Homebrewing a Sirio Gainmaster using RG58 and 2.5mm wire.

[kamikazeandi]

Hello,
yesterday I was on the "Ham radio" for the first time and probably the last time!
For me, the show was a little disappointing when you know big fairs like the "Aero" in Friedrichshafen, where I was this year also. The only interesting topics for me were the stand-alone full functionell 5W-SDR-TRX FDM DUO from Italy, with which one I could play, and a SDR-TRX-series from Russia, I did not know. The big 125W-SDR-TRX SunSDR-MB1 (160m to 2m - max 80MHz Panadapter) even has touch-screen (http://www.sunsdr.com/en/home.html). The transceiver makes a very good impression, but unfortunately for my wallet a little too cheap (3700 EUR).
End "Off topic"!

The low-loss coax cable I did not get as much as some other things for other antenna projects. So I must now order coax cable.
OK, I'll start with 11 turns in the stub and test approach me. Thank you for your reply and the good idea, Psi.
Also, now a bit more work coming back into my job to me. So my new building of the gain master can take a little. But then I will report!
Regards,
Andi

[Python]

Hello from Finland, made a homebrew gm two weeks ago and im getting very good reports now compared to j-pole and slimjim antennas i have. Old friends ask me "what have you done to your equipment?" Stations that hardly heard me before tell im coming s3-5 or so. Conditions have been great this summer, wish i had this hbGm done earlier. Big thanks to you all who took part to this conversation and research.

Coaxial was Urm67 PE cable, it has same vf and capasitance as rg58, but attenuation is better. Like rg213, not the best but good enough. The cable is very stiff, so i made a coil of 5 turns on 105 mm plastic tube former. Coil is not axial with the pole, but on the side of it like a reel on the fishing pole, looks ridiculous ... works ok, no common modes. 5r on 105 mm has good reactance on cb band. Stiff cable was hard to work a good T-joint on the matching stub and lower radiator. Used a lot of black glue-sealant ( dont know what you call it in UK) on it to make it rigid. Its the stuff builders use when glueing things together, not silicone gasket thats too soft.

Dimension are a bit longer than in Psidocs original Gm: lower radiator 3.51 meters, upper is about 3.56 meter. Easy to adjust , cut off cable ties and roll the coil lower and you get longer lower, upper rad you can solder more wire " on the field" with cigarette lighter... so tested different lengths. Stub point dont change this way but maybe not big problem.

I suspect that when you glue thin wire on the glassfiber pole its electrical length , VF , changes, i mean it must be longer than in free space? Have noticed this some times with thin wire made antennas glued on poles, but not sure, so im asking if anyone have realized same thing or am i totally wrong or theres something else going on. SWR is now very good, 2 low points almost 1:1 and the CB band just midle of them 1:1,2. Maybe this upper length thing is not very important at all? What about radiation pattern with longer upper rad?

The best thing to do may be to make upper radiator of the same coax as lower and same length.
But anyway, these lengths work well on CB band based on reports from stations 30-100 km away.

73 to all, Python

[vkrules]

The ant is so broadband that slight differences in length wont make much difference it will just move the swr curve a little higher or lower. Anyway a little longer is better than a little shorter . Have a look at the ENZEC model posted earlier. As for the pole changing the length I haven't seen that . Pole is only on one side not surrounding the radiator so Vf shouldn't change significantly . Make sure you do not use carbon fiber pole . If you are unsure of poles construction , take a small scraping of fiber material and place in microwave oven for a few seconds, if it gets hot material is carbon.Changing the gauge of the wire will change the length .Have fun my gainmaster is still in use daily.

[slamjam]

Hi any chance of some dimensions for a 15m version?

[bigpimp347]

a few pictures of the Gain Master naked

Coax to tuning stub.






top section coax capacitor.





certainly could have been lacquered or insulated better than just heat shrink tubing..

[Irishman1127]

Not what you'd expect for the money eh? mark...

[bigpimp347]

£120 for a couple of bits of coax and some wire..!!
oh and a poorly built up bit of fiberglass tube and a plant pot to use as a choke former..!!

terrible when you think about it..

[kamikazeandi]

.. I'd go with 11 turns at 100mm, if the swr starts acting strange - Shooting up quicker than you'd expect - at either end then unwrap half a turn and try again... Then unwrap andother half turn etc. You know the drill. But with 11 I think you'll be very close if not there.

Si

Hello PsiDOC,
long time ago. That's not so funny! Sorry for that!
Now I have build a new GM, completely with H2010 (vf=0.83), diameter 10.2mm with the following dimensions:

GainMaster H2010-2.png

I've started with 11 turns with a choke at 100mm diameter but not so happy with the SWR:

GM_H2010_vs_RG-213.jpg

I have used 2 different SWR-meters, the one in my FT-857D and an old Wipe 110, that is a bit more sensitivly.

The temperatures these days are not so friendly here in West-Germany, and for now, i will let the GM at the mast on the roof. But as soon as the temperatures will rise a bit, I'll climb up again and try 10 turns at the choke.

Or do you have a better idea? Maybe shorten the lengths? Cut the stub a bit?
Or maybe you see a big mistake in my calculations?

Andi

[INTERCEPTOR]

Can we extend this GainMaster to a broadband vertical SKYPPER for the 10m to 12m band?
Regards Andi

Andi,
RE: The skypper no that's not crazy. It'll be interesting to see if we can model it out to a 5/8 wave broadband antenna, although putting the Gainmaster on it's side does give you about 8 dbi in 2 directions on it's own.

Si

I have read this thread but I don't full understand all the technical side really, but I was interested when I read the above quote.

Has anyone tried the antenna horizontal/flatside?

Is it as simple as mounting it horizontal and using it directionally? How does it perform? Would the SWR change?

Hopefully I will get the opportunity to try this antenna for myself soon once I learn more.

Thanks for taking the time to discuss this and for your time experimenting.

[sec1223]

has anyone got a definitive build yet?.

iv read so many versions now its doing my tits in.

[INTERCEPTOR]

has anyone got a definitive build yet?.

iv read so many versions now its doing my tits in.

I'm confident that if you follow PsiDOC's instructions on page 1 that you will have a perfectly operational antenna for 10/11 Meter band.

The discussion has,on the later pages, been about using the antenna on other bands.

What bands are you going to use?

Are you going to make this antenna?

I will be making one soon....once I have some time.

Please let me know if you make this antenna, I would like to know how you find it perform.

[bigpimp347]

or just get a gain-master and dissect it and get all the measurements..
like i have, if i get time i'll do the write up to go with the pictures..

[lambrettadave]

or just get a gain-master and dissect it and get all the measurements..
like i have, if i get time i'll do the write up to go with the pictures..

I will enjoy reading that Mark

[DJT979]

Hallo, I can´t see the pictures from the first post, anybody saved them and would send them to me?
I like to homebrew this antenna for me here

Regards, Dennis

[INTERCEPTOR]

Hallo, I can´t see the pictures from the first post, anybody saved them and would send them to me?
I like to homebrew this antenna for me here

Regards, Dennis

Dennis I printed some copies of the Pictures PsiDOC kindly created.

I have pictured them with my phone.

If you cant see anything on the picture ask and I will tell you what is says.

I have this antenna as my only home antenna and it seems to work ok. My SWR is about 1.6 on the UK 40 Channels FM AND ABOUT 1.2-1.3 on CEPT/MID BAND.

It was my first antenna build and I solder joined everything and used really thick RG213 coax for everything except top radiator which was a couple of pieces of wire soldered together! BUT IT WORKS! If it was made as well as others on here have done it is probably as good as any factory antenna (or better!)

Please let us know how it goes for you.




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