothing more than two brass (silvered brass for the fancy version) pieces of wire: one going up and the other going down. Just like the little wire antennas that come with FM radios.

You will have to cut off most of that cable and solder a good plug on. You can use an N-type connector like suggested by others. Do this on the bench, before mounting it. Then, On your cable also put the same type of connector (but it will be for a thicker cable) and use a barrel adapter to connect the two. You can see the pictures of that in the other thread.

I would not put a wifi antenna at the masthead. I wouldn't even put it on a spreader. If you want an omni-directional setup, get a Ubiquity Bullet (the M2 of-course as that is the new tech) and a small 8dBi antenna with female N connector. Assemble the antenna with Bullet, wrap the connection in rescue tape, and hoist it with a flag line to under the spreader. That is how I do it when I don't use a directional NanoStation instead.

ciao!
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Old 27-03-2013, 14:13   #5
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Re: VHF *and* WiFi antennas on masthead

My Bullet is mounted at masthead on the starboard side with the VHF antenna on the port side (also at masthead).
Being a multihull, I went with a 12 db antenna for the wifi, and I made absolutely sure to get it vertical.
The VHF is a typical 3 db affair which came with the boat, and it serves the AIS receiver as well.
I tweaked the mounting bracket just a bit for the VHF so it's leaning aft a few degrees just for the heck of it to keep it from possibly banging into the wifi in big waves.

No interference at all.

Steve
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Old 27-03-2013, 19:40   #6
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Re: VHF *and* WiFi antennas on masthead

Thanks for the responses:

@Nick - Is the reason for not putting the WiFi antenna & bullet on the masthead because servicing it may be difficult, or is there a problem with the antennas being close and on the same horizontal plane? I really want a permanent install. My other thought was above the radar on the backstay, but I'm also planning on a backstay ham/SSB antenna, and that might present it's own issues.

@Steve - Glad to hear it's working well. What you have is pretty much what I had planned. I'm not an RF expert, I leave that black art to the RF magicians. I know just enough to know I need to ask. I want the WiFi to be optimal, but I can't have the VHF/AIS performance seriously affected. Sounds like it's working pretty good for you. I've read some other older threads on the subject and there seems to be a taboo about mounting the two antennas on the masthead. I'm trying to understand why not?

Thanks
-Tom
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Old 02-04-2013, 14:44   #7
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Re: VHF *and* WiFi antennas on masthead

I would mount the Wifi antenna lower because they are large and will probably block your tricolor masthead light. I have my Wi-Fi antenna installed on the radar arch so it's down out of the way of lights, yet still high enough to get good reception.

Newer 2.4/5GHz high gain Wifi antennas are very large and would definitely bock 30 degrees of your nav light visibility unless you get very creative. That's also a good amount of extra windage and gear aloft that could break and damage your nav lights.

Hope this helps, and if you want more info on my setup I did a blog post a while back about the setup. Wi-Fi for Astraea | Aboard Astraea
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Old 02-04-2013, 17:40   #8
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Re: VHF *and* WiFi antennas on masthead

Quote:
Originally Posted by n8kraft View Post
I would mount the Wifi antenna lower because they are large and will probably block your tricolor masthead light. I have my Wi-Fi antenna installed on the radar arch so it's down out of the way of lights, yet still high enough to get good reception.

Newer 2.4/5GHz high gain Wifi antennas are very large and would definitely bock 30 degrees of your nav light visibility unless you get very creative. That's also a good amount of extra windage and gear aloft that could break and damage your nav lights.

Hope this helps, and if you want more info on my setup I did a blog post a while back about the setup. Wi-Fi for Astraea | Aboard Astraea
Thanks! Yeah, I've pretty much abandoned the idea of WiFi at the masthead. There is enough up there already and I think that the space is high value real-estate for several reasons. As you mentioned, weight and windage aloft are important to think about. Also, WiFi technology may change (likely) or be obsoleted (inevitable), leaving a masthead install a big PITA to update or remove. The WiFi is not necessary for safe sailing whereas the other things up there are. VHF antenna, Nav lights, and wind instruments are not likely to have the same technology half-life. Not sure where I'll put the WiFi antenna, but as it's not on the masthead, I'll cross that bridge when I come to it.
-Tom
BTW - I enjoyed reading your blog. Good stuff. I'm also originally from Pittsburgh.
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Old 11-06-2013, 06:33   #9
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Re: VHF *and* WiFi antennas on masthead

I want to mount my vhf, wifi, and ais on top of the mast

Does anyone know of a bracket for mast top mounting that will provide adequate separation?

What is adequate separation?

How high should the tv antenna and radar antenna be mounted?

Thanks
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Old 11-06-2013, 07:16   #10
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Re: VHF *and* WiFi antennas on masthead

OK, Bullet is great......sometimes! There have been instances where I have had to do a factory reset. OK again, that's not a big deal UNLESS one has to shimmy up a 40'+ mast to push the reset button.

One more comment, be extra sure that where ever you locate your bullet that it is secure from the weather. Antenna--I am using a 15db which satisfies my needs.
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Old 11-06-2013, 11:50   #11
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Re: VHF *and* WiFi antennas on masthead

Just a suggestion... When you mount you Tricolor, much sure it isn't hidden by the other stuff up there.

When I commissioned my boat the electrician he mounted the Orca Green Tri Color flush to the top of the mast and it was blocked by the TV Antenna... It was remounted on a short mast and is visible 360 degrees.
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Old 01-11-2014, 14:09   #12
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Re: VHF *and* WiFi antennas on masthead

The issue of mounting antennas of different frequency bands in proximity is the same issue as the concern of mounting an antenna parallel to any conductor. Be it a mast, a shroud or another antenna any conductive parallel elemment will distort the radiation pattern. i.e. the antenna will be less sensitive in certain directions. Separation of one wave lenght or more reduces the effect. One wavelength in the marine VHF band is about is a little less than 6 feet. Not easy to achieve at the masthead.
If mounting at a spreader the same issue exist relative to spacing to the metal mast and shrouds. If on the spreader consider mounting pointing antenna down to minimize fowling a halyard.
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Old 01-11-2014, 17:32   #13
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Re: VHF *and* WiFi antennas on masthead

If you are going to go to the trouble of putting up a new vhf antenna you may want to use a really good one. These guys build one very good unit.
Metz Communication Products Page
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Old 01-11-2014, 18:59   #14
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Re: VHF *and* WiFi antennas on masthead

I can say with certainty that our Bullet affects our VHF if they are both on at the same time. We get interference on the VHF with the Bullet powered up and they are about two feet apart. Under way they are usually not both on but often at anchor we have the VHF on while also using the wifi. Chuck
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Old 02-11-2014, 05:36   #15
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Re: VHF *and* WiFi antennas on masthead

Greetings and welcome aboard the CF, biminijack.
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