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Author Topic: Rocket 88 antenna  (Read 7518 times)
N8DV
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« on: August 20, 2009, 01:01:14 PM »

Is there anyone running the Rocket 88 antenna from QSradio.com? It's supposedly better than a G5RV at 35 feet. 73
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WB5JEO
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« Reply #1 on: August 20, 2009, 06:24:42 PM »

There web site has nothing I could see about theory of operation, methods of determining gain, or really anything else, other than a description that sounds pretty much like a description of a G5RV. Now, there being no magical incantations (like calling your bundle of wires a "Rocket88") or other than major enhancements to wire flattop antennas, you're just not going to see striking differences in gain beyond some directional changes that result from various ways the wire is arranged and the frequencies on which it's operated. Take antenna makers' claims about like you take nutritional supplement claims.

And even when a manufacturer's claims of a gain figure is technically valid, there are various aspects of how that gain is expressed that tells you how that antenna might perform for a particular task. Take-off angle is one of them, and even if given a valid angle modeled for the antenna at significant height, what that means in terms of how the radiation lobes are arranged is also something you'd like to know. And of course the actual antenna over real Earth is going to do something more less different. Low horizontal wires of no very great length just don't vary all that much from a dipole at the same height. 35 feet is not much height, and this class of antenna is always going to be pretty high angle, if not a cloud warmer. Of course, that may be what you want. And you can beat all of them by simply giving the dipole more height.

And when you're talking about antennas within a particular class, others' experiences don't tell you much about your situation. You know, if I took their radiation plots as literal truth, I'd be wondering if limiting my wire's usefulness to two directions was an okay trade-off for small gain. Not that I believe their plots. Well, maybe I should say I believe that on some frequency and at some height above some ground, the plot might look something like that.

The bottom line on this is that noticeable differences between the G5RV and whatever this thing is are going to be differences in interactions with the Earth and environment and how their radiation patterns change with frequency. Those changes with frequency are difficult to predict in the real world and will, at any rate, not be really much better or worse in terms of hearing and being heard, at least not in any way that you'll come to make sense of from operating them.
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N3OX
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« Reply #2 on: August 20, 2009, 08:57:57 PM »

"Now, there being no magical incantations (like calling your bundle of wires a "Rocket88") or other than major enhancements to wire flattop antennas, you're just not going to see striking differences in gain beyond some directional changes that result from various ways the wire is arranged and the frequencies on which it's operated"

Well, yeah... I mean for *most* antennas that's true, but this one is special:

http://www.eham.net/articles/20174
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
AC4RD
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Posts: 1236




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« Reply #3 on: August 21, 2009, 05:03:18 AM »

N3OX says:  "Well, yeah... I mean for *most* antennas that's true, but this one is special:

http://www.eham.net/articles/20174 "

 <snoooooooOOOOOOOOOOoooororrrk!>

Now I've got coffee all over my monitor and keyboard, darn it!

And it was still WORTH it!  ROFL!

I'm gonna buy some rope this weekend and try building my own N3OX special!   :->
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WB5JEO
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« Reply #4 on: August 21, 2009, 06:37:13 AM »

Finally. A real reason to seek a shorter vanity call. Think of the wire I'd save.
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KE3WD
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« Reply #5 on: August 24, 2009, 01:13:29 PM »

I remember when a Rocket 88 was an Oldsmobile...
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WB5JEO
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« Reply #6 on: August 24, 2009, 03:32:22 PM »

Funny thing about names and memory. The engine was the Rocket V8. (A 303. Very hot.) The models Olds put it into had undistinguished names that hardly anyone remembers, except maybe the Delta. But the name that never went on a car (the rocket logo did), "Rocket 88," is what everyone remembers.
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KE3WD
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« Reply #7 on: August 25, 2009, 09:50:29 AM »

That is true as I remember it also, the name was on the engine and not the car itself.  

It was the general public who called the cars that had the engine with "Rocket 88" silkswcreened across the top of the huge air cleaners by that monicker.  

Then there's the old rock song, "It was a four-fifty-five Roc-ket!"  --Which also didn't jive with the facts all that much.
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K3AN
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« Reply #8 on: August 25, 2009, 11:59:20 AM »

"The 455 was built from 1968 through 1976, produced from 210hp to 400hp, and were installed in just about every car Olds built in that period at one time or another, including the Cutlass/442, Delta 88's, 98's and Toronados (not the Omega, though)."

http://www.442.com/oldsfaq/ofe455.htm

Can't determine whether "Rocket 88" was emblazoned on this particular engine. Looks like it was called a "Rocket V8" according to Wikipedia.

 http://en.wikipedia.org/wiki/Oldsmobile_V8_engine
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K2TL
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« Reply #9 on: September 03, 2009, 02:58:56 AM »

This antenna appear to be nothing more than the Cebik Dipole by W4RNL (sk).
I have used one for years.  I don't use it because it is better than a G5RV ( which is no great accomplishment ).  I use it because the pattern of an 88 foot dipole fed with balance line and used multiband maintains a normal dipole pattern on all bands.  Unlike a G5RV or 1/2 wave dipole used multiband, the pattern becomes crazy with nulls and lobes all over the place as the frequency increases.  My personal experience with this antenna has made me quite happy.  And before the flames start, I don't care if you use one or not, hate W4RNL, love W8JI, or have a shrine erected to G5RV in your backyard.  The 88 foot twinlead fed dipole is the best multiband antenna I have used in 45 years of Ham Radio and I just snicker at the nay sayers.
Jim
K2TL
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N3OX
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« Reply #10 on: September 03, 2009, 06:56:07 PM »

". I use it because the pattern of an 88 foot dipole fed with balance line and used multiband maintains a normal dipole pattern on all bands. "

No it doesn't.

It "lobes out" into a four lobe pattern on 17m.  A **44ft** total length antenna, then, will get similarly lobey around 34MHz.

Cebik himself writes:

"If I wanted to aim at both Europe and at Australia and New Zealand on all bands from 40 through 10 meters, then the 44' doublet is the superior antenna to the longer 67' doublet. Of course, larger (102' or 135') all-band doublets break into fragmented lobe patterns at lower frequencies than the 40-meter dipole with which we started. So, if we make aiming one of the criteria for our antenna, the 44' doublet may be the way to go."

Unless you don't consider 17m, 15m, 12m, and 10m to be contained in "all bands," your statement about the lobes is incorrect.

On the Rocket 88 webpage, they show the pattern comparison for 20m.  But on 17m, the Rocket 88 has four lobes.... A good rule of thumb is somewhere between 1.4 and 1.5 wavelengths total length, the quadrupole pattern becomes comparable to the dipole pattern, period.  So you don't go lobey on 20m with the Rocket 88, but you lose some 80m performance compared to a good G5RV.

"I don't care if you use one or not, hate W4RNL, love W8JI, or have a shrine erected to G5RV in your backyard"

I respect both the late W4RNL and W8JI, think they both have made a lot of good contributions to the state of ham radio antenna knowledge,  and recognize that they have a slightly different point of view on this particular antenna Re: use on 80m.

The analysis in either case is the same.

Cebik writes:

"For either the 88' or the 44' doublet, the lowest band of use (80/75 and 40, respectively) present challenges in line losses and matching at the shack end of the line. Hence, the short doublet--only 1/3 to 3/8 wavelength on the lowest band--should be considered as a back-up antenna on those bands. "

W8JI's analysis expands on this statement that W4RNL didn't focus on much:

http://www.w8ji.com/short_dipoles_and_problems.htm

Tom's analysis is a good expansion of W4RNL's comment regarding the 88 foot doublet for the operator most interested in efficiency on 75/80m.

"The 88 foot twinlead fed dipole is the best multiband antenna I have used in 45 years of Ham Radio"

Great!  I'm glad it's a success.   But that doesn't change any facts about what a doublet is or does.  There are ALWAYS lobe and reactive power tradeoffs if you try to span all of HF... you can just slide that up or down the spectrum.

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

Monkey/silicon cyborg, beeping at rocks since 1995.
K2TL
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Posts: 40




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« Reply #11 on: September 07, 2009, 04:25:54 PM »

One of the big problems with a G5RV is the loss on the coax due to the mismatch it sees following the twinlead.  Often, the coax is running low to the ground, on the ground, along a fence, in a wall, in a basement, and generally no place the radiating coax will do you any good at all.  I prefer to have my signal at the antenna.
The 88 foot twinlead fed doublet still has a better pattern and lower loss than a G5RV.  So does most any doublet fed with balanced line and installed properly. Hams have been using a 1/2 wavelength on their lowest band and feeding it with balanced line for multiband use forever.  I did as well for probably 40 years.  The 88 foot doublet performs better for me multiband on 40 and up than does a 66 foot, and its works just fine on 80.  If a length of coax is necessary to get into the shack and avoid coupling issues, then a very short length of coax and 1:1 or 4:1 current balun does the trick.  The G5RV is probably the last antenna I would put up.  Someone asked " if the G5RV is so bad, why are they so popular". I think it is because many Hams don't bother to do a little research, or have some issue with soldering 2 lenghts of wire together with 3 insulators and some twinlead.
K2TL
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K2TL
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« Reply #12 on: September 07, 2009, 04:29:48 PM »

One of the big problems with a G5RV is the loss on the coax due to the mismatch it sees following the twinlead.  Often, the coax is running low to the ground, on the ground, along a fence, in a wall, in a basement, and generally no place the radiating coax will do you any good at all.  I prefer to have my signal at the antenna.
The 88 foot twinlead fed doublet still has a better pattern and lower loss than a G5RV.  So does most any doublet fed with balanced line and installed properly. Hams have been using a 1/2 wavelength on their lowest band and feeding it with balanced line for multiband use forever.  I did as well for probably 40 years.  The 88 foot doublet performs better for me multiband on 40 and up than does a 66 foot, and its works just fine on 80.  If a length of coax is necessary to get into the shack and avoid coupling issues, then a very short length of coax and 1:1 or 4:1 current balun between the coax and balanced line does the trick.  The G5RV is probably the last antenna I would put up.  Someone asked " if the G5RV is so bad, why are they so popular". I think it is because many Hams don't bother to do a little research, or have some issue with soldering 2 lenghts of wire together with 3 insulators and some twinlead.  Or maybe they read in a magazine how great the G5RV is and you can get a 59 report from England.  Wow!, I gotta get one!
K2TL
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K2TL
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« Reply #13 on: September 07, 2009, 04:32:09 PM »

sorry for the double post..don't know how that happened.
K2TL
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N3OX
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« Reply #14 on: September 07, 2009, 06:32:22 PM »

"One of the big problems with a G5RV is the loss on the coax due to the mismatch it sees following the twinlead. Often, the coax is running low to the ground, on the ground, along a fence, in a wall, in a basement, and generally no place the radiating coax will do you any good at all. I prefer to have my signal at the antenna. "

I detect a myth in there.  Coax doesn't radiate because it's mismatched.  Coax radiates because something is driving current on the outside of the shield.  That's independent of the mismatch.

It has internal loss because of mismatch, and it has loss  potential because of shield currents if there's no effective balun, but that's very installation dependent and not something your rocket 88 is immune to.  With a good balun and low-loss coax a G5RV used with a tuner can be every bit as effective as a Rocket 88, and *very* likely more effective on 80m.

Now, I'll grant you that most G5RV's sold today probably don't have low loss coax or an effective balun.  So there is that.

But you could be putting just as much power into the dirt around your station ground system if you didn't put a good balun between your tuner and twinlead as would be put into the dirt around a no-balun G5RV's coax.

And you could be losing more power in your twinlead on 80m than you would inside the coax on a G5RV.

A ladder line fed doublet covers more bands than a G5RV.  That's the fundamental difference if the G5RV is not put together poorly with lossy coax and the wrong type of balun to favor low SWR over all other parameters.

Yes yes, I've heard that G5RV said not to use a balun but the record's been corrected on that.

This is how to build a good one:  http://www.w8ji.com/g5rv_facts.htm

I don't have anything against the Rocket 88 except that it's a new "name" for yet another doublet... complete with comparison modeling plots and a price tag, and therefore carries some aura of being "designed" ... without suffering from being the nasty four letter word that poor old Lou Varney's antenna has become.

If this one sells well, in ten years 75m will be full of the wailing of old grumpy kilowatts lamenting them damn newbie LIDs runnin' barefoot power into their 15 foot high
Rocket 88's ... just like they do with the G5RV today.

We need to separate the performance facts and the design details from the name brand.  

"Hams have been using a 1/2 wavelength on their lowest band and feeding it with balanced line for multiband use forever"

Absolutely!  And that's a great antenna!  So's one that's longer or shorter than 1/2 wavelength by a little.  But the G5RV's matching section, if properly executed allows people to solve what is often a major problem: how to run coax to their multiband tuner-fed antenna without getting ATROCIOUS line loss.  A properly executed G5RV is actually a design... now a lot of companies have screwed up that design while keeping the name...

But this is what I'm saying.  New ham goes to W8JI's page.  W8JI says a G5RV is a good antenna and shows in detail on his page how to build a good one, then BadHamAntennaCorp sells new ham "their" version for $159.99 and it's no good.

Then someone else sells new ham some other named wire for $129.99 and it happens to work great... new ham becomes a devotee.

YOU know that a ladder line fed doublet is a good antenna.  But what it's not is something other than a ladder line fed doublet of a certain length.

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

Monkey/silicon cyborg, beeping at rocks since 1995.
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