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Old 11-10-2012, 10:46 AM   #141
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............ Why not just try it for yourself? Fold your antenna down horizontally and try this - Automated Radio Check Service | Sea Tow
Because I would not have the controlled conditions and test equipment to do a scientific and reliable test.

With the antenna broadside to the SeaTow station, I would probably receive a response and I might (if I didn't know better because of my background and understanding of these things) come to the conclusion that an antenna worked as well horizontally as vertically.

If the antena was pointed directly at or away from the SeaTow station, I would get the results I would expect, no response (unless I was very close to the station).

There's no good reason for a boater to try any tests or experiments when he or she can just follow the manufacturer's instructions. Very few boaters have the expertise the manufacturer has with its own products.
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Old 11-10-2012, 12:18 PM   #142
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Laying down an antenna that already has a tilting base and then doing a "radio check" while pointing the bow in various bearings to the station doesn't really require much "expertise" but then again, no point in busting a good myth .... or maybe proving it.

Regardless of one's background, if the antenna worked just as well horizontally to the station as vertically up to some range, then it works ... no background required. If it doesn't work then at certain bearings it doesn't. Maybe your have just learned a direction finding technique that might come in handy one day ... Isn't anyone interested in knowing or would that ruin the thread?
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Old 11-10-2012, 01:10 PM   #143
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Because I would not have the controlled conditions and test equipment to do a scientific and reliable test.
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The manufacture provides theoretical and bench test modeling, which provides average predicted performance. Real world conditions may result in slightly different performance, which is to be expected. There are performance variation from product to product and the environmental conditions of the site install will also cause differences in performance. After we install a new site or move an antenna on the tower, we conduct a field test to determine the real world result.

FM Frequency Modulation - Vertical Polarization (the antenna will perform best when oriented in a vertical position.) That shouldn't be construed to mean it won't work at all in the Horizontal, because they will work, just not as good. We frequently will put up temporary antennae, because of location constraints, in the horizontal and they work fine until we can do a proper site install.

For us boaters using VHF Marine Radios, around 150.x - 162.x MHz frequencies, Range is a product of and limited by elevation (curvature of the earth), limited transmitter power (maintaining a sufficiently high signal-to-noise ratio) and environmental considerations. (mountains, antennae orientation, radio performance, operator skills, etc.)

If you're having performance problems and haven't had your radio checked recently, have a shop take a look at your radio and installation.

p.s. If you swivel your antenna to a horizontal position and it won't work at a short range, like under a mile, then you probably have a broken/ shorted coax cable or corroded/poor connectors. Take it apart and clean connectors, look for cold solder joints at the connectors and replace the cabling if there are any signs of wear.

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Old 11-10-2012, 06:32 PM   #144
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----------------------------------
The manufacture provides theoretical and bench test modeling, which provides average predicted performance. Real world conditions may result in slightly different performance, which is to be expected. There are performance variation from product to product and the environmental conditions of the site install will also cause differences in performance. After we install a new site or move an antenna on the tower, we conduct a field test to determine the real world result.

FM Frequency Modulation - Vertical Polarization (the antenna will perform best when oriented in a vertical position.) That shouldn't be construed to mean it won't work at all in the Horizontal, because they will work, just not as good. We frequently will put up temporary antennae, because of location constraints, in the horizontal and they work fine until we can do a proper site install.

For us boaters using VHF Marine Radios, around 150.x - 162.x MHz frequencies, Range is a product of and limited by elevation (curvature of the earth), limited transmitter power (maintaining a sufficiently high signal-to-noise ratio) and environmental considerations. (mountains, antennae orientation, radio performance, operator skills, etc.)

If you're having performance problems and haven't had your radio checked recently, have a shop take a look at your radio and installation.

p.s. If you swivel your antenna to a horizontal position and it won't work at a short range, like under a mile, then you probably have a broken/ shorted coax cable or corroded/poor connectors. Take it apart and clean connectors, look for cold solder joints at the connectors and replace the cabling if there are any signs of wear.

Larry B
This post matches most of my theoretical understanding and practical use of VHF.

With digital VHF... line of sight is often exceeded when everything else is correct. On winter nights I often hear Maine to North Carolina USCG stations on CH 16 in southern NJ.
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Old 11-10-2012, 10:00 PM   #145
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This post matches most of my theoretical understanding and practical use of VHF.

With digital VHF... line of sight is often exceeded when everything else is correct. On winter nights I often hear Maine to North Carolina USCG stations on CH 16 in southern NJ.

Digital VHF???

Please explain what digital VHF is.
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Old 11-10-2012, 10:30 PM   #146
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Digital VHF???

Please explain what digital VHF is.
Really can't...just know what marketing calls them on how they process the radio signals/waves (???)(DSC capable???) and that some of the radios and big systems like the USCG's and Sea Tow's definitely improved by a quantum leap in the last 10 years...the reception distances are astounding.
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Old 11-11-2012, 03:03 AM   #147
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Digital VHF???

Please explain what digital VHF is.
------------------------------------------------
In the simplest form, digital radio is a processed signal which turns sound into patterns of numbers or "digits". The digital receiver converts the digits into audio and sends it to the speaker. Analog signals are radio frequency waves which are transmitted and then picked up by a radio receiver which converts, amplifies and then sends it to the speaker. Digital radios are usually clearer, crisper sounding. But they do have their drawbacks as well.

The current VHF Marine system is an Analog based system. Digital VHF systems are not directly compatible with Analog systems. Although some of the new digital radios can switch back and forth between Analog, Digital and Digital Trunked formats. (Like the new Motorola 7000 series mobile radios. They're also about $7000 each and the portable is $6000.)

Other users of the VHF radio spectrum are being forced by the FCC to switch to APCO P25 compliant narrow band radios in another month. For many of us we're also switching from Analog VHF to Digital VHF trunked radio formats at the same time. Our old analog radios were not P25 capable and had to be replaced anyway.

I am not aware of a digital voice use of the VHF 150.x - 162.x MHz marine frequencies in the US. However, I wouldn't be surprised to see marine VHF FM switching to a digital format sometime in the future. You will have to buy a new digital radio to use the new system and Analog will go the way of Loran.

There is a new add on for VHF radios called DSC (Digital Selective Calling). The US Coast Guard is experimenting with them under a program called "Rescue 21". But it is not a voice calling system here in the US. The DSC device is programmed with your boats preregistered MMSI (Mobil Maritime Station Identifications) number. When you press the emergency button it transmits your GPS Lat/Lon and your MMSI number over Channel 70 on your VHF radio. If you're out of range of a shore station and other DSC equipped boats are between you and the shore station, there DSC will automatically re-transmit your distress call from boat to boat until it eventually reaches the shore station. I hear this is all over Europe now and they have some voice capabilities as well.

Anybody know about DSC??

Larry B,.
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Old 11-11-2012, 04:08 AM   #148
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DSC has been around in the US for quite awhile. Six, seven years or more. All marine VHF radios sold new today have it. It's the covered red button on the radio. In addition to the automatic emergency transmission signal that can indlude your lat and long if you feed the radio a GPS position signal (like from a plotter), you can use DSC for initiating radio conversations with other boats that have an MMSI number. The DSC calling feature eliminates the need to establish initial contact on 16 and instead directs both the sending and receiving radios directly to the pre-selected working channel.

The emergency-broadcast-with-position feature is very useful. The "discreet" calling feature is not in my opinion athough some people might find some value in it. We used it a few years ago on a couple of longer cruises in the company of another boat but in the end we simply reverted to making our initial calls on 16 and switching to a working channel.
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Old 11-11-2012, 06:12 AM   #149
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...DSC has been around in the US for quite awhile. Six, seven years or more. All marine VHF radios sold new today have it...
In mid 1999, the FCC required radio manufacturers to include DSC capability in all new models. This applies to fixed mount radios only, not handheld.

Larry B: Here's a link to a recent bulletin from the USCG on DSC.

Digital Selective Calling
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Old 11-11-2012, 08:26 AM   #150
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DSC has been around in the US for quite awhile.
The analogue version has been on aircraft since the '60s ... Selcal.
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Old 11-11-2012, 09:07 AM   #151
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As so often happens on this forum, the discussion has gone fro the original "what to do when someone passes you throwing a big wake" to the use of VHF radios, to the propagation characteristics of antennas in the mountains and now to the DSC feature on marine radios.

The original topic was answered as best it could be several pages ago.
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Old 11-11-2012, 10:17 AM   #152
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In mid 1999, the FCC required radio manufacturers to include DSC capability in all new models. This applies to fixed mount radios only, not handheld.

Larry B: Here's a link to a recent bulletin from the USCG on DSC.

Digital Selective Calling
---------------------------------------------
Larry M
Good article, Dated May 2012 - Sounds like the Coast Guard is putting DSC in all their rescue centers. I haven't bought a new Marine VHF since about 1985, so out of the loop on DSC. Maybe it's time to upgrade my radio's, But good to know regardless.

Thanks
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Old 11-11-2012, 11:33 AM   #153
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[QUOTE=rwidman;112210]As so often happens on this forum, the discussion has gone fro the original "what to do when someone passes you throwing a big wake" to the use of VHF radios, to the propagation characteristics of antennas in the mountains and now to the DSC feature on marine radios.

The original topic was answered as best it could be several pages ago.[/QUOTE]

And, so you imply... that no intelligent morphing in relation to topic on first post should develop from the initial intelligent topic/thought train/pattern... onto/into another/others?? I respectfully disagree... in that I have been following this thread carefully and appreciate much of the added (morphed) info beyond initial thought pattern. IMHO - Shows we're all still thinking!
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Old 11-11-2012, 12:51 PM   #154
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It wouldn't be trawler forum without topic creep.
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Old 11-11-2012, 12:52 PM   #155
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While we could be more clever in starting new threads such as by carrying over a quote from another thread when that thread starts to drift, I agree with Art. We could end up with two parallel threads.
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Old 11-11-2012, 01:14 PM   #156
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"Topic creep." That's a great name for the phenomenon. If it's not already an official internet term it should be.
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Old 11-11-2012, 01:24 PM   #157
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Larry M
Good article, Dated May 2012 - Sounds like the Coast Guard is putting DSC in all their rescue centers. I haven't bought a new Marine VHF since about 1985, so out of the loop on DSC. Maybe it's time to upgrade my radio's, But good to know regardless.

Thanks
Larry B
Cape May, NJ area was one of the first to get it..it has some bugs but pretty good so far. I think many other but not all USCG sectors have it.

Sea Tow has it in their remodeled Marine operator radio system..the USCG often double checks with the Sea Tow system when their equipment didn't get what they needed.

I'm guessing that is why a few of the older thoughts on VHF are no longer completely accurate such as line of sight limitations.
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Old 11-11-2012, 07:08 PM   #158
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Digital VHF???

Please explain what digital VHF is.
You've never seen the "Digital" marine antennas?
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Old 11-11-2012, 08:13 PM   #159
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You've never seen the "Digital" marine antennas?

I had to ask... although it was a loaded question.

I'm a FCC licensed radio tech, but haven't dabbled in two way for several years. I spend my RF time on digital microwave. The FCC license dates me. New techs see the copy of my original on the wall of my office from 1982 and realize that they were not alive when I got it.
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Old 11-12-2012, 11:29 AM   #160
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The original topic was answered as best it could be several pages ago.
The funny part is that the new topic is better than the original topic.
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