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New antenna from Sirio Gain-Master
- Thread starter dxswe
- Start date
Hi Marconi, I am afraid I do not. I planned to shoot them out on the same pole one after another with a couple of other antennas but a few jealous people put me off the idea on another forum.
I am told that the Imax2K is up on signal compared to the GM locally but this is not conducted in a blind test so there are the normal variables.
I have great difficulty in general knowing which one is best. I think the RX on the GM is a little better, slightly less noise and lighter so that is the one I tend to go for.
I always feel I am only using 1/2 an antenna with the IMAX2K without a good large ground plane. This goes in favour of the Gain Master. I think this might mean some low angle radiation is scuppered slightly on the IMAX2K but The DB said that a ground plane should not lower the angle of radiation if you have isolated common mode from the coax. I do always use it with a 1:1 MJF line isolator with the IMAX2K to help with the common mode that can be evident especially with 5/8 verticals. Unless I have just been unlucky on the day the GM just pips the post on the IMAX2000 but there is not much in it. I would guess 1-2dB difference. I mean the IMAX2000 looks good on paper with decent energy coming out at 6-7 degrees on this plot without radials at 1/2 wave over ground which is roughly where I normally mount...
I once questioned if the Gain Master's 0 degree take off was too low and that in fact the RF might be attenuated by the landscape and buildings in the way. But on here someone said that 0 degree would never be realized above actual ground so not to worry about that. I understand that in principle now as well from the ARRL Antenna book. It seems Sirio plots are in non existent free space and not much use. It is indeed hard to ignore the endless stream of anecdotal reports on the Gain Master's 1-2 S point increase.
It is rather hard to say or compare on DX of course. It beckons the question of whether there is a correlation with good dx antennas against their line of sight/point to point performance. I think people agree there is which seems to be contrary to the increased local reports from the IMAX2K.
The answer is I don't really know. I seemingly do as well with a 1/2 wave silver rod when the DX conditions are good.
I think the GM has the edge when dx conditions are weak and with point to point - line of sight, I can often still get through with patience. But that is not categorically proven on the DX side of course. It used to be very important to me to know which antenna was best but I have found I can never really find out to my satisfaction without a local test (and would that say anything of DX ? Probably not due to it's random nature) which I don't have the time or inclination to do anymore.
I am personally very happy to listen to others IMX2000 vs GM views. It seems across the board... a hell of a lot of IMAX2000's were replaced with GM's with increased signal reports local and DX.
I still mull this over but much less intensely now and not on a daily basis. I think I have gone through verticals in my mind relative to my operation style (i.e. ground planes are not viable) and there is nothing more to chew on with verticals.
My heart sank when I read that if ground planes are to work the they must be extremely accurately designed, both in terms of dimensions and angles. If they are out you can lose gain ! They need to be symmetrical, at exact angles (if you slope or even horizontal) and also exactly equal dimensions otherwise your pattern gets skewed. It almost makes them not worth bothering with in practical terms unless you can guarantee these factors. Impossible for a mobile station.
Given I cannot control 99pct of what happens other than my poles and antenna height/choice I pretty much put one up and see what the day brings. The GM is very light so tends to win out being a mobile static operator. If I do a few hours then I mount at lower heights (only 3 - 4.5M above ground) and use the IMAX2K or a Silver rod as the GM is not going to be happy at all unless a minimum of 1/2 wave above ground (given it's 5/8 wave dipole design, I think it turns into a bit of a cloud warmer at less than 1/2 wave above ground). I think the ground plane types seem to do better at lower heights for a very quick 2-3 hour dx session.
I can not longer concern about what I cannot change. My overall radio enthusiasm of recent weeks is a little less than before, I have spoke to a lot of places round the world now and getting out does not seem quite as urgent.
There is however one thing I am considering... I plan to try the MJF 1:1 on the Gain Master as I heard that a coiled coax is not a guarantee of complete eradication of CMC on coax.
I will be out again soon but work/ earning a living is taking the priority at the moment.
I am told that the Imax2K is up on signal compared to the GM locally but this is not conducted in a blind test so there are the normal variables.
I have great difficulty in general knowing which one is best. I think the RX on the GM is a little better, slightly less noise and lighter so that is the one I tend to go for.
I always feel I am only using 1/2 an antenna with the IMAX2K without a good large ground plane. This goes in favour of the Gain Master. I think this might mean some low angle radiation is scuppered slightly on the IMAX2K but The DB said that a ground plane should not lower the angle of radiation if you have isolated common mode from the coax. I do always use it with a 1:1 MJF line isolator with the IMAX2K to help with the common mode that can be evident especially with 5/8 verticals. Unless I have just been unlucky on the day the GM just pips the post on the IMAX2000 but there is not much in it. I would guess 1-2dB difference. I mean the IMAX2000 looks good on paper with decent energy coming out at 6-7 degrees on this plot without radials at 1/2 wave over ground which is roughly where I normally mount...
I once questioned if the Gain Master's 0 degree take off was too low and that in fact the RF might be attenuated by the landscape and buildings in the way. But on here someone said that 0 degree would never be realized above actual ground so not to worry about that. I understand that in principle now as well from the ARRL Antenna book. It seems Sirio plots are in non existent free space and not much use. It is indeed hard to ignore the endless stream of anecdotal reports on the Gain Master's 1-2 S point increase.
It is rather hard to say or compare on DX of course. It beckons the question of whether there is a correlation with good dx antennas against their line of sight/point to point performance. I think people agree there is which seems to be contrary to the increased local reports from the IMAX2K.
The answer is I don't really know. I seemingly do as well with a 1/2 wave silver rod when the DX conditions are good.
I think the GM has the edge when dx conditions are weak and with point to point - line of sight, I can often still get through with patience. But that is not categorically proven on the DX side of course. It used to be very important to me to know which antenna was best but I have found I can never really find out to my satisfaction without a local test (and would that say anything of DX ? Probably not due to it's random nature) which I don't have the time or inclination to do anymore.
I am personally very happy to listen to others IMX2000 vs GM views. It seems across the board... a hell of a lot of IMAX2000's were replaced with GM's with increased signal reports local and DX.
I still mull this over but much less intensely now and not on a daily basis. I think I have gone through verticals in my mind relative to my operation style (i.e. ground planes are not viable) and there is nothing more to chew on with verticals.
My heart sank when I read that if ground planes are to work the they must be extremely accurately designed, both in terms of dimensions and angles. If they are out you can lose gain ! They need to be symmetrical, at exact angles (if you slope or even horizontal) and also exactly equal dimensions otherwise your pattern gets skewed. It almost makes them not worth bothering with in practical terms unless you can guarantee these factors. Impossible for a mobile station.
Given I cannot control 99pct of what happens other than my poles and antenna height/choice I pretty much put one up and see what the day brings. The GM is very light so tends to win out being a mobile static operator. If I do a few hours then I mount at lower heights (only 3 - 4.5M above ground) and use the IMAX2K or a Silver rod as the GM is not going to be happy at all unless a minimum of 1/2 wave above ground (given it's 5/8 wave dipole design, I think it turns into a bit of a cloud warmer at less than 1/2 wave above ground). I think the ground plane types seem to do better at lower heights for a very quick 2-3 hour dx session.
I can not longer concern about what I cannot change. My overall radio enthusiasm of recent weeks is a little less than before, I have spoke to a lot of places round the world now and getting out does not seem quite as urgent.
There is however one thing I am considering... I plan to try the MJF 1:1 on the Gain Master as I heard that a coiled coax is not a guarantee of complete eradication of CMC on coax.
I will be out again soon but work/ earning a living is taking the priority at the moment.
Last edited:
New GAINMASTER 1/2 wave version, just seen a post about it over on Simons page:
http://simonthewizard.com/2016/02/19/exclusive-gain-master-goes-12-wave-part1/
http://simonthewizard.com/2016/02/19/exclusive-gain-master-goes-12-wave-part1/
With a Sirio GM 9' above the metal roof I doubt it's having much effect on your signal. The GM was designed to work without a groundplane and has a low angle of takeoff so at that height above the metal roof I wouldn't think it would make much difference.
My post here is regarding the 5/8 wave Gain Master. I hear and know nothing about the new .50 wave performance from Sirio.
I've reported that my real world GM was ill-effected by an antenna on the ground below at about 20' feet...a little less than your 26' foot installation. I would think I would still expect some bad effects, but his Eznec model below does not support that idea in any significant way.
The difference in gain may be due to the building changing the mast currents to being in phase with the radiator. See the model without the building included. The first few rafters show some currents (red lines) from the antenna, but I have not checked this model out any further.
I possibly could ad a choke to the antenna, intending to remove mast currents...and that might make some additional difference.
Right off I would agree with Big Kahuna...there likely would not be much difference.
Good luck and keep us posted.
I've reported that my real world GM was ill-effected by an antenna on the ground below at about 20' feet...a little less than your 26' foot installation. I would think I would still expect some bad effects, but his Eznec model below does not support that idea in any significant way.
The difference in gain may be due to the building changing the mast currents to being in phase with the radiator. See the model without the building included. The first few rafters show some currents (red lines) from the antenna, but I have not checked this model out any further.
I possibly could ad a choke to the antenna, intending to remove mast currents...and that might make some additional difference.
Right off I would agree with Big Kahuna...there likely would not be much difference.
Good luck and keep us posted.
These last few pages of this thread must've happened back when my computer was in & out of the shop, because I missed them, so I wasn't ignoring you... apologies.
- And No, two Hams running tests from Ham radio to Ham radio isn't what I'd call a "Typical CB claim".
- And Yes, you can measure a single, or even 2-3 dB difference on the Icom 756 Pro3 analog meter, presuming it's designed to be somewhat close to 10dB between S9 and 10dB over S9.
- Looking at one you'll notice the needle appears to be about 1/10th the thickness of the space taken up by the area between S9 and 10dB over S9, so one would then logically surmise that every needle-width in that area would closely represent right about a dB.
Now of course this post and the rest of this thread are within the framework of real-world application of radio equipment so none of this would therefore pretend to be accurate within 100ths of a microvolt, in case you were confused by the context.
OK, well in the spirit of continuing to be of possible further assistance to you in your admitted deficit of understanding*, here's a video which might also be of some help.
You'll notice the needle is in white, and the ~10dB measurement area between S9 and 10dB over S9 is in red.
You see, it's really not that hard, but then I'm rather well-accustomed to reading analog meters, since clear back when I was only 8yrs old or so, back in the '60s, my Elmer would let me enjoy tuning around and listening to the bands on his Collins 75S-3 receiver, but some people just aren't good at certain things so, as Clint's character has famously stated, "A man's got to know his limitations", and I certainly won't fault you for your honesty in admitting your issues with analog S-meter reading.
Well, I hope that helps and now go ahead and give it a try. With some practice and maybe after a year or five you, too, will be able to say, "I now know how to read dB differences on an analog meter!".
73
Just to make a small comment. My GM has been in the air since 2012 bolted to a 40' tower. I wrapped a few rounds of black electrical tape around the coil when new, (to keep the red coil from fading). Anyway, the tower and antenna have never been back on the ground since Oct 2012 and the antenna is just as reliable now as it was then. Still has extremely low SWR across the entire 11 meter band. Always great reports. Best antenna I've ever run...