sirio changed the top one . no longer an astroplane clone

[Marconi]

BOB85 i am very curious to know your take on this "new" antenna design.

why is a gamma match needed on a 1/4 wave antenna???

looks to me like its a 1/4 wave vertical dipole using a capacity hat on the top to make up the extra length.

we need to know where this thing is fed from and if there is a patent sheet.

i for one think it really SUCKS that they changed the design.
it was all but perfect before!

LC

loosecannon, I think this antenna is a shortened 1/2 wl dipole with slanted down ground
radials at a steep angle. I think this New Top One is similar to a Starduster or the Merlin
than it is to the original Astro Plane/Top One.

To me it looks like this antenna uses a gamma, allowing Sirio to build the kit without the
use of a supporting insulator near the middle of such a long radiator, which is almost 12'
feet long. Same idea that Maco and many others uses in the design of their beams. Using
a gamma allows the designer to use plumber delight construction. This technique provides
improved durability and helps eliminate failure prone insulators at critical stress points for
the support of a long radiator.

Sirio does not have a good reputation in this area however, because I understand they use
mostly poor quality tubing, so the idea is probably a good one in this case.

The rod of the gamma match sticks out about 2' feet, so the gamma is probably pretty long,
maybe about 3.5' - 4' feet. With this particular setup, it appears to me that it would be very
hard to nearly impossible to tune easily from below without taking the antenna down each
time to make adjustments. I can't tell for sure, but I suspect the tuning of this antenna is
really design in this antenna to be fixed, and is not actually intended to be adjustable.

Personaly I can't imagine this New Top One preforming better than the AP or the Starduster.
I see that it might respond similar to the the AP or the Merlin with top hat designs, in that
this new antenna may show improved responses to horizontal DX signals---and make your
skip a bit better. You might see a little loss in gain with local signals, however.

Like it is said, "there is no free lunch." and it likely will be costing you a lot more money for
this one and the new M400 Starduster.

 

[Wire Weasel]

Summbody needs to make an EXACT dupe of the original Starduster. They'd sell gobs of 'em.

 

[Marconi]

That dialog sounds like Zeppo Marx - with the 'boss' usage...

Isn't the change in top of this antenna meant to create more capacitance - and therefore shorten the electrical length?

BTW- weren't these antennas notorious for throwing off a lot of RFI/TVI?

And weren't they originally a 3/4 wave in electrical length?

Yes Rob, we must have our commercial refrains least we become to serious.

Yep, that is what happens when capacitance is added or increased. Avanti
originally used this idea to maintain a higher maximum current node than other
ground plane antennas and still stay within the FCC rule for height of CB
antennas, 60' feet max.

I think it is probably true that the AP antenna can cause TVI, just like any other
antenna. If the AP is soundly constructed with suitablely good materials, then it
should NOT act as you say. In fact, I find that even though it can act bad, it
has a potential in this area to be much better than most. I attribute this to the
use of a long feeder working against a suitable ground.

There has been and continues to be much discussion about what the electrical
nature of the AP is, and I don't think that will change any time soon. I have never
heard it said that it was a 3/4 wavelength now or in the past however.

I have described what I think is going on with the AP, and have changed that idea
in my mind several times. I am currently making another change in that thinking,
but for it to be complete I would have to be a lot smarter than I am. Too bad
better minds don't do some work and give us some better answers.

My latest thoughts on the AP; it is actually an end fed 1/2 wave radiating element
with a 1/4 wave open ended feeder, working against a random length grounded mast
that must be at least 12 feet to a 1/2 wavelength long in order to keep the pattern
efficiently low. This feeder idea allows for direct coax feeding at a current node that
is also grounded on the opposite side of an open loop and it feeds a 1/4 wl open
loop at the voltage node of the antenna. This closed loop then feeds on the opposite
side a shortened 1/2 wl element at the bottom end of the element, a voltage node.
This may produce a bit of distortion in the pattern due to the asymmetry as noted in
the patent, but the advantage is a very low angled for the maximum radiation intensity,
also supported by the patent.

 

[loosecannon]

bob,
you are too funny!LOL

marconi,

i think you have a pretty good handle on whats going on with this "new" design, at least it makes sense to me.

i am SOOOO bummed that i didnt buy an astroplane/top one months ago when they were still available.

its the only antenna that will work for my current living situation, and i have no leads on finding one.

oh well, maybe someone will get smart and start making them again.
LC

 

[bob85]

hey presto, knocked this together this evening, ran out of light

 

[mackmobile43]

box it up and ship it bob. you have the address.

 

[Marconi]

I put one up too!

Kidding aside Bob, that was pretty fast. How much US $ over there, how is it performing, and how is the construction?

 

[bob85]

i made it tonight from vector parts eddie, just like my comic post said
needs a good clean and maybe change a couple of tubes before i tune it, the dirty thing its sat in is an old sigma4 bottom section.

 

[bob85]

well it works but not as intended,
we started with the dimentions shown in the pic and had the anenna tuned great on 30.5mhz vswr1.04:1 x=0 on the minivna,
we altered the radiator and i hurredly cut a longer gamma tube,
best we managed on 27mhz was 1.2:1 on 27.6mhz but the bandwidth was narrow,
we now know what the problem is,
sirio have made the radials longer on the new antennas, they increased radial length by 16" taking them to 106" on the vector ( claiming a lower angle of radiation )
on the top-one sirio use 102" radials a full foot longer than the old style vector which weighs in with 90" radials,

next job extend the radials for testing purposes and see how we go.

 

[CDX-007]

A-99's

...suck?

 

[CDX-007]

...i am SOOOO bummed that i didnt buy
an astroplane/top one months ago
when they were still available.

its the only antenna that will work for my
current living situation, and i have no
leads on finding one...
LC

I have an unwanted, original Avanti Astroplane
laying on my roof that I thought I'd sell
on fleaBay, since they seem to have a real
dedicated group of followers. Email me.

The bolt holding the top-hat radials is in need of
an easy-out, which I have but haven't yet
applied sweat to, but I believe it's all there,
straight, and, ...fun to ship?

- Oh that's right, the fiberglass center stress rod is
missing so you'd have to devise one of your own,
maybe try some small size Dacron/Kevlar line
tied in a Mercedes emblem style three-legged support
from the mast to the ring every 120* like we did
to WR-007's Top One.

Seems to do the job nicely. Keeps it well centered
in the wind.

Needs a good polishing, or I'll polish it for big $$$!!

Let me know.

 

[BOOTY MONSTER]

well , its available at H&Y now .
NEW ASTROPLANE ALPHA WEB SPECIAL-Amps, CB Radios, Maco, Antennas, Meters, Coax, Mics
$114.95 + S&H .

 

[SmackDown]

interesting posts.... I have the CTE A/P copy and when I got it I downloaded the Avanti assembly instructions from another site and followed them to a tee. After putting it up and grounding it properly my Radio Shack digital meter shows 1.00 when keying my barefoot 2950 into it with no change when modulating and 1.10 when keying the same 2950 into a Nitro 300 and a small increase in the SWR from 1.10>1.13 when modulating. I've been dxing with it on 10 (yes I've got my ticket) and 11 meters and as Marconi said flatsides can't escape my ears or my mouth. I guess I've been out of touch with who's building what but from reading this thread I guess Sirio bought out CTE ???? Looking at the new Sirio design I wonder if the mast is considered the counterpoise as with the original A/P. It also looks as if the feedpoint on the new Sirio A/P doesn't electrically energize the hoop and the radials. Maybe Bob and Marconi can get more indepth on the subject of this imitator. Loosecannon this site is still advertising and appear to be selling CTE top ones Amateur Radio Antennas Made By Amature Radio Oporators Our Mission Is To Bring You Quality VHF / These are the people I bought my A/P from albeit a couple of years ago.
I'm going to post a pic of my A/P...oh and it has survived two winters and some serious wind storms > 60mph with no damage whatsoever.


73's ....."the unknown soldier' in the keystone

 

[david wicks]

TOP-ONE GROUNDING.

HI TO ALL, INTERESTING READING QUOTES ABOUT THIS SIRIO TOP-ONE AVANTI 101 COPY.ONE THING THAT I WOULD LIKE TO NO DOES THE ANTENNA BASE HAVE TO BE FIXED TO A METAL CONDUCTIVE POLE OR CAN IT BE FIXED TO A FIBREGLASS POLE MAKING IT INSULATED. IF BEING FIXED TO THE FIBREGLASS POLE CANNOT BE USED CAN A THICK WIRE FIXED TO THE ANTENNA BASE AND RUN DOWN OR INSIDE THE FIBREGLASS POLE TO A GROUND ROD OR RADIALS BE USED. NOTHING IN THE MANUAL BUT THE PICTURE OF THE ANTENNA SHOWS IT FIXED TO A DARK COLOURED POLE SAME COLOUR AS THE LEG SPREADERS. HAVE CONTACTED SIRIO ABOUT THIS BUT HAVENT RECEIVED A REPLY, REGARDS DAVID.

 

[BOOTY MONSTER]

DOES THE ANTENNA BASE HAVE TO BE FIXED TO A METAL CONDUCTIVE POLE
yes
http://www.cbtricks.com/ant_manuals/avanti/av101/graphics/astro_plane_av101_om.pdf