What kind of cable to connect AT-140 to backstay?

[suiramor]

I am about to start installing my IC-803, a step up from my current level of expertise of changing light bulbs. I have two immediate questions: what kind of cable do I use to connect the AT-140 tuner to my already isolated backstay? Is it just some coax whose inner wire I then clamp onto the backstay? Any recommendations where to get these items would be appreciated.

The approximate distance from the AT-140 to the place where I can connect that cable is 15 feet (partly though hull, partly vertical). As part of the package I was given a 1:1 balun. Do I use it as part of that setup? Where? (from my net research I understand that a balun is used to convert balanced to unbalanced cable so I am not sure I even have that scenario here).

[sv_pelagia]

GTO-15 cable (NOT coax)

Note, the length of GTO-15 to your backstay is part of the antenna.


https://ca.binnacle.com/p7786/Ancor-...duct_info.html

https://www.westmarine.com/buy/ancor...pool--16274953

[suiramor]

Thanks. Do I just clamp the naked wire to the backstay with something like: https://www.globalindustrial.com/p/s...dbe396846b1de7

[jt11791]

I crimped a ring terminal to the wire and then used a small hose clamp to hold that to the backstay. It has worked well for many years.

[sv_pelagia]

I just use a couple SS hose clamps on the bare wire.

(I find I have to remove clamps and clean wire every 1-2 years... even when covered with self-amalgamating rubber tape.)

I have seen a special connector for this purpose. Or a brass Kearney nut. But hose clamps work for me.

[Brian.D]

Use what works best for you. When you are done, make sure to completely seal the connection from the environment. Tape, shrink tube, what ever you have, but make it so it will not corrode or rust.

JMHO

[Jammer]

Lots of things will work. GTO-15 is mainly used for neon sign wiring and is often recommended for the backstay connection. It is a good choice because it has high-voltage insulation that reduces the risk of electric shock if someone touches the wire. Fisheries Supply has it as do many other chandleries.



In reality, ordinary THHN building wire, with a 600 volt rating, will work just fine at the power levels you'll get coming out of the AT-140. The antenna voltage may, theoretically, exceed 600 volts on the 2 khz band, depending on your backstay length, especially very close to the AT-140.


You can also use electric fence wire, or use bare wire inside an insulating tube. Insulating tubing can be purchased and places that sell electric fence or you can use 3/8" pex (or smaller if you can get it). The design voltage of electric fences is usually at least 40,000 volts.


Use standoffs to keep it away from the part of the backstay below the insulator, and any other metal parts, even if you use high-voltage wire. Short pieces of plastic pipe, with a nylon cable tie in a loop going through it, work well.


For clamping the copper wire to the stainless steel nothing is ideal. I would use a couple of split bolts about 1"-2" apart:


https://www.mcmaster.com/split-bolt-lugs/ - some home centers have them but size selection may be limited.



Using two of them helps secure the wire mechanically and improves your odds of one of them working. I would use some kind of contact grease and brush it into the backstay, the wire, and the split bolt. The stuff that they sell at home centers for aluminum electrical wire works ok.


I probably wouldn't try to seal it up because I'd rather be able to see it but others may feel differently. I don't think it matters much.

[StoneCrab]

Stainless steel corrodes in the absence of oxygen. I don't think you will be accomplishing anything by wrapping it with rubber tape. The water will still travel down the strands into the "protected" oxygen deprived area under the clamp.

[sailcrazy]

When we installed ours, we used 2 of the "Split-bolts", then black electricians tape, and then the waterproof stretchy electrical tape designed to keep water out. It was a big "lump" on the backstay. I also made stand-offs using a 3"-4" piece of hose(small pvc pipe will also work) and a long zip-tie. Run the zip-tie up thru the hose, around the ant cable, back down thru the hose, around the backstay, and zip it tight. Simple, it worked, and we had pretty good reception/transmission.
About 2 years later, we were in a yard having some major work done, and I got to talking with the local Electronics guy. He saw my setup, and told me to take off all that tape asap!!! Unless you want to run the risk of Cr on your backstay, let the connection be exposed to the air! We took the tape off, and the Split-Bolts. We cleaned the s/s backstay, then reset the connection-without any tape. and reset the connection........it worked even better.

[StoneCrab]

We are all familiar with the dangers of stray currents destroying metal thru-hulls. The flow of electrons and saltwater accelerates the corrosion.

Think of all the electrons you are introducing to the stainless steel backstay every time you transmit. If you have a soup of saltwater trapped beneath the tape, between the lack of oxygen and the electrolysis, you've created the perfect environment for a dismasting when that backstay lets loose.

[Frankly]

I took a small section of the copper foil (ground strap), tinned the inside and soldered the GTO15 to the outside. Wrap the foil around the back stay, tape over the assy, unwrap the tape and take a look every couple of years, retape, keep on keeping on. Use a section of 3/4" PVC pipe over the lower section in case someone might contact the wire.

My policy is to have anybody in the cockpit sit away from the backstay while transmitting.
The AP can stand the radiation.


Frankly

[Jammer]

Originally Posted by StoneCrab

We are all familiar with the dangers of stray currents destroying metal thru-hulls. The flow of electrons and saltwater accelerates the corrosion.

Think of all the electrons you are introducing to the stainless steel backstay every time you transmit. If you have a soup of saltwater trapped beneath the tape, between the lack of oxygen and the electrolysis, you've created the perfect environment for a dismasting when that backstay lets loose.

We need to have a little talk about two kinds of electricity, AC and DC. It's not just the name of a band.

[MJH]

Originally Posted by suiramor

I am about to start installing my IC-803, a step up from my current level of expertise of changing light bulbs. I have two immediate questions: what kind of cable do I use to connect the AT-140 tuner to my already isolated backstay? Is it just some coax whose inner wire I then clamp onto the backstay? Any recommendations where to get these items would be appreciated.

The approximate distance from the AT-140 to the place where I can connect that cable is 15 feet (partly though hull, partly vertical). As part of the package I was given a 1:1 balun. Do I use it as part of that setup? Where? (from my net research I understand that a balun is used to convert balanced to unbalanced cable so I am not sure I even have that scenario here).

I used Ancor #150102 GTO 15, 14AWG, high voltage cable attached to the backstay with a Split Bolt connector I bought at Home Depot's electrical department. The GTO wire is spaced away from the backstay wire with three inch rubber standoff spacers (cut pieces from old hose) and attached with long wire ties wrapped through the hose piece. Curve the covered wire at the top so as to repel rain/saltwater getting under the wire covering and corroding the wire.

Cable is available at your better marine dealers or direct from Ancor.

Tested on roundtrip to Hawaii and worked great both sending and receiving.

Good Luck.

~ ~ _/) ~ ~ MJH

[waterman46]

All the replies so far failed to mention one very important thing. You wrote that your AT tuner is 15 feet from the bottom of the backstay. That should not be the case. Your transmitting antenna begins at the tuner, so if you have the first 15 feet of antenna buried somehow below the deck, and no doubt parallel to some other wiring in the boat not that far away, you will lose a great part of the radiation inside the boat. Not good for any other electronics in the area either.

The connection in coaxial cable from tuner to radio will then be longer, which is just fine. At these low HF frequencies there is low loss in a well matched transmission line (that's the job of your tuner). Of course it should be good quality 50 ohm marine rated coax. The same type you would use for VHF radio.
There is lots of info on that in other threads.

After you move the tuner, you will also need a short connection from the tuner's ground terminal to a seawater ground, or you can use an internal ground of a network of wires, lots of info on those in other threads.

A good do-able installation will have the length of antenna wire inside the boat down to less than 3 feet, and the connection to ground less than 8 feet.

Others gave you good advice about the type of wire to connect to the tuner. I have never had any problems using normally insulated marine (stranded, tinned) quality wire. It should be fine up at these power levels.

You don't need or want to use a balun. The backstay is an unbalanced load and the tuner is designed to handle it as such. Baluns are only needed when you are driving a balanced load like a dipole antenna.

[suiramor]

Originally Posted by waterman46

All the replies so far failed to mention one very important thing. You wrote that your AT tuner is 15 feet from the bottom of the backstay. That should not be the case. Your transmitting antenna begins at the tuner, so if you have the first 15 feet of antenna buried somehow below the deck, and no doubt parallel to some other wiring in the boat not that far away, you will lose a great part of the radiation inside the boat. Not good for any other electronics in the area either.
.

The 15 ft is my estimate from the tuner terminal to the place on the backstay above the bottom insulator. Probably 3ft inside the boat (horizontal) and the rest vertical. Probably 8-10ft. Thanks for calling this out.