Moderated Discussion Areas
ContinuousWave: Small Boat Electrical
VHF antenna recommendations
|Author||Topic: VHF antenna recommendations|
posted 07-29-2012 09:11 PM ET (US)
I’m in the market for a VHF antenna for a Whaler that does a lot of slow-speed trolling. Anticipating some significant roll and pitch from time to time, I am leaning toward a 3dB gain antenna atop an extension vs a 6dB 8’ example.
I recently read NMEA’s Marine Electronics Buyers Guide (2006) on antennas. http://www.marineelectronicsjournal.com/pdf/CBG_Marine_Antennas_2006.pdf
As I read the article I recalled jimh’s [reference article] on the GAM SS-2 antenna with 4-foot extension combo he uses on his boat. Not knowing the development cycle of marine VHF antennas I wonder how some other antenna currently available might compare, specifically the MORAD VHF-156 DELUXE 3dB gain @ 156 MHz part#9122 or the Shakespeare Phase III 3dB gain part#6400. Does anyone have any first-hand experience, conjecture, or opinions among the three antennas?
posted 07-29-2012 09:33 PM ET (US)
I've been using a MORAD 156-HD for many years. They are nearly indestructible. It has
posted 07-29-2012 11:20 PM ET (US)
The benefits of the GAM SS-2 are explained in my article. At the time I wrote the article, which was six years ago, as far as I could tell the GAM SS-2 in conjunction with the ADAP-II mount gave the cleanest installation on an extension mast.
Since then the style of the GAM SS-2 has been copied by some other manufacturers. You may be able to find a similar antenna with a similar mounting arrangement. I have not investigated because the GAM SS-2 is still working perfectly, now going into its seventh season of use.
I believe the MORAD is significantly more expensive, and you will need their special mounting adaptor, too. I think the antenna Dave P is talking about is not the same one as mentioned in the initial article. I believe Dave P has the VHF-156HD model, and also has the appropriate Morad mounting so it can thread into the standard rachet mount used almost universally for marine antennas.
Six years ago when I was looking for antennas I don't think Morad even had a website, and it was hard to find any information about them. They have a website now, but it still seems unnecessarily hard to get information from that website. It would be useful if we could get a direct link to information about the VHF-156HD and the mounting adator. I would also like to know the prices. I am sure the MORAD antenna works a lot better than their website does.
posted 07-29-2012 11:29 PM ET (US)
I didn't find too much in the NMEA buyer's guide to change my thinking. My opinion about VHF Marine Band radio antennas for small boats is simple:
--mount the antenna as high as possible to improve the range and reduce interference with other electronics on the boat; height is the most important factor
--antennas with metal whips are much more durable than fiberglass encased antennas;
--there is too much obsession with eight-foot antennas, most of which comes from people who have no basis to give an opinion; a half-wave radiator, which is typically a three-foot or four-foot antenna, can provide excellent performance on a small boat;
--all antenna gain comes from concentrating radiation into a narrower pattern. The gain is only obtained if the main lobe of the antenna is aligned with the remote station. Anytime the main lobe of the high gain antenna is not aligned with the remote station, there is a good probability the gain will actually be less than a smaller antenna would provide due to the broader lobe of the smaller antenna; the remote station may fall into a null in the pattern of a high gain antenna and be severly reduced in strength.
posted 07-30-2012 08:07 AM ET (US)
When I bought my antenna, MORAD did not have a web site. I found a PDF document of their products on the web somewhere and contacted them directly to purchase the antenna.
My experiences with MORAD were overwhelmingly positive. When I called them, I spoke directly to one of their engineers and he was happy to answer all my questions.
Their web site is a little difficult, but if you click on the "Technical" tab, there are two links to PDF documents describing what mounts to use for what antenna and a retail price list. The "Pictures" section also describes the mounts.
Incredibly, the price for the VHF-156HD ($147.00) is the same as what I paid in 2007.
posted 07-31-2012 10:09 PM ET (US)
Do you see a significant value in the silver plated element or type N connector used on the Shakespeare Phase III?
posted 08-01-2012 02:06 PM ET (US)
The N-series of coaxial cable connectors is typically used at higher frequencies than the 150-MHz of the VHF Marine Band. If an N-connector were really needed on a VHF Marine Band installation, one would think that the radio itself would have an N-connector. I don't see an N-connector on an antenna for a small boat has holding much advantage. It will increase the cost of the installation because the mating connector for the feed line will will be more expensive.
Silver plating is often used in electrical applications because silver oxide is conductive. When the silver plating oxidizes it will still be conductive. However, intrusion of water into the interior of an antenna contained in a fiberglass enclosure should not occur.
I think the silver plating and N-connector are a bit excessive on a VHF Marine Band antenna that will be handling 25-watts of power.
posted 08-01-2012 06:57 PM ET (US)
I have silver-plated PL-259 connectors on both ends of my coax because that's all my local Ham store stocks. I can't say if they work any better than any other type of PL-259.
They tarnish, and they're a pain to shine before company comes over.
West Marine sells gold-plated connectors, but that was too flashy for my tastes...
posted 08-01-2012 07:39 PM ET (US)
I have to wonder then about the N connector. Could this be a high end convenience connector to simplify installation more than a performance enhancement?
posted 08-01-2012 07:51 PM ET (US)
I'd have to say no, because no radio manufacturer that I know of supports it (without an adapter, that is, and an adapter will introduce loss).
The two connector types use different coaxial cable. The type N connector uses RG-58 and the PL-259 uses RG-8X. I didn't look up the specs for each, but I suspect they're slightly different, with RG-58 being the poorer performer of the two.
Of course for less than 50' runs and 25W of power, they might perform identically.
posted 08-01-2012 09:59 PM ET (US)
N-series and UHF-series connectors are available to fit many sizes of coaxial feed line, from very small to larger than 1-inch. The cable size is not a determinant in selecting the style of connector.
The N-series will have slightly better performance in terms of VSWR insertion bump than a UHF-series connector, but I don't consider this to be significant.
posted 08-01-2012 10:19 PM ET (US)
I did not know that.
The only applications I have ever encountered using the connectors mentioned used the cable types I referenced.
I'm still not sure why Shakespeare would equip their Phase III antennas with the type N connector.
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