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colbysmith



Joined: 02 Oct 2011
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PostPosted: Tue Jan 08, 2019 1:06 pm    Post subject: VHF Antennas Reply with quote

I'm in the process of replacing one of my VHF radios and antennas. I'm looking to replace my Shakespeare Mariner 8500 with the Shakespeare 5225 XT. In doing a little bit of research I see the 8500 is 1/2 wave and the 5225 is 5/8 wave. In simple terms, which is a better antenna, how does wave relate to performance? For those of you that I have cruised with, the 8500 is on the radio I get most of the complaints about not being heard clearly. My SWR meter shows good connections on both my radios/antennas, so that's not a factor.

I'm also replacing that SH Eclipse radio with a newer SH GX1700. (I do not need the AIS, as my GX2150 has that and the loudhailer bells and whistles, and I also have the new Simtex AIS transceiver) The GX1700 has an internal GPS and DSC, and is just an upgrade for my old technology Eclipse.

Colby
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gary f



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PostPosted: Tue Jan 08, 2019 4:20 pm    Post subject: Reply with quote

Hi Colby,

When we bought our boat I told the folks at Rogers Marine Electronics in Portland, Or. to give us one of the best VHF radio and antenna for our C-Dory.

We don't follow the current electronic technology advancements like we should and so we trusted them to make the right decision for the install on our boat.

We have a Lowrance Link-8 VHF/AIS radio with the Shakespeare 5225-XT Galaxy 8' VHF Antenna. We are happy with this set-up. You mention the 5225-XT and so that may be a good choice for your boat also.
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C-Val



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PostPosted: Tue Jan 08, 2019 4:45 pm    Post subject: Reply with quote

Hi Colby
Just for your info I am buying a 5225 xt right now from Hodges Marine on sale for $113. I am trading in my 5101 as I am done with cheap antennas.
My last boat had a 5225 xp (I think the predecessor to the xt)
It was well built and had great for reception, even though the meter shows a high swr (over 3 1/2)

The only thing I donít know is Dr Bob says we should test the swr of each antenna before we buy it as some are better than others.
I donít know how a person is supposed to do that when you buy on the internetóbesides these antennas donít come with ends on them which you need to test ? ? ?

David and Val

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colbysmith



Joined: 02 Oct 2011
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PostPosted: Tue Jan 08, 2019 5:05 pm    Post subject: Reply with quote

I am on the phone now with West Marine, ordering some stuff. I had already found that antenna with it's lowest price at Hodges Marine, and getting the price match. Also getting the GX1700 for 191.84 price matched to Hodges. (WM list of $249.99).

While some have bad mouthed West Marine, I am more than happy to recommend them. I also have the West Advantage gold membership. With my recent Garmin Auto Pilot purchase, (which I price matched saving $150), I received $480 in coupons. (When I purchased the AP, it was a triple points special weekend.) The nice thing about using West Marine then, is I can have shipped direct to my local store, or if my order is over $50, I can have it shipped free to my home. And, if I change my mind or have a problem, I can return the product directly to the store for a refund or replacement. Very Happy

I can't remember what my other Shakespeare antenna for my GX2150 is, but I know it was more expensive than the 8500 I'm replacing. That side of the boat (radio and antenna) have had no issues getting out and receiving. Hopefully the 5225 xt and GX1700 combination will do as well as the GX2150 and it's antenna have! Many of us will find out at Hontoon in March! Mr. Green

BTW, regarding the testing. I do have a meter and check my radio's and antenna's whenever I replace them or start having problems. I think I've always been able to stay somewhere around 1.2 or 1.3: 1. The antenna and radio do have to be installed, with the PL259 connector as well. I'm willing to help check others radios at Hontoon during the gathering, if your antenna connection to the radio is easily accessible. Colby
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thataway



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PostPosted: Tue Jan 08, 2019 5:19 pm    Post subject: Reply with quote

To put it simply: even experienced hams, who make their own antennas cannot agree on the 1/2 over 5/8 for the 2 meter (close enough to the Marine VHF for all purposes). The 1/2 wave, does better with a minimal or no ground plane--which is what a fiberglass boat is. The 5/8 with a good metal or radial ground plane will have more gain--but it needs that large ground plane. You will do as well with a quality 1/2 wave antenna. A 6 dB gain antenna is a good compromise for our small boats.

The biggest differences are the quality of the antennas, and how carefully they are manufactured. This includes the quality of the fiberglass tube and finish. As I noted in another post, I take my antenna analyzer to the store to test antennas. There is a huge variations even in the same brand. Generally the more expensive the antenna, the better quality will be the parts, and assembly. The 8 foot antenna usually has the same "guts" as the 4 foot antenna. The lower part of the 8 foot is just a feed wire. Height is important...but a foot or two does not gain a lot of distance. (typically a mile at the most. For two antennas at 10 feet the range of reception is 8 miles. If one is at 14 feet and the other still at 10 feet, the range is 9 miles. That is the boat with an 8 foot antenna, will have only a one mile range further than one with a 4 foot antenna. Some quality antennas, with have two half wave antennas coupled.

I have used "Digital" antennas (they are analogue) but generally better quality than "Shakespeare. " antennas. I am currently using a Morad antenna. They are high quality, use their own cables a mini UHF fitting (so you can thread the cable thru areas just slightly larger than the coax cable, and no worry with soldering.) Each antenna is checked for VSR at the factory. They are 6 dB Gain. They are used mostly by commercial, LEO and Military--costly, and the mount and cables are extra.

One of my worries with most fiberglass antennas (the fiberglass is just a support for the wire inside.) is that people grab them, or pull on them--and they break if hit a tree limb etc. So I often have used a base loaded 39" whip, on a SS 1" base. The cheaper antennas, will have the gel coat or paint wear after a few years--and become fuzzy with glass fibers exposed.

Also Marine VHF antennas should be at right angles to the water surface. The "doughnut" shape of the radio wave, is flatter the higher the gain. For example for sailboats 3 dB is often used, since the boat's heeling, may sent half of the transmitted power off into the wild blue yonder and the other half to Davey Jones if they had a very expensive 10 dB antenna. The high end Cost over $800) 10 dB antennas are more often used on stabilized large power boats. Never slope your antenna backward, because it looks "cool"--you will loose a lot of power.

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colbysmith



Joined: 02 Oct 2011
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PostPosted: Tue Jan 08, 2019 6:03 pm    Post subject: Reply with quote

Thanks Bob for all the good info. I was going to ask you how you test the antennas at the store, as commonly the PL259 connector is included but not installed. But you answered the question saying you use Morad antennas that already come with the connector installed. Those antennas do usually show up with the highest ratings in reviews. Rather or not they perform any better relative to the cost for our pleasure boats is up to one's opinion. The majority of antennas I have replaced have been for breakage rather than upgrade. Crying or Very sad I tend to trailer with my antenna's all the way down. I tend to... sometimes I will travel locally with them up at 45 degrees. And I always put them up or take them down at the ramp. That works great until somebody plants a short tree next to the ramp or you park under some trees while stopping to eat locally.... and then have to back out catching the tree limb under the antenna... Then there are also the tight coves with trees overhead, like where I like to dock at Hontoon!...
I've used 4' SS whips before also, but don't think they do as well as the 8' fiberglass, just due to their height above water. But they hold up better to trees! Rolling Eyes
Any way, the 5225xt describes as a 5/8 wave. Or it did in one of the descriptions I read, so that's why my curiosity. I thought all the 8' fiberglass VFH pretty much had the same specs. However, I do know they can be "packed" different inside the fiberglass, with possibly varying lengths of wire. In any case, looking forward to getting the new electronics and hopefully none of you will tell me to speak up or that you can't copy me when I use that radio. Mr. Green
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thataway



Joined: 02 Nov 2003
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PostPosted: Tue Jan 08, 2019 6:14 pm    Post subject: Reply with quote

The in-expensive antenna analyzer does need a radio, and a short piece of coax to hook into the PL 259. It will only give you the SWR for one frequency--that on which you transmit at that time. Often these are not quite as accurate as an antenna analyzer. The antenna analyzer measures other perimeters.

The antenna analyzer is set up so that it has a signal generator, which puts out a specific frequency which the operator controls--that way you can map what the SWR is at each end and the middle of the frequency spectrum used in Marine VHF. The spectrum is from 156.050 Mhz to 157.425 MHz. Channel 16 is 156.800 MHz and is where the lowest SWR should be tuned at--since this is the emergency channel. There are several receive channels on Port ops and Public comms, at 161.800 to 162.000. AIS is very close to 162 MHz--the AIS antenna should be tuned to this frequency for best reception and transmission.
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colbysmith



Joined: 02 Oct 2011
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PostPosted: Tue Jan 08, 2019 6:22 pm    Post subject: Reply with quote

When I do install my meter in line, I check several frequencies. Usually 9, 13, 16 and 69. I figure that pretty much covers the spread. I also check in both lo and hi power. I believe I have the Shakespear ART-1 or -2. Maybe not top of the line, but seems to do the job. Smile Colby
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jkidd



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PostPosted: Tue Jan 08, 2019 7:35 pm    Post subject: Reply with quote

I like the Morad antenna same gain as an 8 foot in 4-1/2í and made of stainless and aluminum with a 10 year life. The cheap 8 footers just have a copper wire in them and the more expensive ones have a brass element. At four or five years the sun will make them fall apart or the cable will rot right where it goes into the antenna making it useless. The nice thing about the Morad is the cable is replaceable. 100-200 dollars for something that your going to bet your life on seems pretty cheap. Why compromise.


The analyzer that I use is this one https://www.gigaparts.com/mfj-259c.html?gclid=EAIaIQobChMI3cbpu8Tf3wIVGMRkCh1DnACvEAQYASABEgJGzvD_BwE

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ssobol



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PostPosted: Tue Jan 08, 2019 7:42 pm    Post subject: Reply with quote

thataway wrote:
...
One of my worries with most fiberglass antennas (the fiberglass is just a support for the wire inside.) is that people grab them, or pull on them--and they break if hit a tree limb etc. ...


This happened to me. We were docking the boat. I went to get the trailer. While I was gone the boat started to get away from my wife due to the wind. In a panic she grabbed the antenna (it was folded down) to pull the boat back to the dock. She ended up bending the SS antenna mount. The FG antenna and the roof of the boat (where the antenna mounts) were undamaged. It is a Shakespeare antenna.

I used to be a bit concerned about the antenna because we fly a flag from it. Thought it might cause strain on the roof were it attached. Don't worry about it anymore.
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pcg



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PostPosted: Tue Jan 08, 2019 10:11 pm    Post subject: Reply with quote

thataway wrote:
--the AIS antenna should be tuned to this frequency for best reception and transmission.

Iím interested in knowing how you do this. Do you have an antenna tuner in-line, or do you make changes to the feedline or antenna itself?

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thataway



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PostPosted: Tue Jan 08, 2019 10:20 pm    Post subject: Reply with quote

pcg wrote:
thataway wrote:
--the AIS antenna should be tuned to this frequency for best reception and transmission.

Iím interested in knowing how you do this. Do you have an antenna tuner in-line, or do you make changes to the feedline or antenna itself?


The average Shakespeare or Digital antenna cannot be tuned. There are specific AIS frequency antennas built. Morad makes a 6 dB gain 162 MHz AIS antenna. The simple 36/39" whips with a base loading coil are easily tuned by changing the length of the SS whip.

An antenna tuner just fools the radio to sense it is sending power into a properly tuned antenna--A good tuner will tune a cyclone fence or any straight wire. The signal strength will be best with a properly designed and tuned antenna.
The feed line is not part of the antenna in a VHF Marine antenna--it only has to be 50 ohm impedance or close. The higher quality the line; the less the loss. Yes, the antenna itself is modified--but those fiberglass encased antennas can not be tuned without taking the tubular fiberglass off.
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colbysmith



Joined: 02 Oct 2011
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PostPosted: Tue Jan 08, 2019 10:37 pm    Post subject: Reply with quote

Quote:
The simple 36/39" whips with a base loading coil are easily tuned by changing the length of the SS whip.


This was the common way to do it on CB antennas. Still have my old meter from my CB days too. Smile Colby
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Foggy



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PostPosted: Wed Jan 09, 2019 9:39 am    Post subject: Reply with quote

On installation of your VHF antenna, you may want to be aware of a potential
problem of interference of VHF reception (static, noise) if the antenna is
mounted close to LED lights. LEDs can also affect AIS nav reception as well as
often it is shared w/VHF antenna.

To test: Tune into an unused channel. Adjust the squelch. Turn on your LED
lights. If there's noise or static your LEDs are interfering with your reception.
You now get to change light bulbs or your antenna location.

This could bother those garrulous at night on the VHF.

Aye.
Ref: USCG Bulletin # 13 - 18

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JamesTXSD



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PostPosted: Wed Jan 09, 2019 9:48 am    Post subject: Reply with quote

"garrulous"

I had to look it up. It's a good word, and apropos for that usage. Thanks for expanding my vocabulary this morning.
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