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Old 09-03-2013, 05:09   #1
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Please Recommend a Quality VHF Masthead Antenna

My existing masthead VHF antenna is a skinny steel whip combined with winded, fed by a skinny coax cable. My mast is down and I'm taking the chance to replace everything.

I have no complaints about VHF comms. I use an Icom M604 and get good signal reports from great distances (75 feet of height probably don't hurt), but why not take the chance to install something good? Anyone have any recommendations?

Maybe some kind of dual band VHF/UHF antenna? I now have an amateur radio license and might play around with the VHF/UHF amateur frequencies - guess I could use an antenna switch.
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Old 09-03-2013, 05:21   #2
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Quote:
Originally Posted by Dockhead View Post
My existing masthead VHF antenna is a skinny steel whip combined with winded, fed by a skinny coax cable. My mast is down and I'm taking the chance to replace everything.

I have no complaints about VHF comms. I use an Icom M604 and get good signal reports from great distances (75 feet of height probably don't hurt), but why not take the chance to install something good? Anyone have any recommendations?

Maybe some kind of dual band VHF/UHF antenna? I now have an amateur radio license and might play around with the VHF/UHF amateur frequencies - guess I could use an antenna switch.
This is the best one; it gives noticeable imrovement: http://shakespeare-marine.com/antenn...ntenna=5400-xt
It is a dipole so no ground plane or coil. The negative is that it needs a coax coupling at the masthead so use a good glue-lined heatshrink for that.

I have been experimenting with a 2m/70cm dual band HAM antenna and it works better on marine VHF than it oes on 70cm so very usable. I would only put it up as a second antenna, maybe share with AIS using a switch? A 2m radio works well with the 5400-xt antenna too and when I tried 70cm I opened a repeater 75km away with 15W power no problem, althouh SWR must be bad (didn't check that).
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Old 09-03-2013, 05:50   #3
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Re: Please Recommend a Quality VHF Masthead Antenna

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This is the best one; it gives noticeable imrovement: Shakespeare Antenna Specifications: Galaxy Little Giant™ 5400-XT VHF Marine Band
It is a dipole so no ground plane or coil. The negative is that it needs a coax coupling at the masthead so use a good glue-lined heatshrink for that.

I have been experimenting with a 2m/70cm dual band HAM antenna and it works better on marine VHF than it oes on 70cm so very usable. I would only put it up as a second antenna, maybe share with AIS using a switch? A 2m radio works well with the 5400-xt antenna too and when I tried 70cm I opened a repeater 75km away with 15W power no problem, althouh SWR must be bad (didn't check that).
Thanks for that. So would you go for the ham antenna at the masthead, or not? Since VHF/UHF ham operations will benefit just as much from height as marine VHF, wouldn't it make sense to do them all from a single antenna at the masthead, rather than trying to do ham operations from an antenna lower down shared with AIS?

For AIS, I was thinking of using one of the very short ones optimized just for that frequency, on the first spreader.
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Old 09-03-2013, 05:55   #4
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Re: Please Recommend a Quality VHF Masthead Antenna

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Originally Posted by Dockhead View Post
Thanks for that. So would you go for the ham antenna at the masthead, or not? Since VHF/UHF ham operations will benefit just as much from height as marine VHF, wouldn't it make sense to do them all from a single antenna at the masthead, rather than trying to do ham operations from an antenna lower down shared with AIS?

For AIS, I was thinking of using one of the very short ones optimized just for that frequency, on the first spreader.
You have one stick on your boat, right? I have two so that is different. In your case, the 5400-xt goes on the masthead and a HAM dual-band on the spreader. No doubt about that and would never use an AIS antenna, which is just nonsense.

I'll check my images for some relevant info and to see which HAM antenna I have...
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Old 09-03-2013, 06:03   #5
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Put money into the best antenna ( low attenuation) wire you can find and make sure the connectors are attached well. Then make sure it will not flop in the mask. If the mask is down new LED spreader lights would be on my list also. That I hate heights thing has kept me from doing this.
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Old 09-03-2013, 06:04   #6
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Re: Please Recommend a Quality VHF Masthead Antenna

We have this stuff:

BANTEN RADIO ANTENNA NAUTICAL MILITARY WEHICULAR AIR TRAFFIC

It is good. 10+ years of life in sun/rain. I would buy again.

b.
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Old 09-03-2013, 06:08   #7
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Re: Please Recommend a Quality VHF Masthead Antenna

I know the paint on my mast is in horrible state... it was struck by lightning twice before I got it

here is the 5400-xt in black of-course:


clearance with windex:


final SWR testing before heatshrink goes on:


Cabling with coax connectors and heatshrink; you have to shorten the cable that comes out the antenna:


Antenna has standard 1" threads so a real sturdy base can be used. Check out corrosion around base: this is where a strobe light used to be...

(and my masthead running backstays are also on this pic I see!)
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Old 09-03-2013, 06:26   #8
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Re: Please Recommend a Quality VHF Masthead Antenna

Here is the HAM dual band; it is a Diamond 770 series with NMO mount, which is the sturdiest for on a boat


You have to select one of their bases (or other brand; it's a standard. NMO stands for New Motorola something...) for that. Something like this would work:


cheers,
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Old 09-03-2013, 06:37   #9
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Re: Please Recommend a Quality VHF Masthead Antenna

Quote:
Originally Posted by Dockhead View Post
Thanks for that. So would you go for the ham antenna at the masthead, or not? Since VHF/UHF ham operations will benefit just as much from height as marine VHF, wouldn't it make sense to do them all from a single antenna at the masthead, rather than trying to do ham operations from an antenna lower down shared with AIS?

For AIS, I was thinking of using one of the very short ones optimized just for that frequency, on the first spreader.
I have a 2m/70cm ham antenna on the radar arch, works fine for AIS, 40 odd miles. Receiving on 2m the 2m/70cm is better than the VHF antenna on the mast head. Not sure how much being tuned to different freq would affect that on receive though.
Do people use the 2m or 70cm bands much cruising? The HF bands seem much more busy.
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Old 09-03-2013, 06:52   #10
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Re: Please Recommend a Quality VHF Masthead Antenna

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Originally Posted by s/v Jedi View Post
You have one stick on your boat, right? I have two so that is different. In your case, the 5400-xt goes on the masthead and a HAM dual-band on the spreader. No doubt about that and would never use an AIS antenna, which is just nonsense.

I'll check my images for some relevant info and to see which HAM antenna I have...
So you would share AIS and VHF/UHF ham, instead of marine VHF/UHF? I don't quite understand the logic of that, unless that Shakespeare dipole antenna is much better than the ham dual band antenna. Please explain your logic.
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Old 09-03-2013, 06:54   #11
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Re: Please Recommend a Quality VHF Masthead Antenna

Quote:
Originally Posted by s/v Jedi View Post
Here is the HAM dual band; it is a Diamond 770 series with NMO mount, which is the sturdiest for on a boat


You have to select one of their bases (or other brand; it's a standard. NMO stands for New Motorola something...) for that. Something like this would work:


cheers,
Nick.
Thanks very much. I'll look for that.
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Old 09-03-2013, 06:55   #12
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Re: Please Recommend a Quality VHF Masthead Antenna

It may not be a concern for you, but I like the skinny steel whips because they occasionally end up acting as feeler gauges on the bottoms of bridges, here on the East Coast where we have a lot of them. The fiberglass ones don't have enough bend and they can break. Despite my set up being nothing special, using an antique whip antenna, etc., I've never had a problem with range or clarity. I'm sure Jedi's would be better, but I'm not sure enough so anyone would notice.
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Old 09-03-2013, 07:06   #13
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Re: Please Recommend a Quality VHF Masthead Antenna

The best recommendation I can give is don't go cheap on the coax cable to minimize power loss.

Also place your AIS antenna as high as you can. AIS is VHF and as you know is line of sight. Remember the receivie distance is the combined height of both the transmitting and receiving antennas....

The lower your antenna is, the less distance you will see over the horizon... That is ok for cargo ships with their Class A AIS (12 watt) Antenna 200 feet, off the water, but how about a 40 foot boat, when their Class B (2 watt) transmitting antenna is only 15 feet off the water.

We have been using the "Cheap Shakespear 36" Whip" for 6.5 years with no problem... I thougt about a fiberglass antenna for the mast head, but wondered if they would hold up on the strain of being whipped back and forth on the mst head.

Our Raymarine AIS has an antenna splitter and shares our mast head antenna. With our antenna about 65 feet off the water, we routinely see Class B targets at ten miles or more and Class A targets at well over fifty miles (Up to 100 miles).

The down side to a mast head AIS Antenna is during rough seas, when the boat is rolling. There is a phenomena that causes the VHF antenna to lose AIS signals when it is swinging from side to side. The radio geeks can expain it better I m sure. With our mast head antenna, in rough conditions, the Class A targets will come and go until within about 10 miles and Class B are ussually steady at about 2-3 miles.
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Old 09-03-2013, 07:53   #14
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Re: Please Recommend a Quality VHF Masthead Antenna

I'm not meaning to be argumentative but my dedicated AIS antenna is mounted 12 feet off the water and I get far more than enough warning (distance to) other vessels with AIS.
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Old 09-03-2013, 08:22   #15
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Re: Please Recommend a Quality VHF Masthead Antenna

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I'm not meaning to be argumentative but my dedicated AIS antenna is mounted 12 feet off the water and I get far more than enough warning (distance to) other vessels with AIS.
My first spreader is 30 feet off the water and I've decided that's good enough for the AIS antenna.

For ships, who have their antennae very high, the difference between 30 and 75 feet for my antenna is irrelevant. For sailboats moving at 5 or 6 knots, likewise -- line of sight, even if their antenna are three inches off the water, will be 6.5 miles, which is plenty. I guess the only target where you might really want your AIS antenna at 75 feet would be a mobo travelling at 30 knots and with an antenna only 10 feet off the water. But since I'm never going to avoid a mobo travelling at 30 knots in any case, even that is useless, probably. I would have 10 miles (more, actually, since horizon is further for radio waves), with my antenna at 30 feet; 13 with my antenna at 75 feet -- not enough to worry about, IHMO.
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