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sirio 827 5/8 vs gainmaster

gamegetter said:
good catch marconi...Bob and friends are seeing a better than advertised db gain,,, for 1 s unit is about 6db if i remember right!
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Well gamegetter, my personal comparisons using the GM shows less than 1 Sunit difference in all test I've done, but different areas and installs will show different results. That is why Bob said, "...you mileage may vary." Also, I don't necessarily agree that all radio receive meters read 6db = 1 Sunit, plus a lot may depend on how your radio's "cut back circuit" handles the signals...among 100's of other things at work. It is hard to be categorical with radio and antenna performance.
 
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i have never seen a radio with the old standard 6db/ s-unit, even 3db/ s-unit is a lazy meter by todays standards, if meters were 6db/s-unit you would hardly see any difference between any two vertical antennas :)
 
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bob85 said:
i have never seen a radio with the old standard 6db/ s-unit, even 3db/ s-unit is a lazy meter by todays standards, if meters were 6db/s-unit you would hardly see any difference between any two vertical antennas :)
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If that is so Bob, then that is pretty much what is going on here. I think all of my radios are pretty close, but I've never checked them nor thought about checking them to see what the db/Sunit is. I can't do such work myself, and I don't know anybody I could trust.

I tend to agree with what you guys see as a difference however, because that is all I've ever heard. So, I'm the odd man out on this count...even though my results are closer to what Sirio has published. I think they probably got their published results using their free space modeling program. So your analysis of what is going on probably better explains my dilemma regarding my results.
 
Marconi said:
Booty Monster, the GM is a center fed 5/8 wave dipole and dosen't need radials, all the antenna is already there. All end fed 1/2 or 5/8 wave verticals are not balanced, and can use radials.
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so inside the vertical about 11 ft is radiator and about 11 feet is ground element ?
im guessing the metal mounting bracket is insulated from the actual antenna so the mast/ground wire wont become part of the ground element and upset the balance of the center feed ?
 
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I think Marconi's point on the effects of the AGC/auto gain control and antenna testing/'real db gain on the meter' is more than fair to bring into the discussion.

I know that when I align a radio's receive, that the generator needs to have the output set so the radio sees 4 S-units or less so that the AGC doesn't influence the alignment. 5-6 S-units is when the AGC starts to kick in and affecting the incoming signal.

Doesn't that kick in at different points with different radios?
What it is supposed to do - and what it actually does - are often two different things.
Having said that, not only can it skew 'real world testing' - but wouldn't the need to use similar radios on either end of the test be necessary for some kind of consistency?
Not to forget leaving out the power levels and distance/terrain?
Or - am I missing something else here?

Not that I am negating what Bob85 is saying.
I'm sure 'seat of the pants' testing does count.
Subjectivity is credible.
 
It's been almost exactly one year since I put my GM up to replace my Vector 4000. At 40 feet to the connector I'm still impressed there was no signal loss going from a 30 foot antenna to a 22 footer. So long as there is sufficient height above ground (at least 6 meters or more) there will not be a 5/8 wave ground plane that can equal a Vector or the GM. At lower heights the GM is unable to maintain it's low angle of radiation. Being a balanced antenna it is more negatively effected then any groundplane by being mounted low.

Booty, the top 11 feet of the GM are just as active as the bottom 11 feet since it is a balanced antenna. The bottom is not ground, it is energized with the same radiation currents as the top. It's also worthy to note that any problems with the S-827 used for this test would have shown up on the VSWR meter. The design of the S-827 makes it almost impossible for it to have a defect and hold a good VSWR. Almost all failures with an S-827 are related to connections with the set screws for the matching coil. The antenna does not have the tuning range of a Vector for example where it is possible to have a good VSWR while the radiation elements are not tuned for maximum gain. An inch or two out of adjustment or a bad RF connection on the S-827 cannot be hidden on the VSWR meter.
 
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eddie you can test it yourself if you get a precision attenuator, it won't be dead balls on but it will be more than good enough for your purposes,

im not saying the gainmaster is the best thing since sliced bread, im just reporting what we see in tests, its pathetic power limit stops plenty of people including me buying one,

i don't believe there is as much difference in gain as what we see in tests, i think other factors are effecting the results, even though others have reported similar results i don't expect that to be true for everybody's location,

if i told you the increase in signal seen on the ft847's meter you would be saying get outta here with your booolshit but its there and its repeatable,
847's have VERY happy meters,


robb,
traditionally when using a uniden export and somebody wants a signal comparison you back the gain down to put them around s-3 so the agc don't mask any small change in signal.
 
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shockwave,
i wish sirio had made the gm handle 1kw fm, i would try one mounted at the same tip height as my sigma hybrid and have a much neater looking antenna.
 
bob85 said:
shockwave,
i wish sirio had made the gm handle 1kw fm, i would try one mounted at the same tip height as my sigma hybrid and have a much neater looking antenna.
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Hey SW, didn't you design an effective matching solution for the GM to allow for more power? If so, send the idea to Bob, he wants to put more RF in the air, 500 watts is not enough.

Bob be careful, those guys on MD's can overly influence you with their seeming hunger for power.
 
Shockwave said:
All you need to do in order to get your GM to handle the desired 1KW FM is listed right here http://www.worldwidedx.com/cb-antennas/103100-1-5-kilowatt-pep-gain-master-modification.html One should also keep in mind that since the first production runs, I have not heard a single complaint about someone burning up the matching cap on the newer models. It is noticeably more rugged right out of the box then the first ones made.
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Thanks SW. Does your GM have this mode?

I got mine early on and I've had no trouble. On occasion I've put about 1000 watts in the GM. I don't do it on purpose however, and I don't recommend even trying.
 
lol@ eddie, you know they don't influence me, im not into high power, could not use it here if i had it but i like some headroom in the antenna,

shockwaves 1.5kwpep mod looks like a good idea if teflon coax of that diameter was available here in short lengths, he made a nice job of it imho,

i need to either finish my sigma4i or change antenna, im not happy with how the i10k works in dx to the usa at the height its at,
its embarrasing getting your ass whipped into the states by locals on imax 2000's using less than half the power, that never happened when i was using the vector hybrid;)
 
bob85 said:
i need to either finish my sigma4i or change antenna, im not happy with how the i10k works in dx to the usa at the height its at,
its embarrasing getting your ass whipped into the states by locals on imax 2000's using less than half the power, that never happened when i was using the vector hybrid;)
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oh my goodness !!!! :LOL::LOL::LOL:
whats holding you up on your sigma/vector ?
 

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