Conference unifix::sailing

Please see notes 18.9 and 18.12. The higher your VHF antenna above the 
water, the better. This means that you should use a masthead antenna 
if at all possible. The physical length of the antenna is related to
wavelength radio waves. The antennas are usually 1/4 wavelength (about a
half meter). 

    The only exception to -.1 Ive ever seen is the argument that if
    it is placed on the masthead and you lose your mast you may have
    a tough time calling for help etc.  Emergency antennae I've used
    aren't that good either.  Still, the best overall place is at the
    masthead.
    
    Dave

re .2:

A simple solution: Don't use an 'emergency' antenna if your mast falls 
down. A normal antenna isn't very large -- just keep a spare with a 
length of cable attached tucked into an odd nook or cranny (we do). 

    I the masthead, however the question is between a 3 or 6 Db antenna.
     The 6 Db antenna will give greater range but it radiates a narrower
    single, thus if you are heeled over the signal will be directed
    towards the water or the air.  This wont happen with a 3 Db antenna
    (as much).  I feel that a 6 Db antenna is better.

    Re: -.2
    
    Of course, why didn't I think of that.  Would take VERY little space.
    I'd make the coax long enough to reach outside the cabin and maybe
    up the stump of the mast (if any).  Good idea.
    
    Dave

    I found our radio lead looking rather frayed and grotty at the
    connector last week. Went and cleaned it up a bit. Radio started
    recieving. When I went to call for a launch the other day, the marina
    said they never heard me. A friend said the radio could be ok, and the
    antenna could be the culprit.
    
    
    I intend to do a transmit check tonight. Failing it, how do I track
    down whether it is the radio transmitter, the wire, the connector to
    the mast lead, or the antenna itself. It there a given resistence I
    should be looking for.
    
    thanks
    
     john
    
    

The "fancy" way to verify correct antenna connectivity is with a SWR meter
(That's "standing wave ratio"). It tells you whether you're delivering power
into the load, i.e. the antenna.) Unfortunately they cost money, so most
boaters don't have one...

There are three things that can go wrong with antenna wiring: open signal
conductor, open ground conductor, or a short. The first of these is by far
the most common. Check each connector to make sure the center conductor is
soldered. Crimp connections are frequently not reliable.

If the connectors look OK, test the signal conductors and grounds for
continuity with an Ohm-meter or continuity tester. You'll need a second
long wire to perform these checks, and if your mast is up, you'll need to
go aloft to test the connector at the antenna. The resistance should be
zero Ohms � 1 Ohm. Resistance between the signal conductor and the ground
braid should be very high, i.e. meg Ohms. 

To verify that the radio itself is working, connect your radio to a known
working antenna (perhaps on another boat in the marina) and test it.

To test the antenna itself, take it to a known good radio, and test whether you
can transmit from there. 

You might want to invest in a spare antenna to help you with these tests. (A
spare antenna can be very handy if your mast decides to fall down!)

--RS    

Remove the antenna connector from the radio and measure the resistance 
between the center and outer conductors. It should be approximately 
zero. 

If it is, then connect a known good antenna to the radio and do a 
transmit check. If the transmitter appears to be not working, you have 
the option of having the transmitter repaired or buying a new radio 
(I'd buy a new one if the current one is more than a few years old -- it 
is costing me about $150 to have the volume control in my car stereo 
replaced -- bleah!).

If the resistance is high to infinite, then either the cable or the 
antenna is bad. 

If the cable and antenna are permanently connected, buy a new antenna
and cable. (I'd recommend the Metz stainless steel whip antenna -- it has
worked very well for us -- and RG8 cable. RG8 is the stiff 3/8" diameter 
cable. It has much lower loss than the think RG58 kind which becomes 
significant as cable length exceeds 50' or so.)

If there is a cable connector at the antenna, go to the masthead (I 
assume that's where the antenna is) and disconnect the cable from the 
antenna. Short the center and outer conductors and measure the resistance 
between the center and outer conductors at the other end. It should be 
about zero. If it isn't, the cable or connectors are bad. 

Depending on the quality of the antenna and antenna cable and their age, 
you might want to consider skipping all this troubleshooting and simply 
replace them. Water does tend to wick into the cable and connectors, 
eventually causing corrosion. I left an extra 15' or so on my cable so I 
could replace the connectors if need be (from corrosion or, as has 
happened more than once, from damage by inept yard workers). 
    
Alan

re .7:

I imagine some transmitters might be damaged by trying to transmit into 
a open load, ie, a defective antenna. I wouldn't test an antenna this 
way.

    	Could be a number of things ranging from simple to expensive.  The
    trouble shooting tools are a volt ohm meter, and an SWR meter.  Exactly
    what was the nature of the cleanup up.

    1) Check for short in the coax by using a ohm meter.  One lead to the
       center connector the other to the shell of the connector.  If you
       have a short replace the cable.  Do not try to transmit......

    2) Borrow a VHF/UHF SWR meter and a short length of COAX cable.  Hook up 
       the coax from the antenna to the meter, and the short length from the
       meter to the radio.  Set the meter to read SWR and check the reading
       while trying to transmit.  If the SWR is greater than 2 to 1 you
       have a mismatch between the antenna and the transmitter.  Probably a
       short of some kind or the antenna is the wrong length.

    3) Also using the SWR meter check the check to transmit power.  Most
       SWR meter have a power setting.  If you are not getting out of the
       radio it is possible the transmitter finals are fried.  This can
       happen if the radio transmitted into a shorted antenna cable and
       does not have the circuitry to protect against this.


    	If you cannot borrow a meter you can pick up a cheap one at the
    local radio shack it is under $50.  I may be able to hunt one down for
    you send me mail if you want me to try.




    Forrest

    John, your boat is next to mine.  We should be able to hook your radio
    to my cable and antenna over the weekend.
    
    Heck, being the sport that I am, I could be convinced to crank you to
    your masthead so you can do your testing of the cable.
    
    Does your radio receive okay?
    
    djc
    
    

    The radio wasn't working at all at first.
    
    I went to the cable connector between the boat and the mast and the 
    boat side was a mess. I cut off 6 inches of cable and rescrewed the 
    socket together. I did notice the outside ground wire still had a lot of 
    black color to it (ie bad looking copper). The inside was still a nice
    shiney tin color.
    
    I will try the ohm test to ensure no shorts tonight. Better make sure
    my insurance is paid up before I let Dave crank me up the mast with one
    of my bad winches. Maybe I can get my crew to go up instead ;>) ;>) .
    
    May get that extra antenna anyways. I have been using my cellar phone
    as a backup (seems to be the hottest electronic toy in the marinas this
    year). But a Plan C never hurt anyone!
    
    Thanks all
    
    john

    John,
    
    There were two microphones I used for that radio.  One worked and one
    didn't.  You could receive but not transmit.  I don't remember whether
    I left both on the boat or only one.  In any case, try another
    microphone and (from another boat) and if things work ok then maybe I
    have the other microphone at home.  Let me know.
    
    	Regards,
    
    	Ron
    
    ps: otherwise, the radio has been working great for about 4 years.
    

    No shorts in the cable. After the test I recut and cleaned the cable
    before reassembly and testing.
    
    re .13
    
    Interesting Ron. I did a check at the mooring last night with the 
    launch attendent. He said he could hear me key the mike, but did not
    hear any sound. I will give the microphone swap a try.
    
    john

    
       A buddy of mine in the office gave me a bad radio for it's mike. It
    turned out to be the same brand so this was a straight plug in.
    
    Radio works fine now.
    
    john

    Seeing how the mast is down for new rigging this winter, I decided to
    rewire the mast. For the antennea, Practical Sailor suggests the 
    Radio Shack RG8M/rg8X as a best buy $.28 a foot. They also said the RG8U
    at .52 a foot is also good, but not needed.
    
    Anyways, I go down Radio Shack last weekend and there is RG8U (printed
    down the cable every 2 feet) on a spool that says RG8M on it. The price
    is .$.32, so I get 50 feet. 
    
    I'm feeling pretty smug about this as West wants $1.05 a foot for RG8U.
    When I get home, I look at the West Catalog as I read they had the best
    connectors for the job. While there I notice that thier RG8U is thick
    stuff, and the RG8U I have is thinner. 
    
    So, is my cable mislabeled every 2 feet (ie RG8M), or can RG8U be the
    thinner cable?
    
       john

    RG8/U is larger cable with a diameter about 0.405 inches.  RG58, which
    looks like cable tv coax (tv coax = RG59), is about 0.195 inches.  If
    I remember correctly, RG8X is closer in diameter to the RG58.
    
    How tall is your mast?  I ask because I believe that RG8X and any of
    the foam cables (RG8, RG58, etc. with foam dielectric) aren't really a
    good choice for unsupported vertical runs.  Heat causes the foam in
    many of these cables to soften significantly and gravity does its
    thing.  The foam flows down and you end up with a tear-drop cable, thin
    at the top and bulbous at the bottom.  The situation is a bit better if
    the cable is tie-wrapped ever 2 feet - the foam doesn't have that far
    to flow.  
    
    The net effect of the tear-dropping is the impedance of the coax is no
    longer constant and in simple terms there is some loss of power and
    efficiency.  How much?  I don't know off hand, but I do remember some
    real problems reported in vertical runs around 75 feet.
    
    My other comment is to apply solder connectors, not crimp-ons, unless
    you have access to the high-quality professional crimpers and
    connectors.  I wish I had a nickel for every "radio" problem I've seen
    that turned out to be corrosion in the connectors.
    
    Good luck with your project.
     

John, because Radio Shack (Tandy) makes their own cable 
in Texas I suppose that they could put whatever they want
on the side :-)

The difference in price between your Tandy cable and that
which West Marine sells is, most importantly, that the
wire is tinned. Because it is designed for marine use,
the outermost layer of insulation may be thicker than 
that offered by Tandy. Take a piece of Tandy cable to 
West Marine and compare the diameters of the conductors
to verify this. 

Because of the higher db loss (3db or more) from using less-expensive 
cable (and considering the hassle of running it up the 
mast) I'd not spare the dollars for such an application.
The good cable should be somewhat less than half an inch
 -- maybe .41 or so. Hey! If you want *really* low loss you
could look up the suff Boeing uses on their jets (diameter
of about an inch) :-)

Michael

    Another consideration is whether or not the inner conductor and braid
    are tinned for corrosion resistance. Ancor (the expensive brand West
    sells) tins both the braid and inner conductor. Most less expensive
    cable (probably including Radio Shack cable) is not tinned. One end of
    our RG8/U (the thick stuff) was dropped in the ocean while the mast was
    being stepped. A couple of years later the braid had corroded so badly
    that we had to replace the cable. Even soldered connectors aren't
    watertight. Eventually water and salt will penetrate the cable at the
    ends (especially at the masthead end) and cause corrosion. The question
    is when, not if. Dropping our cable in the ocean only accelerated the
    process. We now use Ancor cable for both the masthead VHF and the
    masthead AM/FM antenna. Good tunes are important, too. Seems like a
    worthwhile investment. It is probably a good idea to check the cable
    continuity annually with a good ohmmeter. Larger cable has more braid,
    so it may take longer for it all to corrode away.
    
    Finally, the lower loss in the larger cable means a stronger
    transmitted signal, which usually isn't critical, but who knows when it
    might be. 
    
    Alan

    You can get RG58 (and probably others) with a solid dielectic versus
    foam.  The foam is absorbent and will wick water through the cable over
    time.  The solid stuff will not.  RG8U is better for longer runs as
    there will be a lower signal loss especially if your radio to antenna
    length is over 50 feet or so.  We used RG58 for the Loran and it worked
    fine.  It was recommended by the manufacturer and that is what size the
    conectors were.  I bought the cable at a large consumer electronics
    place off of 128.  It has slipped my mind at the moment though.  I have 
    a bunch of it left along with a handfull of connectors if anyone wants
    it.  FREE too.  
    
    Brian
    

    re .20:
    
    As I recall, signal loss in coaxial cable increases with frequency.
    Loran signals are 100 kHz, VHF signals are around 150 MHz, so long,
    small diameter cable may be satisfactory for loran but may not be so
    for VHF.

    Checking with a friend of mine, he said the stuff is new. It is smaller
    in diameter than RG8U but because of the trick foam, it works as well.
    So I used some RG8x adapters from West with their Pl-259 connectors
    (this stuff is all AMPROL (sp?) and consider the best ).
    
    The friend did all the soldering (he builds communications satillites 
    for a living), then wd40'ed everything. all connectors were then
    double wrapped in high quality silcone tape. All connections were
    brand new. We did use the original 20 yr old Antenna.
    
    Because it was not tinned (the original 20 yr old RG8U wasn't), I added 2
    feet of extra at the base of the mast and also in the cabin headliner.
    If corrosion starts, I'll just cut it and get some new connectors for
    $5. First time we fired it up it was incredible. We were recieving twice the
    range we used to get on the old cruddy RG8U. When sending, we were getting 
    the same range (you don't want to know I found this out!). The only problem
    is now we get nimrods babbling from twice the distance. They outta have
    a local switch like my car stereo. ;>)
    
    The best part is that not only is it thinner and easier to route, but it
    is half the weight aloft. So you get lightweight vhf wire at 1/4 price and
     can use non-kelvar low stretch line for 1/4 the price which saves LOTS
    of money (probably enough to buy the vhf cable, connectors, soldering
    gun, antennea etc) and you still have the same weight aloft as the 
    diehard racers.
                    
    I intend on sending a couple feet to Dan Spur at PS for analysis.