‘Delta’ Antenna for SSB?

[Dougal]

I came across an article on the internet about using the entire standing rig as an HF/SSB antenna (called a Delta).

Just wondering if anyone here has ever tried it.

I have a smallish ketch rig which doesn’t, I think, lend itself to the traditional insulated backstay method. Besides, I don’t really want to cut it.

 

[gianenrico]

Well I saw an american system, consisting in a plastic extrusion with 3 "channels": the central one clips all along the backstay (or, for that matter, to any standing rigging of suitable lenght) while in the other two are inserted the two arms of a V-shaped antenna; these arms are just made of copper braid with palstic covering. I'll see I I find the url.


GOT IT:
http://www.panbo.com/archives/2005/06/ssb_backstay_antenna_a_new_way.html

Obvious advantage: no cutting, possible removal; disadvantage: a little more windage.

Never tested personally.

Cheers

 

[john_morris_uk]

Well I saw an american system, consisting in a plastic extrusion with 3 "channels": the central one clips all along the backstay (or, for that matter, to any standing rigging of suitable lenght) while in the other two are inserted the two arms of a V-shaped antenna; these arms are just made of copper braid with palstic covering. I'll see I I find the url.

Obvious advantage: no cutting, possible removal; disadvantage: a little more windage.

Never tested personally.

Cheers

The other major disadvantage with such a system is that there will be side effects from interaction with the rigging. Even if you don't connect the ssb antenna directly to the rigging, by having it alongside the rigging and closely coupled for any appreciable distance, you would induce RF currents into the rigging and this will almost certainly be seen as losses rather than gains!

To the OP, why not put proper insulators in the rigging? So long as you have one reasonably long length of backstay on your mizzen, it will work.

If you want to use the whole rig, you would have to insulate everything. Remember a bit of salt and some water is a very good conductor for RF energy, so don't think that the GRP will be a good enough insulator. You also might have some very odd effects by having almost everything on the boat energised by the RF of the transmitter. The final problem would be the risk of RF burns from anyone touching any part of the rigging when you are transmitting.

 

[Bilgediver]

I came across an article on the internet about using the entire standing rig as an HF/SSB antenna (called a Delta).

Just wondering if anyone here has ever tried it.

I have a smallish ketch rig which doesn’t, I think, lend itself to the traditional insulated backstay method. Besides, I don’t really want to cut it.

There used to be a poster on the old forum who lived on the East Coast USA
who used his standing rigging. You have to have a full tuner IE not one of those balance jobbies built into the set and he used the closed loop between a capshroud chain plate and the base of the mast. Apparently it worked well.

The down side of this system is that there must be no one in contact with the masts or standing rigging when in use as expose is to high RF voltages which can give nasty RF burns.

It is easy enough to try but in practice risky.

 

[William_H]

HF SSB antenna

I tend to agree with all the negative comments about this antenna. It will be effectively a virtual connection to the backstay. Now modern automatic antenna tuners could possible get a reasonable coupling to any connection to the rig. As said you might get a lot of losses through wet hull etc.
The fact is modern SSB has an improvement in performance through narrow bandwidth receiver and higher peak transmitter power so that much less efficient antennae will often seem fine.

My opinion is that if HF SSB is part of your safety arrangements then you must either use or carry (as emergency) a whip antenna mounted out of the transom. This so that you have communications even with rig lost. So you might as well go straight to a whip and antenna coupler.
Certainly around here cat 1 ocean racers must have a whip antenna for compliance.

If you want to use the backstay and don't want to spend up on expensive yacht rigging insulators then some of the older style radio mast insulators known as egg insulators could be used. They have a clever design where 2 loops of the wires are insulated in compression by porcelain. So a failure of the porcelain will not part the backstay.

There is a good reason why we insulate the backstay rather than simply haul a wire up to the mast head by flag halyard. The reason is that the backstay (insulated) gets the antenna as far away from the mast and rigging as possible. olewill

 

[Dougal]

Thanks all for the help.

Guess I'll probably end up having to use a whip antenna.

 

[Bosun Higgs]

The other major disadvantage with such a system is that there will be side effects from interaction with the rigging. Even if you don't connect the ssb antenna directly to the rigging, by having it alongside the rigging and closely coupled for any appreciable distance, you would induce RF currents into the rigging and this will almost certainly be seen as losses rather than gains!

.

I tried both a dipole and a half sized G5RV on my boat and this is exactly what I found. It was a pita that the tuning of the aerial responded even to such things as movement of the boom

I often wondered about simply connecting the mast itself to the SSB since in theory the grp of the hull is insulating. Never tried it and trying it is the only way you will know if it works - its so complicated a set up that theory wont help you much.

 

[oldfatgit]

Some useful information and an interesting alternative here. Don't know if they are any good though.

 

[Beadle]

I do not like the idea of lighting up the whole rig with RF. I've had a few RF burns and didn't enjoy any of them.

With a ketch the obvious one to try is the inverted "L".

It involves insulators, 4 of them. Top and bottom of backstay and each end of the stay between the tops of each mast.

Feed the bottom bit of the backstay and link the "live parts of the stays at the top of the mizzen.

It should give reasonable low angle radiation for long range working and high angle for shorter range.

I'm going to try this on my boat when I get a round tuit