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Tune-A-Tenna


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Great concept but not really an easy install if starting from scratch.

This antenna will require a steel mast so a fiberglass pushup mast won't support the weight. A tall steel mast to get optimum height especially below 20m needs to have the antenna motor box attached on the ground then erected and guyed for a new install or use a boom lift.

I didn't see any overall length given for each side of the dipole legs on this antenna but if it's truly capable of full lengths on all bands advertised,160m is 266 ft.

Just to get 80 meters on an inverted V will require around 80 feet of yard space per side, Any shorter will cause an inside angle of the V to be shorter than 90 degrees which is crucial that it isn't. The mast will also have to be at least 45 ft high so the dipole ends will be about 6 ft off the ground. Double all of this for 160m.

sp5it makes a good point about steel cable for the antenna, copper is a better conductor but probably not durable enough for something like this but the steel would work. The trade off here would be having instant multiple dipoles of the correct length vs less than ideal antenna wire.

If you already have at least a 50ft tower up and ample yard space this might be a great addition for other bands you don't have. Using some stand-off brackets off the tower will easily mount this and you"ll have 6 thru 80m covered real well.

If you had the room for 2 of these oriented different directions, it would be like having an antenna farm of 22 dipoles for the 11 amateur bands.

One feature that would aide in tuning this antenna would be some sort of visual counter on the control head so you can see in the shack where the antenna is and last tuned to. That would also be useful for reference points to tune other bands easier.

If I had the room and a tall tower I would consider this.
 
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Screenshot (101).png

That support wire will have to be kept damn tight and at a fairly sharp down-angle to allow the element wire to consistently unspool if going from say 10m to 80 or 160. And how would this system hold up in high winds?? Could the element end-weight flip around the support wire in a good t-storm?? If it does you're scuppered.
 
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Crawdad said:
View attachment 71631
That support wire will have to be kept damn tight and at a fairly sharp down-angle to allow the element wire to consistently unspool if going from say 10m to 80 or 160. And how would this system hold up in high winds?? Could the element end-weight flip around the support wire in a good t-storm?? If it does you're scuppered.
Click to expand...
Good points!

Of course too sharp of a downward angle may get the inside V angle under 90 degrees which will effect the feedpoint impedance. I would use 4ft metal stakes driven deep with ratchet straps to hook onto the antenna ends to get it real taut. The counter weight looks good enough if it was on a tight line.

That is a rather thick diameter mastrant guy rope supplied with this antenna. I use a thin 1/8 diameter mastrant rope on my inverted V and has a 800 lb break strength so the one I see with this antenna should be rated over 1500 lbs so it can be pulled very tight since it's not holding up very much weight.

Another thing to consider is people who live in cold winter climates will get ice on it that may last for days and weeks rendering the antenna useless. Then again, beam antennas have the same problem being stuck in position till the ice melts enough for the rotor to break it free.

Also wonder if there is any maintenance like grease on motor bearings/pulley shaft because like you said this antenna is dependent on the quality of the motor/components that is a concern because I see no warranty on this product.
 
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All good points fourstring.
I wonder how much inductance is introduced in the wire when on the upper bands and most of the wire is in a random wound coil on the spool. (Just playing devils advocate here)
 
Crawdad said:
All good points fourstring.
I wonder how much inductance is introduced in the wire when on the upper bands and most of the wire is in a random wound coil on the spool. (Just playing devils advocate here)
Click to expand...
Good catch!

I see nothing in the motor pulley box photo that shows some sort of decoupling to prevent some inductive coil values. This is how mobile screwdrivers antennas work to keep the unexposed coil from affecting the tuning.

However, an inductor coil wire is covered in insulated material like enameled paint to prevent any coils that may touch each other from shorting out. I would say the bare excess coiled antenna wire is automatically choked off from the antenna circuit at the point it meets the inside pulley. But then again, RF current is still flowing around it so it should have an effect. I don't know?
 
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fourstringburn said:
Good catch!

I see nothing in the motor pulley box photo that shows some sort of decoupling to prevent some inductive coil values. This is how mobile screwdrivers antennas work to keep the unexposed coil from affecting the tuning.

However, an inductor coil wire is covered in insulated material like enameled paint to prevent any coils that may touch each other from shorting out. I would say the bare excess coiled antenna wire is automatically choked off from the antenna circuit at the point it meets the inside pulley. But then again, RF current is still flowing around it so it should have an effect. I don't know?
Click to expand...
Yeah, me neither. But current is flowing thru all that wire in a coil so something is happening. I'm betting the higher bands like 12, 10 and 6 are not terribly efficient/as efficient as the lower bands. And because of the seperation distance between those spools, wouldn't they radiate?
 
A few thoughts on this antenna.

motor_internals-400x284.jpg


There is a lot being shown in this image that relates to how this antenna works.

A few things that strike me with this image.

The first is the feed-point that feeds the antenna seems to be under the label that have covering up the motor. There is some method to transfer the RF from a static wire to a wire on a turning element that is used to turn the pulleys and change the length of the antenna. The wire then coils and attaches to or goes through the pulleys.

The pulleys themselves are metal, and the wire appears to be unclad as well as braided. I didn't find any info on what wire was used on their web site, so I am going to guess that the wire was made out of braided stainless steel wire. This would give it the mechanical strength and flexibility it needs, as well as being very resistant to corrosion.

With this layout, said wound wires and pulleys will act as a single very thick piece of metal, so even though wire is wrapped around as a coil, I don't see it acting like a coil here.

We also see, at the top of the image, and better in this next image what appears to be a coil of wire below the motor.

IMG_20211104_194453797-400x284.jpg


On one page they call this a "transformer", and another they call this a "current balun", but from what I can tell is it is just a coil of coax wound around a ferrite core, so neitehr of the above. Perhaps there is some part of this I cannot see that might change things, but with what I can see I will simply call this a ferrite choke, at least until I am shown otherwise. Honestly, this is a very good option to be built in to this type of antenna, so I would have no complaints just because something more fancy wasn't included...

There are a lot of things not well shown so I am going to stay away from the assumptions of said items and stick with what I do know.

It needs a (close to) 12 meter vertical pole that is strong enough to hold up the box and the wires under tension, although they can be used as guy wires. If its just a pole I would suggest adding more guy wires than just the two antenna guide elements. If you happen to have a freestanding tower it is likely strong enough to hold the antenna setup on its own.

When it comes to antenna performance and other characteristics, there are three things in the box to comment on, and one outside of said box.

If your someone who thingks pl-259 coax connectors are "lossy", the connection in the box that goes from a static wire to one attached to the turning element will have at least as much losses as such a connection, and very likely more. How much more, that is hard to say, especially when I can't see how they did it.

The next thing to note is how the wire then coils to the pulleys on both sides. These will act as base loads. These will have less and less of an effect as you go to lower frequencies.

The third thing to note is the metal pulleys and bare wire. These will act as a capacity hat placed at the worst possible location for said cap hat. Luckily
they are very small, so I doubt they will affect the antenna much. Honestly the only reason I am mentioning this is, if someone purchases this antenna and something strange happens, this could be the cause.

The thing to mention outside this box is how when you go down in frequency, your losses will go up. The reason for this is the earth below. The tips of the antenna will get closer and closer to said earth. This ever decreasing proximity to the earth will cause other potential tuning issues.

I haven't looked at the instructions for this antenna, but when it comes to setting this antenna's length, it should actually be an easy thing. All you need is the reflect needle in an SWR meter. You simply transmit with a low amount of power, and adjust until the reflect needle shows as low a reading as possible. Then if you are concerned about SWR you can easily check it.

Wow, this ended up being longer than I intended... But I am almost done...

The price for this antenna is $1000. I think that will be the first hurdle for many people. If your really set on resonance or low SWR, fan dipoles will be far cheaper, if less elegant. There are also ocf dipole options out there that are also far cheaper, and in this case more elegant. If you are someone who has moved beyond the need for SWR and resonance, there are an infinite number of other antennas out there that are far cheaper, easier to set up, and more effective than this antenna will be.

I wish the makers of this antenna the best, but it isn't the type of antenna I would purchase or recommend.


The DB
 
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The DB said:
A few thoughts on this antenna.

View attachment 71645

There is a lot being shown in this image that relates to how this antenna works.

A few things that strike me with this image.

The first is the feed-point that feeds the antenna seems to be under the label that have covering up the motor. There is some method to transfer the RF from a static wire to a wire on a turning element that is used to turn the pulleys and change the length of the antenna. The wire then coils and attaches to or goes through the pulleys.

The pulleys themselves are metal, and the wire appears to be unclad as well as braided. I didn't find any info on what wire was used on their web site, so I am going to guess that the wire was made out of braided stainless steel wire. This would give it the mechanical strength and flexibility it needs, as well as being very resistant to corrosion.

With this layout, said wound wires and pulleys will act as a single very thick piece of metal, so even though wire is wrapped around as a coil, I don't see it acting like a coil here.

We also see, at the top of the image, and better in this next image what appears to be a coil of wire below the motor.

View attachment 71646

On one page they call this a "transformer", and another they call this a "current balun", but from what I can tell is it is just a coil of coax wound around a ferrite core, so neitehr of the above. Perhaps there is some part of this I cannot see that might change things, but with what I can see I will simply call this a ferrite choke, at least until I am shown otherwise. Honestly, this is a very good option to be built in to this type of antenna, so I would have no complaints just because something more fancy wasn't included...

There are a lot of things not well shown so I am going to stay away from the assumptions of said items and stick with what I do know.

It needs a (close to) 12 meter vertical pole that is strong enough to hold up the box and the wires under tension, although they can be used as guy wires. If its just a pole I would suggest adding more guy wires than just the two antenna guide elements. If you happen to have a freestanding tower it is likely strong enough to hold the antenna setup on its own.

When it comes to antenna performance and other characteristics, there are three things in the box to comment on, and one outside of said box.

If your someone who thingks pl-259 coax connectors are "lossy", the connection in the box that goes from a static wire to one attached to the turning element will have at least as much losses as such a connection, and very likely more. How much more, that is hard to say, especially when I can't see how they did it.

The next thing to note is how the wire then coils to the pulleys on both sides. These will act as base loads. These will have less and less of an effect as you go to lower frequencies.

The third thing to note is the metal pulleys and bare wire. These will act as a capacity hat placed at the worst possible location for said cap hat. Luckily
they are very small, so I doubt they will affect the antenna much. Honestly the only reason I am mentioning this is, if someone purchases this antenna and something strange happens, this could be the cause.

The thing to mention outside this box is how when you go down in frequency, your losses will go up. The reason for this is the earth below. The tips of the antenna will get closer and closer to said earth. This ever decreasing proximity to the earth will cause other potential tuning issues.

I haven't looked at the instructions for this antenna, but when it comes to setting this antenna's length, it should actually be an easy thing. All you need is the reflect needle in an SWR meter. You simply transmit with a low amount of power, and adjust until the reflect needle shows as low a reading as possible. Then if you are concerned about SWR you can easily check it.

Wow, this ended up being longer than I intended... But I am almost done...

The price for this antenna is $1000. I think that will be the first hurdle for many people. If your really set on resonance or low SWR, fan dipoles will be far cheaper, if less elegant. There are also ocf dipole options out there that are also far cheaper, and in this case more elegant. If you are someone who has moved beyond the need for SWR and resonance, there are an infinite number of other antennas out there that are far cheaper, easier to set up, and more effective than this antenna will be.

I wish the makers of this antenna the best, but it isn't the type of antenna I would purchase or recommend.


The DB
Click to expand...
When I read the sales pitch I was puzzled on why the feedpoint would need a "transformer" when its design is for resonance on each band. There should not be any impedance transformation required. The photo clearly shows a 1:1 CMC choke.

I'm curious as to why the pulleys and wound wire would be capacitive rather than inductive.

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