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SSB Antennas

Discussion in 'Boat Electronics' started by Vito, Jan 29, 2004.

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  1. Vito

    Vito Guest

    Tests of mobile antennae in the Amateur Radio 75 meter band (4MHz) yielded
    the following results:

    * Well-designed Bugcatcher or Screwdriver with top hat 0 dB reference
    * Bugcatcher or Screwdriver with no top hat -3 dB
    * Hustler or Outbacker -9 dB
    * Hamstick -12 dB
    * Whip with autotuner -14 dB

    This suggests that the common insulated-backstay-with-autotuner used on
    sailboats could be improved by adding a capacitive top hat immediately below
    the upper insulator and/or a tapped coil in parallel (ie around) the lower
    insulator to tune whatever length of antenna one can physically accomodate
    to resonate on or near the Marine frequencies of interest, such as 2182 MHz.
    Has anyone any experience doing so?
     
  2. Most noncommercial boaters do not have the expertiese to understand,
    let alone install, what you are describing. Most commercial vessels
    have enough Mast Height to accommodate a "Total Antenna Length" of 75 ft
    so that common autotuners can resonate the system to 2182 Khz. On
    SOLAS Required Vessels MF and HF Antenna Systems are designed to
    be resonate on all the specific SOLAS Required Frequencies and are
    TESTED and Logged once a year by Licensed Marine Radio Tech's.

    Bruce in alaska
     
  3. Gary Schafer

    Gary Schafer Guest

    Yes the top hat would help out on 2 and 4 mhz frequencies. Problem is
    where to put it where it is not in the way.

    A loading coil on the stay would also help out but it would work even
    better if it was up high nearer to the top of the stay.
    Problem is that usually only one antenna is available for all bands on
    a boat. At the higher frequencies that loading coil would act as a
    choke and effectively disconnect the upper portion of the antenna.
    Which may not be all that bad if there is sufficient length below the
    coil for the higher frequencies.

    The other problem that you may run into is that the auto tuner may not
    like the impedance it sees. Most auto tuners do not like to see a
    resonant antenna near 50 ohms. But on 2 mhz it would probably help a
    lot.

    Regards
    Gary
     
  4. Licensed Marine Radio Tech is a person who has an FCC GROL/w
    RADAR/GMDSS-M and is licensed to maintain Maritime Mobile Radio Service
    licensed systems aboard US flagged Vessels. The SOLAS Requires that
    Title III Part II, and title III Part I Vessels be inspected on an annual
    basis and that inspection by a Licensed Marine Radio Tech, be logged in
    the Vessel Station Log and a renewed SOLAS Certificate be Issued and
    Posted for Public Inspection. In the passed, these inspections were
    done by FCC Field Agents, and the SOLAS Certificates, Bridge to Bridge
    RadioTelephone Certificates, were issued by the FCC Field Agents, on
    completion of the inspection. A similar inspection of Title IIi Part
    IIi Vessels needs to be completed every 5 years for those class vessels,
    and is done, now, through the same method.

    Bruce in alaska
     
  5. Yep, I feel the same way about my GROL, as I keep my First Phone, and
    First Graph/Aircraft Endorsement up on the wall, and I only keep the
    Pocket version of my Lifetime GROL/Radar/GMDSS-M-O in my wallet.

    Bruce in alaska
     
  6. Yep, every CB nut with a screwdriver can now fiddle with any Land Mobile
    Radio, Broadcast Transmitter, Microwave System, and Public Safety Radio
    System, in the country. And folks wonder why interference complaints
    are doubleing every three years.

    Bruce in alaska
     
  7. Nope Doug, no License Required anymore. Knowledgable Tech's recomeended
    but not even required. That's why I got out of the Broadcast Business
    35 years ago. To many Carneigie, and Elkins, First Phone's showing up,
    and getting OTJ Training on my license as Chief Engineer. There's no
    such thing as an Automated 50,000 Watt AM Transmitter. When those
    puppy's decide to melt down, they do it in a hurry, and usually with
    lots of sparks and steam from the liquid cooling systems. Usually
    the finals are pulled at 50% of rated time, but nowdays with skimpy
    maintaince money, owners are pushing that out to 80% and catastophic
    failure is happen a lot more often. Reminds me of a very cold January
    Night when KRAB-FM's antenna took a hell of a wet snow load, and
    unbalanced the two 5Kw finals explosivly. I came around the corner
    and the DJ on duty was out in the street with a bunch of steaming holes
    in the snow where hot final Parts had melted down through the snow.
    Took the consulting engineer and I, 8 hours to rebuild the final cage
    (Lots of plumbing parts) and get it back on the air.

    Bruce in alaska
     
  8. Larry

    Larry Guest

    I had a 1st as well, but frankly thought the 2d was a good deal harder. If
    nothing else, it was a lot longer! I recall the 1st was 50 questions (and
    it seems like it was mostly law) and the 2d was 200 questions. I passed
    them both, but I recall spending a long time on the 2d. Never did the
    GMDSS/M or radar.

    I thought that after the FCC went to General Commercial that NABER or
    someone like that handled endorsements for a while, but then they gave that
    up. Do you remember what happened to that stuff?
     
  9. Gary Schafer

    Gary Schafer Guest

    The nitrogen was for the transmission line.

    Regards
    Gary
     
  10. Tuuk

    Tuuk Guest

    Ok guys,, what's your comments on the 2m homebrew antenna? Anyone build one
    and had a particular preference or reasons why one over the other?

    Thanks
     
  11. Well I have now been updated on Broadcast Transmitters...... thanks
    Larry. It has been a few years since I inspected an AM Broadcast Station
    and the one's I did do were out in the small communities of alaska.
    I got out of the Broadcast Industry as an Engineer, many years ago,
    so it isn't to suprising that I am a bit out of date on the technology.
    Oh well, age gets us all eventually. Thank goodness Marine Radios
    are still using 1990 technology, cause I still have a bit of a handle on
    them.

    I also talked to my buddies at SEA, and they are just coming back
    into production on their SEA157 VHF Radio's and even a few of the SEA235
    MF/HF Radio's. This is very good news for the thousands of folks who
    have SEA Products onboard. I also had a chance to talk to Mark Johnson
    of ShineMicro about AIS. He is really big into this new (to me) Position
    Reporting System now being mandated for ships of 65Ft in the US.
    Way cool stuff if you got the money, and still way cool when the ClassB
    stuff for Volitary Compliance comes out later this year.


    Bruce in alaska
     
  12. Yep, your R one, and with this little slip of paper, you can now LEGALLY
    adjust Marine & Aircraft Radio Systems so as to make them compliant with
    Parts 80 & 87 of the FCC Rules and Regulations. Oh yea, you need an FAA
    Certificate if you mess with Aircraft systems in actual Aircraft, or you
    need someone who has an FAA Certificate to sign off on any work on
    Aircraft Radio's.

    All that said, there really isn't much to adjust anymore unless your
    working with some of the older MF/HF Radio's around. Mostly just
    setting the Master Osc. on frequency, and then setting the power output,
    and your done these days.

    Bruce in alaska
     
  13. Jack Painter

    Jack Painter Guest

    Larry, are you aware of any "findu" type charts that are adaptable to APRS?
    Mapquest "maps" display a poor graphic when plotting a vehicle on long
    bridges like the type that interlace the Hampton Roads Va area. It's not
    that the position reported from GPS is inaccurate, but a graphic
    representation becomes muddled when bodies of water are shown by Mapquest.
    We're thinking the mapquest maps would accordingly be of little use in this
    area as a result, but have not actually tried the equipment from a boat yet.

    Jack
    Va Beach Va
     
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