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Discussion in 'CB Antennas' started by dxswe, Oct 8, 2010.
New 5/8 antenna from Sirio Italy.:drool:
Gain-Master, the new reference in its class of antennas
According to Sirio, this antenna is due to be available at H&Y in November. They must be shipping the current production into their market in Europe.
I was sure surprised when I saw the internals described by Sirio for this one. If the CB world goes silent like it has with the "New Top One," then the price will drop and it'll be a bust. Could it be yet another antenna designed for dreamers only.
It looks like a very interesting antenna, but due to its reported modest power handling ability it could be in question whether or not it draws much favor in the US with CB seemingly hung up on current day raw power. I'm also wanting to see how Mother Earth affects this antenna's real radiated pattern and if we can realize the claims made---whether it's balanced as claimed, or not. It does appear to be fed at a current null for a 5/8 wl radiator, so maybe this is true it is a .625wl.
I remain open minded simply because the bandwidth curve seems to indicate something else is going on. There is a little SWR skew to the higher side of frequency to be noted in the SWR bandwidth curve and that may explain something about it being more than a simple 1/2 wave dipole if understood. It is also noted to be resonant as high as 27.800 mhz in the technical info on the Website, with a nice 4+ mhz BW to take care of both 10 & 11 meters without a tuner.
I hope this one meets expectations, because I like my 1/4 and 1/2 wave antennas, in some cases even when compared to my much bigger and longer antennas---at least on the local scene. Plus I can get those little skinny antennas up much higher and without nearly as much worry about the weight and the length.
Can't wait to see some real pictures of this thing unassembled and close up.
looks easy enough to build, or at least to try.
Very basically, Sirio has just changed their advertising, this antenna 'type' is nothing new at all, it's been around for a very long time. The only change I can see is in it's 'looks', not it's general electrical characteristics. It may show 1 - 2 dB of gain over another 5/8 wave antenna? Good grief, you can say that about any two antennas! That's more an environment thing than any electrical 'improvement' in an antenna.
'Stub' tuned? I don't think that's any particular benefit, although it can certainly make things easier in construction. The fiberglass thingy is also one of those 'ease of construction' things. (Oh boy! More fiberglass/metal controversy/debates!)
Got to say it's probably going to 'help' their sales, maybe, so it ain't bad advertising. It's also not exactly a super reference though, guess that just depends on what 'class' of antenna it is, huh?
A Big Stick with a capacitor between the middle/upper part of the radiator - and a built-in RF choke at the base. Cleverly packaged and marketed; built with the right materials.
Probably will work well. But to say that they have beat the common-mode current problem of the Big Stick - has yet to be seen. Think it is a matter of the power put in it - as this would make the difference - right?
the only difference more input power would make to common mode current is a stronger rf field radiated from the coax with more disruption to the radiation pattern and possibly worse rfi.
less power won't stop common mode current but may reduce some of its detrimental effects.
if an antenna is properly balanced as this one may well be then common mode current is eliminated and the coax effectively becomes a balanced feeder with equal and opposite currents trapped within the inner of the shield eliminating coaxial radiation and its adverse effects.
i wouldn't be too quick to write off sirios ability to improve on the big stick design,they managed to improve on the avanti sigma 4's design from a signal not mechanical point of view,which in itself was no mean feat.they may not build the best mechanical antennas but they make very effective radiating antennas.
i do agree though it still has to be seen.paper claims are one thing,reality is something completely different,but on this one looking at the design i wouldn't be at all surprised if they have produced something a bit special.
theres plenty of electrical changes built in to it.
if anything from a manufacturing point of view a fibreglass antenna is more difficult to construct than aluminium,its just easier to put together for numbnut cb'ers who can't setup aluminium antennas properly,the term used in the uk is idiot proof.
i don't see what relevance an environment thing has when it comes to this antenna,its not designed to be easy on the eye,its designed to perform,the fact its easier on the eye than a 5/8 wave gp is probably insignificant if you appreciate the thought that has gone into designing it.
Everything around an antenna affects that antenna, what it's near, particular things that may be around it, etc, etc. All of those things can and do affect an antenna's impedance, no way around that, it's absolutely normal behavior.
It's been quite a long time ago, but I put together an antenna simular to this Sirio new one, it used two sections of coax, one a 'stub', connecting to a vertical 5/8 wave length of wire (no capacitor though). The whole thing mounted on a chain-link fence into a tree. It worked just dandy. Wish I still had the information about the particular coax and lengths etc. But, that's gone and I can't find the 'old' information anywhere. Oh well... if it were easy it wouldn't be any fun!
With respect to power handling on the Gain-Master, it is only 1000 watts PEP. When my sample arrives in about two weeks I'll be able to determine how difficult this antenna is to take apart. I've already though about how to increase it's power capacity if this is possible. Depending on the room available inside the radome, one might be able to replace the cap with a small doorknob or at least a Semco metal cased mica.
I suspect the internal coax may be limited too. My first thought was just replace it with some Teflon coax but then I thought about possible changes in velocity factor effecting length that would need investigation. I'm also curious if W5LZ's 5/8 wave vertical was fed in the center with the coax choked off like the Gain-Master? It would appear this is the trick for the lower TOA.
i think you'll find this antenna is designed to be mounted in free space seeing as its mountable from the end,choked for cmc and isolated from the mast.which pretty much leaves the environmental effects non existant except from height above ground and type of ground.
Fed in the 'center'? Just depends on where/what/how you consider the thing as being fed. Where do you think it starts? That Sirio antenna is NOT center fed, it's end fed using an impedance matching device. That might put the 'feed point' approximately in the physical 'center' of the thing, but that certainly does not mean it's center fed.
Wanna increase it's power handling abilities? I think you'll find that antenna was never meant to be taken apart, so that might be a lot of fun all by it's self. Power handling abilty does depend to some extent on the 'quality'/characteristics of components. But, the state of 'tune' of the antenna can make a much greater difference than just high rating components.
Good luck with it.
Designed to be a 'free space' antenna! That's true, but how many antennas ever wind up being in anything resembling 'free space'?
That choke is a sign that there are factors affecting that antenna, some of which has to be what it's 'near', or 'near' it.
The RF 'ground' for this antenna is the feed line, just like the 'A99' and Imax antennas. Being 'isolated' from the supporting device and dirt ground does not provide any significant benefits RF-wise. Just depends on 'how' that 'isolation' is used or compensated for. If it's not 'compensated' for, then you have a 50% chance of it not being the 'best' solution. That's a hell of'a lot better odds than winning the lottery!
The way RF sees the Gain-Master is totally different then the way the eye sees it. The antenna is absolutely center fed with the coax making up the lower half of the radiator. Because this internal coax is part of the radiator it requires the choke to define the location where the radiator ends. This is done specifically to insure the feedline does not radiate like many other splatter sticks. Being isolated from the mast and feedline provides significant benefit to the Gain-Master since without this the antenna could not be center fed and would lose it's TOA advantage.
I will agree with Doc`s point here, I do not think it is center feed, and I do not think Sirio claims that is is a center feed antenna.....
The quote says "Behaves as a center feed antenna" Not that it " is " a center feed antenna.
Again, from Sirio, " A balanced Antenna that function`s as a center feed Dipole"
Note the Antenna Phase center statement.
I think it is indeed a end feed antenna that has been designed to "act" like a center feed antenna, with a slight gain ( 0.6 db ) due to creating a balanced antenna where the RF currents on both half`s of the antenna are "in Phase " and the advantage of pulling the angle of radiation down to horizon.
This is just how I look at it, I do realize that the coax termination is "At the Phase center" but over all, the antenna ( at least to me) should be considered a end feed.
This Part is simply a war of words so to speak, and bases on were one look`s at the "starting point" of the antenna.
The advantage of the 5/8 antenna over other design`s is due to the fact that it has a lower angle of radiation , And the Gain Master look`s to take advantage of this even further as well.
Now , the 64 million dollar question.....
In real world testing, will it live up to it`s
"1-2dB, corresponding to 26%-58% more gain" claim as is posted from there testing in the modeling.
The Built in Choke is a good design to de couple it from the Mast, and the posted bandwidth looks great, the biggest downfall i see in the data is the 500 watt power handling limit....
I can not wait to see some hard real world data from user`s.
From an RF point of view it behaves as a center fed antenna. That's why I say it doesn't look center fed to the eye but to RF it is. It is the same as saying it behaves as a center fed to RF. There is no ground for the antenna since it also behaves like a balanced vertical antenna.