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Old 24-05-2016, 16:07   #1
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Masthead antennas and interference

Hey all,

I'm about to pull my mast for stripping and repainting, and I'm planning out the masthead instruments now. I'll have a LunaSea LED tricolor light that purportedly has no RF leakage... but I'm considering a few other things up there and would love a sanity check if you've got experience and time.

I'd like to have an ultrasonic wind instrument, like either the Maretron WSO100 or the Airmar 220wx, but I'm hearing that these both go a little haywire if they're mounted near a VHF antenna...

I've got a Standard Horizon GX2150 VHF with AIS reception that I'd definitely like to have mounted as high as possible, since it's the radio I use the most, by a wide margin.

I've also got an Icom IC-7000 ham radio that isn't yet setup - the HF antenna output will go to an insulated backstay, but I'm wondering a bit about the 2m/70cm antenna output...

Lastly, I'm planning on installing a Ubiquiti Bullet-M2-HP wifi router up as high as I can, for wifi access in ports and anchorages.

My questions are basically these:

- would it be better to have the VHF share a masthead antenna with the ham radio (for the VHF/UHF bands only), and use an antenna switcher, or would it be better to have the ham radio have its own antenna on the stern arch?

- I hear the VHF interferes with ultrasonic wind instruments, and vice-versa - any tips on avoiding that, other than "mount one higher than the other"? has anyone tried adding shielding (ie metal tape) to an ultrasonic wind instrument?

- what sort of interference can I expect from putting the wifi antenna up there? is this another one that would make more sense on the stern arch?
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Old 24-05-2016, 22:56   #2
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Re: Masthead antennas and interference

Hi Drew,

First of all, the ultrasonic wind gauge generates a lot of noise on HF - at least on my boat. I have not noticed any VHF interference, but my VHF antennas are well away from the wind gauge.

As for sharing a marine VHF and 2m/70 cm, you will find it difficult to get an antenna with enough bandwidth and gain. Best separate the two.

WiFi is more complicated since placing the antenna high up means loss in the coax cable. If you have an amplifier for it, no problem, but if not losses may counter the longer range due to the higher antenna. I have not experienced interference to WiFi from my wind gauge, but distance to the WiFi antenna is large enough on my boat, so I'm a bad sample. As for interference to the wind gauge keep in mind that the WiFi signal is substantially lower in power than a marine VHF or ham radio signal.

Cheers, ....Erik.
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Old 25-05-2016, 10:36   #3
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Re: Masthead antennas and interference

I put a Ubiquity Bullet on the masthead. It's not been a problem with interference from or to the VHF.
Also, there is no coax involved. The antenna (mine is a 12 db) screws directly onto the Bullet which is powered by and transmits its data via Ethernet cable.
The longest distance I've ever seen with it was a couple of years ago on the way to Desolation Sound. We were going up the Strait of Georgia and I had a connection for a very long time. When the signal got choppy and I finally lost it, I checked on the distance to the station given on the Bullet's page. 18.5 MILES !!
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Old 25-05-2016, 13:17   #4
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Re: Masthead antennas and interference

Quote:
Originally Posted by ve7mdl View Post
Hi Drew,

First of all, the ultrasonic wind gauge generates a lot of noise on HF - at least on my boat. I have not noticed any VHF interference, but my VHF antennas are well away from the wind gauge.
Hey Erik, thanks for the reply - can you tell me which wind gauge you have?

regarding wifi signal loss - as @senormechanico says, it's not a coax connection, a Ubiquiti Bullet is a wifi router that attaches directly to the antenna itself, and then is fed with CAT5 (and powered via PoE), so there's zero signal loss to contend with.

@senormechanico - holy heck, eighteen miles is amazing!!
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Old 25-05-2016, 22:23   #5
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Re: Masthead antennas and interference

Hi Drew,

It is the Maretron 100. I have had it for quite a few years.

Cheers, ....Erik.
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Old 04-07-2016, 02:54   #6
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Re: Masthead antennas and interference

Hi guys!
I'm also playing with antennas.
I have a
- VHF masthead antenna fed into Standard Horizon for VHF/AIS reception
- Insulated backstay fed to Icom IC-706
- VHF antenna on stern pole
- WiFi 5db antenna with Ubiquity Bullet Titanium on stern pole with Cat 6 cable going to it.

What I found is the Bullet connects the DC - (negative) to the antenna ground, so I somehow need to insulate the antenna mount now - since I have a metal boat and my DC system is floating. Anyone has experience with this?

Also, for the VHF antenna on the stern pole, should I connect it to the Icom as 2-nd antenna? What if I plan to use it as antenna for AIS transmitter? Do I need to put a splitter?
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