New Sirio 1/2 wave Gain Master

[Handy Andy]

And a PDF...

Or Two...

If you need more help, like if you can't review the PDF because your device prevents it - I can "screengrab" and re-post it - more of it - becaue there's a lot, and of course you have to have every language except ours as ahead of it - it's a lot to wade thru... - let us know...

 

[Riverman]

And a PDF...

Or Two...

If you need more help, like if you can't review the PDF because your device prevents it - I can "screengrab" and re-post it - more of it - becaue there's a lot, and of course you have to have every language except ours as ahead of it - it's a lot to wade thru... - let us know...

Thanks, Andy.
I should have paid closer attention. And known better.

 

[Marconi]

CB Radio: Build a GainMaster HALFWAVE on a DX Commander Pole..Another detailed upload

This may be a bit late for this old thread, but I think the video could be informative for folks wanting to know how Siro's designed their 1/2 wave GainMaster. I think this antenna as been discontinued however.

 

[bob85]

1/2wave is still on sale here Eddie, only 1 local has the 1/2wave version,

modding your snapped 5/8 into a 1/2wave is one way to make use of a broken 5/8,
depending on where its broken they can be cut down to make a 4 section 1/2wave,

stronger & stiffer in wind than either factory gain-master & handle more power on FM than the 5/8wave..

 

[Marconi]

1/2wave is still on sale here Eddie, only 1 local has the 1/2wave version,

I think Serious use to make the HW GM for CB, but I see the frequency range is 27.2 - 30 Mhz and that basically makes it good for 10M.


I also see this tuning chart shows 10M, but the Bandwidth Chart below shows a CB Bandwidth. Sorta confusing.

 

[bob85]

They are cut for cb frequencies when you buy them Eddie,
tuning for 10mtrs = cutting the top wire.

 

[Marconi]

They are cut for cb frequencies when you buy them Eddie, tuning for 10mtrs = cutting the top wire.

Bob, that makes sense.

I read here on the forum somebody saying the HW GM shows it starts at 27.205 with a 1.80 SWR and goes up into the ham bands, and he said they might have stopped making it for 11 meters. When I looked to check I only found the Original GM, so I thought Sirio must have stopped making the HW.

Do you know of any information on performance, bandwidth, and construction?

 

[bob85]

externally its the same antenna as the 5/8wave minus the top section Eddie,
inside is a coax dipole using the same red coax,

bandwidth is narrower than the 5/8wave as they don't have the top coupling capacitor
& cleverly positioned stub to broaden the low vswr bandwidth,
it also means the 1/2wave is not DC grounded,

the upside of having no stub is you don't have high vswr between the feed-point & stub,
which allows the 1/2wave gain-master to handle more continuous power without vswr going up & smoking your amp,

lacking the 4th section its also stiffer & stronger in wind.

 

[MarkIV]

Interesting that the specs state "tunable from 27.2 - 30 MHz. Apparently only covers 1/2 the CB band.

The original Gainmaster is tunable from 25.5 - 30.

It’s a typo!

 

[Riverman]

…it also means the 1/2 wave is not DC grounded.

What is the downside of this?

Thanks,
Jim

 

[The DB]

What is the downside of this?

Thanks,
Jim

DC grounded antennas tend to have less static, and thus are said to be quieter. This is essentially because the cause of the static has someplace else to go rather than build up on the antenna itself.

This isn't the only technique of lessening how much static you hear, nor does it work on all sources of static.

This antenna (the half wavelength gainmaster) would be half DC grounded and half not, as the bottom part is directly connected to the coax shield, which in a proper setup should be grounded somewhere along the way to the radio, while the top generally isn't.

Also, the 5/8 wavelength Gainmaster is the same way, and when it comes to static, in my experience it is a quiet antenna.


The DB

 

[Riverman]

Thank you, Steve!

 

[snippits75]

I watched the Gainmaster 1/2 wave build video. It's not that much different than a T2LT vertical dipole antenna. The top half of the Gainmaster build is using 16 awg(1.5mm) stranded copper wire while a T2LT is using RG58 coax with the outer covering, and ground wires removed.

I have been thinking about making a T2LT antenna, and putting it up on a 40 foot Spiderbeam. Just wondering how it would compare performance wise to the home made Gainmaster? I think the Gainmaster build would be more durable especially for the top section being coated copper wire versus the T2LT with just the center conductor of the RG58.

 

[Riverman]

I just ordered a Gainmaster 1/2 Wave and will report back once I receive it and have it up.

 

[Eldorado828]

I just ordered a Gainmaster 1/2 Wave and will report back once I receive it and have it up.

Will be an interesting read so will be waiting to hear from you sir.

I've been curious about that one for a while but as you know I don't live in the most antenna weather friendly part of the world.