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

[j.g.evans]

If you have an isolator on the lower end of the back-stay and if it has a swaged fitting on each side then I recommend clamping your connection to this beefy fitting. Even SS on SS can corrode and you don't want a back-stay wire failure.

I connected my tuner to an un-isolated back-stay just below the deck and thus my connection was very short.

[Poeme]

I would like to second j.g.evans' suggestion of connecting to the upper swaged end of the lower insulator. Adding only to use Frankly's suggestion of using a copper strap sandwich as a better connection than clamping down on bare GTO cable. Also easier to get a watertight seal if that's your preference. No big split bolts, no water ingress coming down wire strands. I've got my best signal reports doing this.

[sck5]

It seems everyone reflexively recommends standoffs for the connector wire. You dont need them. I have had two boats, one with the SSB professionally installed and the other I did myself. Didnt use standoffs on either boat and didnt need them either. One benefit of not having them is that it makes it far easier to grab the backstay to steady yourself.

[Poeme]

About the stand-offs, I read somewhere that they're not necessary IF the remaining shroud beneath the insulator and chain plate are not grounded. I installed stand-offs years ago but don't like them...thinking of removing to clean up the look.

[MJH]

Originally Posted by Poeme

About the stand-offs, I read somewhere that they're not necessary IF the remaining shroud beneath the insulator and chain plate are not grounded. I installed stand-offs years ago but don't like them...thinking of removing to clean up the look.

RE: GTO Wire Standoffs

I don't question individual success without standoffs. I'm not a marine radio expert/electrician, just a sailor following manufacturer's instructions.

However, the iCOM installation web site below includes an excellent installation diagram titled "Marine HF SSB Feed-line Installation" and it shows 3" standoffs used, so I installed them on my setup and had excellent results...if your SSB works for you without standoffs, I'm happy for you. The middle of the Pacific is no time to screw around with the radio. I would include that page here but it would not let me copy it.

https://us.binnacle.com/pdf/Marine%2...0Grounding.pdf

~ ~ _/) ~ ~ MJH

[StoneCrab]

Originally Posted by Poeme

I would like to second j.g.evans' suggestion of connecting to the upper swaged end of the lower insulator. Adding only to use Frankly's suggestion of using a copper strap sandwich as a better connection than clamping down on bare GTO cable. Also easier to get a watertight seal if that's your preference. No big split bolts, no water ingress coming down wire strands. I've got my best signal reports doing this.

How do you prevent water ingress coming down the water strands. The twisted wire does have space between the strands?



In thinking about this issue, I got to wondering why a Gamma match is not used in this application. Oversimplifying it, a Gamma match puts a driven element adjacent to the resonant element to drive the RF. It is sort of like having a tuning fork next to a glass bowl. Properly tuned, the tuning fork will make the bowl start singing as the sound waves hit resonance with the bowl.

On VHF yagi antennas, a gamma match is common for matching the impedance of the antenna to 50 ohms. The resonance is set by the element length.

Anyone out there using a gamma match on HF?

[team karst]

Originally Posted by StoneCrab

….



Anyone out there using a gamma match on HF?

Prolly nobody reading this has done a gamma match on a hf whip on a multi-band marine install.
Popular on multielement/narrow band antennas tho.

[goboatingnow]

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).

15 feet is quite a distance from the tuner to the backstay. Usually you mount the tuner directly under the deck near the backstay.

[sv_pelagia]

Originally Posted by goboatingnow

15 feet is quite a distance from the tuner to the backstay. Usually you mount the tuner directly under the deck near the backstay.

Alternatively, 15 ft sounds pretty high up on the backstay. Will you be able to reach it for attachment and future maintenance?

[Hartleyg]

In the FWIW department, I DON'T use copper wire as an attachment from tuner to backstay. I use a piece of that vinyl-covered stainless steel lifeline - the one that is about the same size as RG-58.

At the tuner, I have crimped a lug onto the wire - since this end is generally dry, I haven't noted any serious corrosion there in 18 years.
At the backstay end, I crimped a tinned copper lug (the heaviest one I could find) onto the wire then clamped it to the backstay. I covered this with tape for a number of years, but as others have pointed out, water proceeds down the interior of the stay quite nicely, so I've left the tape off. I also noted that the copper lug was showing green grundge, so I deleted it and clamped the bare SS wire to the backstay instead.

This setup has worked with my IC-M700Pro and 130 tuner without fail. I also have a 16' whip and SG-230 I use for the higher frequencies.

I inspected it last fall (unfortunately, the insulator is high enough it requires a ladder to reach the connection) and while the connection looks good, it appears that after 18 years, the vinyl is failing, with cracking showing up in several places -- so it looks like I'll need to replace it here soon - I'll be back aboard in a bit over a week, it's on the list!

Hartley
S/V Atsa

[wsmurdoch]

A ring terminal crimped and heat sealed on the end of the GTO-15 slipped under the nut on one side of the U-bolt of a stainless steel cable clamp clamped onto the backstay.

[Frankly]

"How do you prevent water ingress coming down the water strands. The twisted wire does have space between the strands?"

The water just keeps on going. Just because I have wrapped a piece of copper foil/ tape around the outside has little effect on the spaces between the strands. I have checked on it over 16 years and no problems.

5 or so years back I did away with the lower insulator (replacing all standing rigging). Seems to work just as well, my stbd backstay(IP has two)is not grounded.

10 years back I did away with my Damn jumbo (always needed scraping) Dynaplate. Switched to my SS centerboard cable/ tube. Couldn't tell a bit of difference on the MM Service Net (14,300).

Frankly

[Jammer]

Originally Posted by StoneCrab

In thinking about this issue, I got to wondering why a Gamma match is not used in this application. Oversimplifying it, a Gamma match puts a driven element adjacent to the resonant element to drive the RF. It is sort of like having a tuning fork next to a glass bowl. Properly tuned, the tuning fork will make the bowl start singing as the sound waves hit resonance with the bowl.

There are two reasons:


1) A gamma match is band specific.


2) The main purpose of an impedance match at the antenna is to reduce feedline losses in coaxial cable between the antenna and the tuner. Since sailboat installations do not use coaxial cable between the antenna and the tuner (in essence the antenna starts at the tuner output; there's no real feedline at all), a gamma match would serve no purpose.

[Jammer]

Originally Posted by Poeme

About the stand-offs, I read somewhere that they're not necessary IF the remaining shroud beneath the insulator and chain plate are not grounded. I installed stand-offs years ago but don't like them...thinking of removing to clean up the look.

They reduce the inductive coupling between the lower portion of the backstay and the wire. If you don't use the standoffs, you're more likely to get enough power in the lower portion of the backstay to pose an electrical shock/RF burn hazard if someone contacts it while transmitting -- which defeats the whole point of having the lower backstay insulator.


There is a school of thought that says that, on a fiberglass boat, it isn't worth using a lower backstay insulator, and instead caution should be used to keep crew away from the backstay while transmitting (which you should do anyway).

[DMCantor]

When you attach the cable to the backstay, bent it into a u-shape so that the bare wire is pointing down. That way the odds of getting water into the cable are much reduced. The whole U should be clamped to the backstay for strain relief.