SSB backstay aerial

[Andrewpatrol]

If I was to use the backstay for the aerial on a 30’ Hess cutter with the Pardey style wind vane, as in picture, would I have to put the lower insulator above the top of vane or could I put it just above the “wheel” near turnbuckle.
I’m imagining the longer the better! Or is this electrically difficult? Dunno how I’d run the cable with its stand-offs to suit this style of wind-vane
Just curious. Thanks

[Andrewpatrol]

[team karst]

Depends on where the tuner will live. Consider driving the system from the stay just above the waterline.

[Polar Opposite]

The true SSB advocates can chime in, but more length isn't necessarily "better". As long as your backstay antenna has 7m of usable length, your tuner should be able to receive in the 1.6m band. So you can put the insulator where you want as long as you have 7m above it.

[S/V Illusion]

Originally Posted by Polar Opposite

your tuner should be able to receive in the 1.6m band. t.

Thats VHF. The back stay wire is almost certainly intended for HF SSB and the length of the antenna can be important for two reasons - many auto tuners are incapable of matching short antennas and as a general rule, longer is better for end-fed wires.

As long as the vane is not conductive, it’s location relative to the wire won’t matter

[Brian.D]

I'm sure that 1.6m was a typo and meant to read 160m, common error.

As for the length, longer does not always mean better. Try putting on a bigger head sail or main sail. You'll soon find out that the boat might not sail any better, but might be worst.

7m to 9m is a good length for working all bands. Not all frequencies are workable due to harmonics that the tuner might find difficult to level out. However, most bands are doable with a 7m to 9m antenna length.

Remember that the point the antenna begins is at the output of the tuner, not where the connection is made at the antenna. The wire leading from the tuner to the "antenna" is also a very important part of the antenna overall.

I see it will be difficult to accomplish what you want. Have you looked at the possibility of running the antenna amidships? The stern is too busy and the boom would interfere with an alternate backstay. Moving the the antenna aft would mean running the feed almost parallel to the water.

Good luck, and if you can try experimenting.

[Celestialsailor]

There is a bit of an art to antenna length for SSB. A little searching on the internet will reveal some lengths that work. In generally go slightly above head height. Then the amount of wire left, I know the length can use from this link...


http://www.svsoggypaws.com/files/Cho...Forum_2010.pdf

[ka4wja]

Andrew,
I was emailed a link to this thread, asking for my input....and, while I'm tied up and need to be brief...here you go:

Originally Posted by Andrewpatrol

If I was to use the backstay for the aerial on a 30’ Hess cutter with the Pardey style wind vane, as in picture, would I have to put the lower insulator above the top of vane or could I put it just above the “wheel” near turnbuckle.
I’m imagining the longer the better! Or is this electrically difficult? Dunno how I’d run the cable with its stand-offs to suit this style of wind-vane
Just curious. Thanks

1) General advice: You do not need any "backstay stand-offs".....this is old-school thinking, based on older antenna installs on steel hull / steel super-structure vessels, where rigging / masts, etc. are all grounded to the sea water and the installers not wanting to shunt even a small amount of their transmit power to ground (and even then, it would be a very small amount).

With non-metallic hulls (wood or fiberglass/GRP), all you need to do is make sure that the lower part of the backstay isn't grounded (remove the "bonding wire" on the chain-plate, if it has one)....and, you're good-to-go!

Further, even if you didn't remove the bonding wire, and/or even if the lower part of the backstay was grounded because it was wet with sea-water, etc...the small amount of transmit power that would be coupled to this short length of the stay would be minor....(btw, this is the whole principle behind the "GAM Split-Lead" antenna....and, yes, I have often commented that while it can work, the fact is that "coupled" antennas do have issues, such as sporadic tuning / efficiencies at various bands, etc. as well as RFI issues....but, a few feet of GTO-15 wire run along a stay isn't as bad as 40 - 50 of the GAM Split-Lead antenna...)

{FYI, it was 1973 that I assisted in my first HF Maritime installation....so, while I don't go back quite as far as some....I'm also not as old as some of those guys... }

Sorry, to digress!

2) Specific advice: Looking at your pic, I'd recommend:

a) installing your lower rigging insulator above the wind vane....and, running a GTO-15 wire down from there, to the stern rail, and from there down to the tuner....having the tuner in the lazarette / under the helm seat (under the tiller arm)....you probably should use a length of teak from the stren rail, going up...to take some strain off the GTO-15 wire, and keep it from flying around, etc....(I would usually recommend PVC pipe, but with all that wood / brightwork, PVC might look to gawdy?)

--- Or ---

b) There are other (some, fairly poor) choices for feeding the backstay and locating the tuner....but, haven't the time to run through them all, especially as they will spur further discussion, etc. that I also don't have the time for, at the moment.
(but, maybe later...if it is necessary?)


3) Also, I don't have the time to, once again, dispel the 5/8-wave HF antenna myth....just understand that it is not a "magic" length!

On HF, where the ground / earth / ocean is still part of the antenna (yes, it is...even with a 5/8-wave), and where, for all practical purposes, the antenna is mounted ON the earth/ocean, the pattern of a 5/8-wave on HF is not like you see in the books of a 5/8-wave in free-space nor even that of a VHF or UHF 5/8-wave mounted up on a mast 5 to 10 wavelengths high! It just isn't what most think....in actual fact, unless you can control all of the antenna ground currents, most long-range HF comms angles are better served with a 1/4-wave vertical (or 3/8-wave vertical...or 1/2-wave vertical, mono-pole or dipole)...or, of course with high-mounted horizontal yagi's, but that's not gonna happen on our boats!

Again don't have the time to delve into it....and besides, here in Andrew's application, it would only be applicable at freqs above approx. 16.5mhz...


4) Further, while some older remote auto-tuners (and many/most "ham radio"-type manual tuners), had some difficulty tuning the very high impedance of base fed 1/2-wave antennas....two good things here...

a) Modern Icom remote maritime auto-tuners (AT-130, AT-140, etc.) have no problem here at all.

b) The size of the rigging wire, being much larger in diameter than the "nominal 14 ga copper wire" that most hams and antenna engineers use as a design spec, this actually reduces / limits the impedance of the antenna when operated at its half-wave freq.



5) But, in reality here, most of this "antenna length" discussion is a non-issue here...

As, a 30' cutter / the Bristol Channel Cutter, has a mast height of about 41' - 45' (I've seen the 28' BCC's mast spec's at 41' 6" off the water)....so, depending on where you install the tuner (yes, the antenna starts at the tuner!), and exactly where you place the upper insulator, you'd have an antenna length of approx. 35' - 40'....which is darn near ideal for optimizing HF comms for 8mhz and 12mhz maritime bands (actually good for 6mhz thru 16mhz), and for both 40m and 20m ham bands!

So, there is no worry here, either!


6) So, to sum up...

Place the lower insulator above the wind vane, place an upper insulator about 3' - 4' down from the masthead, install the tuner in the lazarette as close as you can to the stern rail as you can....run a 3" wide copper strap (not thin "foil") from the tuner ground lug to a close bronze thru-hull....and, you're good-to-go! Easy-peasy!


I gotta' go!
Hope this helps!

73 and Fair winds,
John

[MicHughV]

Here's a thought...instead of using the backstay...just run a separate wire from the transom to the mast.....that's how I did it....stopped the wire about 15" short of the top of mast, fitted a small inexpensive ceramic insulator (about the size of your thumb), and then used some waxed twine to tie to the top of mast. My wire was a 1/8" galvanized steel cable covered in a plastic sleeve.
On the lower end, did much the same, but connected to a piece of pvc pipe I had attached to the stern pulpit..this done to keep the wire high enough so it didn't cause any issues
Ran some GTO cable from tuner, up thru' the pvc pipe to just above the lower insulator.

Worked like a charm. You want a minimum lenght of 23' for the wire......

I never had any issues sending or receiving, but there were occasionally times, when the direction my boat was aimed at in relation to the other station, would make a difference, but it was a simple matter to change course for the short period I'd be on the air.

[Andrewpatrol]

Thanks for taking the time John. I actually read about using a seperate “dummy” backstay as MicHugh suggests which sounds a good workaround. Just need to work out if it’s possible given all the other things going on such as boom gallows etc,
Anyway thanks to everyone for input.

[MicHughV]

I met a guy one time on a ketch. Whenever he wanted to use his Ham/SSB equipment, he'd use a halyard to hoist a wire up to his main masthead. His tuner was located under the cockpit somewhere near the wheel. He had some or other connection between the wire and tuner....presumably, some GTO cable. The wire/antenna was more or less located where the topping lift would be...ie, toward the end of the boom. The GTO connection was always there, requiring only to be connected to the wire.

I never saw this in operation, but was told it worked just fine.

It's not a permanent situation off course, but I can see this working most of the time. With some thinking it could be made into a permanent location.

Interestingly enough, my first boat was a ketch, my antenna was run from the transom to the top of the mizzen. Thinking to increase the wire/antenna lenght, I concocted a system to extend the wire/antenna to the main mast, much like a triatic stay, but thru' experimentation with other hams found that the inclined angle between main and mizzen was not conducive to extended range, so I took it down.

I think, that all things considered, a simple end fed wire, works best on a sailboat.

I had originally considered a typical insulated backstay from the main mast, but was concerned that the split backstay of my ketch ran mighty close to the shrouds of the mizzen....only inches away. My concern was that the tuner might misread the length of the main backstay due to the proximity of the mizzen stays.

At the time, I was a member of a local Ham club, and a lot of support and thinking went into my situation, but my simple end fed wire proved to a superb setup.

[MicHughV]

As a follow up, I can't remember the exact details anymore, but the guy described above eventually made his main boom topping lift from wire, so it was always up, needing only to be connected to the tuner.

[Brian.D]

Well, that is basically what a backstay antenna is, an end-fed wire.

If one wanted to try something totally different, get one of those ham stick mobile antennas and mound it to your stern rail. Take some copper wire, attach it to the mount and drop it in the water. Maybe put a lead weight to keep it in the water. See what happens. Got nothing to lose except the time and effort to do this. Might make a nice emergency SSB antenna if you ever lose your mast.

[MicHughV]

When I first put a HF radio on my boat, my knowledge of antenna's was a bit sketchy.

So I had considered installing a manufactured whip, as they are relatively inexpensive....often seen on big sportfishermen boats, etc...but soon cooled to the idea of having a 23' whip on my transom, thank goodness, though I have come across some boats that have had this whip installed.

[sck5]

I was on a another guy's boat and he had no insulator at the bottom at all. His antenna started at the tuner. He said it was never a thing to worry about for receiving but you wouldnt want anyone to put their hand on it while transmitting. I am not sure whether this is a good idea or not but he said it worked fine.

I can testify to the non-importance of standoffs, having skipped them on both of my boats and the ssb worked just fine.