New antenna from Sirio Gain-Master

[CDX-007]

On the MFJ it has a 1.5:1 VSWR bandwidth from about 26.800 to 29.700 with the vast majority of that spectrum covered at 1.2:1 or less. The coax used is about RG-58 sized or just slightly larger however, it is very high quality Teflon insulated. Possibly even Mil Spec as it has that appearance. There is not enough room on the coil form to wrap the choke with RG-213.

I did find it odd that they used so many turns. The last chart I recall reading showed the highest 27MHz impedance at only 5 turns of RG-213 or RG-58 at 4.25" diameter former, air core, ~8 turns if ferrite core.

I know when I'm finished testing against the Penetrator500 I'm just going to have to play and try a beefier capacitor and 213 or 1318 coax at ~5T just to see if I can load all 2400w pep @ .64.

 

[Marconi]

Eddie and all take a look at these antenna plans and notice it uses a shunted stub of coax for matching. Like the gain master . While not identical in design .I have played with this design mounted inside an old commercial fiberglass housing. I used quarter wave radials at the base straight out no angle and below the radials a wound choke coil. This antenna had 1.5 swr at 49mhz and at 53.8 mhz

The Bazooka Vertical

Later RCB

Harvey is that you? I don't recognize the handle. If not give me another clue.

Thanks for the link.

 

[bob85]

my buddy ordered a gainmaster today, he uses an imax with radials at the moment, i will try and get some analyser sweeps with the minivna when we install it,

imagine an 827 converted to centerfed dipole with rg213 and some delrin

 

[CDX-007]

my buddy ordered a gainmaster today, he uses an imax with radials at the moment, i will try and get some analyser sweeps with the minivna when we install it,

imagine an 827 converted to centerfed dipole with rg213 and some delrin

I'm imagining dissecting the Saliut and creating a 30' tall, phasing coil coupled top 1/2 wave(18'+ 6" of 3/4" fiberglass rod) over a 5/16 Gamma fed DC grounded radiator(11.3') with steep downward 5/16 radials for a phased 1/2 over a center-fed 5/8 the *same length as the .82 Vector.

(*Not including the downward radials)

Ah oh, you know what's gonna happen now...

 

[Shockwave]

Robb, I found the VSWR poor below 26.800 MHz. The GM does not appear to cover to cover the 12 meter band without a tuner. I will say the antenna maintains decent sensitivity on receive down to at least 20 MHz and will probably work OK with a tuner at low power in this range.

CDX, I believe there are variables such as the spacing between wraps that will determine what the maximum impedance of the choke can be in terms of wraps. The choke on the GM has a serious task to accomplish when you consider the RF voltage at the base of this antenna.

Because the RF voltage is the same at the base as it is at the top of this balanced antenna, I think they used more wraps with spacing to provide near perfect RF isolation. I also think it will be difficult to modify this antenna to handle multiple kilowatts.

The radome simply does not have enough room to use the type of capacitor this power would require. I suppose you could stack a few smaller caps in series to handle the voltage. I suspect the coax will fail at some point but not because of the current or heat.

This failure would most likely occur between the wraps on the choke and arc across the braid because this is where the RF voltage drops on a coax choke. This also suggests changing the cable may not cure the problem. You need better insulation on the outside of the cable.

I'm not sure how you would make a collinear antenna that used a center fed radiator constructed of aluminum. The center feed system requires a insulated radome in order for the coax part of the antenna to radiate. Placing the lower section in aluminum would certainly complicate the design even with an insulator because it will alter the velocity factor considerably.

 

[CDX-007]

Yeah, I'll probably just enjoy the SGM in the tree with <500w and call it good. If I need more performance than that the quad should cover any weak signal issues.

However, - I have a feeling Bob85 is tracking with me. I think that ice cream cone should be facing down.

 

[bob85]

what do you guys think of this idea,

827 dipole

 

[Henry HPSD]

If been following the tread along ofcourse, and wanted to give a thought aswell..

First take a look at some center fed antennas:

Antennes - Slappe Arnold
Bobs idea...
The sleeve antenna
or ordinary broadcast dipoles..
And have you taken a look at your mobile antenna ??
Etc.

Oke, here goes the point i would like to make:
Is that no one of the above is know for its 0 Angle Take off angle.
Take off angle has got everything to do with heigth above ground/ground conductivity/polarisation/antenna.
Although i must mention the normal 1/4 wave ground plane is underappriciated in respect to TOA.

So the guys referening to the 0 degree Take off angle, Yes for sure in a test enviroment i can get many antennas with a 0 degree TOA.
But that will never happen in real life. It is strange that you see plots where ones is in freespace and the other antenna is not to my believe. Perhaps someone could explain.

What also is intresting, for the guys using Eznec/MMANA/4NEC2 etc..do yourself a favour and construct a vertical dipole then shift with the sources from down to halveway.
And take a look at what TOA does.

Lol, already i feel the claims comming on about not know what eznec will or will not do...but those claims can be made from any field testing aswell.
Todays eznec is quite close to feko (that software costs a bit more than those studios).
Not that a price proves anything...but where do we stop...
As is with everything combined is strongest, guess thats in this case aswell.

Now, dont get me wrong im not a anti-guy, i honestly believe it is a great antenna...simply cause the "dont need ground" thing.

But keeping in mind that a sufficient ground system needs less radials when it is elevated.
Grrr..see where im going at again..

Regards,

Henry
11 meter Dx antenna systemx

 

[bob85]

henry, the more input the better
i agree that ground plays a large part in how antennas perform, what cebik says about upper hf monopoles over different ground is very interesting,

look at skirt monopoles, they don't need an extensive groundplane to provide a very low radiation angle.

 

[Marconi]

Well guys I think this will explain why Sirio put the connector into the coaxial radiator on the Gain Master. Pretty smart planning.

 

[Shockwave]

Marconi,

That is an interesting picture. The arc happened close to where I expected it to break down but not exactly. I thought for sure the cap would be buried inside that lump in the heat shrink tubing. Looking at this makes me wonder if they put a metallic sleeve around the black wire to serve as the cap? If you can provide more info once the heat shrink is removed, I'd be curious.

Henry, of the antennas you mention only the broadcast dipole is a true center fed antenna. Additionally many FM broadcast stations using these antennas have a TOA below 0 degrees as a result of downward beam tilt. This is done to provide service when the tower is at extreme height over the market area. Granted, this has more to do with coax phasing then antenna type.

I also agree it looks like Sirio has done the modeling in free space mode rather then over true ground. Keep in mind, when they compared the TOA to a 5/8 wave ground plane, the same conditions were used. The model still shows significant improvement with the Gain-Master over the 5/8 wave ground plane.

 

[AudioShockwav]

Marconi, good work. Do you know the power level?
Also, I saw Sirio on the Forum last night looking at this thread, maybe we can get some feedback from them if they choose to post in the thread.

73
Jeff

 

[Marconi]

Marconi, good work. Do you know the power level?
Also, I saw Sirio on the Forum last night looking at this thread, maybe we can get some feedback from them if they choose to post in the thread.

73
Jeff

Jeff, the info is on Charlie Tango. I think there was talk of 800 to 1KW on FM maybe, which is an abuse. I don't recall the specifics right now. I think Sirio sent a new harness out with an updated capacitor design, I've asked for more pictures of the inside of the shrink wrap. I think maybe they were anticipating some arcing.

I like the people at Sirio, they're smart business folks and treat their customers right, thank you.

 

[Oggy]

Check out Charlie Tango for more details

Jeff, the info is on Charlie Tango. I think there was talk of 800 to 1KW on FM maybe, which is an abuse. I don't recall the specifics right now. I think Sirio sent a new harness out with an updated capacitor design, I've asked for more pictures of the inside of the shrink wrap. I think maybe they were anticipating some arcing.

I like the people at Sirio, they're smart business folks and treat their customers right, thank you.

Yes this is Simons Gainmaster after trying some power. I have done tests now on 10 meters and not run more than 80 Watts. I do have big valve linears that I run on Ham bands , but don't intend to run QRO on my Gain Master. I do honestly think Sirio have ideas to up the spec of this area .

 

[CDX-007]

Here's what I just emailed to HY Electronics:
__________________

Dear hyelectronics_store,

Hello, You may wish to add;

Sirio have accomplished what up until now was impossible.

The Sirio Gain Master 5/8 stretches the high current node over the full 5/8 wave vertical area, adding 66% more effective RF-active area over all other brands of 5/8.

Standard metal or fiberglass 5/8 antennas lose the bottom 1/4 (2/8) wave of radiation due to reverse-phase current in the bottom 1/8 wave which cancels the next 1/8 wave above it, leaving only the top 3/8 wave as the working part of the antenna.

The Gain Master re-phases the bottom 2/8 (1/4) wave to work in unison with the upper 3/8, increasing the gain over standard metal or fiberglass 5/8 while lowering both the radiation take-off angle and RF interference without ugly radials which cause added weight, wind loading and noise.

This breakthrough design keeps your power at the horizon where other stations are located instead of wasting power to lost higher angle radiation.

The Sirio Gain Master makes all other 5/8 antennas obsolete.
_______________________

I am beginning to wish I would have waited for the upgraded version. :blush: