V.H.F. ANTENNA?

Mr.Kitch'nPass · 03-16-2004, 02:35 PM

When I had my boat built I told the manufacture to install a good V.H.F.Well I should have asked more questions :blush: Now I have a antenna that is only 3ft tall. From what Ive read on the board sounds like I need somthing taller

I went to look and they range from 45.00 to 200.00 Can anyone tell me how much do I need to spend to get a good one. [img]graemlins/1zhelp.gif[/img] Thanks

edsr · 03-16-2004, 03:46 PM

Dave - An antenna is good for line of sight only. A short antenna is alright for on the river but not the ocean. If you don't feel comfortable installing the thing yourself take your boat to Rogers Marine in Portland and have them do it. You should also replace the bracket with the "heavy duty" one, especially where your mount is located. If you put a tower above your cabin top the longer antenna will work even better. Also, add that other speaker you have plenty of room. Sweet boat - would make a real tuna slayer.
edsr

DriftR · 03-16-2004, 04:08 PM

Dave,
There are three (3) manufacturers of marine antenna's that I have considered. Shakespeare, Comrod and Digital.
In the Shakespeare models you have the 5225 XT series 8' length with 6 db gain. Run around 100.00
The Digital antenna is the 529 VW 8' vhf. These run around 110 to 150 bucks.
Comrod Antenna's. AV60BI is their 8' VHF. These are spendy but truly a quality antenna. 150 to 175 and this should include the cable.
These prices are close and remember no rachet style mounts are included. I would go with the Heavy Duty stainless steel mounts either rail or canopy in place of the plastic mounts. Just my opinion. One more bit of info to really get you confused. Shakespeare was supposed to come out with a new 5225 XP (extra performance) antenna this month. They have delayed it until April. It is supposed to be a step up from the 5225 XT(extra tough). I am not promoting any of the above. I have researched all of the above for my own benefit as well as actually saw the Comrods at the Seattle Boat Show. Made in Norway and are really built to stand up to marine conditions in Norway. All antenna manufacturers listed above have websites.
Good luck and remember, your best communication equipment on board is a quality vhf with DSC and a quality antenna.

WP · 03-16-2004, 04:14 PM

I used to think that one antenna was like any other. I used a shakespeare until it broke off last year and did some research on the internet. It convinced me to get my current antenna. Both antenna were/are 6' and use the same mount but the reception and reach are significantly better with the new antenna. I know that line of sight is the limiting factor with VHF but the antenna quality makes a huge difference in signal quality and reach! The one I got was a "Marine Antenna" unit. Talk tom Rogers and see what they recommend for a top quality unit and then get one. You won't be disappointed. I wasn't!
Dave

sturgn · 03-16-2004, 04:24 PM

Your question spurred some research on my part, and I found everything you could ask for about VHF antennas, heres the link. VHF Antenna's

Mr.Kitch'nPass · 03-16-2004, 04:46 PM

Hey,Thanks guys really appreciate the response.
DRIFTR,I have a shakespear now but its the 3ft wire type,good news is its on a stainless rachet type mounted to the gunnel :grin: So Instead of starting over I think I can upgrade to any shakespear antenna.
Ed,I think I can wire my vhf into my stereo speakers so everyone can hear it

sturgn thanks I will study that link Im sure it will help!

hot wire · 03-17-2004, 08:28 AM

Another idea--

I was a Coast Guard Electronics tech. Most of the time people will push fiberglass antenna's due to their height. Although that is always going to reach farther than a short antenna. I chose a different route. I chose a 6db stainless 35" whip mounted atop my boats windshield. Kinda the best of both worlds. If I had mounted a 6'fiberglass whip, (also a 6db antenna) I would have appreciably had the same performance +/- a very little. The other positive about stainless whips are their inhearant durability issue that fiberglass looses over time in the sun. (I can't remember how many I had to replace due to cracks or people stepping on them while not raised and secured.
The antenna is a GAM SS-2. (link below) Price was about $40 bucks. Alot less that a Shakespere.

http://www.sailnet.com/store/item.cfm?pid=17396

Tom

edsr · 03-17-2004, 09:43 AM

Hey Dave - That would be great stereo-boom-box tuna reports!!
edsr

BUGLEMAN · 03-17-2004, 10:16 AM

What would the drawback be to a very long steel whip ant. I used to have a very long one on my pickup. Am I missing something in thinking that you don't see very many on boats?

[ 03-17-2004, 11:19 AM: Message edited by: BUGLEMAN ]

hot wire · 03-17-2004, 01:17 PM

The longer whip itself is fine. It's the issues that arise when you are doing 30+mph on the water and controlling the whip is scarey! Honestly, I really don't know of a whip for VHF that goes beyond a 6bd gain. The remakable thing about that GAM antenna I bought was it is the only manufacturer that I know of the OFFERS a 6bd gain stainless whip in only a 35 inches. GAM also hand-wraps the loading coils for their antennas. So, could you imagine the loading coil on a 12 foot whip!!

Shakespere only offers a stainless whip in a 35" in a 3db. So, effectively I double my range/reception. (Of course you only get the max bennies if you mount these ABOVE the gunnels. (mine is 4'off it, and above my head by a foot or so too)

Tom

[ 03-17-2004, 02:18 PM: Message edited by: HewesFisher ]

BUGLEMAN · 03-17-2004, 01:44 PM

Hewsfisher,

Can you please explain the implications of what a 6bd gain is in terms of physics and practicaly what does that mean in radio performance. I could do a google but thought I would ask if it was easy to explain.

Also what do the loading coils do?

Thanks,

Kevin

rojo · 03-17-2004, 02:28 PM

Here's a brief break down of dB(antenna gain).a gain of 3dB means a doupling of signal strength, 6dB is a fourfold increase and 9dB an eightfold. also height plays a factor. a 5' hi antenna going to a 5' hi antenna has 5mi. range, 10' to 10' a 10 mile rnge a 10' to a 25' a 11mi rnge and so forth.One of the big problems with marine radios and antennas are the connectors, the first place to check when something seems not right....Roger

hot wire · 03-17-2004, 02:30 PM

http://www.catfleet21.org/rigging/June.htm

Sturgn's post and subsequent link is awesome for explanations. Quite frankly, that link puts things in very simple terms.

The higher an antenna---the farther it transmits AND receives.

The higher the db, the greater efficiency. The standard antenna you buy is 3db. If you buy an antenna that is rated at 6db, that antenna is 4x more efficient than a 3db. That is a BIG deal.

So, now you can see the significance of a 35inch whip that is ALSO rated at 6db.

The loading coil is an impedance matching device that electrically matches the physical length to the output of the ever frequency changing VHF radio....ie, ch1,2,3, up to 84. Kinda like a pressure regulator in a hose never letting 40psi out no matter what you turn up the spigot to.

Tom

DriftR · 03-17-2004, 03:00 PM

All good advice. but one thing to remember. The higher gain the higher the price. The longer the antenna the higher the price. Least of all don't forget that when you purchase an 8' or longer antenna upto the point where the manufacturers send the unit in 2 sections you will pay a premium shipping charge for overlength. Keep that in mind. Actually those little whip antennas look pretty good at the price. Might just have to purchase one for a backup in case of a broken 8' offshore. Thanks for the headsup on that Gam antenna.

BUGLEMAN · 03-17-2004, 04:26 PM

Thanks guys! I just saw sturgn's link.

Spotted Owl · 03-29-2004, 02:03 PM

I did the math for the 6db and the 9db on the link and it said only a 3 mile for the 6 and 5 miles for the 9 is this for real or is actual use distance better than what the book tells you?

Mark Mc · 03-29-2004, 03:03 PM

Sled, that is only the distance to the horizon. You are forgetting to add the "receiver" distance. That is to say, the height of the antenna of the person receiving your signal. Another boat / antenna identical to yours adds the same distance. But the Coast Guard antenna on the bluff over Yaquina Bay is probably > 200 feet above sea level.

BTW... there are other factors involved; that formula is a simplification.

Spotted Owl · 03-30-2004, 06:15 AM

Every thing that I have read says don't mount near metal objects the anteana needs to be 3 feet away from metal. Is there some sort of a buffer or something that you can use. Or what do you do if you have a metal boat on mine there is no way I can get 3 feet away from metal without mounting the anteana on some sort of a post or mast. I also haven't seen such a post on any site or boat at least that I new that is what I was looking at. Is there any were I might look to find a solve for this problem.