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Author Topic: TAK-tenna...Really that good/  (Read 5773 times)
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« on: April 07, 2008, 01:03:14 PM »

Is the new TAK-tenna really as good as the EHam reviews have it?  More info. on this phenomenon would be appreciated.  Tnx Bill
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K5LXP
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« Reply #1 on: April 07, 2008, 01:33:44 PM »

Right up there with Isotrons.

Mark K5LXP
Albuquerque, NM
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WA3SKN
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« Reply #2 on: April 07, 2008, 01:38:24 PM »

I have not read the reviews.
But, just from its picture, it appears to be one of those "Too good to be true" type antennas.
For radiating efficiently, you really need to have a certain amount of area.  Reduced antennas equal narrow bandwiths.
Will it work on a single frequency?  Yes.
How about a band of frequencies, or bands of frequencies?  probably not.
Stick with full size dipoles, loops, etc. unless you HAVE to make do with something smaller!
73s.

-Mike.
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KC2RGW
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« Reply #3 on: April 07, 2008, 02:03:59 PM »

Does it radiate?  Yes.

Will it beat a dipole?  No.

Could it be useful for someone who has to put something up on a balcony or for portable and camping etc?  Sure.
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WB2WIK
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« Reply #4 on: April 07, 2008, 02:04:40 PM »

I made one out of two BBQ wire griddles and made a lot of contacts.

Reminds me of the Gotham ads.

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K6AER
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« Reply #5 on: April 07, 2008, 02:05:08 PM »

Notice they don’t reference gain of their antenna to a dipole. That should give you a pause.
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N6AJR
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« Reply #6 on: April 07, 2008, 02:38:42 PM »

it is mbasically a resonant circuit, the coile act like inductors and the spaces in between act like a capacitor, os you get a resonant circuit at a value the radio can use.  but not much capture area.  will it work , yes, will it work well, no, is it better than a paper antenna , yes.   a pair of ham sticks will priobably beat it, my guess.
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AJ4DW
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« Reply #7 on: April 07, 2008, 02:40:15 PM »

The folks who have actually used it like it... thus the 4.8/5 rating in the reviews. You've got 47 reviews there, six opinions here.

I haven't used it, but with odds like that I'd be willing to give it a try... I'd like to put one up sometime in the near future and compare it to my present antennas. If it doesn't measure up I'll sell it. Don't forget, the bumblebee isn't capable of flying either (OK... now we know why it can fly, but we didn't for quite a long time).


BTW... "gain" as quoted in antenna ads is a pretty unreliable number.
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AA4PB
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« Reply #8 on: April 07, 2008, 03:17:30 PM »

You can't get something for nothing. Physically small antennas equate to low radiation resistance and usually high loss resistance and this equates to inefficiency (more power turned into heat and less power radiated). Its always that way - there are no exceptions. That doesn't meant that the antenna won't "work", depending on how you define "work". It doesn't mean you can't make any contacts with it. It does mean that it won't perform as well as a 1/2 wave dipole, which generally has an efficiency somewhere above 90%.
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W8JI
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« Reply #9 on: April 07, 2008, 03:29:10 PM »

Eham reviews are probably not even as valuable as opinions here. Eham reviews are for the most part just subjective unscientific emotional feelings from someone who has spent money. Some terrible things get very good reviews, and not all bad reviews are accurate. Like E-Bay member reviews, they are largely meaningless except for personal feelings.


Everything everyone said here is absolutely true.

There isn't a greatly reduced size antenna in the world that radiates anything like a full size antenna. There isn't any magic, there isn't any free lunch. If you have room for a full size antenna use a full size antenna. If you don't, then any antenna is better than no antenna at all. Even if an antenna is 10dB or 20dB down from a full size antenna it will make many people happy.

If you see an antenna that is 5% or 10% of the physical linear size of a full size antenna it will ALWAYS have significant loss. There is no way around it without terrible expense and very narrow bandwidth. That doesn't mean it isn't a good deal for people without room for anything larger.

73 Tom
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N3OX
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« Reply #10 on: April 07, 2008, 04:39:16 PM »

A #12 wire Tak-Tenna type antenna 3 feet long that resonates on 18.150 MHz shows -4.3dBi free space in EZNEC, so what, -6.4dBd or so?

This is a little longer and a little higher frequency than the actual TakTenna.

Anyone actually have one of these things so I can have a go at modeling it accurately?  Length of straight section, pitch and # turns of the spirals?

My Tak-Tenna-esque model can be downloaded at:

http://www.n3ox.net/files/eznec/TakTenna.ez

Haven't had the patience to sit through an SWR curve calculation on this computer ;-)

Anyway, I think the "real thing" probably comes in better than -10dBi, plenty to make people think it's a good antenna.  I have a wild-***-guess that the cutoff for shortened antennas where random reviewers will start to give it bad ratings is probably just about -20dBi.

That's where your 100W transmitter is down to 1W with respect to, say, a ground plane vertical.... still plenty of power to make contacts with strong stations, but rough going otherwise. That's where even folks with only one poorly performing antenna will start to get dissatisfied, I bet.


-10dBd to -6dBd ... equivalent 10-25W to a full-size dipole at the same height?  *plenty* of ERP ;-)  So, 5/5 eHam review....

Of course, -6dBd in my model is at a spot freq.  You use your tuner to "stretch" the "useful" bandwidth and you'll get lots of loss in the feedline...

For what it's worth, I think there are certainly worse short antennas out there.  This one's end loaded, and the loading device, while far from optimum (and irritatingly difficult to model (intentional?)) could be worse.

If you used big airwound coils and a regular capacitance hat at the ends of a 30 inch dipole it would work okay on a spot frequency, and I think that's more or less what this does.

The thing that I think is most bizarre about this antenna is that it's unnecessarily short.  Why not a six foot end loaded dipole?  Why not eight?  That would fit on people's apartment balconies just fine.

It's a weird antenna.  It's probably not the worst choice in 30" long 20m antennas out there, though.

73,
Dan
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
Guest

« Reply #11 on: April 07, 2008, 07:34:10 PM »

 I have noticed the comparison of this antenna and the one at this site.. http://hometown.aol.com/n0lx/spirals.html

It seems  quite expensive for just what it is compared to what you would pay for a dipole.  Bill
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N3OX
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« Reply #12 on: April 07, 2008, 07:46:36 PM »

As another modeling exercise, I tried what I would consider a *best case* scenario for the TakTenna, something that's not a terribly difficult to construct antenna.

The radiator is a 30" long 1" diameter copper tube.  

The antenna is end loaded with 30" diameter 10 spoke capacitance hats (no perimeter wires) and enough inductance (about 4.6uH) at each end between the cap hats and the horizontal radiator to resonate it on 20m.  My model uses Q=300 for the coils, something you should be able to get with good #12 or #10 wire inductors on air cores.

The antenna uses a hairpin match ... an 18 ohm inductor (Q = 300) is installed in parallel across the feedpoint to bring the feed impedance up to around 50 ohms at resonance.

The antenna I modeled resonates (with the hairpin match) at about 14.240 MHz, right where your favorite DX net is ;-)

The 2:1 SWR bandwidth is about 40kHz.

The efficiency is about 22%; the gain about -4.9dBi.  

- - - - - -

Now let's stretch to the band edges with a tuner.

14.350MHz , impedance is about 3.6+j3.3.   Mismatch loss (according to VK1OD's loss calculator) in 30 feet of RG-8/X is an additional 1.9dB, for a gain of -6.8dBi, overall efficiency about 14%.

14.000MHz, impedance is 1+j25, additional loss in 30 feet of RG-8/X about 5.3dB, overall gain about -10.2dBi, overall efficiency about 6.5%.

- - - - - -

So the punch line:  a well implemented Tak-Tenna sized antenna on 20m will radiate between 6.5 and 22W of your 100W transmitter power.  If you tune it for the SSB portion of the band, we can even allow for the 12dB CW advantage, 6.5W CW is like 100W SSB, right? ;-)

The real Tak-Tenna with it's probably non-optimum loading structures will work somewhat less well than this, but honestly it could be worse!!! If you put up a 30" long antenna that radiates 22W at your favorite frequency and 6.5W or better across the whole band,  you'll have a ton of ham radio fun.  If it's your only antenna, it gets a 5/5 for sure.

If you put the thing at 35' on a rotator and get that  ground gain from the elevated height working for you, you might even end up with an antenna that's within a couple dB of a ground mounted 1/4 wave vertical for a large range of incoming elevation angles... plus it's got potentially useful side rejection.

So is the TAK-tenna really that good?  Well, a "best-practices" version with good high-Q loading actually isn't that bad as far as such small antennas go.  As with all decent small antennas, the SWR bandwidth would be quite narrow, but I would probably be happy with the lower 40kHz of 20m if I were stuck with it.  

Would I run one?  No way.  A couple of 16 foot fishing poles and some wire would go on pretty much the same rotator and mount that a Tak-Tenna will, and will legitimately cover the whole 20m band under 2:1 SWR and be nearly 100% efficient... giving you a 6dB+ stronger signal!

That's like going from 100W to 400W... and it probably saves you money anyway.  Fiberglass telescoping fishing poles are about a buck a foot.

I can understand why the Tak-Tenna is so popular though.  Like I said, a 30 inch long antenna for 20m  could be much, much worse ;-)

However, keep in mind that the antenna I modeled here was NOT a Tak-Tenna but was rather a conventionally end loaded super-short dipole; you can probably knock off 2-3-4 more dB due to the weird loading scheme, who knows.  This is especially true if the antenna covers the whole band!!  Even then, you're still probably going to be able to get 5-10W radiated power from your 100W, and that'll make a lot of folks quite happy.

73,
Dan






 








 

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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
WD6S
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« Reply #13 on: April 08, 2008, 07:00:29 AM »

I have one, and it does work. Compared to a Hustler vertical with about 20 radials in the desert, it is somewhat more directional, probably a little less sensitive overall. It seemed to work better than the random wire that I had up there. It does have a wind load so its needs support if at any great height (mine is at 20 feet and was blown over despite a tripod weighted with a couple of hundred pounds of rocks.

It is no miracle by any means, but it works ok. It is compact, easy to build, and easy to maneuver. Good for camping or RV'ing I suppose.

On the 20 meter version about 20-21 feet of copper clad solid steel wire is used on each side.
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WD6S
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« Reply #14 on: April 08, 2008, 07:01:15 AM »

I have one, and it does work. Compared to a Hustler vertical with about 20 radials in the desert, it is somewhat more directional, probably a little less sensitive overall. It seemed to work better than the random wire that I had up there. It does have a wind load so its needs support if at any great height (mine is at 20 feet and was blown over despite a tripod weighted with a couple of hundred pounds of rocks.

It is no miracle by any means, but it works ok. It is compact, easy to build, and easy to maneuver. Good for camping or RV'ing I suppose.

On the 20 meter version about 20-21 feet of copper clad solid steel wire is used on each side.
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