Antenna Coax Short

[r.oril]

I was checking my HF radio on my 26D and found a short at the coax. I had crushed the coax at the base so I ordered and installed 35 feet. Man, what a job that turned out to be! I forgot that the coax and electrical were zipped tied together.
1. Undo the mast deck light, cut off the cable and coax ends at the base and pull it out the old cable and coax thru the top, dragging the new cable up, remove a zillion zip ties.
2. Drag the old cable back up with the new coax.
3. Attach the new coax to the electrical cable with a zillion zip ties and drag them back down with the old coax. Must have made a million trips from the bow to the stern.
4. Attach the coax connectors and test......still has a @#$%^& short!!!
How can that be?? I then tested the antenna, Shakespeare 5215, and it was the bad guy.
O'well, now I have a new coax, new connectors, new antenna and I know that the lights work. So does the radio three hours later.

 

[Ken Palmer]

There are some antennas that will measure a DC short measured with an ohm meter. Before buying a new antenna you should check with the manufacturer. Coax cable rarely develops a short unless it is crushed (perhaps by the mast during stepping). The coax connectors are the most troublesome because of poor installation.

 

[Don12364]

For info it is quite normal for a VHF antenna to read short circuit on a meter, especially if there is a small 'pot' at the base of the antenna.
It is a matching coil and is made of thick copper wire!

 

[Forrest15112]

For info it is quite normal for a VHF antenna to read short circuit on a meter, especially if there is a small 'pot' at the base of the antenna.
It is a matching coil and is made of thick copper wire!

This is most likely what you are seeing especially if there is no short until the antenna is connected. Are you receiving any signals? The crushed cable needed to be replaced anyway so your work was not wasted.

 

[r.oril]

Very interesting info on the shorting with the antenna. Thanks for the info.
I figured to replace the antenna anyway just for drill.

Now I am trying to get the top light, mid light and deck light wired. Black, white, red, brown, orange, yellow and green. So many wires and only 4 pins. The PO never got it working.

Top light uses a Black & Brown together (?) and Orange.
Mid Light uses Black and Red.
Deck uses black and White on a different switch same plug.

I had everything working until I raised the antenna.....Still needs more checking.
All the running lights and interior lights are good to go.

Good brain exercise!

 

[Don12364]

Co-Ax Short & Mast Wiring

You have three lights so, if they all use a common return then they only need four wires.
I presume by 'Top light' you mean a 'Tricolour'.
Tricolours have a vital navigational role and normally use a 24watt bulb (2 amps current draw).

Typically your cable could drop 2 volts in the supply and return paths for the tricolour bulb thus leaving only 10 volts for the bulb. It would be dim and not meet international standards for brightness. So a six core cable is quite a good choice for your mast because it provides the opportunity to use two wires on both the feed for the tricolour and the common return wire. It also provides the opportunity to have a masthead anchor light as well.
If there is no tricolour read anchor as for tricolour but then doubling up the wires is not really necessary, though could be done for the deck light instead.

To establish which wire goes where it would need a person at the masthead to look or a slightly more complicated measurement using a meter at the plug at the bottom.
A meter should read which wires, if any, are connected together at the masthead. Meter each wire to every other and write down the resistance readings. Where wires are simply in parallel the resistance would be about 2 ohms or less. Where there is a bulb between the wires the resistance should be somewhat higher than, say, 4 ohms.
Is your mast up or down? Down is easy.

The attached diagram might help but note I HAVE GUESSED AT YOUR WIRE COLOURS based on your last post - so suggest overwriting mine with yours as necessary.

 

[r.oril]

Re: Co-Ax Short & Mast Wiring

Donalex - Thanks for the info.
GREAT DIAGRAM!!
I can raise and lower the ant. The light at the top is an Anchor Light white only I think. The lower lights are a combo of Mast and Deck. I want to put the Deck light on a separate system and I have two batteries. With your info I know now that I have to use one ground for the top and mid lights and setup the deck light with it's own ground.
Thanks again

 

[Don12364]

Separate grounds for deck and other lights are probably not necessary because it is normal practice to make the negatives of all batteries common. i.e. only the positives of different banks are isolated from each other.
If you do this then all negatives will be connected together anyway.