Best Antenna Location for my Ketch ?

[SV Demeter]

Whip antenna mounted on the mizzen itself? I have a similar split backstay ketch rig with the delta plate. I hope to install a proper SSB rig next year but don't think my backstay legs are long enough. Prior owner insulated the triatic but I'm starting to think that's not a good way to go because of the need to get the wire up to the triatic and issues with signal loss.

[daddle]

The insulated triatic may suffer some feed losses, but it may be more efficient as it is away from and not parallel to other rigging. A long enough triatic implies a fairly large boat. How long is it between insulators?

[SV Demeter]

Insulated portion of my triatic is maybe 25'? Boat is a 43' Wauquiez Amphitrite. Would have to measure as I'm just guessing on the length. Please note I am not the OP here just another ketch owner with SSB aspirations.

[daddle]

25' is minimal for getting a tuned antenna. The Icom AT-xxx tuner manual specifies a minimum length of something like that...but I don't have the manual here...

[SV Demeter]

Originally Posted by daddle

25' is minimal for getting a tuned antenna. The Icom AT-xxx tuner manual specifies a minimum length of something like that...but I don't have the manual here...

Thanks! Will have to measure to be certain. Are there issues I should be aware of with running the antenna wire inside the mizzen? Or other concerns with this setup?

[daddle]

Originally Posted by SV Demeter

Thanks! Will have to measure to be certain. Are there issues I should be aware of with running the antenna wire inside the mizzen? Or other concerns with this setup?

Hmmm...that is a problem I had not considered. The tuner is meant to be at the base of the antenna. That is problematic with the triatic. Someone else will need to speak-up here ...

[SoonerSailor]

How far off horizontal is the triatic? The antenna may tend to have a null in the direction the boat is pointing, and more so aft. The more vertical it is the less likely that is to occur, depending on the frequencies used.

The presence of mast and rigging means that the radiation pattern will be difficult to predict, but keep the above in mind if the antenna doesn't perform as hoped for.

A vertically oriented antenna is generally going to be best on a boat.

Running the antenna wire, presumably GTO-15, up a metal mizzen to the triatic might not be be a good idea, and could give very unpredictable results. If the mizzen were wooden or another non-conductive material it would be fine.

Chip

[NahanniV]

My triatic may be the longest stay on the boat.

It runs from the top of the main to a block at the top of the mizzen and then down to a turnbuckle attached to the mizzen at boom height. (see green line on attached diag.).

I might be able to move the vertical leg away from the mizzen by adding an insulated stay between the mizzen top and the block that the triatic runs through. (see orange line on diag.)

Going this route would require more insulators and a bit more work, but if it would be worthwhile I would do it.

[daddle]

That arrangement would have three conductors surrounding the antenna. As they would presumably be without insulators should would make for a poor antenna.

Same situation with using shrouds, or as one poster above said an antenna hoisted alongside the backstay. Might work, but certainly not advisable.

You have a tough situation there. Difficult to predict.

Fortunately one only needs to emit a few watts to make contact much of the time. That is why many cruisers with less-than-textbook antennas report good performance. But sometimes one needs more power.

I think the textbook solution would be to insulate the backstay and the triatic. Then drive the base of the backstay with the tuner. The triatic will be an unconnected part of the antenna at the higher frequencies. If you have a wire topping lifts on the booms they should be replaced with synthetic line.

As one poster pointed out, the horizontal antenna will be somewhat directional, aftwards, this can be used to advantage by changing the heading to put the other station generally aft.

But who knows ??? Consider a sat phone?

[NahanniV]

I'm still trying to decide on the antenna installation for my ketch.

I'm now leaning toward replacing the Triatic stay(green on diag.) with synthetic and running a wire (pink on diag.) to a point on the Triatic where it will be away from the mizzen but not interfere with the main boom.

Sorry about the messy diagaram, it's a mess of rigging !

Anyone have any thoughts on this ?

Thanks,
JM.

[svinshallah]

The comment that "longer is better" is simply wrong when talking about antennas. The antenna tuner will have trouble tuning an antenna less than 23' long at low frequencies. It will also have trouble tuning an antenna that is an even-multiple of a half-wavelength. So, at 22MHz (very roughly 15 meters wavelength) you wouldn't want the antenna length to be an even multiple of 7.5 meters. The longer the wire, the more likely you are to have some frequency where the antenna won't tune well.

Also, the length of the antenna is measured from the antenna tuner terminal to the top insulator. With the tuner mounted below the backstay the feed wire will be perhaps 6' long. Add the length of the backstay below the splitter block and install the insulator below the splitter giving a total length of 25-27'. Any more length won't improve your performance.

[Goudurix]

JM,

I think your last idea (the purple line) is a good idea!

It even gives you the opportunity to run 2 wires of different length, one each side.

As pointed out in the previous reaction, antenna wire (from top of wire until the automatic tuner) matters and is best chosen in function of favoured frequencies and range of communication.

If you want really long distance DX, you need low take-off angle for the vertical radiation pattern.
In that case do not make your total wire longer than 0.625xwavelength of the highest frequency you favour. This is the "EDZ" "extended double Z length for which you develop (in a vertical EDZ) a high angle lobe aka "cloud warmer" (which by the way IS what you would want for local short range communications like on 80m or 40m).
On the other side, once you get below total wire length < 0.15xWL for a given frequency, the antenna system will become rather inefficient.
Like a 23 ft whip antenna will not be very efficient on 2.2Mhz or the 80m band although a good ATU with good RF ground might be able to match it.

Jan
ON3ZTT