Homebrewing a Sirio Gainmaster using RG58 and 2.5mm wire.

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Re: Homebrewing a Sirio Gainmaster using RG58 and 2.5mm wire

Post by PsiDOC » 31 Jan 2014, 09:15

VK.
Yes I do take into account the PVC coating on the wires as well as the differing wire diameters etc etc.
On 54 mhz you can actually go to about 6.75 meters total antenna length before the radiation angle starts going skywards. That's 1.28 wavelength.
How can this be? What happened to the 0.64 wavelength rule? you may well ask.
There's a simple answer to that. The 0.64 rule still applies here, however the rule is per radiating element. The unique thing about the gainmaster is it's a centre fed vertical antenna so it has 2 radiators, unlike your antrons / imaxes etc that are end feds so only have 1 radiator. This means we can in theory double the size of the antenna and increase the gain.
If you look at the the attachments below I have modeled a 1.28 wavelength (2 x 0.64 wavelength) and a 1.32 wavelength (2 x 0.66 wavelength) for you. You can see the 2 x 0.64 has a nice low angle of take off with some high angle to -6db.
The 2 x 0.66 wavelength one shows the high angle has now increased to 0 db and it's now robbing the gain from the low angle as well as it had droped below 6dbi of gain.
The downside to going supersized is matching it and bandwidth. As you go longer you lose the bandwidth to the point where the 2 x .64 version has a bandwith of about 300 khz.

Hope this helps.
Psi
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Re: Homebrewing a Sirio Gainmaster using RG58 and 2.5mm wire

Post by vkrules » 31 Jan 2014, 22:15

Thanks for that, explains a lot.

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Re: Homebrewing a Sirio Gainmaster using RG58 and 2.5mm wire

Post by PsiDOC » 01 Feb 2014, 21:15

Welcome. If you fancy modelling the gainmaster for yourself the nec modelling file is attached below in the .zip file. Download and unzip it as usual.
The software I use is 4nec2 http://www.qsl.net/4nec2/ it's freeware and every bit as good as eznec. Load up the gainmaster.nec file and then click Edit >> Input (.nec) file.
Click on the symbols tab and the rest should be self explainatory if you look at the comment section. Aside from changing the symbols section and the frequency don't muck about with the rest of the settings, else you may not get the right results!
Happy modelling.

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Re: Homebrewing a Sirio Gainmaster using RG58 and 2.5mm wire

Post by 43cs44 » 02 Feb 2014, 20:00

Thanks for the modelling info PsiDOC, I had the program some time back but lost it in a computer change.

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Re: Homebrewing a Sirio Gainmaster using RG58 and 2.5mm wire

Post by PsiDOC » 02 Feb 2014, 20:42

Welcome :)
Any questions give me a shout
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Re: Homebrewing a Sirio Gainmaster using RG58 and 2.5mm wire

Post by Kaos » 03 Feb 2014, 06:12

Here is my hombrew GM in the place of my IMAX2K.

I was gobsmaked at the lack of a noise floor. I usually have about 5 S points at the time the video was filmed, 1630hrs.

I can hear the low stns and they are not lost to static.

http://www.youtube.com/watch?v=AKm2TV4o9aM

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Re: Homebrewing a Sirio Gainmaster using RG58 and 2.5mm wire

Post by vkrules » 03 Feb 2014, 08:51

there is a lot to love about the hb gainmaster , not surprised at all Tim. Just built gm no 6 for a friend of mine. I'm getting good at it.Will pass on your link to the Vid.

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Re: Homebrewing a Sirio Gainmaster using RG58 and 2.5mm wire

Post by PsiDOC » 03 Feb 2014, 11:58

[quote="vkrules"]there is a lot to love about the hb gainmaster , not surprised at all Tim.[quote]
Must admit it's one of my more successful projects. ;)
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Re: Homebrewing a Sirio Gainmaster using RG58 and 2.5mm wire

Post by pu2thw » 15 Feb 2014, 19:01

Hi everyone. Hi PsiDOC. How is it going?
Now i bought a 7.2m fishing rod on ebay and in this week i will build a new Gain Master.
When I have finished I will post some pictures to give more ideas about mechanical build.

And my next objective is a GainMaster for 6 meters band. Of course, a 3 elements Yagi is better but the gain master is awesome antenna.

73 for all.

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Re: Homebrewing a Sirio Gainmaster using RG58 and 2.5mm wire

Post by PsiDOC » 23 Feb 2014, 08:12

PU2,
All good here mate. Please do post pics. All ideas about the mechanical construcion and mounting are appreciated.
If you're looking at a 6 meter version have a read in this thread. A few of us have built them. :)
Happy building.

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Re: Homebrewing a Sirio Gainmaster using RG58 and 2.5mm wire

Post by Kaos » 23 Feb 2014, 08:17

Regarding the stub thing.....

I had the stub thing hanging out of the thrid bit of the T Piece and right angles, then looking around my local rip off merchant electical shop I spies a PL259 right angle plug.

So now it (the stub) lies vertical and again I swear this has changed the characteristics of the AE. It HAS bought the SWR lower across the whole range.

Its suppoerted by a 7m fishing pole with the stubb hanging underneath it. This seems to be OK also.

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Re: Homebrewing a Sirio Gainmaster using RG58 and 2.5mm wire

Post by Warden » 23 Feb 2014, 09:14

Kaos wrote:Here is my hombrew GM in the place of my IMAX2K.

I was gobsmaked at the lack of a noise floor. I usually have about 5 S points at the time the video was filmed, 1630hrs.

I can hear the low stns and they are not lost to static.

http://www.youtube.com/watch?v=AKm2TV4o9aM
The lack of floor noise could be a deaf antenna. :D Those low stations may have been strong stations.
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Re: Homebrewing a Sirio Gainmaster using RG58 and 2.5mm wire

Post by Kaos » 23 Feb 2014, 11:32

Warden wrote:
Kaos wrote:Here is my hombrew GM in the place of my IMAX2K.

I was gobsmaked at the lack of a noise floor. I usually have about 5 S points at the time the video was filmed, 1630hrs.

I can hear the low stns and they are not lost to static.

http://www.youtube.com/watch?v=AKm2TV4o9aM
The lack of floor noise could be a deaf antenna. :D Those low stations may have been strong stations.
Thankfully they were just that. Low stns.

The AE is not deaf or so 41 Div says.

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Re: Homebrewing a Sirio Gainmaster using RG58 and 2.5mm wire

Post by kamikazeandi » 14 Jun 2014, 14:19

Hello,
Thanks PsiDOC for the GainMaster file. So I tried the antenna to optimize for the 10 to 12m band, pressed the adjustment approximately 1MHz down (see image):
GainMaster 16.png
PsiDOC, maybe you can check the data? Thank you! If you want to, then I put my file here. However, I believe that out of the picture all the necessary information can be removed.
So far I have the new lengths not yet been implemented and tested. For this I am waiting for your reply. Even my current version works well on 12m, but with less than perfect SWR.

Then I have a few pictures of my antenna on my 9m fishing pole in high winds with about 80km/h unguyed and a picture of guyed antenna design before the thunderstorm hurricane on Whit Monday here in the western Ruhr area in Germany. The hurricane did not survive the whole antenna structure. But I have a GainMaster with the old antenna cables were installed again:
GainMaster & Langdraht-Antenne bei Sturm 1.jpg
GainMaster_abgespannt_Langdraht_GP_2m_kl.jpg
Andi
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Re: Homebrewing a Sirio Gainmaster using RG58 and 2.5mm wire

Post by PsiDOC » 15 Jun 2014, 11:42

Andi,
You and I have been working on the same thing although with different parameters. Last weekend I built a 24 - 29 mhz version that's working well.
Your 3.65 lengths are what I'd expect to see, I am assuming that you are using coax with a velicity factor of 0.86 for the lower radiator of the antenna with an attach point of 1.759m? If you are that looks about where I'd expect it to be. The stub length is good as well. So it's all good to go in my opinion. :)
You may want to add a few 0.1's of a pf to the capacitor and remodel the stub and attach point to suit if you're aiming for the 12m band as well. This will widen the bandwidth downwards and bring the centre band swr (the hill in the middle of the swr curve) upwards a little but you should be able to get it just about all in without going past 1.5:1 swr in the centre.

Psi
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