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Old 13-03-2015, 01:47   #1
Jd1
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backstay HF antenna and split backstay

I have a Catalina 36 MKII. It uses two short backstays to a triangular stainless fitting and there is a single backstay from the fitting to the mast head. The triangular fitting is about 15 to 20 or so feet in the air.
I am reluctant to run a feeder wire from my antenna tuner to above that triangular fitting because the feeder would be part of the antenna and would run right next to the backstay for a considerable distance.
I am wondering if anybody has tried to using the entire backstay setup as an HF antenna ? In other words, I would install a single isolator at the top end, a few feet from the masthead, and lead the tuner output to one of the backstay chainplates. The backstay chainplates are not grounded.
The issues I am wondering about are how the second split backstay leg will affect things, how the RF signal will take to passing through the triangular fitting with possibly intermittent DC contact and lastly how a cross bar about 8 feet up between the two backstays that holds up 2 antennas (VHF AIS, WiFi booster, the bar is DC isolated from the backstay) would be affected.
Since this would be a fairly costly experiment (isolator and rigger to install isolator), I would like to know what my chances of success are before I waste a lot of money.
The alternative is a 23 ft vertical antenna.
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Old 13-03-2015, 02:38   #2
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Re: backstay HF antenna and split backstay

Quote:
Originally Posted by Jd1 View Post
I have a Catalina 36 MKII. It uses two short backstays to a triangular stainless fitting and there is a single backstay from the fitting to the mast head. The triangular fitting is about 15 to 20 or so feet in the air.
I am reluctant to run a feeder wire from my antenna tuner to above that triangular fitting because the feeder would be part of the antenna and would run right next to the backstay for a considerable distance.
I am wondering if anybody has tried to using the entire backstay setup as an HF antenna ? In other words, I would install a single isolator at the top end, a few feet from the masthead, and lead the tuner output to one of the backstay chainplates. The backstay chainplates are not grounded.
The issues I am wondering about are how the second split backstay leg will affect things, how the RF signal will take to passing through the triangular fitting with possibly intermittent DC contact and lastly how a cross bar about 8 feet up between the two backstays that holds up 2 antennas (VHF AIS, WiFi booster, the bar is DC isolated from the backstay) would be affected.
Since this would be a fairly costly experiment (isolator and rigger to install isolator), I would like to know what my chances of success are before I waste a lot of money.
The alternative is a 23 ft vertical antenna.
If your entire backstay, including the split part is metal - you need to be aware that it will be carrying current. When you transmit at full power - anyone touching the backstay (between the isolators) will get a very nasty (up to and including fatal) shock.
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Old 13-03-2015, 03:57   #3
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Re: backstay HF antenna and split backstay

I have both.... backstay and a whip... both work well.. so I guess it comes back to $$$

If you are going to use the backstay then put a second insulator above the 'monkey face' ( the triangle bit ) and run an insulated feeder from there to your tuner using 'stand offs'.
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Old 13-03-2015, 04:08   #4
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Re: backstay HF antenna and split backstay

I have an insulator at the top about 2 feet down and one right below the triangle piece on the port side and one about a foot above the cap rail on the starboard side. It is fed right above the starboard insulator. Has worked well for about 20 years.
Bob
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Old 13-03-2015, 05:17   #5
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Re: backstay HF antenna and split backstay

That is indeed the best way to do it (insulate one leg of the split backstay).

You can feed the backstay belowdecks at the chainplate.

The risk of RF burns in this situation is WAY overblown. I wouldn't worry about it.

Bill
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Old 13-03-2015, 06:26   #6
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Re: backstay HF antenna and split backstay

Take a look at a GAM electronics antenna. Pundits will tell you they do not work but we attest that they do and well. We have only had ours for 9 years or so and when we were in the carib were constantly told how well our radio worked. It worked great all the way across the Atlantic.
But then i am a user and not an expert but know what works for us.
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Old 13-03-2015, 07:30   #7
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Re: backstay HF antenna and split backstay

What is the crossbar made of ? If stainless, I would be concerned even if it is DC isolated. Not so much about how the HF antenna would work, but the possibility of damaging the equipment mounted on the bar.

Also, what is the length of the backstay legs below the triangle plate ?

If your crossbar is non conducting, and the length of a lower backstay + cable to output of your tuner is 23' or greater, you could just put an insulator at the top of one backstay leg.

Bottom connection can be either to chainplate inside the boat, or above an insulator in the stay above head height; This depends on your boat and your comfort level with the setup. Either way would be aproximatly the same antenna length.

Cheers,
JM.
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Old 13-03-2015, 08:44   #8
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Re: backstay HF antenna and split backstay

Wow, I am impressed about the number of replies from just last night ... thanks guys!
carstenb - I single hand mostly so shock is not a problem. The split backstays are also covered and padded.
El Pinguino - The split backstays are quite long and run right past the steering station and are used as a handhold a lot. A system of standoffs would be very awkward and would likely not survive too long.
chuckr - I did consider the GAM but the setup with the backstays was driving me nuts and I could not decide how to set that up. I definitely did not want to run a standoff feed line all the way up to the 'monkey face'.
NahanniV - the cross bar is indeed stainless.
I will measure the actual length of the lower section to see if it is long enough. I had not considered just using that section! I would be surprised if it was long enough but will double check - thanks!
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Old 13-03-2015, 08:45   #9
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Re: backstay HF antenna and split backstay

We too have a split backstay, to a "monkey face", to a single backstay up to the masthead. We have an insulator on the single backstay just below the masthead and another (about 7' above the deck) on each leg coming down to the chainplate. When we replaced the rig about 3 years ago (age), the rigger did the new same as the old. Our tuner feed wire goes up one of the lower legs (with standoffs) to just above the lower insulator. Seems to work well for us.
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Old 13-03-2015, 09:10   #10
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Re: backstay HF antenna and split backstay

It might be cheaper and easier, since you have to get a rigger involved, to just run dual backstays up to the masthead, and then insulate and use one of them for your antenna. We did that during one rigging replacement (previous configuration was identical to yours with the 'monkey face') and never had any problems.
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Old 13-03-2015, 10:58   #11
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Re: backstay HF antenna and split backstay

Hi, I hate to throw another question in - but it might be pertinent given dsanduril's post #10.

I just bought a boat that has a split backstay (two independent stays from top of mast to transom P/S). Each has separate insulators top and bottom - effectively making two antennas. The SSB is hooked to both of them - how exactly, I'm not yet sure (we're coastal cruisers and this the first summer upcoming on the boat - the SSB is way down on the priority list).

Is this set: a) good, b) overkill or c) a problem waiting to happen. As far as I know the system worked for the previous owners. Thanks.
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Old 13-03-2015, 13:08   #12
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Re: backstay HF antenna and split backstay

Quote:
Originally Posted by Dsanduril View Post
It might be cheaper and easier, since you have to get a rigger involved, to just run dual backstays up to the masthead, and then insulate and use one of them for your antenna. We did that during one rigging replacement (previous configuration was identical to yours with the 'monkey face') and never had any problems.
Interesting ... another possibility I had not thought of! Thanks!
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Old 13-03-2015, 13:27   #13
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Re: backstay HF antenna and split backstay

Quote:
Originally Posted by Dsanduril View Post
It might be cheaper and easier, since you have to get a rigger involved, to just run dual backstays up to the masthead, and then insulate and use one of them for your antenna. We did that during one rigging replacement (previous configuration was identical to yours with the 'monkey face') and never had any problems.
I checked that out but unfortunately it will not work - great idea though!
The chain plates are angled in line with the pull of the back stays and the direction of the pull would change quite a bit which would put stress onto the chainplates in a way they were not designed for. It would also require substantial modification of the bimini and existing antennas.
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Old 15-03-2015, 05:57   #14
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Re: backstay HF antenna and split backstay

Hello Chuckr,
Noted your location. We are there also (or at least will be back to our yacht in early May). If you are still there, I would like to see your antenna, as this season on my list is to get our HF antenna sorted.
David
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Old 17-03-2015, 12:10   #15
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Re: backstay HF antenna and split backstay

jd1,
Bill gave you the definitive answer in his post here, post #5...
Take his advise and it will work fine!!!
(no need to reinvent the wheel....it's been done...





As for ztsf's "dual insulated backstays"....that was an idea of mine I had many years ago...
--- I was going to have one insulated right at the top and use it's entire ~ 60'+ length on the low bands (3.6mhz thru 9mhz) with a remote tuner...
--- And have the other one insulated about 1/3 - 1/2 way up, giving me a shorter (~ 20' - 23') antenna, fed with its own remote tuner, for the higher bands (12mhz thru 26mhz)...
BUT....
But, after having excellent results from the one "long" insulated backstay, and experimenting with a 1/2-wave vertical dipole for 12mhz and 14mhz, I found no need for the "shorter" antenna...

But even further, I did insulate one of my aft lower shrouds, and feed that from the chainplate, as my HF-DSC Receive antenna / WeFax receive antenna....
And, I've had excellent results from this as well, for the past 10 years....


So....
So, if the original owner/installer of your system had ideas similar to mine....no worries...it will work...
Or, if one of the insulated stays is used for an HF-DSC Receive antenna / WeFax Receive antenna (as my starboard aft lower shroud is), there is also no real worries (except that HF receiving from this stay, while transmitting thru the other adjacent stay, will not be very good....I will many times be on-the-air, ham or maritime, with my M-802 while at the same time receiving a few WeFax charts on my Furuno FAX-408, and you can see the "static" / dark bands / interference on the WeFax charts as just some fine dark lines where there shouldn't be any....I understand the issue, and it doesn't bother me at all, but just wanted you to be aware that if you choose to do the same, if you're receiving a particularly important wefax chart, just stop talking on the radio for 5 minutes!)
Quote:
Originally Posted by ztsf View Post
I just bought a boat that has a split backstay (two independent stays from top of mast to transom P/S). Each has separate insulators top and bottom - effectively making two antennas. The SSB is hooked to both of them - how exactly, I'm not yet sure (we're coastal cruisers and this the first summer upcoming on the boat - the SSB is way down on the priority list).

Is this set: a) good, b) overkill or c) a problem waiting to happen. As far as I know the system worked for the previous owners. Thanks.
ztsf, the "exactly how" part is the important part here!
If it is done as I had originally planned, OR is done as my current system is, (see above for these details)....then all is fine and the answer is "a" this is "good"....
BUT...
But, if someone has done something else, perhaps tried to use some sort of "switch" after the output of the tuner, etc....then this may be "c" or worse than "c"....a "problem that IS there right now"....
BUT...

But since we do not know how the original owner / installer did your install, we cannot be certain...

So, my advice / recommendation is to LOOK at the set-up, LOOK at the radio...
Report back here what radio you have, what remote tuner(s) you have, where the GTO-15 wire from the tuner output goes, etc...
Or perhaps even easier...do it backwards....and start by looking at the GTO-15 wire as it attaches to the backstays....find where that wire goes for each stay....and then also include the info about what radio, tuner, etc...

Once we have all of that info, we can give you a more absolute answer...






Finally, regarding the GAM Split-Lead antenna....
This is NOT a new idea, and is not snake oil...
But, that also does NOT mean that it is a good choice....

I don't have the time to write a treatise on this, but in brief...
"Coupled antennas", "shunt-fed antennas", "slant-fed antennas" (which is what the GAM on a backstay IS...), have been around for almost 100 years....and much commercial experience has been amassed from the 1930's thru 1960's, and much ham experience has been more recent (1950's thru recent years)....
And, the bottom line is, they are very difficult antennas for multiband/wideband operation (which is masked by our modern remote antenna tuners/couplers)....AND they can also induce transmit RFI into the structure and wiring attached (and into some systems on-board) that would not be the case with a direct, non-coupled, antenna....

So, while the GAM Split-lead antenna is not a "bad" antenna, it can be a less efficient antenna, and can be one that causes problems...
There are so many variables that it is impossible to determine ahead of time, whether one will work well for someone, versus another one not...
(if you look at the reports from users, they're almost all, either 100% positive or 100% negative....which is completely understandable, as this backs up the long-established science behind it....)

As for me and my recommendations go....I have always recommended against it....NOT because it doesn't work, but because we cannot know how well it will work up front (as we do with either the ubiquitous insulated backstay, or the very inexpensive "alternative backstay antenna", or even with a whip...), nor can we be certain about any potential RFI issues....
So, with an "alt backstay antenna" being so inexpensive, and a proven/known performer, anyone who wishes for a wideband HF antenna without using their backstay, should consider it before spending the $$$ on the GAM...
{BTW, I suppose you can guess that I have no issue cutting a stay and adding an insulator as desired....
But, for those that worry about rigging insulators breaking and causing a dismasting....in all my years of sailing, I've seen some dismastings and quite a few broken/damaged masts and rigging....but NEVER seen a broken rigging insulator, ever!! They are designed to be stronger than the wire size they are attached to....
But, for a "belt-'n-suspenders" approach, you can use Hydn Hi-Mod "fail safe" rigging insulators....if for some weird reason the insulator fails, the stay does NOT...
FYI, most rigging failures I've seen were almost always from lack of maintenance!!}





I hope this helps..

Fair winds...

John
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