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Old 04-01-2012, 15:14   #31
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Re: Attaching Antenna Cable to Backstay

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got a way to show a picture?
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Reload your page, I posted two pictures in my post.
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Old 04-01-2012, 15:16   #32
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Re: Attaching Antenna Cable to Backstay

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Drew23,

Any chance you could use an "alternate backstay", i.e., an antenna secured, say, near the base of the Canadian flag? That would save you removing or cutting the backstay entirely, or spending money for a 3/8" insulator.

To see if that would work, bring the bottom end of a halyard to somewhere aft and as far away from the split standing backstay as you can. Now, if you have adequate clearance for the roach of the main, as well as for the boom, then you're golden. Make up an alternate backstay from 3/16" insulated s/s lifeline, haul one end up with a spare halyard, tie the lower end there in the corner, and run GTO-15 wire from the tuner belowdecks to the bottom of the antenna. That works every bit as well as an insulated backstay.
Hey Bill,

I actually went down this path, but by the time the wire, insulators, turnbuckles and fittings are purchased the difference in price between having my backstay cut and building a new backstay are negligible... I have a quote for under $400 for the backstay work, including two insulators! I'm just wondering if I should go with the two insulators or if I'll benefit from using just one?
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Old 04-01-2012, 16:02   #33
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Re: Attaching Antenna Cable to Backstay

No way would the "alternate backstay" solution cost anywhere near what the cost would be for altering your backstay and installing a quality insulator. For a 3/8" insulator, you'll pay upwards of $300 for a single Haydn...the only fail-safe insulator I'd put in. Plus the rigger's costs.

Anyway, with your split backstay arrangement you'll probably need two insulators, one near the top of the backstay and one just above the split. $600. Plus installation costs. Say, $800-$900 all told.

Compare to less than $100 for an alternate backstay, including installation.

Bill
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Old 04-01-2012, 16:16   #34
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Quote:
Originally Posted by drew23

Hey Bill,

I actually went down this path, but by the time the wire, insulators, turnbuckles and fittings are purchased the difference in price between having my backstay cut and building a new backstay are negligible... I have a quote for under $400 for the backstay work, including two insulators! I'm just wondering if I should go with the two insulators or if I'll benefit from using just one?
Hi Drew:

I use a wire floating inside a rope with the upper end tied to the masthead and the lower end tied to the stern pulpit. I used an old double braid and replaced the core with the wire -- almost free. Would have been free had I used old discarded lifeline or wire halyard instead of purchasing the wire.

hth...
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Old 04-01-2012, 16:20   #35
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Quote:
Originally Posted by btrayfors

Ham myths

- you must ground the radio as well as the tuner

Bill
You have my attention now!

As owner of an aluminium boat I underwent hell to run a 3 inch wide copper strap from radio to tuner and then from tuner to hull.

Laying it was not even the hard part - isolating the copper from the aluminium hull was....

Are you saying I can scrap this, and the associated issues, and not loose any tx or Rx range?

Also since the antenna starts from the top of the tuner and my tuner is in my aft lazzerette, should I have a stand off on the meter of cable that lays on the hull before it goes above deck as well?
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Old 04-01-2012, 16:36   #36
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Re: Attaching Antenna Cable to Backstay

I am new to all of this. With all the various opinions about all this stuff it is hard to know what to believe. I do not have a SWR meter on my ICOM 802. Is this the best way to judge how well you are operating? I am sure getting an idea on how far you are transmitting or receiving is good information but I would like a device that would give me a read out on how efficient my unit is working. I recently did the Caribbean 1500 and did well with my radio but the Pactor modem would kick off and lock up my computer (I think because of RF) and it was often slow 200-300 instead of 1500 at its best.
I am open for suggestions.
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Old 04-01-2012, 16:40   #37
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Re: Attaching Antenna Cable to Backstay

I also have another problem of interest. My Questus mount for my radar attaches to my backstay above the bottom insulator. From all I know this is bad for the radio but I have also heard from Questus that it is very bad for the radar. They did not say what it would do to the radar but STRONGLY suggested fixing it ASAP. Anyone know what it is doing to my radar?
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Old 04-01-2012, 17:06   #38
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Re: Attaching Antenna Cable to Backstay

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Originally Posted by btrayfors View Post
No way would the "alternate backstay" solution cost anywhere near what the cost would be for altering your backstay and installing a quality insulator. For a 3/8" insulator, you'll pay upwards of $300 for a single Haydn...the only fail-safe insulator I'd put in. Plus the rigger's costs.

Anyway, with your split backstay arrangement you'll probably need two insulators, one near the top of the backstay and one just above the split. $600. Plus installation costs. Say, $800-$900 all told.

Compare to less than $100 for an alternate backstay, including installation.
Ok, so, like I said, I went down this path already.

60' of 3/16 lifeline, at $1.50/foot: $90.
Two cheap dog bone ceramic insulators at $5 each: $10.
5' of 3/16 steel cable at $1/foot: $5
Nicopress fittings, four of 'em at $0.50 ea: $2
Stainless turnbuckle with 1/4" threads: $45
Shackles, four at $8 each: $32
Stainless ring bolt: $8

That's $192, plus my time. The quote for backstay cutting is just under $400 for both insulators - I forget the brand, but the rigger said he'd installed hundreds of them and never had a hint of a problem. He showed me the insulators and they looked pretty solid to me, and the rigging shop in question has been around for 40+ years... if the difference between a "this is cheap and it works pretty well" and a professional, proven installation is only $200 I'm willing to skip going to the bar a few times.

Mind you I will still need to pick up feed wire and a gland fitting for the transom... that's why I was questioning the idea. If I can keep my transom neat, imho that's one less thing to break off in heavy weather.

If I can get away with one insulator, I'll definitely go for the higher-end insulator. the rigger was pretty confident though, even after I mentioned heading offshore.
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Old 04-01-2012, 17:09   #39
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Re: Attaching Antenna Cable to Backstay

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Originally Posted by foolishsailor View Post
As owner of an aluminium boat I underwent hell to run a 3 inch wide copper strap from radio to tuner and then from tuner to hull [...]

since the antenna starts from the top of the tuner and my tuner is in my aft lazzerette, should I have a stand off on the meter of cable that lays on the hull before it goes above deck as well?
Yes, you should not route the antenna feed wire directly against the aluminum hull. Use insulated standoffs to provide a few inches of isolation.

It's quite likely that your tuner will be able to provide a match to the existing arrangement, but it's also likely that you will have fewer losses and a better match at all frequencies if you stand the wire off from the hull.
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Old 04-01-2012, 17:19   #40
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Re: Attaching Antenna Cable to Backstay

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I have a fiberglass-over-plywood trimaran [...]

and would like to attach directly to the chainplate instead of going up eight or nine feet with standoffs to attach to an insulated portion.[...]

my backstay is split at the bottom!
OK, why are we recommending insulators for the lower end (ends) of the backstay? The chainplates are bolted through fiberglass and plywood, and if the plywood is dry (!) this should be a reasonable insulator. It seems to me that drew23 could connect his tuner to one leg of his backstay, and let the other leg remain connected without creating a major tuning problem. He will need an insulator at the top end of the backstay, and he may want to put some insulating tubing over the lower sections of the backstay so people can't grab the RF-hot wire.

Why won't that work? Don't we trust the plywood?
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Old 04-01-2012, 18:09   #41
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Re: Attaching Antenna Cable to Backstay

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OK, why are we recommending insulators for the lower end (ends) of the backstay? The chainplates are bolted through fiberglass and plywood, and if the plywood is dry (!) this should be a reasonable insulator. It seems to me that drew23 could connect his tuner to one leg of his backstay, and let the other leg remain connected without creating a major tuning problem. He will need an insulator at the top end of the backstay, and he may want to put some insulating tubing over the lower sections of the backstay so people can't grab the RF-hot wire.

Why won't that work? Don't we trust the plywood?
I'm not an expert, but as I understand this, the idea is to insulate the lower portion of the backstay to keep someone from grabbing hold of the wire/antenna while transmitting, which could lead to shock and burn. The lower insulator 4'-5' raised off the back. Please correct me if I am wrong,
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Old 04-01-2012, 18:20   #42
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Re: Attaching Antenna Cable to Backstay

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I'm not an expert, but as I understand this, the idea is to insulate the lower portion of the backstay to keep someone from grabbing hold of the wire/antenna while transmitting, which could lead to shock and burn. The lower insulator 4'-5' raised off the back. Please correct me if I am wrong,
Don
Don,

You're correct, that's the conventional wisdom. However, earlier in the thread several people reported that it isn't based on fact, and that the RF burns would only occur at the far end of the antenna, i.e. grabbing the wire near the top of the mast...
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Old 04-01-2012, 18:31   #43
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Re: Attaching Antenna Cable to Backstay

And even if we are worried about RF burns from the lower portion of the backstay, just slice some plastic tubing and slip it over the hand-accessible sections of the backstay. At some frequencies, and some antenna / feedline dimensions, the voltage can get pretty high at the bottom of the backstay. I personally would want some kind of insulation there.

If the plywood had too much moisture content I might be concerned about RF heating around the chainplates. I don't know if this is really a potential problem or not.
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Old 04-01-2012, 18:36   #44
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Re: Attaching Antenna Cable to Backstay

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Ok, so, like I said, I went down this path already.

60' of 3/16 lifeline, at $1.50/foot: $90.
Two cheap dog bone ceramic insulators at $5 each: $10.
5' of 3/16 steel cable at $1/foot: $5
Nicopress fittings, four of 'em at $0.50 ea: $2
Stainless turnbuckle with 1/4" threads: $45
Shackles, four at $8 each: $32
Stainless ring bolt: $8

That's $192, plus my time. The quote for backstay cutting is just under $400 for both insulators - I forget the brand, but the rigger said he'd installed hundreds of them and never had a hint of a problem. He showed me the insulators and they looked pretty solid to me, and the rigging shop in question has been around for 40+ years... if the difference between a "this is cheap and it works pretty well" and a professional, proven installation is only $200 I'm willing to skip going to the bar a few times.

Mind you I will still need to pick up feed wire and a gland fitting for the transom... that's why I was questioning the idea. If I can keep my transom neat, imho that's one less thing to break off in heavy weather.

If I can get away with one insulator, I'll definitely go for the higher-end insulator. the rigger was pretty confident though, even after I mentioned heading offshore.
The comparison isn't between a "professional, proven installation" and a "cheap and works pretty well installation".

Look, the alternate backstay doesn't cost anywhere near $200. And, it's just as "professional" as the insulated backstay solution which...were it to be truly "professional"...would utilize Haydn fail-safe insulators which cost $300 each.

Your calculus is way off. Here are actual amounts I billed a client last month on a new ocean-going 57' sloop:

60' of 3/16" s/s lifeline @ 1.08/ft....................$ 64.89
10' of GTO-15 high-voltage transmission wire....$ 8.50
s/s thru-deck fitting for GTO-15.................... $ 2.28
TOTAL............................................. ..........$ 75.67

I don't know what the s/s turnbuckle and shackles in your estimate are for. They're not needed. Just tie a 2' section of 3/8" Dacron line at each end. You don't need any other insulators. And, you don't need 60' of lifeline. You may not even have room for that. Anything over 23' is OK, with shorter lengths favoring the higher (longer distance) bands and longer lengths favoring the lower bands. Approx. 40' is a good compromise length.

I don't really care what you choose to do, and hope you'll be happy with whatever you finally do. Just wanna be sure you're comparing apples to apples :-)

RE: the two vs. one insulator question, with split backstays it's general practice to use two, in places as I noted, in order to provide a more-or-less straight antenna. Generally, the idea is to isolate one of the legs of the split in order not to have cancelling signals from the other out-of-phase leg. But, yours are very close together and, who know? Maybe a strap between the chainplates belowdecks would help???? Anyone wanna try to model this??

Good luck,

Bill
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Old 04-01-2012, 19:18   #45
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Re: Attaching Antenna Cable to Backstay

Sorry to reveal my total ignorance of this subject. Why connect the antenna to the backstay? Wouldn’t the radio be installed near the nav. station amidships? Why would you not attach to a lower or upper stay? The chain plates are right where the radio would be installed.

Also, my mast step sits atop two keel bolts. Is there a danger of electrolysis (or something) with a current going up the stay and back down the mast to ground through the keel?
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