What W8JI says about a 1/4 wave vs. 5/8 wave

[Marconi]

Here is a thread on QRZ.com where W8JI and others comment just a few days ago concerning modeling, and as it applies to 11 meters no less:

http://forums.qrz.com/showthread.php?294930-So-Much-For-Computer-Modeling-Huh

 

[jazzsinger]

Nothing said on that thread surprises me,

i've always been a huge fan of the starduster/1/4 wave gp antennas as you know Eddie, they are cheap, robust as they are thinner so offer less resistance to wind, they have no coils to go oc/sc, they tune very easily and generally cover a decent bandwidth, but best of all they work superbly well both on line of sight and dx. give me a 1/4 wave gp anytime over one of the radialless fibreglass piece of crap antennas (a99,i max,black pirate,etc) that do little but cause olympic standard rfi.

if i had the real estate i'd have a 5/8 wave vertical, a 1/4 wave gp and a 3 ele yagi/quad, between them they cover just about every eventuality for dx. if i could only have one, i'd be happy with any of them, they are all proven performers.

 

[Marconi]

Nothing said on that thread surprises me,

i've always been a huge fan of the starduster/1/4 wave gp antennas as you know Eddie, they are cheap, robust as they are thinner so offer less resistance to wind, they have no coils to go oc/sc, they tune very easily and generally cover a decent bandwidth, but best of all they work superbly well both on line of sight and dx. give me a 1/4 wave gp anytime over one of the radialless fibreglass piece of crap antennas (a99,i max,black pirate,etc) that do little but cause olympic standard rfi.

if i had the real estate i'd have a 5/8 wave vertical, a 1/4 wave gp and a 3 ele yagi/quad, between them they cover just about every eventuality for dx. if i could only have one, i'd be happy with any of them, they are all proven performers.

I agree George, and I've said much the same thing for years, but hardly anyone listens and typically the big shots like W8JI don't discuss specific CB antennas or even allude to them in their normal discussions, but here is an exception.

I know you guys don't have any faith in Eznec modeling since Cebik told Bob the truth about how limited it is to get right, but here are my models of a Starduster vs. 5/8 wave center fed dipole that I consider close to what we should see if the Gain Master was modeled to specs including tune. This might surprise you guys, and maybe explain how and why W8JI makes such a claim.

I guess after digesting this word from W8JI he too will be and outcast regarding modeling at least.

View attachment Affects on Pattern due to height .pdf

 

[Marconi]

Nothing said on that thread surprises me,

i've always been a huge fan of the starduster/1/4 wave gp antennas as you know Eddie, they are cheap, robust as they are thinner so offer less resistance to wind, they have no coils to go oc/sc, they tune very easily and generally cover a decent bandwidth, but best of all they work superbly well both on line of sight and dx. give me a 1/4 wave gp anytime over one of the radialless fibreglass piece of crap antennas (a99,i max,black pirate,etc) that do little but cause olympic standard rfi.

if i had the real estate i'd have a 5/8 wave vertical, a 1/4 wave gp and a 3 ele yagi/quad, between them they cover just about every eventuality for dx. if i could only have one, i'd be happy with any of them, they are all proven performers.

I agree George, and I said much the same thing for years, but hardly anyone listens and typically the big shots like W8JI don't discuss specific CB antennas or even allude to them in their normal discussions, but here is an exception.

I know you guys don't have any faith in Eznec modeling since Cebik told Bob the truth about how limited it is to get right, but here are my models of a Starduster vs. 5/8 wave center fed dipole that I consider close to what we should see if the Gain Master was modeled to specs including tune.

This might surprise you guys, and maybe explain how and why W8JI makes such a claim.

The models below that are .25 is not a Starduster. I made a mistake. It is my Marconi with 4 slanted down radials, where I used 102" ss whips. It is the model I used in my modeling presentation entitled "102 in Whip" a 1/4 wave radiator.

View attachment 4611

 

[Henry HPSD]

The claim W8JI makes is already known for quite a while, and this one is correct.

@ MARCONI:

M8 perhaps it already got out of hand with guys who disagree about NEC in some thread..im sorry i missed that then, not that active at present times

You start of big ... "you guys dont have faith in modeling...."
"cebik told the truth about how limited it is to get it rigth"

But to my my believe thats a bit blown up..I recall bob just mentioning:
"Regarding the Vector 4000 cebik said it would be difficult".
Not, that it couldnt be done.

In my ears that sounds different doesnt it?
Perhaps you are rigth and there are people who do have such thougths in that case:

Besides the "truth" about NEC/MiniNec etc. is and was already out there and can for the biggest part be referred to "read the manual".
Besides that "truth almost any designer of any antenna modeling programm is quite easy to get in contact with and will reply to questions.
In fact they value people who report bugs etc.as for them it is a good input to get close to perfection.

But again the most important thing..those guys will answer honestly any question.
However if one has questions, please would do first put them somewhere else as most of the designers have better things to do then to explain to people questions wich are most of the time already described in the manual.
Infact there are complete "groups" and "forums" concerning moddeling so there is no way to hide any "truth"..the world is open, one only needs to investigate.
Perhaps i am misinterperting again as i have had the case with you before, if so..you know

I havnt seen anyone who disagrees with Eznec. (within its capability)
All i have seen are the carefull words of bob who expressed the concerns Cebik had.
Afterwords the first concerns were expressed, i have had contact with the Roy and let him have a look at one of the models.
He mentioned there isnt any indication why it isnt correct.
(taken in mind we already solved a few "problems" wich to my believe were the issues Cebik was thinking of...but thats guessing for everyone and sadly will remain the case.

If there are guys who do have no fait in Eznec, then to my believe
there is a lack of understanding regarding modeling and regarding antennas in real life.

There are "things" that computer modeling program using either Nec or miniNec or whatever, is very good capable of and there are things when a programm is pushed to the limit. Often the guy who sits behind the computer is the limit by the way...
Within thouse bounderies wich are clearly stated in all the manuals one can be more certain of how precise a antenna will function then anyone can measure in real life.
(not thinking about the cst studios in this case).

I cant put it more simple than to ask a car driver to fly with his car...
though there are exeptions ofcourse, 99,9 procent will have difficulties flying a car..and im not even discussing the about what could be called flying.

Value those with specific thougth about anything that is true or is not true,
who base it on facts or trying to write it down in such a way it is open for discussion.
Those who dont...well..he did waste a couple minutes of your life lol.

Kind regards,

Henry
11 meter Dx antenna systemx

 

[Moleculo]

What is a 5/8 wave dipole?

 

[Marconi]

What is a 5/8 wave dipole?

I simulate what a Gain Master might look like modeled. The idea in this presentation was to suggest what happens on raising the antenna above the 1.25 wavelength commented on in the QRZ.com thread link noted above. I just used the Marconi x because W8JI brought up the idea of the Starduster and the 5/8 wave dipole (center fed 22.5' foot vertical radiator) just happend to be another antenna...that was close by in my index list of models.

The choice of this antenna was easy to modify and was just a coincidence, but one I thought everyone probably knew about.

View attachment Model of simulated Gain Master a .625 wave center fed dipole.pdf

 

[BOOTY MONSTER]

"What you will find is the 5/8th wave can vary from being just slightly better than a 1/4 wave with three or more sloping radials to being much worse at low angles. Statistically the 1/4 wave is more reliable."


that was not my experience when i went from a wire starduster copy to maco type 5/8 with four sloped 1/4wl radials . both were at the same mounting location , but the 5/8 was about 2 ft lower to the feed-point (1/4 was about 19 ft to feedpoint) . and no , they were not up at the same time .

before i ever made the 5/8 i had noticed on the SD that i seemed to have a donut shaped area about 25 to 35-40ish miles away where i just didn't hear folks that other near me herd . they typically didnt hear me either then it would pick back up again . when i first got the 5/8 together on a pipe in a hole in the yard it did much better than the SD and the donut was gone . when put up to a 17 ft feedpoint tx and rx improved again . maybe the SD had a problem i wasn't aware of . but it got compliments locally , and skip being about conditions it seemed to take good advantage of those conditions compared to the contact success other locals were having . i may have been a bit biased with opinion of the success of my wire contraption , i was suprised it worked !!!!

in that situation the 5/8 was a clear winner . but i know for a fact a 1/4wgp can be a very effective antenna

 

[Marconi]

In my recent testing, when I mounted my SD'r I took a chance to get it up another 7' higher, I used part of an old RS Crossbow boom. When I stuck the boom into the hub, the set screws seemed to tightened up fine, but when I took it down later the boom was loose, with the hub just sitting on the mast.

I also found the small cap hat on the radiator was loose, and again one of the set screws was loose. I can't be sure, but I think that affected the performance...because it came in dead last on my 03/21/11 recap, and I sure didn't expect that. The antenna also react odd when I ran my analyzer bandwidth curve, and that is when I did a video showing my VOM test...where the antenna was registering a current with just one VOM set in continuity mode and with only one probe contacting the shield and/or center conductor.

Booty Monster, do you remember my talking to you about radials on your 5/8 wave? If so, was that why you slanted some of your radials down? W8JI, in a few words confirms some issues that I've claimed for years, and again nobody would listen. You wanted to know about how long and how to position the radials on your end fed 5/8 wave radiator, see here:

Nope.

The 5/8th wave depends heavily on a large highly conductive reasonably flat groundplane at the BASE height of the antenna. That groundplane has to extend out in all directions for a considerable distance. The reflection out some distance is how the antenna works and gets gain. Without that groundplane at base height for some distance, the feedline will radiate and the pattern also will not form properly. You ALWAYS wind up with an unpredictable mess because key parts of the system are missing.

The 1/4 wave with sloping radials acts as a vertical dipole. It decouples a bit better from the feedline shield, and it has no area carrying out-of-phase currents.

What you will find is the 5/8th wave can vary from being just slightly better than a 1/4 wave with three or more sloping radials to being much worse at low angles. Statistically the 1/4 wave is more reliable.

The reason you won't find CB'ers who support that is they:

1.) Generally don't understand antennas

2.) Generally don't do valid A-B tests, just like Hams don't.

3.) Like Hams, they are trained to think a 5/8th wave antenna universally has 3 dB gain.

4.) Went through the work of installing the 5/8th wave, so like a Ham it makes them "feel" it is better.

Models are, within known limits of the model, very good. When given the right input they are much better and more accurate than most people are.


73 Tom

IMO and as usual with W8JI, he likes to be somewhat evasive the way he describes things. His style makes one have to think in order to really get a handle on his ideas. I think if you read his comments here you will get his answer to your question. I will re-model one of my models to check his idea on length and angle for the EF 5/8 wave.

 

[W5LZ]

So your 03/21/11 recap was flawed because at least one antenna in that group was set up incorrectly. that tends to put the whole thing in a 'shady' light, wouldn't you say?
- 'Doc

 

[Marconi]

So your 03/21/11 recap was flawed because at least one antenna in that group was set up incorrectly. that tends to put the whole thing in a 'shady' light, wouldn't you say?
- 'Doc

I know you would like to think that 'Doc, but I don't know that to be true. On my camera there is a nice auto focus feature that also controls the light quite nicely, so there shouldn't be any shady light problems. :closedeyes:

In most of those test, I was testing one antenna at a time as I promised, rather than A-B testing, so I'll look through the stuff, check my notes, and see for sure.

 

[HomerBB]

Thanks for the interesting reading you linked, Marconi.

Just sandbagging and seeing what happens.

BTW, the first 5/8 I ever posted about building was a good antenna compared to the A99 it replaced. It has four drooping radials instead of flattened out like the most of them are. I was under the impression in that configuration it would help with matching. . . In a different location than it was up originally it seemed to not do as well. When I switched to the horizontal elements I noticed no improvement over the slanted version.

What do I think?

Only one thing, actually, without further thought - location. After reading some of the info on the links you provided perhaps I'll pay more attention to coax lengths, reconsider GP formation, and more analysis of height. It seems the one thing that no one can accurately model, or plan for, is earth type or conditions.

BTW, the 12 x 3' long GP set up on the latest 5/8 has been a dismal disappointment. I have a 102" whip above my 4el Yagi now which seems to do as good as, if not better, than the 5/8. I will be removing the radials from the 5/8 and remounting it directly above the Yagi to see if that improves its response on rx and tx.

Okay, back to sandbagging. None of this is based on knowledgeable scientific data.

 

[bob85]

eddie,
i posted a link to what w8ji had to say on his website about 1/4waves vs 5/8waves such as imax a few years ago and a couple of times since then, he talks about the imax2000 or similar no radial endfeds and what clearly is a starduster style antenna,
what he says imho answers why you see a funky pattern when you add the mast to your new top_one model,

i also posted about what cebik had to say about 5/8waves at different heights above different conductivity ground in his upper hf monopole article,

i don't have an issue with eznec,
why you would think myself and other people have no faith in nec because of something lb.cebik told me about modeling the sigma style antenna is beyond my comprehension,
plenty of people use nec to good effect, its out there for peer review,
many of my own ideas come from people who use nec,

we have used ideas from w8ji based on his models and seen positive results more than once that the j-pole camp poopoo,

lb.cebik did not say modeling the sigma style antenna was impossible, what he said was that it would be very difficult to model that antenna and get accurate results, w7el also gives us a warning in the manual.

when we test antennas we use an unmodulated carrier, same mast/feedline, make sure there is no skip and signals are stable, make sure there are no locals pumping the receivers agc,
there is always a winner and the winner is always ahead, there is no flipflopping between which antenna is best, its not scientific but it is usually consistant/repeatable,

whenever there is skip/multipath all bets are off, you can get the flipflop even when using two identical antennas on different masts.

 

[W5LZ]

Marconi,
Contrary to what you may think, I'm not happy that your testing was flawed. I am happy that YOU found the flaw and reported it. And like it or not, it does introduce some doubt.

As for EZNEC and any of the modeling programs, there will always be 'catches' in them, won't always give accurate results unless the input data is accurate and extensive. They certainly do give -indications- of what you can expect, but those indications have to be interpreted by the user. That part requires being very familiar with that program and RTFM!
- 'Doc

 

[Kamikaze]

How about someone test two identical antennas but tell the folks on the other end one is a fiberglass model and the other an experimental aluminum type?