Conference unifix::sailing

I would never trust a crimp connection for something as critical as an 
antenna signal connection. Don't even  think about a crimp connector. 
Solder! 

You-Do-It Electronics just off Rt 128 carries various types of coaxial 
cable. Newark Electronics (offices around the US) also stocks many types 
of cable, and they accept MC for phone orders. To minimize signal loss,
use cable identical to what you have now. There are various grades of
cable -- the cable made by US manufacturers (eg, Belden) is to be
preferred. You should also use good quality connectors (eg, Amphenol). 
I personnally wouldn't use Radio Shack connectors unless absolutely 
necessary. 

Oh yes, cable may not be available by the foot. It is usually sold in 
(minimum) 100'. 

    Loran is transmited at something like 100Khz.  This is a very forgiving
    frequency w/regard to your cable connections because it is so low.
    I wouldn't mess with splicing  (I would never attempt it and I worked
    in the microwave industry for half my career).
    
    Just go to RS and by a BNC barrel (female to female) and a piece
    of preassembled RG58 from RS.   They sell it in various lengths.
    Go for the stranded if you can get it.  If you can't, don't worry
    too much about it.   Keep it dry and it should last a long time.

    I have been using Radio Shack crimp type connectors and an additional
    10 feet of cable now for over four years with not a single problem.
    However I do carry two spare connectors just in case.
    
    Paul

    I caller Voyager Marine in Essex and was told the following.  Very
    helpful and friendly these folks were.
    
    RG58 A/U is stranded and MARINE grade and should be used.
    Plain old VHF type connectors should be used for the splice - SOLDERED
    A new BNC is no big deal to put on but it should be soldered.
    Up to 75' of cable is recommended for our unit/antenna 
    The splice should be placed in a relatively dry spot (dry locker) and
    corrosion should not be an issue.
    
    Thanks for the responses - decisions to make now.
    
    Brian

    Skipper says... RG58 U is fine and use solder connectors if you can get
    them.  Crimp ons will work if not subjected to alot of vibration.  So
    it seems that performance wise there really isn't a problem but it is
    more a question of longevity of the installation.  I guess if done
    properly, it really doesn't matter.  I will use the solder type of
    connectors though since the prosfessionals leaned in that direction.  I
    thank you all for the responses.  Newark electonics does have the stuff 
    but they will not sell cable in less than 100' lengths.  You do it
    Electonics has the connectors but not the RG58 A/U.  Voyager has it
    all as does Skipper.  Now where did I leave my wallet...... 
    
    Brian
    
    

    Why not just solder the Radio Shack connectors. That's what I always
    do. (You should tin the center conductor of the cable before assembly.)
    Of course the shield connection is still just a "crimp" fit.
    
    I always solder all wiring changes on my boat. I just don't trust a
    crimp connector in a sea environment. The other reason boats require
    a solid connection is because of the large amounts of current carried
    by most of the wiring. It takes ten times the current to light a 50
    watt bulb at 12 volts than at 120 volts.
    
    -John
    
    

    My Loran has been having problems with Signal to Noise Ratios (snr) as
    a result of both the engine and some flourescent lights in the main
    cabin.
    
    I can turn the lights off easily and as the Nav light is incandescent
    and the Loran has its own built in backlight that is not a major
    problem.  The engine is a bigger problem though as you lose the LOArn
    when it is on.
    
    All my research to date indicates that I could have an earthing
    problem on the boat.  I do not have a built-in earth/ground plate.
    
    One suggestion that I read in an electronics book was to take tin foil
    and spread it in the bliges (presumably not in contact with any metal
    parts) and then bring an edge up to a bulkhead where it could be joined
    to a ground conductor.  I guess that the idea is that although the
    Hull fiberglass is not a conductor, it should act more as a capacitor.
    
    Has anyone tried such an arrangement ?  If so, did it end up working or
    did you damage the hull ?
    
    Any other ideas on improving the SNR would be appreciated.
     

    Try a alternator filter.  A couple of easy ways to check if you need
    one.  If you have an RDF.  Tune it to the bottem of the band and listen
    with the engine running.  IF you hear a whine that changes pitch with
    engine speed and gets louder with higher electrical load.  You need a
    filter.  The other test is to look at the SNR numbers with engine at
    idle and with it running at cruise.  IF the SNR numbers are ok at idle
    and poor at cruise. You need a filter.  The other thing to try is
    connect a big capacitor (10k+ ufd's at 20+ volts) across the output of
    the alternator.  Use short leads.  This is basicaly what you are buying
    when you buy a filter.  
    
    I Had the same problem.  TRaced it down with a multi band radio that
    covers 150khz to 500 khz band.  The fix was a computer grade filter
    capacitor wired across the alternator.  I attached it on with shrink
    tape and tye (sp) wraps.  Has worked well for two years.  
    
    
    Ken Chester
    
    
    

    I dont think you want a big capacitor as a filter- you are trying to
    eliminate high frequency noise off the DC line. You want small caps to
    ground, with VERY short leads, or inductors in series. Most noise
    filter are simply inductors, of a wire size suitable to the current
    output of the alternator.
    
    A 10K+ mfd cap might help reduce the ripple in the DC, but since the
    alternator has a battery on it, that removes any ripple problems.

    Does it make a difference that I have a generator Vs. an Alternator ?

    Only in that generators create MUCH more electrical noise than
    alternators. Generators have 30-40 commutator bars, each makes its own
    spark and noise every time it passes the brush. Alternator slip rings
    have no breaks, should only make minor sparks/noise.
    
    So generators need even more filtering than alternators. Same kind of
    filter applies.

    I have had very good results in eliminating generator noise from an
    a.m. radio (in the same ballpark as Loran) in my 1962 VW beetle
    using a good sized " feedthru capacitor. They have a mounting lug on
    the side of the can which is grounded and no wire leads but a screw
    in each end of the can, where the hot lead passes through the cap.
    Because of the mechanical arrangement of a feedthru cap, there is
    almost no lead inductance - (lead inductance is what keeps noise from
    being filtered [shorted to ground] by a traditional cap w/ wire leads).
    
    I have forgotten the electrical value - maybe .1 ufd or more.
    It was about an inch in diameter and 1.25 " long. It totally cleaned
    all of the noise/while out of the radio. I believe I just fed the power
    to the radio thru the feedthru cap.
    
    Bill
    

I suggest that you first improve your grounding system.
What does the current system consist of?

    To be honest, there is no grounding system.

    I agree that a grounding system for a loran is important, but if we are
    talking about an unfiltered generator (i.e. with brushes, and not an
    alternator with slip rings), a grounding system won't do much for
    an inherently noisy d.c. generator. It will need filtering, if none
    is already present.
    
    Bill
    

	A ground is essential to proper LORAN operation. 
The service manual of every brand is very clear on this 
point. Of course all the filtering suggestions could
be necessary as well but first I'd start with a proper
installation. 
	On another tack, what brand is the unit? I
know Micrologic is notorious for interference problems.
There is however a shield which can be acquired from
the factory to alleviate it. There is some discussion 
about this in the power boats conference.

Paul

    Proper grounding might be essential, not "is" essential.   My Apelco
    DXL6300 runs just fine with no ground.  And in fact runs fine with only
    the lower 4' of the 8' antenna.  (This unit is truly amazing in terms
    of signal pickup).   When installing a Loran, you should be prepared to
    follow through with grounding, but I would first see how it performs
    before proceeding with expensive or complex measures such as dynaplate
    installation.

    My experience is the same as Jim's, with the same loran (Apelco
    DXL6300).
    
    I added a #12 gauge ground wire from the loran to my aluminum rudder
    and can barely perceive the improvement in signal to noise ratio
    i.e. Nantucket changes from 92% to 93% signal quality.
    
    I also have been using a short antenna. My 8' whip is too heavy (or more
    precisely has too much leverage) for my pulpit mount and tips it over
    unless I use a lanyard to the backstay - which I am prepared to do
    and would do if I were in a critical (fog) situation.
    
    The rest of the time, I run a 38" (I think) stainless whip which is 
    lightweight.
    
    I was motivated to get a short whip after I found myself getting
    useable numbers last summer (30-50% signal) quality one day when I had
    forgotten to screw ANY antenna into the coupler.
    
    Bill
    

re .7

If you have a SNR problem, there are two basic approaches to fixing it. You can
try to enhance the signal, or you can try to reduce the noise.

When you improve the grounding, you will effectively improve the signal
strength, but only to the extent that the signal from the antenna is
coupled into the ground on the unit. Even a fairly weak ground will usually
leave you with a reasonable signal. If you sail in an area where the
LORAN signal is marginal, it will be important to have a good ground.

When you add power filtering, you are isolating the unit from a "noise" source.
If your SNR is good without the noise sources (flourescent light and generator),
then I would suggest adding a filter. It should be fairly easy to attenuate
noise from these sources by 20dB or more.

--RS

I'd like to second the comments in .17.  I have had a good Raytheon on a 
sailboat with an outboard and also an Apelco 63xx on a power boat with a 
diesel and both worked good with only the antenna on the stern.

    I just completed installing my own Marinetek loran and had similiar 
    antenna connection problems as Brian described in his base note. The
    antenna wire came with a connector already installed and would have
    necessitated drilling a rather large hole in the deck before routing
    inside the boat. 
    
    Being the "I hate to put holes in my boat type", I took apart the 
    connector to reduce the beast to its lowest common demoninator part.
    Sure enough, when I put everything back together I wasn't able to
    raise the 9960 primary station consistently. Trying to find a new
    connector for stranded cable turned out to be a major effort, and
    for now I am using a compression connector, which seems to be working.
    
    I agree with the soldering suggestions, and also intend to redo the
    connections once I can obtain the correct solder-type connector from
    either of the companies suggested. 
    
    JC