Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: Prev 1 [2]   Go Down
  Print  
Author Topic: Petlowany Antenna  (Read 4270 times)
KD0AFK
Member

Posts: 245




Ignore
« Reply #15 on: September 02, 2007, 01:41:32 PM »

I finally got mine built and tuned. The SWR is at about 1.4 but the reactance is at around 14. Any suggestions? I would like to see how well it will perform so would anyone like to have a QSO session with me?
Logged
KD0AFK
Member

Posts: 245




Ignore
« Reply #16 on: September 02, 2007, 07:05:01 PM »

here are the photos of the antenna hoisted up and a close up. Looks pretty cool and works pretty well. Like I said in the last post, the reactance is a bit high. A balun is probably needed for that. It seems to cancel noise out. I tune to a QSO in progress with my tarheel and then switch to the petlowany and rotate it to the best signal and the comparison is unbelievable the noise is allot less.
Logged
KD0AFK
Member

Posts: 245




Ignore
« Reply #17 on: September 02, 2007, 07:06:02 PM »

here are the photos of the antenna hoisted up and a close up. Looks pretty cool and works pretty well. Like I said in the last post, the reactance is a bit high. A balun is probably needed for that. It seems to cancel noise out. I tune to a QSO in progress with my tarheel and then switch to the petlowany and rotate it to the best signal and the comparison is unbelievable the noise is allot less.
http://img167.imageshack.us/img167/6647/picture004ou8.jpg
http://img108.imageshack.us/img108/4499/picture005bs4.jpg
Logged
N3OX
Member

Posts: 8847


WWW

Ignore
« Reply #18 on: September 05, 2007, 08:21:57 PM »

"One thing that Dan failed to mention is the statement "it would cost you more to build one than to buy one from us." "

Did it?

- - - - - -

Sorry I didn't get here earlier... how have the QSO's been going on it?

Nice looking implementation by the way.

Logged

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

Monkey/silicon cyborg, beeping at rocks since 1995.
KD0AFK
Member

Posts: 245




Ignore
« Reply #19 on: September 06, 2007, 04:31:21 AM »

Nope, Cost me around $15. I haven't gotten any offers on the QSO. I tried to set one up earlier but chose the Marine NET frequency. I would still like to set up a QSO on the 20 meter national calling frequency 14.286 or close to there but I am not sure what time of day would be best. It seems that 20 meters has been opening up around mid day here in the states.
Logged
KD0AFK
Member

Posts: 245




Ignore
« Reply #20 on: September 21, 2007, 06:25:32 PM »

I don't know how well it works because I tried to set up a QSO session but nobody would help me out.
Logged
KF4KQI
Member

Posts: 30




Ignore
« Reply #21 on: September 25, 2007, 09:30:41 PM »

What times do you normally operate, and what time zone?
Logged
KG4RQO
Member

Posts: 2




Ignore
« Reply #22 on: October 13, 2007, 04:23:09 AM »

As we enter "winter" propagation patterns on 20, it may be tough to get someone to help you out in the evenings.  From here in Central Florida we lose the Northeast U.S. shortly after sundown on many evenings.  One of the other contributors to this topic asked about your possible locations and operating times.  Perhaps with that information a schedule could be set up.  14.300 is a good place to "meet and move off frequency" (see www.14300.net)
Logged
KI4OCF
Member

Posts: 2




Ignore
« Reply #23 on: March 10, 2008, 11:01:23 AM »

Hey KD0AFK,

I'm checking to see if you've settled on a personal opinion about the spiral-coil/Petlowany antenna clone.  I realize that you may not feel comfortable or eager about posting your results here, feel free to lookup my address on QRZ.COM.

I've read most of this thread and noticed the reaction of many members is similar to what I've seen elsewhere on the net regarding this subject.  I'm glad to see that you've actually built it and tested it instead of just poo-poo'ing the design without any DIRECT experience with it.  

**A machine that can fly around like a bird, carrying people across the country!? the ocean!?  What a joke, everyone knows that only kites and birds can fly and  besides, with all that cargo and people on board, it would never be 'AS EFFICIENT'!!**

It continues to amaze me how negative some people can be behind the safe bars of the internet, especially when confronted with an issue such as this; one which will never waste any of THEIR OWN precious time or effort (oh, except the time they make to assert their 'expertise by proxy').

Ok, great!  We get the point, its a hat-loaded, shortened dipole, which any builder would EXPECT to be LESS EFFICIENT than a full-sized 65'-long wire dipole.  But, can I build one for $15 so that I can work 40m better than from my 15m inverted-V from inside the 17' wide attic of my tiny, HOA infested duplex?  That is what I want to know.

Also, as antenna building IS my favorite part of this hobby, I'd like to spend more time building and testing than buying and accepting.  We all learn as we go, and while much knowledge CAN BE extrapolated from similar experiences, but not all can, and the only REAL DATA is actual test data, not conjecture.

Maybe I'm venting here a bit after months of trying to find dimensions and real data about this design, the whole intent of the original post's requests.  Like the builder, I've spent a lot of time fishing through hundreds of replies by the nay-sayers and have not found any plans or dimensions to go by.

The most aggravating part is that after he went ahead and built it, no fellow ham would bother to help with an on-air test, even after his repeated requests for help... everyone just disappeared.  What, no one wants to PROVE THEY WERE RIGHT and that this antenna isn't worth building?  Or were they perhaps scared that their negative comments may not have been as relavent or accurate as they once thought?

I'd be interested in the BUILDER'S opinion or an opinion from anyone else WHO HAS BUILT THIS ANTENNA in the spirit of experimentation and cheapness.

Be kind everyone.  Remember, this is a H-O-B-B-Y.

73,
KI4OCF








Logged
KI4OCF
Member

Posts: 2




Ignore
« Reply #24 on: March 10, 2008, 04:09:14 PM »

I would like to clarify my point from my previous post and say that I believe there HAS been some relevant dialog in this thread, and I'm glad to see that it has sparked some beneficial attention aimed at getting to the bottom of this compact design.

I should have specified more clearly that I am talking about the nay-sayers and those who just have to get their opinion in when it isn't relevant to what was asked.  When you ask for help, you are usually awaiting information from informed members about your project, and it can be very dissatisfying to see little information posted about the question you asked.

I think I'm just soured on the pitiful state of internet forums as a whole, but sadly it tends to be A representation of the general publics declining etiquette.

For example, when you go on a forum and ask a specific question, such as:

"Does anyone have construction dimensions for this antenna?"

you immediately get barraged with "I think that antenna sucks (though I haven't ever used or built one)" and "why don't you blah blah blah instead".  Whats so hard to understand about the question?  Either you have direct experience or you don't.  I don't remember seeing:

"Which is better, a 5-element 40m single-band beam on a 200' tower or a 3' compromise antenna of unknown effectiveness mounted in my attic".  The poster should not have to justify why he's building an antenna in the first place.  Maybe some of the nay-sayers would feel better if a poster said outright that "I would really like to apologize for wanting to build this antenna, but I only have 3' of extra space in my one bedroom house and..."?

If anything off-topic, why not post about another antenna which takes up the same amount of space and is more efficient than the Petlowany, like..... ?  I'm sure if a guy could slap up a full-size beam for under $15, he would.  Wouldn't we all?  It's a given people.

I'll anxiously await answers to the questions that were originally asked, and maybe by page 10 or 20, we'll have an answer, even if we and everyone else who searches for the subject in the future has to weed through a hundred posts to finally find it.

Yes, I'm stepping off on my soapbox now.

And yes, sorry for another irrelevant post.

=D





 
Logged
KB5WVK
Member

Posts: 25




Ignore
« Reply #25 on: March 30, 2008, 08:18:44 PM »

Cmon guys where are the antenna guru math guys?

Don;t we have software we can plug this into and play with?
Like additional coils, directorsreflectors and spacing?

At least a formula.

Or is this just a flying tuned circuit that gets its inductance from the coils and capacitance from the disks beings spaced just rigt?

Is this an antenna or an outdoor dummy load?
 
Logged
VK3AIF
Member

Posts: 5




Ignore
« Reply #26 on: April 04, 2008, 08:21:35 AM »


Hello all,

I will throw in my uninformed tuppence worth into this debate for what it's worth.

I have just modeled half the antenna over a perfect ground using many assumptions as I do not have construction details available and there were no surprises in the figures calculated.

You may well ask why only half the antenna?  Well in my opinion, if the second half is a mirror image of the first it is easy to extrapolate the figures obtained from the model to include the missing half.

Firstly, as I understand it short antenna in terms of wave length tend to have low radiation resistance and higher losses that their longer counterparts.  If you still manage to acquire a good match, much of the feed point resistance is made up of loss Resistance that is wasted as heat as energy can neither be created or destroyed.

A typical short antenna R could consist of R radiation say 3 ohms loss R made up of ground losses say 12 ohms and loading coil losses of another 20 ohms = 30 ohms = 50/35 = 1.43:1 SWR.

The results from my less than ideal model are as follows:

   perfect
   conductor   Cu wire      Fe wire

Res ohm   1.044      3.993      81.56

Gain db   4.77      -1.06      -14.18   

swr on   26.5:1      6.93:1      3.46:1
25 Ohm
line (half of 50 ohm)
   
conductor dia was 1.6 mm in all cases. Al wire figures were close to Cu so not presented here.

For the full antenna, R values can be doubled and 3db added to gain figures swr should be right for 50 ohm line.

The gain figures do not take other losses into account which can be large in the concentrated field around physically short antenna.  Perfect grounds and free space is pretty rare where I come from.

I am not trying to knock the antenna in any way as it could be the perfect solution for some, but I am aware of it's probable limitations then again any antenna is infinitely better than none.

I look forward to reading and hearing about peoples findings on this compact antenna and there has been a bulk order from a group of the local Amateurs here in VK3

Cheers
Logged
VE3RPF
Member

Posts: 1




Ignore
« Reply #27 on: October 07, 2008, 12:32:30 PM »

Antenna theory is complex and not well understood.  At least this is the case after reading many of the comments here.  Even the so called experts will tell you they don't completely understand how antennas work.  They can theorise and speculate.
If you have not tried the Tak-tenna, don't be so quick to write it off.  Chances are you don't have a clue about what you're talking about.
Logged
WD4HXG
Member

Posts: 186




Ignore
« Reply #28 on: October 13, 2008, 11:23:35 AM »

On the site:

http://www.tak-tenna.com/Route%2066%20Special%20Event.htm

the testimonial from a user states:

"The TAK was a few S-Units lower,"

1 A few "S Units" is a substantial difference. What is a few "S Units"? 2 or 3? At 6 dB per "S Unit" that implies it was worse by 12 to 18 dB.  If you are running 1000 watts CW as the ad indicated it would handle, you would have an effective radiated power of less than 63 watts at just a 2 S Unit difference and less than 16 watts for a three S Unit difference. Or if you are mobile that would be a paltry 6.3 watts for a barefoot 100 watt rig.

2 The site states that the Collins Radio Association

(Tested, Proven and Endorsed by Collins Radio Association...CRA web site)

endorses his antenna but when I follow the link I can find no endorsement. Either there is none, the link is broken, or he is a poor page designer.

3 He indicates that the SWR (Return Loss) data yields the usable bandwidth. This is extremely misleading. Yes the rig will load but it provides no useful information on the antenna radiation efficiency. The user testimonial does a much better job than the VSWR does at indicating how well the antenna radiates and the testimoinial is not an objective repeatable measurement technique.

A 50 ohm resistor will yield a 1.1 to 1 VSWR but not radiate worth a damn. He needs comparative field strength data - in other words he needs to conduct measurements where a resonant half wave reference dipole and his design are measured on the same range.

-------------------------------------------------------

Does it work? That depends on your definition of work!

On 20 meters yeah you can make contacts but an 18 dB difference is a tremendous difference. When the other ops are after the rare DX in a pileup you can only hope for leftovers. Guarantee you a signal 12 - 18 dB stronger than yours will get the attention. It is like the guy with a Heathkit and dipole 10 feet off the ground going up against the guys with 1500 watts PEP, and a four element yagi on a 65 foot tower.

It is a good way to turn a Kilowatt class station into a QRP rig in my opinion.
Logged
N3OX
Member

Posts: 8847


WWW

Ignore
« Reply #29 on: October 13, 2008, 10:56:58 PM »

". Even the so called experts will tell you they don't completely understand how antennas work. They can theorise and speculate.
If you have not tried the Tak-tenna, don't be so quick to write it off. Chances are you don't have a clue about what you're talking about. "

Well, I'm going to write it off.

I'm not personally ever going to bother building a TakTenna type antenna unless I get really bored.  I did take the time to build a model of an antenna with spiral end hats.  You can play with it if you want:

http://n3ox.net/files/eznec/N3OX_spiral.ez

And here's just a picture for the non-EZNEC folks out there:

http://n3ox.net/files/N3OX_spiral.jpg

The problem is, unfortunately, that I'm sure the details of the antenna are a little off, and people who don't understand antenna theory will nitpick about the pitch of the end spirals and the type of wire and so on and so forth.  Apparently the "real deal" is off center fed too...

So there's no real way, other than me spending some money on an antenna I know has no place in my backyard (because I have a lot of guaranteed better ones), for me to test an actual TakTenna against what I've got.

I do know how antennas work.

You run some current through a wire and the accelerating electrons create an electromagnetic field, some of which escapes as radiation.  If you shorten the wire a lot, you have to run a lot more current to get the same radiation.

Part of what this means is that ohmic loss becomes more important in small antennas.  You can try to eliminate it with heavy conductors, but that will narrow your antenna's bandwidth because the Q will go up with decreasing resistance.  For half-wave dipoles, no one cares much because the radiation resistance is sufficient to broaden the antenna's response to something useful.   For very small antennas, either 2:1 SWR bandwidth will be very narrow or the antenna needs to be very lossy.  That's just a fundemental fact.  Sometimes it's OK to trade off loss for bandwidth, or you can make the antenna remotely tuneable, like a magloop.  

My TakTenna model shows pretty good efficiency.  The antenna is maybe 4dB down from a full size dipole.  However, my model also has a 30kHz 2:1 SWR bandwidth!  That's not uselessly narrow, but it will require a lot of retuning to cover the band, and you can't remote control that.

The "real deal" TakTenna has a much wider advertised bandwidth.  Hence, I conclude it has more loss (quite a bit, in fact).

There is only one end run around that... let the feedline radiate, perhaps even encourage it to do so.  If you do it right, you can end up with a top fed, quite tall vertical, the combined feedline+small antenna give you a higher radiation resistance and possibly a broader bandwidth without simply adding loss.  
K4SAV has done some good work modeling that configuration, the Tak-Tenna as top-fed vertical driver.

http://lists.contesting.com/_towertalk/2008-04/msg00339.html

But you'd get even better results if instead of using the vertical coax feed as your ad-hoc antenna, you used an equivalent vertical run of tubing or wire as a vertical fed at the bottom.

To each his own, but you're not going to convince me that I have to personally try each and every antenna out there to check how they work.  On this one, it either works as well or worse than a conventionally end loaded 3 foot wide dipole, or it works as well or worse than a random wire installed just like the coax run is.

That doesn't mean it's not good for some people in some situations, but I'm perfectly willing to pooh-pooh it without actually trying it because I can imagine better antennas being installed that stay within every single constraint of the installation of one of these.

I don't know what Shawn's status is anymore, but I do wonder what the story ended up being with this antenna.   It'd be nice if he got all sorts of answers to his CQs to vindicate the "you just gotta try it" crew, but who knows ;-)

73
Dan








Logged

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

Monkey/silicon cyborg, beeping at rocks since 1995.
Pages: Prev 1 [2]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!