mobile end fired array question

[loosecannon]

this is the setup where you see two antennas on one vehicle.
(they are fed in a very unique manner)
does this offer any db gain over just using one antenna?

i realize it makes it very directional, but if there is some gain, i might want to try it.

thanks for any help,
loosecannon

 

[W5LZ]

loosecannon,
It can offer about the same gain as a two element beam at about the same height. How much is that? No idea - lol. Don't expect quite as much "gain" as is typically claimed, by either the beam makers or the "users"
- 'Doc

 

[Captain Kilowatt]

I disagree a bit Doc. While it may offer as much as 5dB gain depending on spacing and phasing,that gain is over a single antenna which is typically a low gain or negative gain antenna as compared to a dipole. A two element beam has gain referanced to a halfwave dipole. What I am saying is that if a two element beam has a gain of 5 dB and one of the mobile antennas in question is a short loaded type that offers a TRUE gain of -1.5 dB then the total system gain may result in only 3.5 dB gain as referanced to a dipole.I hope I made myself clear,the morning coffee hasn't kicked in yet.

 

[W5LZ]

QRN,
I know about coffee deprivation! What I can't say I know about is what the actual gain of such an antenna would be, so I'd take your numbers as pretty close. I did make one 'CYA' clause to that guess though, the "at the same height" thingy for the two element beam when compared to the mobile. Which would also be comparing the mobile to a dipole at somewhere around 4 or 5 feet, maybe? So, while I know it isn't accurate by any means, it ought'a be fairly close.
I have no intention of trying to measure a 'mobile array's gain, and am too lazy to 'plug' it into a modeling program. 'At's about as close as it gets at 3:30 AM!
- 'Doc

 

[Captain Kilowatt]

I hear ya Doc. What I was saying is that the gain of a phased array is usually referanced to that of a single element (antenna) in that array.A pair of phased Wilson 1000's for example my show a gain of 4.5dB over what a single Wilson 1000 will do.It will not necessarily show the same gain as another antenna claimimg 4.5dB gain as that other antenna's gain is usually referanced to a dipole (or isotropic) and not a Wilson 1000. I'll stop now as I am starting to confuse myself. I have now had toooo much coffee after having had only 3 1/2 hours sleep in the last 46 hours. :shock: My brain says LET'S GO! while my body says NO WAY!

 

[loosecannon]

thanks for the responses guys.

yes, QRN, you are making sense.

i guess i am only interested in its gain in terms of: one 102" whip, as opposed to two 102" whips.

thats what is used in the literature i have.

so, if i understand correctly (yeah right!LOL)
by using the end fired phased array, there could be a "gain" over using a single 102" whip, and it could be on the order of a doubling of output power? maybe a little more?

im afraid to use the term "db" as it implies some sort of reference, and i dont exactly know what that reference is in this case.LOL

oh great, where's MY coffee!
loosecannon

 

[Captain Kilowatt]

In this case loosecannon,the gain quoted is referanced to a single 102 whip.If you used a differant antenna ,as long as they were both the same, then the gain would be referenced to whatever one of those antennas would provide.

 

[loosecannon]

so, if i call my 102" whip a "dipole", then i really could achieve about 5dbd gain by doing this?
loosecannon

 

[W5LZ]

/|\
.|.
What he said. And then, you have to remember that those 'gain' figures are only approximate. Things change from one situation/installation to another.
And then, if you do the phasing 'right', you can make the thing unidirectional, omni directional, or 'broadsided'. I think you made reference to that to start with though. Oh well, anyway...
- 'Doc

 

[ChrisBama351]

Any luck with the 102" array, loosecannon?

Is there a good, free, easy antenna pattern program to see the patterns of different possible setups? Like if You take this 180 degree out of phase array and add a reflector or director or both. How would the pattern change? That would be kool to play around with.

Is there a way to see the pattern for my actual antenna setup?
or will an analyser, app, or other devise show my actual pattern?
How do I know what my setup is real world doing rather than what a computer calculates the pattern to be? I might have a unwanted null? That's different than an unwanted station which is where we want the null. lol

180 degrees out of phase is half electrical wavelength is that right?
Which is approximately 12 ft with vf .66 on 27.205? is this correct?

Thanks for all the great info!
72's Ala"Bama" in Colorado