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  #61 (permalink)  
Old 05-19-2017, 12:17 PM
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Just because I am pedantic and suffer from OCD...

It is not the type of modulation, it is the frequency range and that has to do with the physics of our atmosphere.

Skip results from the refraction of the radio signals. This is more likely to happen at lower frequencies although it can happen at higher frequencies due to tropospheric ducting and or sporadic E propagation.

FM modulation does have the advantage of something called the capture effect. That is an FM radio will "lock on to" the strongest signal it hears. Most radiated unwanted electrical noise that a receiver might pick up is AM (amplitude modulated) and an FM receiver section is somewhat immune to this.

There is a whole hobby of FM broadcast radio station DXing based on the above.

Finding somewhat unpopulated/uncrowded frequencies can be a benefit for dear hunters truckers and so on.
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Old 05-19-2017, 6:11 PM
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Originally Posted by SteveC0625 View Post
They are FM so no annoying skip for the most part. Better audio. Marine radios are inexpensive and readily available. For those that have Part 90 applications, it's easy to add a couple of marine channels to an existing VHF radio.
Come to think of it I have never seen a marine antenna on a car
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Old 05-19-2017, 6:36 PM
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Come to think of it I have never seen a marine antenna on a car
The Shakespeare CB antennas looks just like their marine antennas so it would be hard to tell.
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Old 05-19-2017, 6:45 PM
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The USCG tend to be overworked and underpaid. They're the first ones to say that their mission statement includes nothing about enforcing FCC regulations or radio operations, they're busy with marine safety. And if, and only if, a radio operator or operation compromises marine safety--then they'll act on the safety matter, not the radio per se.

Boaters routinely use ham radios that are opened up to work the marine SSB channels, which is flat out illegal, instead of buying separate ($1000++) marine SSBs. Rumor is that the FCC may have issued one citation, as the result of numerous complaints, in the last decade. Worldwide. But the USCG? They don't ask what radios you have. They don't ask what licenses you have. The only time they will get involved is with false distress calls, interference on safety channels, and with regulated vessels which are required to carry and monitor certain radio channels at all times.

Radios? There's another administrative agency in charge of that. And that would solely be the FCC, by act of Congress. Who would rather spend their time dealing with the billions to be made by selling frequency allocations for cell phones.
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Old 05-19-2017, 7:15 PM
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Originally Posted by stingray327 View Post
Come to think of it I have never seen a marine antenna on a car


At 156 and 157 MHz, a quarter wave antenna would be pretty much the length as other similar VHF frequencies. It would be extremely difficult , if not impossible, to distinguish an antenna tuned to marine channels from any other common VHF frequency in the 152 to 159 range.
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Old 05-19-2017, 7:17 PM
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Originally Posted by SteveC0625 View Post
At 156 and 157 MHz, a quarter wave antenna would be pretty much the length as other similar VHF frequencies. It would be extremely difficult , if not impossible, to distinguish an antenna tuned to marine channels from any other common VHF frequency in the 152 to 159 range.
With a coil how tall are these antennas?
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Old 05-19-2017, 7:18 PM
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Originally Posted by dmckean44 View Post
The Shakespeare CB antennas looks just like their marine antennas so it would be hard to tell.
I used to have a Shakesphere Big Stik 1/2 base antenna. Very poor performance compared to a Super Penetrator or a Sigma 5/8 ground plane antennas on CB radio.
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Old 05-19-2017, 7:22 PM
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Originally Posted by stingray327 View Post
With a coil how tall are these antennas?


If you mean a 5/8 wave base loaded VHF antenna, again 156 and 157 is right in the middle of all the 152 to 159 Part 90 freqs. Indistinguishable because they're all within a couple of inches of each other.
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Old 05-19-2017, 7:54 PM
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Quote:
Originally Posted by stingray327 View Post
With a coil how tall are these antennas?
5/8th's wave on Marine VHF frequencies will be around 39 inches. 5/8th's wave antennas have a coil at the base.

1/4 wave on Marine VHF frequencies will be around 17 inches.
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Old 05-19-2017, 8:02 PM
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Originally Posted by mmckenna View Post
5/8th's wave on Marine VHF frequencies will be around 39 inches. 5/8th's wave antennas have a coil at the base.

1/4 wave on Marine VHF frequencies will be around 17 inches.
I just replaced a quarter wave with a 3 db 5/8 wave antenna from Childs. The 156 MHz cut length for the base with a spring is 43.3". Without the spring, it's 46.3". Larsen has some different lengths, and I would venture that others do as well. It's all probably relative to the coil in the base.
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Old 05-19-2017, 8:29 PM
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Originally Posted by mmckenna View Post
5/8th's wave on Marine VHF frequencies will be around 39 inches. 5/8th's wave antennas have a coil at the base.

1/4 wave on Marine VHF frequencies will be around 17 inches.
On a car I would probably go for the smaller antenna 17 but if performance is double with the 39 inch antenna then I might consider this longer antenna.

If you can get a marine antenna with a magnet mount for temporary installation, I might go for the longer antenna.
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Old 05-19-2017, 9:02 PM
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Originally Posted by stingray327 View Post
On a car I would probably go for the smaller antenna 17 but if performance is double with the 39 inch antenna then I might consider this longer antenna.

If you can get a marine antenna with a magnet mount for temporary installation, I might go for the longer antenna.
Let's be clear here. These are not marine specific antennas. They are regular commercial/professional grade VHF antennas for installation on cars and trucks. We use the exact same items on fire trucks, ambulances, police cars, delivery trucks, taxis, and so on.

The only difference is that they are cut to a specific length at the time of installation to match the frequencies in the radio. In this case, it would be marine frequencies. But since the 156 & 157 MHz marine frequencies are right in the middle of all the common 152 to 159 Part 90 frequencies, the precise cut length varies by only a fraction of an inch at 1/4 wave and only an inch or so at 5/8 wave.d

My Childs 5/8 wave is tuned to 155 MHz, but gives very adequate performance from 144 MHz (amateur frequencies) all the way up through the marine channels and beyond.
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  #73 (permalink)  
Old 05-20-2017, 2:40 AM
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My van has quite a few antennas - and the VHF business band, the marine and 2m ham ones I often end up with a meter on because I cannot tell which is which - in fact, the marine 1/4 wave is the most useful, because it has a low VSWR on business and 2m, and also works damn well on UHF too.

In the UK, using marine band for anything other than marine is a bit pointless because nowhere in the UK is more than 100 miles from the sea. It does strile me that the mid states in the US wouldn't annoy the Coastguard whatsoever, as there are so many miles to travel. A huge proportion of the US has no sea within thousands of miles!
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Old 05-20-2017, 3:14 AM
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Originally Posted by wbswetnam View Post
I live in NW Arkansas, and this is the height of doe season. I monitor a variety of radio services on VHF / UHF (such as local public service, ham radio, MURS/GMRS/FRS, CB, maritime) and I'm sure hearing a lot of hunters illegally using VHF marine radios to coordinate their activities. Has anyone ever heard of hunters getting busted for using marine radios in violation of FCC rules?

Yes, but normally they are on one of the channels that the USCG monitors full time. Coon hunters, deer hunters and others in southern Missouri use them all the time also.
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Old 05-20-2017, 3:16 AM
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Originally Posted by wa4yur View Post
Not to mention these freqs are regularly monitored by the US Coast Guard ,the US Coast Guard AUX the FCC and the US Corp of engineers law enforcement division just to name a few government agencys that are using them. Using these freqs illegally is just asking to be caught.First time fine is $7000 min and could be much more including jail time. Take this advice from someone who knows what can happen. I have a friend that is fcc engineer in charge at a monitoring station.

Yeah? What monitoring station is he at?
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Old 05-20-2017, 7:46 AM
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Paulears, the Coast Guard run on the major rivers here in the States. Like the Mississippi, Missouri, Ohio and others.

For iamhere300, wa4yur last activity was 2-1-2016. You may get an answer from him, but kind of doubtful. I'd like to know the answer to your question also.
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Old 05-20-2017, 8:16 AM
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I didn't know that - here, they're strictly on the coast and large estuaries, but once they turn into rivers - the Coastguard don't exist, and inland boats rarely have radios.
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Old 05-20-2017, 8:51 AM
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I didn't know that - here, they're strictly on the coast and large estuaries, but once they turn into rivers - the Coastguard don't exist, and inland boats rarely have radios.
On major waterways like the Mississippi River and all of the Great Lakes, marine radios are essential for the commercial traffic. USCG has a strong presence on the Great Lakes. Most any commercial vessel anywhere in the US will have a marine radio as it's required. Recreational vessels smaller than 20 meters (65.6 feet) are exempt, but many will have them, especially the ones that are ocean-going.

I live on the Great Sacandaga Lake in the Adirondacks. The lake is 29 miles long. There aren't any 65'+ boats here, but there are lots 20 to 30' cabin cruisers. The local yacht club has a marine license for a few channels, and it's pretty common to see a VHF marine whip on even smaller boats.
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Old 05-20-2017, 8:52 AM
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Yeah, there's a lot Yanks that don't know also! When I lived in KC,Mo, the Missouri river had a minor flood and the Coast Guard was there helping to keep everybody safe. That was the year the Mississippi had one of it's greater floods. I listened to them on the scanner back then.
Now as far as people using the marine band for hunting, yeah, I've heard them when I was up in the Kansas and Missouri for a few months back in '04.
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Old 05-20-2017, 12:58 PM
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The USCG's domestic response in floods (& Katrina, etc.) is actually an even lesser understood oddity. The USCG is the only "dual role" agency. They are an administrative agency in time of peace, currently under DHS, but in time of actual war (technically, only by Congressional declaration of war) the USCG is transferred to the Department of Defense and only then do they become a military agency.

As Mr. Bush eventually learned after Katrina, there's a section of the US Code that is informally referred to as the Posse Comitatus Act, which expressly prohibited most domestic use of the US military as it then stood, at the time of that law being written. More legal arguments, because some military agencies (like the Air Force) did not exist at that time, so they were not prohibited. But traditionalists point out that it listed everything that did exist, so the ban should apply to all military agencies.

Very handy that the USCG, as an administrative agency, wasn't included at all. (And the National Guard technically being State Militia who are seconded as Federal Militia under Army command, are exempted because they're not enumerated by the law.)

Even more obscure, that section of the USC, which is always referred to by name, was basically thrown out in a minor addenda in the 2006(?) omnibus budget act, over a thousand pages of boring details, one of which referred to that code by section number only (cleverly making it impossible to search on the name). The addenda provides that the President, in his sole discretion, may declare a domestic state of emergency, separate from the usual Stafford Act declarations, and order the domestic use of all US military forces pretty much when and how he pleases, for domestic law enforcement and other purposes previously banned. Somehow, that got no publicity, and I suspect most of the CongressCritters who signed the budget act never even knew that was in there.
One can only surmise that Mr. Bush, frustrated that he could not order military aid after Katrina, asked someone what would allow that next time around, and this is what they came up with.

The USCG can normally operate on all "navigable waterways" which basically means anything that will let you get a canoe down to the sea. Budget constraints and common sense pretty much keep them restricted to areas where there is commercial traffic, heavy recreational traffic, and waterway markers (buoys, daymarks) to maintain. They are so strapped, and spread so thin, that last time I heard they were still recruiting civilian radio operators to join the USCG Auxiliary in order to man the radio watch posts at USCG stations around Long Island (NY). Sending an RDF team to chase hunters in the Mohave Desert or Great North Woods? Not so much.(G)
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