poor mans gainmaster

[Needle Bender]

Without stating what would seem to be the obvious unless I'm missing something, a 5/8 wavelength antenna would show no more advantage over a similar antenna when the TOA is the only thing of issue with each one. As I understand it, the maximum advantage would be in the far field contacts of many miles out, and/or for DX, and we know DX is a fickle mistress where testing is concerned.
For consistently measurable nearer contacts even a 1/4 wavelength antenna has long been at the advantage locally due to its higher TOA. One should not be surprised if a drop in meter readings was reported locally when a longer antenna with lower TOA is put up. . .
I think being able to consistently report measurable advantages of one over the other beyond modeling differences will never happen. All of the reasons we use longer wavelength antennas are because of our quest for greater gain to the horizon that gives us better contacts (hopefully) into distances where conditions are simply uncontrollable: between us and the distances we are aiming at with very low TOA are too many variables to think of.
It's been said before better than I just did . . .
Nevertheless, I am awaiting the results of this poor man's GM anxiously.

But such was NOT the case here. When I compared it to my Imax I saw well over an S unit of gain to a local station only about 9 miles away, as well as a db or so over the 22 1/2 foot metal 5/8 and we have higher ground by at least 100' between us.
They were mounted at 1/8 wave length higher than Jack's 36', at about 41'.

I wonder what height Marconi's Gainmaster is?

 

[bob85]

i don't subscribe to the (a 5/8 is a 5/8) idea, thats not what our none scientific tests and everyday use at multiple locations show,
the gainmaster on a 14ft pole eats the imax on the same pole to some stations in the area,
similar differences are seen comparing say imax to i-10k,
some folk report their gainmaster beats their full size 5/8, some even say it equals the vector and others see the vector ahead,
for me the gm is almost as good as the i-10k but behind the vector hybrid,
the vector current maxima has a 6ft or so height advantage over any of the 5/8waves and that for sure goes some way towards its advantage.

i don't believe for a minute that the differences experienced are purely down to the antennas, the pole/feedline and surroundings are in the equation.

 

[Needle Bender]

i don't subscribe to the (a 5/8 is a 5/8) idea, thats not what our none scientific tests and everyday use at multiple locations show,
the gainmaster on a 14ft pole eats the imax on the same pole to some stations in the area,
similar differences are seen comparing say imax to i-10k,
some folk report their gainmaster beats their full size 5/8, some even say it equals the vector and others see the vector ahead,
for me the gm is almost as good as the i-10k but behind the vector hybrid,
the vector current maxima has a 6ft or so height advantage over any of the 5/8waves and that for sure goes some way towards its advantage.

i don't believe for a minute that the differences experienced are purely down to the antennas, the pole/feedline and surroundings are in the equation.

And that's the pisser, Bob, this comparison with Jack's 16 year-old Imax was in a fairly open field, well grounded mast and coax, real LMR400 and really nothing I can imagine which would either handicap the Gainmaster or benefit the Imax, nothing obvious that is.

And I agree about the differences in the 5/8 designs from bottom fed to center fed. It's an entirely unique beast, especially the way Sirio stretched the current maxim beyond the supposed maximum of 180 degrees, versus the out of phase bottom two 1/8 waves of current on a bottom fed 5/8.

 

[HomerBB]

I believe folks are seeing differences.
What I was trying to speak to was why some are not, and that there is as much anecdotal evidence for not seeing a significant difference as there is for seeing differences. I was just stating why that could be, and in my expectation, there would be reasons not to be surprised by that result.

Were I to mount a GM, and I hope this poor man's project offers that opportunity to me, I would really like to see differences. I have used 5/8, and Sigma/V4k and am constructing a .64 now. It would be great to mount a GM and see improvement.

 

[bob85]

its not aimed at you homer, many people say a 5/8 is a 5/8 some of them pretty sharp with antennas, its just not what we see here,
there are differences and im sure its a combination of factors that cause it, one been how different antennas handle been connected to different length masts/feedlines and their surroundings.

.

 

[BOOTY MONSTER]

it also doesn't allow for the possibility of someone assembling or installing a antenna wrong .
human error , i,m very good at that and i'm sure i'm not the only one .

 

[bob85]

nb read the masts explained link i posted, you will see how a grounded or ungrounded mast of a certain length or multiples can effect a vertical even though it goes against some peoples common wisdom of how to install an antenna,
w8ji says models often fall apart when the mast/feedline is included.

And that's the pisser, Bob, this comparison with Jack's 16 year-old Imax was in a fairly open field, well grounded mast and coax, real LMR400 and really nothing I can imagine which would either handicap the Gainmaster or benefit the Imax, nothing obvious that is.

And I agree about the differences in the 5/8 designs from bottom fed to center fed. It's an entirely unique beast, especially the way Sirio stretched the current maxim beyond the supposed maximum of 180 degrees, versus the out of phase bottom two 1/8 waves of current on a bottom fed 5/8.

 

[Needle Bender]

nb read the masts explained link i posted, you will see how a grounded or ungrounded mast of a certain length or multiples can effect a vertical even though it goes against some peoples common wisdom of how to install an antenna,
w8ji says models often fall apart when the mast/feedline is included.

But wouldn't that be rather a moot point with the choke isolated Gainmaster? But perhaps Jack found the perfect mast length/ height for his Imax, without radials BTW.

 

[bob85]

maybe with the gm but im not sure, it may turn out that the gainmaster is sensitive to mast length too,
you can't isolate the imax just by isolating it from the pole and winding a choke without upsetting kirchhoff, maybe he got lucky with the mast length,

i cannot ascribe the difference seen here between the imax/gainmaster/i-10k to differences in length/height over surrounding obstructions because all three have their current maxima about the same height above ground yet on the same pole/coax they each perform differently.