.64λ Homebrew

[gamegetter]

the patterns are identical, and i see where I was looking at the wrong radiation pattern for the gainmaster, it is fig 6 on the sirio page I posted...back to the drawing board!

 

[Marconi]

the patterns are identical, and i see where I was looking at the wrong radiation pattern for the gainmaster, it is fig 6 on the sirio page I posted...back to the drawing board!

That looks like the same image except that the pattern for the GM is missing, leaving only the 5/8 wave pattern. It is still a Free Space model.

It's not a big deal however, and I don't mean to be picking on you. Just making a distinction.

 

[BOOTY MONSTER]

How can it be a bad idea? Any 5/8 wave antenna @ 1 wave length high is going to reap the benefits the lowest possible angle of radiation and the ability to get it to skip farther.

if ... IIRC ... when shockwave was discussing the $10,000 bet over at the mule droppings forum the bet was supposed to be at about 2 WL high and shockwave said that particular height didn't allow the gainmaster to perform at its best , even though other 5/8 didn't seem negatively effected . ..... IIFC ....

maybe other heights also negatively effect it too ?
hopefully shockwave will see this thread/post and correct me if i'm wrong or describe what what he was referring to again .

 

[Needle Bender]

NB, you reported what you saw no doubt, but in my experience I sometimes see a glaring difference too, so I test as many contacts from the same stations as I can and I try to select stations at different directions and distances. With luck and any reasonable consideration...that should tend to smooth out results and mitigate the occasional aberrant signal that comes our way from some contacts. One test does not seem reasonable enough to make such a judgment IMO.

Do your other local contacts show as much difference in signal with those two antennas?

Marconi it's been the same story in all directions and distances. Truly the best performing omni ever. And when I DX, according to the sig reps I get, it offers a signal comparable to a 2-3 el beam! I'm amazed at the s9+10 & +20 I've received from Europe and Australia with only 100 proof whiskeys.


Sorry I missed your shout out last read:

NB,
How have you been. Haven't heard from you lately.

BUSY! Been helping a friend get the best possible output gain and TOA from his Lazyboy...

...more to come

Too busy lately to play much radio or computer, but picked up a new toy and hope to find some time to sit in front of it.

 

[gamegetter]

i would not use dx to compare antennas, i get 5x9's + all the time on dx in my mobile with a mag mount wilson 5k and 25 watts, while driving.

we started out with a local line of sight comparison of the gm and the imax.

homer, sorry about the jack, maybe we should start a thread on this ,,,just saying- no offense meant-none taken, its just a discussion

 

[HomerBB]

No problem with the direction of the thread. It all relates in terms of antenna performance and modelling and how they either confirm or diverge from each other.

Enjoy the thread.

 

[bob85]

How can it be a bad idea? Any 5/8 wave antenna @ 1 wave length high is going to reap the benefits the lowest possible angle of radiation and the ability to get it to skip farther.

thats not true robb,
a typical 5/8wave installed at that height will often put more energy into its upper lobe warming clouds than it does in its lower lobe towards the horizon,

http://www.cebik.com/content/gp/58-3.html


in our multiple tests at multiple locations using up to 1 wavelength or so of mast the only antennas the gainmaster has not outperformed are my i-10k and my dialed in sigma/vector 4000,

imax a99 sirio827 2012 1/2wave gp 5/8wave gp ect all consistently play second fiddle to the master at those mounting heights in our tests,

we have had two gainmasters break in winds below the 100mph rating,
the first one was assembled with 2" overlap ( dummybuilt ),
the second im not sure not seen it yet but you better have a feel for all things mechanical when you tighten the hose clamps on a gainmaster,
you can overtighten the clamp and crush the grp tubes,

if your the kinda guy that strips manifold bolts, have hands like a blacksmith's striker get somebody with mechanical aptitude to assemble it

 

[Robb]

I like the Sigma 4 and would choose it over the SGM any way (a local has and uses a S4; especially likes the receive with it). But I'm surprised that the SGM doesn't work as well at 1 wave length high. But that is also great news for those who use it and don't have it that high. I like the SGM because of its innovative design; I dislike it because of its cost. For now, I have the Imax 2000 up @ ~31 ft.

 

[bob85]

homer,
seeing you sat on your perch working on the antenna reminds me of fred dibnah

 

[HomerBB]

Glad to help out in any way I can. I take that as a compliment, however undeserved.
I do have a question, Bob; have you put your optimized Vector 4k on an analyzer, and if so, how did it look?

- my thread to hijack if I wish

BTW, everyone, I personally like the broader discussions that are generated by these threads. Adds perspective to the central thread.

Enjoy

 

[bob85]

robb,
the trouble with the sigma style antennas is dialing them in, following makers instructions won't get best results,

reading all 4 parts of "some j-poles that i have known" by L.B.Cebik gives some insight into how they get their low angle gain and why he told me what he did about the design and the controversy from folk who don't understand how they work..

http://www.cebik.com/content/a10/vhf/jp1.html

homer,
nope i did not have the analyser when i was playing with the vector hybrid, it looked very good on the swr meter compared to the narrow banded i-10k, i used signals at distance and swr to dial it and friends sigmas in,
nothing i have read so far has convinced me i was wrong in feeling i was manipulating radiation angle by altering relative current phase in the sleeve and monopole but im still learning.

 

[HomerBB]

As I posted in the "... New MFJ-259B" thread, when I put the 259B on the Sigma IV I had constructed, although it looked good on the SWR meter, I was so put off by the analyzer readings I took it down until I could get back to it later when I've learned a bit more about what I'm looking at on the analyzer.

I just was wondering, and my experience with my Qv4k, and the S4 leaves me no doubt you have every right to trust the performance of yours.

 

[Needle Bender]

Hey gamegetter, I offered the DX info as an addition, not for comparison sake, however, I have never been so continually surprised at how well it seems to bag DX and I've shot DX on many omnidirectional antennas. It's rather stunning at how well it does, surprises me every time.

 

[bob85]

i would not worry about what the analyser says homer, what matters is your radio is happy with the load it sees and the signals are the best you can make them,

heres a plot of a friends homebrew vector, he also felt that the antenna maybe worked better when extended than when adjusted for best analyser numbers, i have not spoken to him about it recently.


http://i5.photobucket.com/albums/y152/ukmudduck/swr.jpg

 

[Marconi]

Hey gamegetter, I offered the DX info as an addition, not for comparison sake, however, I have never been so continually surprised at how well it seems to bag DX and I've shot DX on many omnidirectional antennas. It's rather stunning at how well it does, surprises me every time.

I understand your posting the DX signals, but I agree with gamegetter, those signals prove very little.

I posted the other day that I have my GM and my Starduster up and side by side, and I cannot tell one bit of difference in most of the DX signals I hear. Lately we have not had strong DX signals, so the ones I am able to hear are low on the RX meter, like S2-S5, maybe. That said, if I hear em' on one antenna, I hear em' on the other. There is no difference, and that is not using my meter to determine anything, so my using sideband is not and issue either. Go figure that.

Of course, I have no idea what TX reports I would get with the signals between these two antennas, but if they were different, then I might have to wonder about antennas being reciprocal like you guys talk about from time to time.

I generally don't do TX signal comparisons on the air. But, I have never seen a 2 Sunit or more difference in signals either...among all of the typical CB verticals we talk about. But I think I'm all alone on that score. ^can not stand it^
I think if I ever saw an antenna make that much difference consistently, I would put it up as high as convenient, and leave it up. You guys would also very likely get tired of hearing me talk and rave about that antenna.