What is My Wire Size?

[austinsailor]

I need to order some insulators for my SSB antenna. I also have a question about how to rig them.

First, I don't have one of those little wedge shaped things to measure the wire size, only a dial caliper. I thought it would be real plain what the wire size is using it.

It measures .293 with the calipers, 9/32 is .28125, 5/16 is .3125. I'm pretty sure the wire size is 9/32. Correct?

Next, again, I think I know, but second opinions can save a lot of problems.

The only stay I have that is reasonable is the backstay, but it is a wishbone type, and I can't make one long antenna.

My plan is to insulate the top at the masthead, one side just below the split and the other side a reasonable distance above the deck. I just don't think the angle in the middle of the leg in the antenna will make any difference.

Right now the antenna tuner is in the center of the boat, right below the rear mast. The previous owner ran it about 15' up inside the mast, then just lead wire drooped to the front mast. Inside the mast does no good, the rest of the wire has fallen apart. None of this was good.

Now, I think I need to move the tuner to the side of the boat right under the stay, so that the lead wire goes right up to the stay. Will it matter if the lead wire runs horizontally 8 feet or so to the stay? I do know that the wire is part of the antenna, just not sure if it matters. I have a friend who is a ham who says just hook the lead to anything, let the whole rig be an antenna. Might work ok as an antenna, I don't know, but it also might light up the crew from time to time!

Any thoughts?

[GordMay]

You've probably measured across the "flats", not the "rounds". Rotate the caliper around the rope, so that it measures the largest diameter.

The correct diameter of a wire rope is the diameter of a circumscribed circle that will enclose all the strands; which is the largest cross-sectional measurement, across the rounds.

[roverhi]

if your backstay chainplates aren't part of the boat grounding system or the chainplates immersed in water, you can use the entire backstay and chainplates up to an insulator at the top of the stay as your antenna. Just hook your tuner to the chainplate inside the boat if there is an electrical connection between the fastener and the chainplate or a short run of wire to the antenna wire.

The only caution is keeping people from hanging onto the backstay while you are transmitting. Not much of a problem as there is only minor burn risk even if someone gloms onto the wire and hangs on for a long transmission.

[austinsailor]

I considered hooking to the chainplate, but the one plate holds 2 stays, one side of the backstay and one of the side stays to the back mast.

I think I'll just replace the lower staylock with the insulator.

I still wonder if it makes any difference if the lead wire goes across the boat horizontally, or should I move the tuner?

thanks for any feedback,
Gene

[Jim Cate]

Originally Posted by austinsailor

I have a friend who is a ham who says just hook the lead to anything, let the whole rig be an antenna. Might work ok as an antenna, I don't know, but it also might light up the crew from time to time!

Any thoughts?

G'Day mate,

I know that this always brings out cries of denial, but what you describe here is exactly what we have done for the past 25 years on our two cruising boats.


On the previous (fibreglass) boat we fed the chainplate for the backstay just under the deck. No insulators anywhere, and teh mast was grounded at the base. On our current boat (strip planked and epoxy/glass) we feed a shroud chainplate, again just below the deck level. In this case we found that we had some paint issues on teh steel keel shell with the mast grounded, so we remove the ground wire when using the radio. In both cases we have had signal reports similar to normal insulated backstay antennas on nearby boats. I know that this is not a very objective measure of performance, but it has satisfied me that we get out well enough for our usage. We have never experienced problems with RF burns to crew.

I once had the experience of having a QSO from Tahiti to the UK during which the operator on teh other end was convinced that my antenna couldn't possibly work... despite the fact that we were talking to each other. This was a fairly typical response!

It isn't my place to recommend that you follow this plan, but I can attest that for us it has worked for a number of years.

Cheers,

Jim N9GFT/VK4GFT

[sailorchic34]

Originally Posted by Jim Cate

G'Day mate,
On the previous (fibreglass) boat we fed the chainplate for the backstay just under the deck. No insulators anywhere, and teh mast was grounded at the base.

I've done the same thing. Located the tuner by the rear chain plate just below the interior bolts, short bit if wire to ring connector installed under one nut. No insulators anywhere. The whole rig can radiate that way.

Life is good...