New antenna from Sirio Gain-Master

[MrSuburban]

Makes me wonder if there's a way to mount the Imax upside down so the feed point is on TOP... :blink:

Are you comparing antennas or mast height?

If you compare a ½λ dipole to an end-fed ½λ and placed the two feed points equal, the one with the bottom end feed point would always have the benefit since it would always be taller, however, when you mount a bottom-fed Imax or Penetrator on the same mast & height as the Sirio Gain Master center-fed 5/8 dipole, the SGM still wins.

Perhaps we can draw from this that all center-fed antennas of similar wave portion are superior to end-fed?

I don't consider that a benefit of the feed point as much as a benefit of the overall design allowing the out of phase end current to be realigned into non-destructive helpful current now in the center.

If it were feed point height alone that dictates performance, simply turn the end-fed 5/8 design upside down and you'd then have the feed point on top, (you can't get higher than the top!!) - but would it then outperform the center-fed Sirio because the end-fed 5/8 feed point is now on top?

NO, because the top-end-fed 5/8 still produces the same out of phase end current as does the bottom-end-fed 5/8 even though the feed point height would be as high as possible.

So it seems to me that it's not just about the feed point height, it's the entire design that either performs or doesn't.

we are comparing antennas when doing so the feed point must remain constant with the 2 otherwise you arent playing with a level playing field. Any antenna you are comparing that is placed higher will naturally have a advantage no matter how slight it may be. Other wise you take away the advantage a 1/2 wave has over a 1/4, or a 5/8 has over a 1/2 etc.


This may be a bad analogy but say Me and you get in a fight Im 6'4" you are 5' 8" are you supposed to climb up on a chair so we are now equal height, no it is what it is. In basketball there are short guys (1/4 waves) and there are tall guys (5/8 waves) do they somehow try to level the playing field? No each one is good at something the other isn't good at.

Lets say you have a tower 50' with a 10' mast you have a 1/4 wave on top and want to try a 5/8 wave GP do you remove the mast pipe to lower the 5/8's wave or do you install it in same location and test it. You are trying to take away the advantage that the longer antenna has to somehow make them equal. Turning a antenna upside down is plain dumb think of how the antenna radiates and you will see how you are incorrect on this thinking.


I see guys in this thread who certainly sound very smart reading their posts yet i see them testing antennas with another antenna of the same freq in the near field and yet dont think that will have some sort of interaction ??

Thats why when antennas are modeled in free space to take away any difference from ground it is antenna vs antenna start adding the ground in and varying antenna heights and now you arent comparing apples for apples.


Take a 1/4 wave GP vs a full wave GP your theory would be to put both tips even, if so the 1/4 wave would have a distinct advantage as it's feed point would be 3/4 wave higher which will provide more gain and different TOA etc.

 

[CDX-007]

Remove or see below

 

[CDX-007]

we are comparing antennas when doing so the feed point must remain constant with the 2 otherwise you arent playing with a level playing field. Any antenna you are comparing that is placed higher will naturally have a advantage no matter how slight it may be. Other wise you take away the advantage a 1/2 wave has over a 1/4, or a 5/8 has over a 1/2 etc. [I'm not sure you're tracking with Marconi regarding feed point height...? - He's referring to the point on the antenna where it is fed, not the mast height, as in not changing the mast to accommodate a bottom-fed ¼λ so it's tip is as high as the bottom-fed 5/8λ, but what he is referring to is the location on the antenna shape where the feed point feeds it, as in the bottom, center, or near top like the 'Top One' ]

This may be a bad analogy but say Me and you get in a fight Im 6'4" you are 5' 8" are you supposed to climb up on a chair so we are now equal height, no it is what it is. In basketball there are short guys (1/4 waves) and there are tall guys (5/8 waves) do they somehow try to level the playing field? No each one is good at something the other isn't good at.
[Exactly, that's why basketball players tend to be tall, they tend to have the greatest advantage in MOST situations, an argument in favor of equal mast height comparisons, which is what I voted for.]

Lets say you have a tower 50' with a 10' mast you have a 1/4 wave on top and want to try a 5/8 wave GP do you remove the mast pipe to lower the 5/8's wave or do you install it in same location and test it. You are trying to take away the advantage that the longer antenna has to somehow make them equal. Turning a antenna upside down is plain dumb think of how the antenna radiates and you will see how you are incorrect on this thinking. [Gives it a higher feed point in the design, but doesn't change the performance, now does it. - Refer to the 1st comment above]


I see guys in this thread who certainly sound very smart reading their posts yet i see them testing antennas with another antenna of the same freq in the near field and yet dont think that will have some sort of interaction ??

Thats why when antennas are modeled in free space to take away any difference from ground it is antenna vs antenna start adding the ground in and varying antenna heights and now you arent comparing apples for apples.


Take a 1/4 wave GP vs a full wave GP your theory would be to put both tips even, if so the 1/4 wave would have a distinct advantage as it's feed point would be 3/4 wave higher which will provide more gain and different TOA etc.

Still sounds to me like you're missing the core issue of feed point height. I think you & I basically agree on your point, I'm just not certain you are seeing Marconi's point.

 

[MrSuburban]

Still sounds to me like you're missing the core issue of feed point height. I think you & I basically agree on your point, I'm just not certain you are seeing Marconi's point.

I don't think you and I see the same point, me and Marconi seem to agree upon the same thing the feed point height (where the coax actually feeds the antenna) needs to be the same height from the ground on both antennas not raising the shorter antenna up so that the top of the antennas are the same. If you believe that theory then you and I are in agreeance...

CDX-007 wrote:
[Gives it a higher feed point in the design, but doesn't change the performance, now does it. - Refer to the 1st comment above]

Not sure what you are saying it gives it a higher feed point in the design??

It certainly changes the performance, You are missing the point changing the feed point height certainly changes the pattern and performance, if you are comparing 2 antennas they are both to be mounted the same height from the ground, otherwise the test is BS as you are changing the parameters. If you model antennas you can see this clear as day.

Happy New Year

 

[MrSuburban]

So what your saying is if you put a I-max 2000 on a 40 ft mast and the new
Gain Master on a 30 ft mast the playing field is closer to equal.

No, I have no idea where you gleaned that from my post, what I am saying to compare 2 different antennas equally the place where the antenna is fed needs to be the same height above ground on both antennas. If ones feed point is higher you are giving that antenna a advantage.

 

[MrSuburban]

By this statement wouldn't that mean comparing any one antenna to another equates to :headbang and should be avoided?

Let's make this test really really easy for everyone mount the antennas on the ground now the feed points are all the same and you are comparing the antenna none will have any advantage and no ones favorite antenna will win either... :headbang:headbang:headbang:headbang

 

[MrSuburban]

ive always checked base antennas at same pole/tower height
same location,same coax ,so the ONLY a change is the antenna
mounting one higher than the other .the one mounted higher
should win every time id think .cause height = might thats why
i mount them the same height and everything else the same
this elimates the variables .well ones i know of anyways..lol

Good man


Ps: where the heck is Napco when you need them. :glare:

 

[Shockwave]

When I worked for a Motorola authorized business in the 2-Way field, I saw an interesting installation take place with a 5/8 wave low band antenna. The city had been using an end fed half wave mounted on top of their public works building. When cell phone towers first started going up, one was planed for the parking lot at the public works building. The city filed with the FCC to change antennas to a standard 5/8 wave ground plane and increase height to 160 feet on the new tower.

Their request was granted and the antenna was installed side mounted with standoffs at 160 feet with very good coverage. Although I think they had to accept a slight reduction in transmitter power at the base. This antenna worked great until the solar cycle peaked and the low band frequency was jammed up with stations across the country. It wasn't my suggestion at the time but one of the guys in the shop said to use the side mount to hang the antenna from it's base upside-down.

This indeed altered the radiation angle of the antenna so that it was much less responsive to angles arriving from DX and still maintained a strong signal in the intended 10 mile service area with no dead spots. I mention this because it does simulate a top fed ground plane and indicates this particular installation does not perform in DX. Some of this may be directly related to the full 1/4 wave ground radials being on top or the extreme height. I tell you it looked ridiculous but it served the clients need well.

 

[Oggy]

I was just trying to get a grasp on what was posted a couple of threads above.
But your thread above this one cleared up a lot.
Just from what I have read here I feel the Gain Master may be
a little better than some of the bottom loaders out there.
I haven't bought one yet but I'm giving it some thought.
My biggest worry is mounting it above a 4 element beam.
From what I have read there might be some concern mounting
the GM to close to other antennas.

Well my Gain Master is mounted above three stacked Ham band Yagis on a steel lattice tower and works superbly...check out the first video!.........Happy New Year WWRF guys...Dave in the UK.

 

[bob85]

NAP-CO®

 

[Marconi]

Hey Bob, did you ever scan the Gain Master with your MiniVA?

I did my scan and got two SWR dips, one in the middle of CB and the other across 28 mhz with both analyzer and inline meters showing 5.2 mhz or more bandwidth.

As you will note in the attached BW Report, my Antenna Work Sheet form does not cover such a wide bandwidth very smoothly, but the useful dips in the important areas that this great antenna provides can be easily noted.

View attachment GM Bandwidth Curve 123110.pdf

Even though I'm not seeing the increases in gain that all of you guys are seeing, the great bandwidth can be useful to some operators that want to work both 10 & 11 meters. I work my amp on my GM just about every day and no problems thus far.

Now that I have several weeks of comparison work with the A99 vs. the GM, with both side by side and then each alone, I find there is little difference with both antennas mounted on the same mast at about 35' feet high to the mounts. The GM showing an average S signal of 7.2 vs. 6.9 for the A99 with three 72" horizontal radials attached. Tomorrow I will place the radials slanted down and do another A99 comparison report with the GM mounted about 30' feet away. Then I'll remover the GM and repeat the A99 report. So far, I see no difference when adding the three radials.

I never did get a chance to put the Top One up where the GM was in my previous testing, but I did mount the GM where the AP was and the only differences I was able to detect was that location shows a bit more noise than my new mounting location next to the house. This factor may account for my making comments about how quiet the GM was compared to the AP. I can hardly tell any other differences between the locations however. I hope to test this noise issue out further by putting the AP up next to the house with the GM out back. I think the added noise comes from my electric service transformer located closer to this mount. When conditions are quiet, this transformer is not really an issue, but I think it is noticeable on close observation.

After comparing the A99 I figure trying to compare the AP to any antenna will just create arguments and basically fall on deaf ears, so why bother...I know what the AP will do even though it only has a 4' foot tall top radiator.

BTW, I found out that the guy here that told me he had a New Top One he was going to install was just another CBBS liar talking out of his hat. I'm still waiting for someone to report on their New Vector 4000 and the NTopOne.

 

[bob85]

the shop my local ordered his antenna from are still waiting for new gainmaster stock to arrive eddie,
also changed the laptop and having issues finding vcp drivers for the analyser,
i have a very old laptop i can stick a new hard drive in and set it up just for the vna if i have to

 

[Marconi]

the shop my local ordered his antenna from are still waiting for new gainmaster stock to arrive eddie, also changed the laptop and having issues finding vcp drivers for the analyser, i have a very old laptop i can stick a new hard drive in and set it up just for the vna if i have to

No problem Bob. I must be confused with another Bob that reported on the Charlie Tango Forum.

I've also run into a manufacture's "planned obsolescence" issue with Lexmark Printers, when they failed to provide full functioning driver support for a year old scanner and printer...with my new computer using Microsoft's Vista.

H&Y in the US has been out of stock since selling their first order of the GM in November

 

[CDX-007]

Marconi, I'm perplexed, miffed and almost incredulous as I'm scratching my head trying to figure out what could possibly be going on to allow for the fact that your A99 is holding it's own against the SGM.
All I can come up with is you've got a bunk SGM...????

I've GIVEN away 7 A99s over the years that were mostly given to me by people who upgraded and were amazed at their performance increase by changing away from their A99 (some w/radials) to any other antenna.

I saw a consistent 2 full S-units on my Kenwood TS-930 meter on 4 different local stations when I had my station set up a ½ block from Novakor Stu, and so did they, including Stu at only ½ block away.

Each saw exactly the same, 2 S-units improvement when switching from the A99 to the Imax, both antennas only 6' off the ground, but I was on a ridge which overlooked the bowl of Reno and basically had line of sight to all 4 stations.

That wasn't the only time, but EVERY time I had anything to do with an A99, radials or not, it was 1-2+ S-units down from whatever we replaced it with, usually either a Maco V5/8 (+1-1.5 S-units) or an Imax (+2-2.5 S-units).

I just don't get it.

Why are you seeing such poopy performance from the SGM...?
- I certainly don't doubt you and believe you're telling it like it is, I'm just amazed at what you've got going on there.

I've proven on so many occasions that the A99 is grunge in comparison to whatever, that I can't imagine how you're getting one to work even as well as the AP, let alone the SGM.

 

[hotrod]

[QUOTE

H&Y in the US has been out of stock since selling their first order of the GM in November[/QUOTE]

what bout copper.com. i seen the GM in there antennas section but never
thought to check if any in inventory