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  • #16
    Originally posted by kobuk View Post
    I also have my radio mounted on my ceiling which I like but it's literally one foot away from the antena mount through the roof and I read that that can cause issues when transmitting. Does anyone have any say on that?
    Yes. Does that mean you only have 1' of coax or is there some coiled up? Understand that the coax is usually part of the complete antenna system. You can google "length of coax for VHF mobile" and get some idea. Here is one such explanation: http://www.m5bxb.com/coaxlengthcalc.htm
    Sheep hunting...... the pain goes away, but the stupidity remains...!!!

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    • #17
      Originally posted by Daveinthebush View Post
      I listen to other calls and if I am 12-15 miles out of port not line-of-sight and I can hear a tender trying to enter the harbor I feel much better about my radio.
      Yes, it's a good indicator. But I'm sure you know that rx'ing and tx'ing are two entirely different things. One can insert a random length of wire into the back of a radio and possibly pick up a signal, but try and transmit on that and you will have problems. Most radios can receive far better than they can transmit for a number of reasons. A perfectly matched (impedance) antenna "system" is what we strive for especially when it comes to transmitting.
      Sheep hunting...... the pain goes away, but the stupidity remains...!!!

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      • #18
        Originally posted by kobuk View Post
        Is yours mounted to a ratcheting mount? If so, do you have some sort of cradle or way to carry it down while trailering? Did you use a stantion or just the antena alone? It apears by your measurements that it's a stand alone. Were you able to buy it local or order it. Sorry for all of the questions but I'm not at all familiar with the morad antenas. I also have my radio mounted on my ceiling which I like but it's literally one foot away from the antena mount through the roof and I read that that can cause issues when transmitting. Does anyone have any say on that? I'm definately getting an external speaker, just trying to figure where to mount that for the best sound.
        Yes it mounts to the adapter that macncoke described & then into the SS ratchet that is mounted on the port side of arch. VHF is almost directly below antenna with about 3 vertical feet of separation. No stanchion. I have a chart somewhere that I will try to post that shows separation req'd for different electronic units but I don't think it mentions anything about distance between antenna & radio.
        2007 24ft NorthRiver OS
        Twin 175 Suzuki's
        "Thunderbird"
        MMSI #338033856

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        • #19
          Originally posted by macncoke View Post
          The 156HD is for VHF. You can purchase the M91 Mount Adapter to use it on the same mount you have. You can get a test meter like this one to tell you what is going on with the radio and antenna. The instructions on it are very simple. https://www.amazon.com/Shakespeare-A.../dp/B000OTJAOE The morad antenna will be a good upgrade from anything shakespeare. Standard radios usually have pretty good speakers in them.
          My bad Dev, it is the 156HD on my vhf & the 159HD I bought from you on the AIS... This gettin old stuff is really gettin old!
          2007 24ft NorthRiver OS
          Twin 175 Suzuki's
          "Thunderbird"
          MMSI #338033856

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          • #20
            Originally posted by Daveinthebush View Post
            Good discusion and information. Most boaters I know hail on the radio as they are exiting port for a radio check and the harbor master 150 yards away replies "Load and Clear". I listen to other calls and if I am 12-15 miles out of port not line-of-sight and I can hear a tender trying to enter the harbor I feel much better about my radio.
            Not sure how it is in Valdez, but in Seward there are a several knotheads that try to hail another boat & when they don't get an immediate reply, they ask for a radio check.
            2007 24ft NorthRiver OS
            Twin 175 Suzuki's
            "Thunderbird"
            MMSI #338033856

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            • #21
              Originally posted by akdeweyj View Post
              I have a chart somewhere that I will try to post that shows separation req'd for different electronic units but I don't think it mentions anything about distance between antenna & radio.
              In a perfect world when transmitting all RF will be radiated out the antenna. But for most all accounts antenna systems are not perfect. When the antenna system is not properly matched to frequency then the coax will also radiate reflected RF. If the radio is real close to the antenna then, when transmitting, a lot of this stray RF will end up bouncing around inside the radio. Not good. The higher up in frequency you go, ie, VHF/UHF the more important antenna systems are. Poor quality (high loss) coax plays a huge factor at higher frequencies.
              Sheep hunting...... the pain goes away, but the stupidity remains...!!!

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              • #22
                Originally posted by 4merguide View Post
                In a perfect world when transmitting all RF will be radiated out the antenna. But for most all accounts antenna systems are not perfect. When the antenna system is not properly matched to frequency then the coax will also radiate reflected RF. If the radio is real close to the antenna then, when transmitting, a lot of this stray RF will end up bouncing around inside the radio. Not good. The higher up in frequency you go, ie, VHF/UHF the more important antenna systems are. Poor quality (high loss) coax plays a huge factor at higher frequencies.
                My radio is mounted on the ceiling but i have a long coax. It's been a while but I remember it was quite long and I did coil it up under the dash and then back up to my radio. Would there be any issues if I mounted my VHF on my dash next to my GPS/Sounder combo? My new garmin uses an internal GPS antena. I would prefer the ceiling mount but a dash mount wouldn't be the end of the world. I supose using the morad antena without a stantion would be a little shorter and maybe loose a little range, but maybe being a better antena would be the offset? I'm probably overthing this too....

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                • #23
                  Originally posted by cjjeeper View Post
                  Will that screw right in to replace my garmin antenna? (if you happen to know...)

                  Thx
                  The threads should be the same. Here is a picture of my Morad > Adapter > SS Ratchet mount that is bolted to the side of my radar arch. I lay it back & lock it when travelling.

                  Click image for larger version

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                  2007 24ft NorthRiver OS
                  Twin 175 Suzuki's
                  "Thunderbird"
                  MMSI #338033856

                  Comment


                  • #24
                    Originally posted by akdeweyj View Post
                    Yes it mounts to the adapter that macncoke described & then into the SS ratchet that is mounted on the port side of arch. VHF is almost directly below antenna with about 3 vertical feet of separation. No stanchion. I have a chart somewhere that I will try to post that shows separation req'd for different electronic units but I don't think it mentions anything about distance between antenna & radio.
                    Here is the antenna spacing chart that Nmea publishes.

                    Click image for larger version

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                    2007 24ft NorthRiver OS
                    Twin 175 Suzuki's
                    "Thunderbird"
                    MMSI #338033856

                    Comment


                    • #25
                      Originally posted by 4merguide View Post
                      In a perfect world when transmitting all RF will be radiated out the antenna. But for most all accounts antenna systems are not perfect. When the antenna system is not properly matched to frequency then the coax will also radiate reflected RF. If the radio is real close to the antenna then, when transmitting, a lot of this stray RF will end up bouncing around inside the radio. Not good. The higher up in frequency you go, ie, VHF/UHF the more important antenna systems are. Poor quality (high loss) coax plays a huge factor at higher frequencies.
                      This dovetails with another issue on small craft: RF exposure to personnel. FCC calls for 5 meters minimum distance between any part of the VHF antenna and personnel to prevent dangerous levels of RF exposure. Needless to say, on mastless boats it's impossible to get far enough away from the antenna to meet the requirement and mitigate exposure, and on a lot of boats we're standing only a couple feet if not only a few inches from a 6 or 9 DB gain antenna at ? watts... Might be somewhat less an issue with properly rigged aluminum boats, but definitely a concern with glass or composite construction. I am currently constructing the latter, and am scratching my head trying to figure out a suitable means of integrating functionally effective RF shielding into my pilothouse roof (upon which my antenna will be mounted)...
                      ...he who knows nothing is nearer to truth than he whose mind is filled with falsehoods & errors. ~Thomas Jefferson
                      I would rather have a mind opened by wonder than one closed by belief. ~Gerry Spence
                      The last thing Alaska needs is another bigot. ~member Catch It

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                      • #26
                        Originally posted by akdeweyj View Post
                        The threads should be the same. Here is a picture of my Morad > Adapter > SS Ratchet mount that is bolted to the side of my radar arch. I lay it back & lock it when travelling.

                        [ATTACH=CONFIG]98157[/ATTACH]

                        yep cool.. thats what I bought. Thanks
                        Alaska Armory -- http://www.facebook.com/AlaskaArmory
                        Underwood Ammunition Dealer

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                        • #27
                          Where is a good place to buy or order these antenas?

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                          • #28
                            Originally posted by kobuk View Post
                            Where is a good place to buy or order these antenas?
                            Call morad in seattle
                            sigpic
                            Alaska Shrimp Pots

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                            akshrimppots@mtaonline.net
                            907 775 1692

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                            • #29
                              Originally posted by potbuilder View Post
                              Call morad in seattle
                              Thanks and I'll give them a call.

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