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Author Topic: All band verticals  (Read 13670 times)
W8JI
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« on: September 12, 2012, 04:25:33 AM »

OK, has anyone noticed the change in antennas?

Back in the 1960's, a company called Gotham sold hunks of aluminum in various form, sometimes with a loading coil and alligator clips for tuning, as cheap all-band antennas.

As the Ham population became better educated, antennas evolved into trapped antennas that tuned to every band automatically.  They had the tuning mechanism on the antenna, optimizing length and SWR without any need for tuning. The traps added very little loss, certainly much less than 1 dB total loss for all the traps. Nearly all trap verticals were within a fraction of a dB of a full size monoband vertical, with the exception of really short verticals on 80 or 160 meters.

Around 1980-90 advertisements started appearing tell people traps were lossy, and even assigning silly numbers like "one dB per trap" to trapped antennas. Uneducated consumers would go outside, count the traps, and conclude they lost 6 dB on every band because of traps. People would rush out and buy even lossier systems just to avoid lossy traps.

Some manufacturers that used traps, at least two I can think of, used traps but called them something else!! This way they say "no lossy traps" even though they had a trap that was made lossier than a normal trap just so it would not look exactly like a trap.

Some people started using coax stubs as traps, hiding them inside the vertical. Coax stubs are many times lossier than an L/C circuit, usually having a Q of around 50 or less in common "trap" lengths. A real trap might have a Q of 200-300, 4-6 times better with much lower loss, yet the companies could say "no lossy traps". They would move the feedpoint up, totally misquote some engineering data, and sell a magical ground mounted vertical that needs no ground other than a few wires they don't call a ground. My 8 foot tall mobile antenna would typically BEAT those antennas in signal comparisons. QST and another test compared one of these magical hidden coax elevated gap antennas to an old trap vertical on the ground, and the old trap vertical won.

Then, most recently, the strangest thing of all appeared. Someone re-discovered almost anything will make contacts. It was like artificial Christmas trees appearing in the woods. Many were mechanically well-built antennas, sometimes mimicking the shape and style of antennas known to work very well (groundplanes), but they relied on an antenna tuner to match and were electrically one fixed length. They were just disguised, like the traps that were not traps, so no one really thought about what they were. They were, in effect, just a short "longwire" turned up on end, and a short "longwire" was known to be one of the worse antenna styles to use for performance.

It seems to me we are going backwards in design to the Gotham vertical era, where one length of tubing was magically tuned on all bands. The only difference is we moved Gotham's tapped coil into the house so we don't have to run outside. We greatly increased the losses, because now we have an unmatched coaxial feedline, and on upper bands we have some pretty high radiation angles wasting power, but we can make contacts.

The reviews read like Gotham advertisements. All warm and fuzzy and full of love:

http://www.w8ji.com/gotham.htm
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WD8KNI
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« Reply #1 on: September 12, 2012, 04:48:20 AM »

Very good Tom. 
Kinda like the snake oil salesmen of yesteryear (one bottle cures all). It evolves around anything to make a buck, and the old statement often incorrectly credited to P.T Barnum  "A sucker is born every minute".  I also notice that the more we dumb down our testing, both in ham radio and the american education system the more this occurs. We are building a society of people who can only read a text message, something posted on twitter, or face book, all written with horrendous English and spelling.  The internet has only made it worse, as everyone is their own self proclaimed expert many in every field at the same time.  If someone doesn't agree they just shout them down till they go away.
As for antenna's we have many that think that SWR is the only meaningful measurement of antenna and they will argue even after your remind them that my dummy load has a wonderful SWR and has an almost infinite bandwidth.
My first antenna was a long end fed wire, simply loaded up the transmitter into a 100 watt light bulb, and then threw the knife switch to the antenna.  Provided thousands of contacts, was it better than some of today's designs? I think so, even though it was far from optimum by many credible published works.

Keep up the good work, articles and comments. regards.. Fred
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W5DXP
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« Reply #2 on: September 12, 2012, 04:51:20 AM »

Right on, Tom, true for everything from ham radio antennas to politics and economics: Foolish people who refuse to learn from the mistakes of the past are predestined to repeat those same mistakes (along with the same previously documented failures).
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K9IUQ
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« Reply #3 on: September 12, 2012, 04:58:58 AM »

Around 1980-90 advertisements started appearing tell people traps were lossy, and even assigning silly numbers like "one dB per trap" to trapped antennas.

Advertising can and will sell anything. It does not matter if it is a lie. Telling the same lie over and over and over makes it the truth. Just look at the Political Candidate Advertisements.  Cheesy

I bought one of those Gotham antennas. It was a real pain going outside to change the tap to change bands. But I was only 15 years old and did not know any better. I did know that any Antenna advertised month after month had to be good.  Cheesy Cheesy

Nice rant Tom, now how about taking on OCF dipoles or double bazookas or  ...  Wink

Stan K9IUQ
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WA9UAA
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« Reply #4 on: September 12, 2012, 05:08:56 AM »

Hi Stan,
Same here, I didn't know about the need for a ground plane. The appeal for me was the "easy" setup. One pipe driven into the ground and some coax. hihi
73,
Rob WA9UAA
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N3OX
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« Reply #5 on: September 12, 2012, 07:07:27 AM »

Nearly all trap verticals were within a fraction of a dB of a full size monoband vertical, with the exception of really short verticals on 80 or 160 meters.

Is that actually true these days?   I thought it was but then I've seen stuff like the results from HF Vertical Performance that you posted in this thread a while back:

http://www.eham.net/ehamforum/smf/index.php/topic,67832.30.html

This stuff has all been measured and published in HF Vertical Performance. These are actual measurements using a good protocol and test setup.

6BTV measured dB compared to full size 1/4 wave vertical over very good radial system:

80 meters   -5.5 dB
40 meters  -1.5 dB
20 meters   -3 dB
15 meters    0 dB
10 meters   +2 dB

What's up with -3dB on 20m?  I doubt a drop-in-replacement protocol where you swap a quarter wave for a trap vertical would have errors beyond a dB or so... I got maybe a quarter dB scatter with one half-dB outlier when I was swapping my short 40m vertical against my reference quarter wave here... very, very consistent.

3dB on 20m is hard to reconcile from a dissipation standpoint at 1500W, but I dunno, maybe it's manageable if it's distributed well among the traps.  Do 6BTV's eventually melt down on full-legal RTTY operation?  If I understand it the 'BTV's are among the best trap verticals; if they clock in -1.5 or -3dB on some bands that's similar to an some of the untuned UNUN fed things with reasonable feeder lengths.

What's the deal?  If I order an existing commercial trap vertical like a 6BTV and put it up here, is it going to be "a fraction of a dB" down from a quarter wave on 40m and up or is it going to be some random number 0-3dB down with surprising loss on 20m?  And if that's a brand-new antenna what happens when some moisture and bugs get in?

I have no doubt that someone who knows antennas with a decent budget and ample time could design and build a very low loss trap vertical but that's not really a comparable task to buying and installing a 2012 model BTV vertical. 
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
W5WSS
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« Reply #6 on: September 12, 2012, 07:21:36 AM »

The 1/4 wavelength single band antenna when ground mounted pushing against a radial system that has been determined to be optimized vs a slightly shorter than a quarter wave length vertical with a trap should pose equal enough field strength to the extent that the signals are unable to present any detectable differences in a lab or anechoic chamber therefore advantage trap vertical from the perspective of being more convenient as well.
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W8JI
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« Reply #7 on: September 12, 2012, 08:19:01 AM »

Good points, Dan!

I have problems in eham when trying to requate multiple quotes, so excuse any mistakes I make in formatting or inclusions.


Quote
Is that actually true these days?   I thought it was but then I've seen stuff like the results from HF Vertical Performance that you posted in this thread a while back:

http://www.eham.net/ehamforum/smf/index.php/topic,67832.30.html

I was not speaking of the 6BTV test in vertical antenna comparisons, but a general application of reasonable trap design. I was speaking of the old method using air wound coils and large ceramic transmitting caps popular in the 1950's and 60's. If we look at a good practical trap design, it is tenths of a dB below a full vertical on every band.

Since then, we have been moving backwards. Instead of making traps (which are a much better method) better, we somehow all decided to blame traps universally and go off with much WORSE systems.

Still, if we look at what data there is, the 6BTV as measured in the "HF Vertical Performance" comparisons shines compared to untuned verticals.

Look at this link: http://vk1od.net/antenna/multibandunloadedvertical/index.htm

You'll see the 43 ft vertical is never better than the 6BTV unless an antenna located low-loss tuner is used.  

Quote
What's up with -3dB on 20m?  I doubt a drop-in-replacement protocol where you swap a quarter wave for a trap vertical would have errors beyond a dB or so... I got maybe a quarter dB scatter with one half-dB outlier when I was swapping my short 40m vertical against my reference quarter wave here... very, very consistent.

My results in Conyers when I was looking at the Gap vs. an old Hustler 6BTV  vs.  a full size were well within a dB similar except for 40 and 80 meters. Unfortunately that was a paid project to test a new antenna design.

Quote
3dB on 20m is hard to reconcile from a dissipation standpoint at 1500W, but I dunno, maybe it's manageable if it's distributed well among the traps.  Do 6BTV's eventually melt down on full-legal RTTY operation?  If I understand it the 'BTV's are among the best trap verticals; if they clock in -1.5 or -3dB on some bands that's similar to an some of the untuned UNUN fed things with reasonable feeder lengths.

As for the 6BTV, I've been wanted to look at a 6BTV again and see if it is really -3dB on 20 now, or if they had a test site anomoly. Years ago I ran 1500 watts into a 6BTV on 20 for extended periods with no failures or obvious heating, so I don't believe that antenna could have 3dB trap loss. It also measured very comparable to a full size vertical, within 1/2 dB.

Like you, I think if the antenna really had a 3dB trap issue it would have frequent failures. That would be 500 watts heat in the trap with a reasonable ground.

I'm not saying these 43 ft verticals won't work and make people happy, just that a trap vertical will do better. The exception, of course, is if we get the feedline out of the picture.

I wouldn't buy an expensive remote tuner, plus still pay for the antenna and feedline, just to have a 80-10 meter system that works about the same as a simple trap vertical. What does a 1000 watt tuner that can handle the input impedance of a 43 ft vertical cost? By the time you do that system you could have a Hygain Hytower.

http://www.hy-gain.com/Product.php?productid=AV-18HT


For under $200 you could have a variety of small trap verticals that would handle 1000-1500 watts. It would work the same as a  $470 antenna plus $500-1000 tuner combo!

If advertising had not killed the reputation of traps, someone easily could have a $500 trap antenna that would equal or beat any of the $1000 combos.

Antenna design now is bolting together tubing and making up a story about how good it is electrically, when electrically it is only a length of metal.

73 Tom
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W5WSS
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« Reply #8 on: September 12, 2012, 09:11:31 AM »

Having a test site anomaly is a reasonable possibility and often causes misinterpretation of quantification where antenna analysis is concerned. where as expressed in a percentage can cause enough difference to spoil any confidence in a comparative analysis by skewing the results at a high enough percentage of field strength to draw inaccurate conclusions Unless provisions are made.... $$ expensive. The real world antenna analysis is the hardest to equate or quantify unfortunately.
As for me I know that the trap vertical family is worthy of further evolution and should be considered a basic building block in the multi band vertical family.
I have been quietly investigating these fixed length pressed into multiband service verticals and do find that if all things are optimized IE wx proofed external auto tuner,proper choking for common mode all installed "at the feedpoint then after spending all that money you have a system that does not outperform a simple trap vertical but "can" if all things are optimal meaning primarily no feedline loss in the untuned portion of the network than and only then will the system break even with a simple trap vertical.
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WB2WIK
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« Reply #9 on: September 12, 2012, 09:11:45 AM »

I worked a guy in New England last evening on 17CW.  He was running 100W to a 43' vertical and was 569 or so.

Just up the band a few kHz was the W1AW code practice session on 097.5.  Their signal was S9+30 or a bit better -- on all four of my receivers.  They run a kilowatt to a beam, but this is an awfully big difference between two stations located very close to each other.

I'm guessing W1AW is really running 5 Megawatts. Wink

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W5WSS
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« Reply #10 on: September 12, 2012, 09:25:15 AM »

Lol wik it's so easy even a caveman can do it or cave woman
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WX7G
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« Reply #11 on: September 12, 2012, 10:01:16 AM »

Tom, excellent and I like the way you didn't name names yet many of us know exactly what antennas and brands you are talking about.
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W8JI
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« Reply #12 on: September 12, 2012, 01:12:48 PM »

Tom, excellent and I like the way you didn't name names yet many of us know exactly what antennas and brands you are talking about.

I'm not intending to disrespect anyone or hurt anyone's sales, but antenna technology is really sliding backwards electrically. Some of this stuff today reminds me of the integrity of claims by Joe Gunn CB antennas.   

http://www.jogunn.com/store/antennas/super-audio-flat-series/jo-gunn-sa-4-detail.html
Quote
The SUPER AUDIO Antennas are designed with the flat side Operator's needs of high performance and high-powered operations. These antennas will handle a standard of 12 KW and have extremely high levels of audio. The SUPER AUDIO Series is designed strictly for the serious 11 Meter Flat Side operator.
TYPE: Horizontal 4 elements
    GAIN: 17.5 DB
    FRONT TO BACK RATIO: 45 DB True
    SIDE REJECTION: 45-50 DB True
    BACK REJECTION: 45 DB True
    WEIGHT: 24 lbs.
    LENGTH: 14 feet
    SWR: 1.1
    WIND SURVIVAL: 100 MPH
    POWER MULTIPLICATION: 65X
     AUDIO GAIN: 24 DB
    WIND LOAD: 3.5

Instead of building better antennas, we build better advertisements.
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G0VKT
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« Reply #13 on: September 12, 2012, 03:15:12 PM »

Tom,

I really enjoyed your post. Vertical antennas seem to stir up some strong opinions.
My favourite "miracle" antenna uses a radiating element that uses a motor to change the length so you have a 1/4 from 80m to 6m.
Very clever, until you think a little bit more.

It does not need a tuner
Except for the control unit, which is effectively a "tuner" that is useless for anything other than with this antenna.

Then consider the effective height. Hey the tall pole looks impressive, but ground mount it and think where the element is on 6m.

Then consider the price!!!!!!

Is it still a good buy?

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K0ZN
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« Reply #14 on: September 12, 2012, 09:51:56 PM »


 You hit the nail on the head, Tom.  "Amen..."

 With many hams now being less technically educated and many hams not wanting to pick up a book and STUDY and learn about basic antenna theory,
 they make themselves prey for the Madison Avenue types at various antenna manufacturers. 

 The best proof of the lack of knowledge out there is, as you point out, the 43 ft. verticals..... Following closely are all the "end fed" half wave antennas
 and all the convoluted forms of OCF's.  ALL of these antennas have issues and significant electrical compromises. Many of them do radiate (and a lot of
the RF is actually in the antenna portion....), so they keep selling.

My guess is that when we start back DOWN the sunspot cycle, towards the bottom, many of these "magic, do everything for nothing" commercial antennas will be  disappointing performers in the tougher times.....

 You get out of something an amount equal to what you put into it.......  That sure applies to antennas and knowledge of them.

73,  K0ZN
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