Author Topic: Another VHF antenna question  (Read 786 times)

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Offline HemiGTX

Another VHF antenna question
« on: April 22, 2017, 07:18:17 PM »
I'm interested in replacing my current 8' antenna with a new one.  I seem to always fish in sloppy weather and have been thinking about using a 4' Digital brand antenna (4db) on a 4' extension, and installing the whole shebang on top of my hardtop.  My thinking is that the 4db antenna would give better performance while the boat is pitching and yawing, and raising it 4' would mitigate some of the (potential) loss of range.

The other option is to just buy an 8' 6db antenna and not worry about any potential loss of effectiveness in the slop.

Thoughts?

« Last Edit: April 22, 2017, 07:31:47 PM by HemiGTX »
AKA: "The guy who fishes with Nicole"

Offline wedocq

Re: Another VHF antenna question
« Reply #1 on: April 23, 2017, 08:30:38 AM »
I am no expert, just going on experience. I used the Shakespeare 5225 XT for 10+ years before buying a new radio and antenna. The new antenna was a Digital 529. I can honestly say I liked the performance of the 5225XT better. When the Digital got broken in the snow storm, I replaced it with another 5225XT. It's on sale for $99 at Hodges Marine right now.  Another reason I like this antenna is their claim of durability.
From the MFG:
Embodying Shakespeare's extreme durability standards, the Galaxy 5225/5226-XT is built extra-tough with a stronger, stiffer radome. The extra resistant construction of this VHF antenna undergoes stringent in-house testing to withstand mother nature's tests when placed on hardtops, T-tops, radar arches, or anywhere exposed to high winds and high speeds. The high performance and durability of this antenna maximizes range all while keeping its pristine finish.

As far as buying a 4'er and adding an extension. I dunno.  :shrug9: In all my years on the water, I have never had a fishing buddy with an antenna set up that way, so I can't speak on the performance. :shrug9:

-Shawn
2002 21' Arima Sea Ranger HT  Suzuki DF175 4-stroke.
WEDOCQ= WE DO SEKIU! It pays homage to my Uncle Jay who died of cancer.

Offline StreamFixer

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Re: Another VHF antenna question
« Reply #2 on: April 23, 2017, 08:32:53 AM »
So your choices are using a 4 foot antenna on top of a 4 foot mast (total 8') with a 4 db gain  OR
an 8 foot antenna with a 6 db gain   :shrug9:  Either way you have an 8 foot appendage on the cabin roof.

The longer antenna will be a more efficient transmitter, as is indicated by the larger db gain.  Signal strength doubles for each 3 db gain.
Channel 16 (marine) transmits and receives on 156.8 Mhz.  The ideal antenna length (full wave) would be around 5.2 meters (17'+/-).  The 8 foot antenna is a half wave antenna and the 4 footer is a quarter wave.

The gain with the longer antenna will be about 30% more power in the signal coming off that.  Unless there is a significant weight difference, I recommend you stay with the higher gain antenna.  The range will be essentially the same with a stronger (more easily read) signal on the receiving end.

I would be more concerned with the mounting mechanism backing.  An 8 foot anything will be putting tremendous torque on the mount fasteners and the top of the boat.  Make sure you put a BIG (as in long dimensions in all directions) plate under the mount fasteners to spread that torque load over as large an area as possible.  Having that 8 footer (either antenna you have described) whipping around on the top of a factory hard top will likely result in the roof tearing unless the backing material is stout (that means 1/2" ply or stronger).  Bolts with fender washers will not cut it.  Well actually they likely would -- "cut it" --- holes about the size of the fender washers through the roof.   :rimshot:

StreamFixer
'97 19SC w/ Salt Boss Top
'03 Yamaha 115 EFI
'05 Yamaha T8 Solas 4 blade prop

"By the grace of God we travel upon the rivers and sea..
They, like He, are mightier than me."  Mike Jesperson aka 'Nalu'

Offline wedocq

Re: Another VHF antenna question
« Reply #3 on: April 23, 2017, 09:08:53 AM »
I have mine mounted to the rail up top with no issues.
-Shawn
2002 21' Arima Sea Ranger HT  Suzuki DF175 4-stroke.
WEDOCQ= WE DO SEKIU! It pays homage to my Uncle Jay who died of cancer.

Offline StreamFixer

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Re: Another VHF antenna question
« Reply #4 on: April 23, 2017, 09:18:13 AM »
Rail should work fine,  I was envisioning to/through the fiberglass roof ---  Shame on me   :redface:

StreamFixer
'97 19SC w/ Salt Boss Top
'03 Yamaha 115 EFI
'05 Yamaha T8 Solas 4 blade prop

"By the grace of God we travel upon the rivers and sea..
They, like He, are mightier than me."  Mike Jesperson aka 'Nalu'

Offline HemiGTX

Re: Another VHF antenna question
« Reply #5 on: April 23, 2017, 09:47:41 AM »
My current antenna is 8' and mounted on the hardtop rail as well.  $99 is a very compelling feature of the Shakespeare!

AKA: "The guy who fishes with Nicole"

Offline Yachter Yat

Re: Another VHF antenna question
« Reply #6 on: April 23, 2017, 10:04:07 AM »
   Not sure if I could find it quickly, but I once read a review claiming the Shakespeare 5225XP was the best performing antenna of some that were tested; including the Digital equivalent.  Not saying that because I own it.........just quoting what I read. 

   About those 4 footers.  I actually like the idea of a shorter antenna.  The Digital model I gravitated to was rated at 4.5 db.  It has a wider broadcast pattern than the 6 db. 8 footers.  This could be an advantage on a small boat that likes to "rock n' roll".  I like the idea of that, but might consider mounting it with an extension.  Take a look at the Digital line.......you'll see they offer a number of different sized extensions. 

Yat
Dear Arima:  Please "square-off" the Hunter transom. Next, stretch the Explorer by 9 and steal 2 or 3 from the cabin.  Please hurry, I'm getting old.

16 SC/Honda 60

Offline StreamFixer

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Re: Another VHF antenna question
« Reply #7 on: April 23, 2017, 10:09:08 AM »
While it is always nice to mount your antenna higher (for greater range on our radios), 4 feet higher on our boats will make a range difference equivalent to picking the fly doo out of the pepper.

StreamFixer
'97 19SC w/ Salt Boss Top
'03 Yamaha 115 EFI
'05 Yamaha T8 Solas 4 blade prop

"By the grace of God we travel upon the rivers and sea..
They, like He, are mightier than me."  Mike Jesperson aka 'Nalu'

Online Croaker Stroker

Re: Another VHF antenna question
« Reply #8 on: April 23, 2017, 11:10:29 AM »
...

While it is always nice to mount your antenna higher (for greater range on our radios), 4 feet higher on our boats will make a range difference equivalent to picking the fly doo out of the pepper.

StreamFixer


1987 - 17' Sea Pacer - 2004 Evinrude 90 E-tec
15' Sea Sprinter - **SOLD**

"If a fish will, he will… if he won't, he won't… and that's about it… except… he may take this when he won't take that."

Online Croaker Stroker

Re: Another VHF antenna question
« Reply #9 on: April 23, 2017, 11:12:02 AM »
I like the Digital antenna because it's black and shiny.


I always refer the this drawing....notice although the shorter antenna doesn't shoot as far as the 9db (8')antenna, it may go farther If you boat is listing badly, like a sailboat.  Raising the antenna wont affect distance much unless something is in the way. (Choppy seas)

« Last Edit: April 23, 2017, 11:28:15 AM by Croaker Stroker »
1987 - 17' Sea Pacer - 2004 Evinrude 90 E-tec
15' Sea Sprinter - **SOLD**

"If a fish will, he will… if he won't, he won't… and that's about it… except… he may take this when he won't take that."

Offline Threeweight

Re: Another VHF antenna question
« Reply #10 on: April 23, 2017, 11:27:16 AM »
My two cents.

VHF signals are line of sight, so typically the higher an antenna is placed, the better it will perform.  This is why Coast Guard antennas are typically placed in towers up on a cliff somewhere, vs. mounted to the roof of the CG station at the dock.  However, antenna height is just one factor.  The decibel gain (dB) also determines the shape of the "cone" the antenna broadcasts, and it's range. 

Streamfixer's eloquent description of the range variables in a small boat is pretty accurate, but maybe not entirely.  When you really, really need your VHF (like in 10' swells with big wind chop on top when things go south at Neah Bay), which antenna is going to have greater ability to broadcast over the tops of the waves, an 8' mounted in the roof, or a 4' mounted to the walk-around?

The 4' antennas in the 3dB range are actually made for sailboats, not small powerboats.  The idea is you stick them up on a 30' high mast, and they have a wide signal "cone" that is less affected by the boat yawing in the swells.  The 8' 6dB antennas are a compromise, and what are typically used in a small (under 30') offshore boat.  The giant 16' and taller 10dB units are more typically mounted on larger commercial boats or yachts, or to a building somewhere.

The next factor is construction quality.  What sort of materials are used in the antenna?  How beefy is the construction?  In 5 years, which is most likely to still be working?

From my research, the very high end Shakespears (like the Mariner 8900) are very good antennas.  The mid-range (5225XT and 5226XT) are great at price vs. performance.  You have to be careful though, as Shakespear makes a million different models and many are total junk (pick up the most common model, the 5206, at a West Marine and it will feel like a kids Snoopy fishing rod). 

The higher end brands (Digital, Comrod, Morad) may not offer much advantage in range over Shakespear when the units are new.  The reason they cost more $$ are the materials used and construction quality.  They are more likely to still be working in 5 years.  Sort of like comparing a Hyundai to a Honda.  Both may have the same features and perform just as well when new.  In 5 years, which one is more likely to still be trouble free?

I got to mess with both my radios last weekend, when we were assisting with the flipped boat on the Columbia.  The Standard Horizon+Digital 529 was crystal clear communicating with CG Sector Columbia River from roughly 20 miles away.  On the Shakespeare 5206 and Cobra the dealer threw in for free with my boat, the signal was weak and the static was very noticeable.  Whatever brand you chose to go with, go with a high-end unit.  IMO, the antenna is more important than the radio when it comes to safety, so it is not the place to skimp.

Good read here:

http://www.llelectronics.com/images/PDFs/VHFAntennas.pdf
« Last Edit: April 23, 2017, 11:41:25 AM by Threeweight »
Former Sea Chaser 17 owner
Wild Card, Hewescraft Ocean Pro 220, Honda 225 and 9.9

“Never turn your back on fear. It should always be in front of you, like a thing that might have to be killed.”
       --- Hunter S. Thompson

Online Croaker Stroker

Re: Another VHF antenna question
« Reply #11 on: April 23, 2017, 12:11:02 PM »


The connector on my Digital antenna did not impress me as it did others. There was already a hole in my bulkhead which was large enough to pass a 259 connector. For me, the "extra" connector required for the Digital antenna doubles the future possibility of a bad connection.
1987 - 17' Sea Pacer - 2004 Evinrude 90 E-tec
15' Sea Sprinter - **SOLD**

"If a fish will, he will… if he won't, he won't… and that's about it… except… he may take this when he won't take that."

Offline Markshoreline

Re: Another VHF antenna question
« Reply #12 on: April 23, 2017, 03:16:18 PM »
Shawn/hemi, I will rail mount my new antenna this week- how /where did you route the cable into the cabin?
2002 Sea Ranger HT 21, Yamaha 150, Yamaha 9.9

Offline Yachter Yat

Re: Another VHF antenna question
« Reply #13 on: April 23, 2017, 05:17:24 PM »
   Mark, I don't get it.  Wouldn't a 4' Digital mounted on that top be a better idea? :shrug9:  If I had a T top boat that would be my first choice. 

Yat
Dear Arima:  Please "square-off" the Hunter transom. Next, stretch the Explorer by 9 and steal 2 or 3 from the cabin.  Please hurry, I'm getting old.

16 SC/Honda 60

Offline Markshoreline

Re: Another VHF antenna question
« Reply #14 on: April 23, 2017, 05:47:27 PM »
No, since I have already purchased an 8 footer!  3WT eloquently explained why an 8 foot antenna would be more effective in rough water conditions...
2002 Sea Ranger HT 21, Yamaha 150, Yamaha 9.9

Offline StreamFixer

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Re: Another VHF antenna question
« Reply #15 on: April 23, 2017, 06:03:37 PM »

The explanation 3WT provided must assume the boat has stabilizers or the boat would be rocking and rolling to the extent antenna mounting height would not matter.

Any part of the antenna above the obstructing element will get the message through.  So, if 2 feet of a 4 foot antenna or 2 feet of an 8 footer is clear of the obstruction, the signal is getting out.  It will be lousy reception in either case.  The strength of the signal is a function of the power provided to the antenna and the antenna's gain characteristics.

If you wish to carry the condition of surrounding seas to it's logical conclusion, you will enhance the signal readability by only transmitting when on the crest of the swell and stopping when in the trough...  Not terribly practical from an application stand point.  If the swell interval is 6 or 7 second, that suggests you should only transmit a couple of seconds at a time when on the crest of a swell to maximize signal readability distance.

IMHO the height of the antenna mount on our boats is an academic discussion and has little or no practical effect on the signal being received.  If you are in 10 foot seas with additional wind chop, you are likely to have problems far outreaching the effectiveness of your antenna because of it's mounting height.

StreamFixer
'97 19SC w/ Salt Boss Top
'03 Yamaha 115 EFI
'05 Yamaha T8 Solas 4 blade prop

"By the grace of God we travel upon the rivers and sea..
They, like He, are mightier than me."  Mike Jesperson aka 'Nalu'

Offline Yachter Yat

Re: Another VHF antenna question
« Reply #16 on: April 23, 2017, 06:20:11 PM »
   Fixer;  Some good points.  Nonetheless, I see it differently.  From what we understand, a 4.5 db. antenna, such as the 4' Digital, broadcasts a slightly wider cone than those 6 dbs.  This (to me, at least) seems like it should offer a certain advantage in offsetting the movement of these small boats.  My question has always been this:  Wouldn't that wider beam have a slight advantage, as the signal is not as "concentrated"?   Additionally, wouldn't mounting on the top, thereby being as high as the lower mounted 8', cancel-out the height issue?  :shrug9:  I think we also have to keep in mind how much more stable a shorter antenna can be under certain conditions.  (Don't think I have to elaborate on that)  Like I said, if I had the luxury of a solid top, it would probably be my first option.  Just my 2.

Yat
Dear Arima:  Please "square-off" the Hunter transom. Next, stretch the Explorer by 9 and steal 2 or 3 from the cabin.  Please hurry, I'm getting old.

16 SC/Honda 60

Offline HemiGTX

Re: Another VHF antenna question
« Reply #17 on: April 23, 2017, 06:59:38 PM »
Awwww....my antenna routing is temporary.  I just have the wire snaking into the cockpit and zip tied to my hardtop support.  I have big plans for the roof of my hardtop, but there are some funding challenges to contend with.
AKA: "The guy who fishes with Nicole"

Offline Markshoreline

Re: Another VHF antenna question
« Reply #18 on: April 23, 2017, 08:37:58 PM »
But not snaked through the window opening, right???
2002 Sea Ranger HT 21, Yamaha 150, Yamaha 9.9

Offline HemiGTX

Re: Another VHF antenna question
« Reply #19 on: April 23, 2017, 09:03:32 PM »
Not through the window, lol.  It wraps around the rear of the window.  My stern light is mounted up there as well.  Another temporary measure!
AKA: "The guy who fishes with Nicole"

Offline Markshoreline

Re: Another VHF antenna question
« Reply #20 on: April 23, 2017, 09:10:03 PM »
At least that would alleviate the cooling problem.
2002 Sea Ranger HT 21, Yamaha 150, Yamaha 9.9

Offline Threeweight

Re: Another VHF antenna question
« Reply #21 on: April 23, 2017, 09:53:12 PM »
Here's a helpful chart I swiped from the West Marine web site giving estimates on potential transmission ranges based on the height of the transmitting and receiving antennas.



To the original question... I'd agree with Russ, stick with the 8' antenna.  The relative movement of our boats (and antennas mounted atop them) is quite small compared to an antenna mounted 30' up on a sailboat mast.  Our problem is not the boat yawing so much that our antenna is at a 45 degree angle and transmitting off into space... our problem is getting the signal up above the top of the surrounding swells for long enough that the person receiving of our transmission can hear what we are saying.

Putting a 4', 3 dB antenna on a mast may give you the same transmitting height as an 8' 6 dB, but you have effectively limited your range due to the weaker signal.

« Last Edit: April 23, 2017, 10:02:11 PM by Threeweight »
Former Sea Chaser 17 owner
Wild Card, Hewescraft Ocean Pro 220, Honda 225 and 9.9

“Never turn your back on fear. It should always be in front of you, like a thing that might have to be killed.”
       --- Hunter S. Thompson

Offline Kimbrey

Re: Another VHF antenna question
« Reply #22 on: April 23, 2017, 10:27:30 PM »
Here's an interesting experience I've had a few times with vhf.  Back in the day before cell phones we used a vhf marine operator to make phone calls home from the water.  They were actually quite entertaining to listen to in the evening.  We were fishing Hake close to Destruction Island (WA coast).  I was able to ding the Marine Operator in Newport Oregon a couple of times to make a call home to my wife.  Several years ago fishing pollock just East of the Pribilof Islands in the Bering Sea I was able to ding the Marine Operator in Dutch Harbor, approx 170 miles away, even using low power on the vhf.   Each of these times the atmospheric conditions had a low overcast.  I think it was a condition we learned about when getting our radar certifications for our CG licenses.  Refraction...the radio wave, radar and even vhf will bounce giving you a lot more range.  It doesn't seem to pop up very often though.

I've read your vhf operates best with the antenna mounted vertical to the plane of the water.  These yachts with their antennas mounted swept back for looks aren't getting the best use out of the antenna.

Kim
2005 Sea Legend --Sold--replaced with 26' Duckworth

Offline StreamFixer

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Re: Another VHF antenna question
« Reply #23 on: April 24, 2017, 08:41:29 AM »
Atmospherics play a HUGE part in long range radio communications.  Not often, but occasionally, guys at Camp Pendleton and other Army, Navy and Marine bases would hear comms from the PRC-25's in 'Nam.  Those radios are lucky to make 20 local miles in the rice paddy's and even less in the mountains....  Atmospherics...

There is a segment of the Amateur radio community (Hams) who pride themselves for establishing distance communications using less that 5 watts transmission power.  That being said, you can bet they are not using 8 foot antennae   :biggrin:

As far as antenna orientation goes, vertical antenna are best heard by another vertical antenna.    The same with horizontal. CG facilities often have both orientations with radios connected to each...  (nice to have $$$).  Matching orientation maximizes reception.  As far as the antenna angled to match the lines of the boat ---  I doubt folks who would do that really give a tiddly about what it does to the signal ---  Looks are everything for them...

As the frequencies you are dealing with become lower (marine frequencies are Very High Frequency (VHF) or what is commonly called 2 meter (about the actual wavelength)) the effective antenna lengthens.  Imagine how much fun it would be to mount a 40 meter antenna on one of our little boats     :doh:

StreamFixer
« Last Edit: April 24, 2017, 08:49:37 AM by StreamFixer »
'97 19SC w/ Salt Boss Top
'03 Yamaha 115 EFI
'05 Yamaha T8 Solas 4 blade prop

"By the grace of God we travel upon the rivers and sea..
They, like He, are mightier than me."  Mike Jesperson aka 'Nalu'

Offline fishmiester

Re: Another VHF antenna question
« Reply #24 on: April 24, 2017, 09:20:58 AM »
SF: I have considerd mounting my screwdriver antenna to my chaser, but couldn't figure the grounding challenge. That would give you 2-160 meters. For you non hams, a screwdriver antenna is a motorized adjustable antenna that lets you adjust the length of the antenna to the frequency you are using, with a 12 volt motor.
If it swims, Ill  chase it
84 17' Seachaser, 2010 90hp Tohatsu tldi, BF15 Honda Custom welded kicker bracket.#lovethisboat