Sirio tornado (coil)

[camaro1]

there has to be some other reason why the tornado shows open circuit but does work as it should being a different design than most of the other 5/8 antenna's that use some sort of match ring that connects the radiator to the ground elements,, I have seen some other forums with posts calling it a matching transformer rather than a loading coil. it would be nice to know if there is some other hidden component that makes it work the way it does and still measure open circuit at the connector

here is what BOB85 had to say about it years ago:

NEWS JUST IN :shock:
the tornado is not as it seems in the pic,
i used to own one years back and could have sworn it was like other 5/8 using tapped transformer at the base and 1/8wave radials but it aint,
i talked to a ham buddy tonight who is going to use one modded for the 6mtr shootout, while talking about the matching he informs me that uses an open circuit design unlike any of the tapped transformer setup,
at first he said no tapped coil and i thought he meant no coil at all, i did not agree with that and asked him to describe the exact setup as they definately had a coil,
heres what he said
the coax feeds the bottom of the coil with no shunt to ground no tapping it part way up, the antenna is open circuit not dc grounded like most 5/8 and 1/2wave antennas, its the second one hes had and they are identical, hes thinking of doing what A/S did with the sigma2 and the small internal coil so hes dc grounded.



another from BOOTY MONSTER:

thanks for the fast reply on the pics . thats the first clear pics ive seen of that antenna . i had thought it was similar to the coily enforcer , but the enforcer looks to be a closed circuit antenna and the tornado looks like it could be a open circuit design . tha coil on the tornado looks to be solid rod instead of tubing . i look forward to more pics

 

[camaro1]

Marconi:

Camaro, I seem to recall we had a discussion in an older thread about this particular antenna sometime in the past, did we not?
yes we touched base on this tornado just a bit,

I think you were telling us if we checked the continuity, we would find it had an open circuit when testing the feed point shield and center conductor.
yes this is correct

Seems I recall that Bob85, posted that he once had an old Avanti Sigma II, and that it likely had a similar design to what the Sirio Tornado has, and that is why it shows an open circuit. I think Bob85 further claimed there was some additional matching device inside the base that provided such a circuit, aside from the exposed coil we see. Am I right?

no, he posted that his ham buddy was thinking of doing what A/S did with the sigma2 and the small internal coil so hes dc grounded.

I also seem to recall that I and a couple of other's questioned your claim, or was that discussion about some other antenna? IMO, I think you got us all to realize that the Tornado is probably different, that you were right...and what you explain is why you see an open circuit when doing your ohm's check.

don't have an answer to why it shows open ciruit but still works as it should


CJruger and speak for himself, but I think your presenting the idea of the Tornado type coil design to Cj could be confusing the issue for him. I think he is building a standard 5/8 wave with a coil inductor in series with the radiator, and it will likely be showing a short at the feed point and not an open.

I would be a good discussion to talk about what is going on with the Tornado that makes it different, but maybe it needs to be in another thread...so as not to be so confusing for me at least, and maybe for Cj and others.

How say you?

 

[The DB]

I noticed in some of the pictures that there are some parallel sections between the parts attached to the center conductor and the shield. There is also the fact that the coil is not very far away from the radials relatively speaking. It is possible that said components are acting as a hidden capacitor of sorts. If that is the case it is possible that said capacitor and the coil are effectively making an "L" network to match the rest of the antenna to the feedline.

I'm not 100% on that, but it is the impression I am getting from the pictures posted here at first glance.


The DB

 

[vkrules]

Don't sweat it . There's more than one way to match a 5/8th .Looking at the pic I'd say it is a LC network, the capacitance provided by the way the coil is constructed around the element

 

[Shockwave]

There is no trick or hidden parts to make the coil work without it being grounded. All that is required to raise the 50 ohm cable impedance to the 5/8 waves much higher impedance is a series coil. The extra part is when they add the shunt coil to ground for lightning protection. The Tornado type of matching coil is used in just about every mono band 2 meter 5/8 wave mobile antenna.