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eHam Forums => Elmers => Topic started by: on April 07, 2008, 01:03:14 PM



Title: TAK-tenna...Really that good/
Post by: 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


Title: TAK-tenna...Really that good/
Post by: K5LXP on April 07, 2008, 01:33:44 PM
Right up there with Isotrons.

Mark K5LXP
Albuquerque, NM


Title: TAK-tenna...Really that good/
Post by: WA3SKN 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.


Title: TAK-tenna...Really that good/
Post by: KC2RGW 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.


Title: TAK-tenna...Really that good/
Post by: WB2WIK 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.



Title: TAK-tenna...Really that good/
Post by: K6AER 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.


Title: TAK-tenna...Really that good/
Post by: N6AJR 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.


Title: TAK-tenna...Really that good/
Post by: AJ4DW 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.


Title: TAK-tenna...Really that good/
Post by: AA4PB 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%.


Title: TAK-tenna...Really that good/
Post by: W8JI 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


Title: TAK-tenna...Really that good/
Post by: N3OX 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


Title: TAK-tenna...Really that good/
Post by: 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


Title: TAK-tenna...Really that good/
Post by: N3OX 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






 








 



Title: TAK-tenna...Really that good/
Post by: WD6S 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.


Title: TAK-tenna...Really that good/
Post by: WD6S 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.


Title: TAK-tenna...Really that good/
Post by: AJ4DW on April 08, 2008, 08:46:27 AM
I won't defend the Tak-Tenna because I haven't tested it. Folks make a good point about the utility of the reviews... I like using them and depend upon them to help me make decisions, but I scan for the "less-than-5" reviews, like gymnastics scoring, you remove the highest and lowest scores and look at what's left. A consistently high score over 45+ plus reviews is hard to ignore.

I will defend experimentation, and I am not referring to modelling. (The model noted here was not of a Tak-Tenna but of a dipole with two capacitance hats, and the only comparison was at http://hometown.aol.com/n0lx/spirals.html which may or may not have properties similar to the Petlowany antenna in question).

Judging by the single 1/5 rating in the reviews, the builder, Steve, doesn't have any idea of the true characteristics of the antenna either (assuming we can be sure of THAT review, I don't know the reviewer and can't vouch for him).

There's another review at Ham Universe that's pretty interesting: http://www.hamuniverse.com/taktennareview.html
(again, although I've found Ham Universe a very useful site I can only go along with what the author claims). That review does NOT have any good comparisons either except in terms of *reception* of multiple bands. There are no objective measurements noted. He does mention that the antenna is NOT presented as a "miracle antenna" nor does it purport to break any laws of physics. It's represented as a small-footprint antenna that's effective and "10-14 dB at 90 degrees" directional.

So... we have an antenna that a lot of folks are enthusiastic about, which no one has model of, which theoretically won't do what it's reported to do, and we have no objective measurements, just a lot of opinion. Now that we have the theory it's time to test the theory, and that means actual measurements. I'll have to wait for that to make a decision. But again, I'd be willing to play around with one in the meantime.


Title: TAK-tenna...Really that good/
Post by: AA4PB on April 08, 2008, 11:25:52 AM
If you look closely at the picture on their web page you'll see that each spiral has a feed line attached at about the half-way point. It looks like the two sprirals are the elements rather than capacity hats. The only numbers they give on the site is that it has a front to side ratio of 10-14dB (which isn't much compared to a yagi - but then this is a small antenna). My question would be how does it compare to something like a 2-ele yagi made from HamSticks?


Title: TAK-tenna...Really that good/
Post by: N3OX on April 08, 2008, 12:57:21 PM
"(The model noted here was not of a Tak-Tenna but of a dipole with two capacitance hats"

Well, sort of.  The first model, the one I actually posted the file of, is a three foot horizontal radiator with spiral loading structures on either end.

It happens to resonate on 18.150 MHz and is awfully hard to make changes quickly to that model to make it resonate on 20m instead.  It's not an exact model of the actual TakTenna (and if you've got measurements, I'd be glad to take another stab at it!) but it is a similarly dimensioned end-spiral loaded antenna.

For those who just want to take a look at what I modeled ***the first time*** (which has about -4.3dB loss with respect to a 17m dipole), here's a picture:

http://n3ox.net/files/n3ox_tak.jpg

It's clear to me from the model that the spirals are simply end loading structures.  

Again, if someone has dimensions I'd be glad to try to build an accurate model of the real 20m TakTenna.  

- - - - - - -

Another approach would be to build MY antenna on 17m and measure a the real thing in comparison to a dipole.

You have to be careful with the measurement because if the model is correct, it's not actually that much worse than a dipole on the frequency it's tuned for, and that makes it hard to measure (and also pretty useful for home station use, honestly).  

So AJ4DW, if you're thinking of playing, why not build MY antenna here? We *DO* have a model of that.

The end spirals are #12 wire, about 8.5 turns at approximately 2" pitch... and start about 2" from the center of their form (I had to cut out some segments in the center because the wires were too short)  The horizontal wire is also #12 and is 3 feet long, split in the middle for a feedpoint.

This antenna has a predicted gain of -2.6dBi at the center frequency and a predicted 2:1 SWR bandwidth of 20-30kHz.  

The feedpoint resistance at resonance (about 18.150MHz) is 7 ohms.  If you bridge the feedpoint with a 0.18 microhenry inductor, this gives you a hairpin match that will give you a 50 ohm match to coax at 18.100 MHz (good for some PSK31 ? )

At 18.070 MHz, with the hairpin inductor in place, the impedance is 17+j47.  The additional loss in 30 feet of RG-8/X from the mismatch if you were to use a tuner to bring down the SWR for CW is just 0.5dB.   At 18.165MHz, the feed impedance is 3+j7 ohms, giving an additional coax loss of about 2.5dB in 30 ft of RG-8/X.

So there's a similarly dimensioned and potentially attractive antenna, similar to the TakTenna, that we can all build and try.

I've got predictions for gain and SWR bandwidth, and additional losses using reasonable coax feed and a tuner, and we can go ahead and test those.  

It's not identically a TakTenna but it's a very similar antenna that undoubtedly works on the same concept.  So let's try it out.  We can build this particular quite short version of a Petlowany/TakTenna type antenna for 17m and give it a test drive.  

This one comes with dimensions, a model, and performance predictions, and actually, for an antenna you can probably throw in the trunk of your car or stick in the corner of your apartment, isn't so bad aside from the narrow bandwidth.

I see no reason why you couldn't use the TakTenna's approach of attaching the spirals using fly leads to change the resonant frequency.   It undoubtedly will need some tweaking with such a narrow 2:1 SWR bandwidth.

You need about 39 feet of wire, and a handful of PVC pipe, bamboo, or wood supports.  An antenna analyzer is helpful.

The inductor across the feedpoint would be, say 4 turns of #12 wire on a 3/4" form spaced out over 1.25" .  It will be self supporting and can be compressed or stretched for best SWR at your center frequency.



73,
Dan




















Title: TAK-tenna...Really that good/
Post by: AA4PB on April 08, 2008, 01:42:52 PM
Dan, take a close look at the picture on their web page. Doesn't it look like the feed line goes to a "T" and then off to the center of each spiral? The boom between the two spirals looks like PVC or something. It doesn't appear to be anything more than a support structure. I expect the directivity is off the end of the support boom.


Title: TAK-tenna...Really that good/
Post by: N3OX on April 08, 2008, 02:01:51 PM
"Doesn't it look like the feed line goes to a "T" and then off to the center of each spiral?"

I thought each of those was a single wire.

They do call it an "electrical half-wave dipole antenna" and this:

http://www.tak-tenna.com/Balcony%20Pix.pdf

suggests that it radiates broadside to what they're calling the "boom", to quote:

"Note: Simple 90* rotation....
From horizontal propagation...
to vertical propagation!!!"

So, that's my take on the design.  You might be able to feed a spiral element midway and get it to resonate somewhere but the field cancellation would be huge.


Dan


Title: TAK-tenna...Really that good/
Post by: N3OX on April 08, 2008, 02:15:17 PM
Bob,

Just for kicks I fed a single spiral coil at a random spot on the coil that I eyeballed to about halfway in an arc-length sense.

It resonated at 22.456MHz, very narrow, and had a radiation resistance (lossless impedance) of about 0.09  ohms with a total resistance at resonance including copper loss of about 1.3 ohms.  Overall efficiency is about 7% and the pattern is like that of a bad magloop, vertically polarized, shallow nulls along the axis perpendicular to the plane of the coil.

Gain was something like -11dBi.

Dan
 


Title: TAK-tenna...Really that good/
Post by: on April 08, 2008, 02:35:27 PM
It appears to me that each spiral is a 1/4 wave of wire and the feedline if being around 30" joins the spiral minus that distance from the start of the spiral and is the tap point. This makes the wire a 1/4 wave from the feedline attachment. Any thoughts. Bill


Title: TAK-tenna...Really that good/
Post by: N3OX on April 08, 2008, 03:11:21 PM
"This makes the wire a 1/4 wave from the feedline attachment."

It's a quasi-coincidence.

You can't, in GENERAL, coil up half of a dipole and have it stay half of a dipole.

There's actually a 180 degree phase flip and amplitude minimum in the current at about turn five of eight going outward each of the spirals in my model.  

That's pretty weird.  There's some transmission-line resonance type effect going on with the spirals.  They do seem to support standing waves.

However, the overall effect is nothing exotic.  The radiating bit of the antenna is the central 30" section, at least by comparison with the pattern and performance of an ordinarily loaded short dipole.

This sort of smacks of accidental empirical discovery.  Given a total length of wire of any random length in the range 0.4 to 0.9 wavelengths or so, there are several structures you could build with any one piece of wire that will resonate at a given frequency.

If you had a half wavelength of wire you could stretch it out into a half-wave dipole... or you could twist it and see what else you can come up with, and that may be what happened here.

My 17m antenna happens to resonate right in band with a total wire length of about 3/4 wavelength... each coiled up leg totals 3/8ths wavelength of wire.  

If I had a 0.4 wavelength wire, I could potentially wind small tight coils near the center to give enough inductance to resonate what was left.  If I had 0.7 wavelengths of wire, I could just ball up the ends like a ball of string until it resonated like a half-wave dipole.... or I might come up with some fancy structure like this that happens to resonate.

You pick a different spiral pitch and overall size and it won't resonate on 20m anymore, even with 1/4 wavelength total wire on each side.

Conversely, you pick 1/4 wavelength of wire for each side and there are clearly at least two very qualitatively different structures you can build with the same resonant frequency, and there are countless others that we'd have to argue over whether they were different or not ;-)

73,
Dan


Title: TAK-tenna...Really that good/
Post by: AA4PB on April 08, 2008, 03:21:11 PM
There's a more extensive review at http://www.hamuniverse.com/taktennareview.html

The claim is that the spirals are each 1/4 wave long and that you adjust the tap point for minimum SWR. Obviously there will be some radiation from wires feeding them that run along the boom. I'm not sure what the pattern looks like. It appears that the coils will be more than simple capacity hats since they are in a spiral form and based on the SWR changing by adjusting the tap points.


Title: TAK-tenna...Really that good/
Post by: N3OX on April 08, 2008, 08:25:49 PM
"It appears that the coils will be more than simple capacity hats since they are in a spiral form and based on the SWR changing by adjusting the tap points. "

If I were to try to describe them in familiar terms, I'd say they're loading coils and capacitance hats rolled into one.

From what I can tell, it's the connecting wires that do the lion's share of the radiating, just based on the pattern I get.

Take a look at the .jpg picture I posted back a few..h


Title: TAK-tenna...Really that good/
Post by: W8JI on April 09, 2008, 03:15:51 AM
That's what they are.

Less than perfect capacitance hats that double as less than perfect loading coils that end load a very short dipole.

Since the feed impedance is fairly high we know what losses really are, don't we?

73 Tom


Title: TAK-tenna...Really that good/
Post by: K1CJS on April 09, 2008, 05:40:26 AM
"Stick with full size dipoles, loops, etc. unless you HAVE to make do with something smaller!"

Good, sound advice.


Title: TAK-tenna...Really that good/
Post by: KG4RUL on April 09, 2008, 05:44:10 AM
WA8MEA writes on April 8, 2008:
At the top of the stairs, without a care
it shoots signals so high in the sky.
It won't let you down, even in town
everyone knows its a BIG Slinky.

The best present yet, to give or get
that hams will all want to try.
Take a turn at bat, when you're ready to chat
everyone knows it's a BIG Slinky.

It's a BIG Slinky, it's a BIG Slinky,
for fun it's the best ham radio toy.
It's a BIG Slinky, it's a BIG Slinky
just a coil of ham radio joy.

Everyone needs a BIG Slinky....
You've got to get a BIG Slinky.

73, Bill

........

That is SO BAD that I LOVE IT!!!!!  If I laugh any harder I am going to pop some stitches!!!!!


Title: TAK-tenna...Really that good/
Post by: K1CJS on April 09, 2008, 05:55:14 AM
"It seems quite expensive for just what it is compared to what you would pay for a dipole."

It used to be about half the price it now is--which was a fair deal--the cost of the materials plus an equal amount of money for the fabrication, but it seems the manufacturer is looking to capitalize on his success.  So now its about thirty dollars worth of materials and ninety for the fabrication of the antenna.  

Hey, its his right to do so, but now this antenna CAN be compared to an Isotron--an expensive loading circuit.  I doubt he'll be selling as many of them as he would have if the price was left where it was.  


Title: TAK-tenna...Really that good/
Post by: K4SAV on April 09, 2008, 07:29:40 AM
When this antenna was being designed, he listed the requirements of this antenna discussion group for help in designing it.  This website has some description of the antenna, and a good picture.  Notice the unsymmetrical feeding of the coil, resulting in an off-center fed antenna.  Also notice that the coils are wound in opposite directions.  They called it a Princess Leia Antenna.
http://www.randstadamateur.net/index.php?option=com_smf&Itemid=41&topic=282.msg671

The first page of the TAC website implies there are four models, 40 meters, 20 meter, 11 meter, and 10 meter.  Another page of the website says there are only a standard model and a "More Portable Model".  I found pictures of the 40 meter and 20 meter models.  They look identical to me.

The website has a reference to the Tac-tenna expedition style in the Artic, OX60AD (OX3PG op) in Tule, Greenland.  I can't imagine they used a Tac-tenna when they have a Monster 95 ft boom log periodic at that location.  Maybe he just donated the QSL cards.
http://1.947group.org/gallery/displayimage.php?album=5&pos=1

The Tac-tenna website says the antenna was tested, proven and endorsed by Collins Radio Association, and there is a link given.  I could find no reference to the Tac-tenna on that website, and neither could Google when searching that site.  However, this is a users group for Collins Radio Equipment, not associated with Collins Radio Corp.  So the antenna was probably tested and approved by a member of this group.  You can guess who.

Notice that there is no common mode choke on this antenna,  That is for good reason.  It won't work well if you use one.  According to EZNEC, this antenna functions as an unbalanced load that injects large common mode currents onto the feedline.

With EZNEC I was unable to make the antenna resonate on 40 meters.  I was able to get the resonant point down to 8.8 MHz but no lower. I probably didn't have the right length feedline.  At that frequency with the antenna at 35 ft, using 80 ft of RG213 the gain was -7 dBi.  Adding a choke to remove feedline radiation, the gain dropped to -18 dBi.

Readjusting the taps for a resonance on 15 meters, with the antenna still at 35 ft, the max gain occurred at a very high angle, -1.5 dBi at 45 degrees.  At 10 degrees elevation the gain was -7 dBi.  Adding a choke to remove feedline radiation resulted in a gain of 0 dBi at 18 degrees.  The reason for the high angle radiation was the long vertical feedline radiating at a high angle.  The antenna was placed too high.  The gain would have been higher if the antenna was placed lower so that the vertical section of the feedline contributed some low angle radiation instead of mostly high angle.

You can see the feedline significantly effects the SWR and pattern of the antenna, so it is likely that everyone's experience with the antenna will be different because of different feedline lengths and routing of that feedline.  The antenna should placed a height such that the vertical section of feedline has a good length relative to the frequency of operation.  A long section of feedline on the ground will couple a lot of signal into the ground.  Some lengths of feedline operate much better than others.

Jerry, K4SAV


Title: TAK-tenna...Really that good/
Post by: AA4PB on April 09, 2008, 08:05:37 AM
According to EZNEC, this antenna functions as an unbalanced load that injects large common mode currents onto the feedline.
------------------------------------------------------
This seems to be a common "feature" among several of the tiny antennas. As you say, the problem with allowing the feed line to radiate is that everyone gets different performance, depending on how the feed line is routed. Might be better to just run a random wire out the window and hope for the best. Thats what we used to do years ago. Now we hang a $100 hunk of metal on the end of it :-)




Title: TAK-tenna...Really that good/
Post by: AJ4DW on April 09, 2008, 08:35:36 AM
N3OX (Dan)

Sounds like a plan. I do like your model, thanks for the link. I've already got one end built at home (the crossed PVC supports with notches cut to support the wire), and I'll be starting the other end once I get another two, more pressing, projects out of the way.

Will you be using aluminum or copper wire, and will you try to maintain the smooth spiral (rather than squaring everything off)? If we held the coil loose (no notches) between parallel supports (and if it was stiff enough to maintain it's spacing, or if the supports had foam linings and were held together with rubber bands) we could vary the distance between successive loops to see what effect that had.

Once I've built that and then a wire dipole I can start the comparison (right now I use a full-wave 160m horizontal loop for all my HF work). I really do wish I had a nice antenna range to do some really objective measurements.

FWIW, here's a URL for the original Petlowany article in World Radio from March 1998: http://www.wr6wr.com/newSite/articles/features/olderfeatures/antennaswithtwist.html
Interestingly, he makes a lot more modest claims than the Tak-tenna site. It's a good read.

73
-Carl AJ4DW

I suppose what we'll be testing is "TAK-tenna... is it really THAT bad?"


Title: TAK-tenna...Really that good/
Post by: N3OX on April 09, 2008, 10:31:58 AM
"Will you be using aluminum or copper wire, and will you try to maintain the smooth spiral"

I dunno, I may try to build one that's as close to the model as possible just to provide a one-to-one comparison, so I'd want to keep the smooth spiral.

I don't want to spend too much time on it, because although I do enjoy the idea of having some good educational information on my website, I don't really want to recommend a difficult to construct structure over an easy coils-and-cap-hats dipole. I'm quite convinced that there's nothing special about the Petlowany/TakTenna construction and that it probably won't outdo good lumped loading.

The problem is that it seems few people will BELIEVE that... not from me, not from W8JI, not from established theory.  Like you, they want to see empirical proof.  A model isn't good enough (and there are are enough subtle modeling pitfalls to make that somewhat valid unless the model has been really tested for convergence).  

But there's always that tradeoff; efficiency vs. useful bandwidth vs. size.  There's no way around it. If you want an efficient radiator, you have to shove current back and forth over some distance.  If you want to shorten that distance and keep the same amount of radiated power, you *have to increase the current*.  If you want to increase the current, you have to *reduce the ohmic losses* in the system to prevent power loss to heat.  If you decrease the ohmic losses so that you can efficiently shove large currents around, while simultaneously decreasing the radiation resistance by shortening the antenna, *you will reduce the bandwidth*

This works to judge small antennas without testing them, by the way.  You see an antenna that's 1/20th of a wavelength in the biggest dimension that covers an entire ham band under 1.5:1 SWR?  It is GUARANTEED to be VERY lossy with respect to a dipole.  GUARANTEED.  It doesn't matter how clever the antenna seems.  The bandwidth vs. radiating efficiency vs. size tradeoff is fundemental for the very best antennas.

However, there's basically no limit to the extent to which you can make things WORSE than the most efficient antenna of a given size and bandwidth. At a given size there are all sorts of things you could do to DECREASE the radiation resistance while keeping the total sum of radiation resistance + loss resistance (and by extension, the SWR bandwidth) the same.

The real question is, for a given size and SWR bandwidth, what is *the most efficient configuration*?  The answer to that question is unknown and likely always will be, but it's at the heart of empirical tests we might want to perform.  It's the question at the heart of good small antenna design.  

Unfortunately, that very same question, UNTESTED, is at the heart of most small antenna marketing campaigns.  The physical form of the antenna is novel, raising that question in the minds of buyers.

The test is carefully avoided by the manufacturer, leaving the buyer to do his or her own tests.  The manufacturer knows that many hams will just stick that sucker up and talk to cool places around the world.

Can I say with 100% certainty based on empirical tests that a Petlowany/TakTenna type loading is worse than conventional coil and capacitance hat loading?  No, not yet, and since so many people clamor for empirical testing, it's probably worth doing some.

But I think I can predict the result.  The finished product based on the design I've set forth will be a narrow bandwidth reasonably efficient short dipole that's not quite as good, but maybe within a dB or two in gain of and has a similar bandwidth to a conventionally loaded coils + cap hats short dipole.  

It's too bad we have to build them to convince anyone of that though, because it's EASIER to build the coils + cap hats version, as far as I'm concerned.  I also have a perfectly good magnetic loop that works 17m in the short/small antennas category and a 17m two element beam... so I don't really need another 17m antenna ;-)

Kinda have to build one now, though, eh?

73,
Dan

 




 



 


Title: TAK-tenna...Really that good/
Post by: AA4PB on April 09, 2008, 10:37:30 AM
From the article he states that "if a length of wire is wound into a spiral-shaped coil and excited by a radio frequency current connected to the innermost portion of the coil, it will then, and only then, exhibit RF characteristics that closely approximate those of a resonant linear wire of the same length." He seems to be saying that you can take a 1/2 wave dipole and coil it into two spirals and still it is resonant and performs the same as if it were linear. Why is this true of only the spiral form factor?

Regarding the 2M tests that showed it worked as well as a full sized dipole, this 2M dipole ended up being 50% of the full sized dipole. My experience with traditional shortened dipoles is that they work pretty darn well if the physical size is not reduced by more than 50%. I would not expect to see the same performance from his 40M model unless it was similarly scaled, making it at least 34 feet long.

I wonder what the polarization of the other 2M station was. If it was vertical, radiation from the vertical feed line may have made a significant contribution to the signal. The horizontal horizontal test dipole would however take a significant cross polarization hit.

Lots of questions to be answered and very little technical information from either the original article or the Tak-tenna web site. It would be interesting to see some real-world patterns with the feed line adequately decoupled.





Title: TAK-tenna...Really that good/
Post by: on April 09, 2008, 11:25:42 AM
It sure would be interesting to see what is in the instruction manual that comes with the TAK-tenna wouldn't it?

This antenna is quite interesting from the point of view that it is fun to construct such things. I sure have enjoyed all the posts on this.  73  Bill


Title: TAK-tenna...Really that good/
Post by: W8JI on April 09, 2008, 03:57:38 PM
by AA4PB on April 9, 2008
<<
From the article he states that "if a length of wire is wound into a spiral-shaped coil and excited by a radio frequency current connected to the innermost portion of the coil, it will then, and only then, exhibit RF characteristics that closely approximate those of a resonant linear wire of the same length.">>


Wrong. It is charge acceleration over in-line spatial distance that causes radiation.

1000 feet of wire in a two foot length no matter how coiled, wound, or formed is at very BEST a two foot antenna. It has to have the net or effective common mode current of a two foot long single conductor to radiate the same power.

There is no possible way around this effect.

What this means is if you took the same spatial in-line distance between the end caps and replaced the spiral ends with a metal sheet and added a reasonable lumped inductor in the linear portion of the radiator, you would see a net efficiency increase. This is because the series resistance would decrease.


<< He seems to be saying that you can take a 1/2 wave dipole and coil it into two spirals and still it is resonant and performs the same as if it were linear. Why is this true of only the spiral form factor?>>

It is not true under any condition or any form factor. A five foot linear area antenna is a five foot antenna OR WORSE because radiation is always defined by ampere-feet of linear spatial area.

Linear loaded antenna sometimes use the same false concepts. They claim using more conductor length reduces losses. In fact the opposite is true. That's why there are so many people disappointed by linear loaded 80 meter Yagi's that work poorer than  a simple wire dipole. Some people make big money selling kits that replace linear loading with regular loading coils because the efficiency increases.

The best idea is always minimum series resistance and maximum linear spatial area.

73 Tom  

 


Title: TAK-tenna...Really that good/
Post by: WD6S on April 10, 2008, 07:10:31 AM
On wire length, the instructions that come with the 40M antennas say not to cut off more than 3 feet of wire. Interestingly, depending on how you wind you will have little or a lot of surplus. On one end I tried to maintain a circular pattern and ended up with surplus wire (almost 3 feet). On the other end I "squared the circle" and ended up coming out even.

For the 20 M antenna, the plastic parts are the same size, but the wire is shorter, resulting in many of the inner slots in the cross arms not being used- something that disturbed me enough to send an email. I was assured that this is normal.

The "hot" side, as it is called in the instructions, is fed by the center conductor and is the side closest to boom support clamp.


Title: TAK-tenna...Really that good/
Post by: K4SAV on April 10, 2008, 08:10:40 AM
WD6S, do you have any measurements of the antenna, such as turn spacings, number of turns, or wire length, wire size, etc?  It would be nice to double check my estimated dimensions which were scaled from pictures.  Also there is some question about whether those pictures were even labled correctly.

Jerry, K4SAV


Title: TAK-tenna...Really that good/
Post by: KE6AEE on April 11, 2008, 11:35:10 AM
I personally dont own one or know anybody who does.  Having said that, it sure seems to get good reviews here on eHam. and other places so its not like the builder/company isnt just blowing its own horn.  How good can an antenna be.  Last week I worked Texas from Calif using an Icom 703 at 10 watts with a 23 foot of wire lying on the roof, the other guy running 500 watts into a dipole and he gave me a 54 totally readable and he sent a 46. Just because we might not see electrically/RF wise why it should work.  Lots of crazy designs that shouldnt work but they do.  Thats the thing I love about this hobby.

Richard


Title: TAK-tenna...Really that good/
Post by: N3OX on April 12, 2008, 08:16:51 AM
"Lots of crazy designs that shouldnt work but they do. Thats the thing I love about this hobby"

Richard, that's just the thing.  If you only have one antenna, you're going to love it, because ham radio allows amazing things to happen with tiny radiated power.

Several months ago I worked LA7THA using 5 watts on 160m to an inefficient antenna.   I worked G3ROO on 80m when he was running a chirpy 3W WWII transmitter.  You can probably occasionally work CA <-> TX on much, much less power and much, much less antenna than you were using!  300mW might do it sometimes.

But the fact remains, for each and every path you're interested in working there's an overall total budget for the power and antenna required and if stations on one end  have very small antennas and power, it has to be compensated for at the other.

Keep track over time of how many stations you work that are running 10W to a random wire vs. how many you work that are running 500W to a dipole in the clear or even a beam.  You'll probably find that the number of 10W and random wire stations in your log is generally fairly small.

It's very unlikely I would have ever worked LA7THA with 5W if he hadn't had a much better receiving capability  than I do.  I doubt I would have heard LA7THA if he were running 5W.   I was lucky to hear G3ROO on 80m at 3W.  He was very weak and just at the limit of my receiving capability.  If I hadn't installed the receiving antenna I have, I may not have heard him in the noise.

There's nothing wrong with getting on the air with whatever you've got available for antennas, if you are really limited to those equipment conditions, but don't let the fact that ham radio can do amazing things make you be too complacent about your antenna system.  Maybe it could be *much better* even given your restrictions, and you'd be in here saying "I worked from California to Malyj Vysotskij Island with 10W"

It's fun to work stations using crazy antennas that "shouldn't work" but if you only ever use that one crazy antenna you'll never find out what you've been missing.  There is really no hard lower limit where switching to worse and worse antennas will make you unable to make contacts.  People have literally made contacts using a lightbulb on the end of the coax.

73,
Dan

 


Title: TAK-tenna...Really that good/
Post by: WD6S on April 14, 2008, 03:42:07 PM
Measurements of my Tak Tenna

The end pieces are 30"' long. The 30 inch pieces form a cross. In each arm of the cross there are seven slots cut 1.5 inches apart, starting about .25 inches from the end.

The cross piece is 32 inches long. The coils are separated by 24 inches.

The center conductor terminal is 10 inches from its coil, the hot coil in Tak Tenna parlance.. The braid terminal is 16 inches to its coil, the cold coil in Tak Tenna parlance.

Some notes from the instructions:

Tak Tenna is an electrical half wavelength dipole antenna

If the antennas are not wound in the same direction tuning will be impossible.

If either spiral is cut too short tuning may be a problem.

Rotate Tak Tenna; if you see SWR change it is seeing something.

Antenna feed point changes with elevation.

The Hot spiral affects frequency.
The Cold spiral affects SWR.

It is possible that the antenna will show two minima, one at a lower frequency and one at a higher frequency, both in/around the 40M band. BRING THE LOWER ONE UP FOR RESONANCE.


This information is intended for you antenna analysts to model its performance and I will not give anyone information on the construction details (ie, how the tubing is connected together), as the vendor deserves to maintain his business.

Bob
WD6S


Title: TAK-tenna...Really that good/
Post by: W8JI on April 17, 2008, 03:13:33 AM
It's interesting to hear that two loading coils, both connected in SERIES in a dipole antenna (even at the end), can have different functions.

How can that be?

73 Tom



Title: TAK-tenna...Really that good/
Post by: IRABREN on April 17, 2008, 10:43:42 PM
Well - I have ordered one ( based upon the reviews ) - I haven't tried it yet - but I do respect the e-ham reviews. I am new -  and have built my entire station - based upon the reviews and have not been let down yet! I study the reviews carefully. I don't doubt there may be some fraud in the reviews - The reviews have led me to:
            FT-950 rig
            Ameritron als-600 Amp
            Palstar At1-Kp Tuner
            Force 12 40 XKR antenna
            DX-B alpha delta sloper wire for 160/80m
I am very happy with the equiptment I selected from the reviews. I am so impressed with the e-ham site - I made a contribution.
73, Ira, KE5STP


Title: TAK-tenna...Really that good/
Post by: N4JTE on April 19, 2008, 08:42:19 PM
Trust me, been there did that, it sucks.


Title: TAK-tenna...Really that good/
Post by: N3OX on April 21, 2008, 09:34:01 PM
"I study the reviews carefully. I don't doubt there may be some fraud in the reviews "

Ira, I don't think there's any fraud in the reviews of the TakTenna... just a bunch of people that don't know what they're missing and/or don't understand how the antenna + feedline system works.

They're actually happy with it.  I can't imagine that you would be compared to, say, the Force 12 antenna.

Dan





Title: TAK-tenna...Really that good/
Post by: IRABREN on April 22, 2008, 10:00:52 PM
Well, Dan you may be absolutely correct - but then how do you explain the excellent/outstanding rating of the "Ham Universe" review ? - An advertisement for the Tak-tenna ??( fraud ?? ) Reviewer - a good buddy of designer ??
The Ham Universe reviewer - presumably knows something about antennas and ham radio. ( deception ??) I don't disagree - with what people are saying in this thread - it makes sense that the design of the antenna would not - "make it that good" - However - I personally have yet to try it - so I will reserve final judgement.
Ira, KE5STP


Title: TAK-tenna...Really that good/
Post by: WA8MEA on April 23, 2008, 03:54:30 PM
This is why I hate the term "unbiased" when customers review products or services over the Internet.

I assume they are claiming bias because of possible advertising dollars spent with the magazines/websites/radio programs which review products.

Nothing is more BIASED than an online reviewer who:

1) Really doesn't know what he/she is talking about
2) Is a disgruntled employee or customer
3) Is a a competitor from another company
4) As been coerced into putting a favorable review on eHam because they will win a FREE GIFT from the company
5) The reviewer expects something for nothing (Like this recent Icom IC-718 reviewer.  Best dam radio for the money!  But for $500, many cheapo hams want scopes, audio synthesizers and other assorted bells and whistles found on a $5000 rig.)

73, Bill - WA8MEA



Title: TAK-tenna...Really that good/
Post by: WA4DOU on April 23, 2008, 09:15:45 PM
For $128 you can buy a copy of the Radio Amateurs Antenna Book and make a real antenna for the $88 remaining.


Title: TAK-tenna...Really that good/
Post by: K0OD on May 25, 2008, 02:30:11 PM
This log is provided as proof how well the Tak-tenna performs:
http://www.tak-tenna.com/KB4QQJ%20WAS%20Log.htm

First, I doubt many newbies recognize that those October 27/28, 2007 DX contacts were made during a contest where 59 reports are standard.

Two very rare 40 meter SSB Qs stand out amid the ordinary Caribbean and EU big guns: 6A7YRR, said to be in Egypt, and AP5A logged as Pakistan.

I operated that whole weekend on 40 in the CQWW SSB and don't remember seeing those spotted. Based on nearly 50 years of contesting, I was dubious that such juicy contacts could be made with 5 watts into a Tak-tenna. So I ran those calls thru Google and DX Summit and came up with nothing. (AP5A is shown as a possible pirate in 2006)

The 6A prefix is allocated to Egypt but it is surely a busted call or something else.

There ARE some decent Qs in the log including a couple of big contest stations in Morocco. Those were worked on 20, not 40 meters. Morocco is one of the world's great DX locations.  


Title: TAK-tenna...Really that good/
Post by: W1EBR on June 16, 2008, 06:37:55 PM
I have one of the 40m Tak-tennas, and I just purchased  EZNEC+ 5.0. I don't want to create the antenna description data by hand. Is there an algorithmic way to create the segments of a spiral, or is there a plain text format I can use as input (and output would be nice too) of an antenna description (and then maybe I'll write a short program to create the spirals with the proper dimensions?

I do want to say that Steve offered excellent support - even "pro-active" support, checking up on how I was doing in trying his suggestions to tune the SWR.

I want to understand this antenna better. I don't have a lot of free time but I can run calculations on my PC while I am doing other things :-)

Gene Risi, W1EBR