Tuning dual antennas...and etc ?'s

M8R-1kbf631 · Jul 28, 2011

WA4GCH said: ↑

" Using two identical / properly matched antenna's increases gain by 3 db. "

NOT TRUE ........

Only true if they are stacked ABOVE each other like they do on VHF verticals. Otherwise you get a distorted partern that will show gain and loss ...

Channel Jumper is correct, using two identical / properly matched antennas can and often does result in an additional gain in the favored directions approaching 3db.. as in the case of dual antennas at anywhere between 1/8 to 1/4 of a wavelength spacing. one first has to understand where antenna gain comes from. in this particular situation the additional gain at right angles (broadside) to the plane of the "array" is a direct result of the cancellation of radiation occurring off of the ends (endfire) of the array, in the plane of the antennas. antenna gain is simply the ability of an antenna or antennas to concentrate the radiation in the desired direction by eliminating radiation in unwanted directions. the properties of phasing allow us to "steer" the antennas pattern. this applies to both the horizontal and vertical planes. gain is increased to the front and the rear at the expense of reduced response from the sides. the same principles apply whether the "stacking" is accomplished in the vertical or horizontal planes.

if you can attenuate the endfire portion of the pattern by 3db. then it shows up in the broadside portion of the pattern with this phasing & spacing configuration.

"a distorted partern that will show gain and loss"

distorted, maybe. that depends on the vehicle symmetry. the uniform pattern resembles a slightly elongated figure 8 pattern to the front and the rear when viewed from above. gain and loss? yes, gain in desired directions at the expense of loss in the undesired directions. the trade off is being able to hear and talk up and down the road in exchange for not being bothered from signals coming in from the sides. add a simple antenna switch and another phased line section and you could switch back and forth from broadside to endfire at will. a 3db. increase is equal to a doubling of transmitter power output.
Click to expand...

WA4GCH · Jul 28, 2011

AGAIN ...... Phasing only gives you a poor beam .... I have run phased 1/4 wave wips on 52.520 FM with a switch and found it did little ....

HYGAIN prints a detailed phasing diagram ......

Here it is ....

M8R-1kbf631 · Jul 28, 2011

no, phasing gave YOU a poor beam and your rationale is that if you can't do it then it can't be done.

WA4GCH · Jul 28, 2011

M8R-1kbf631 said: ↑

no, phasing gave YOU a poor beam and your rationale is that if you can't do it then it can't be done.
Click to expand...

No it is a POOR BEAM ......

At 40 meters 2 phased base antennas makes SENSE
AT 11 METERS ON A CAR JUST LIKE ON 6 why bother ......

Lots of wires little in return .....

Dieseldowg · Jun 8, 2017

WA4GCH said: ↑

" Using two identical / properly matched antenna's increases gain by 3 db. "

NOT TRUE ........

Only true if they are stacked ABOVE each other like they do on VHF verticals. Otherwise you get a distorted partern that will show gain and loss ...

Here is a 3 DB Gain antenna stack for horizontal gain .... and 4 stacked for 6 db gain also a 7 db gain vertical antenna using 3 5/8 waves stacked .
Click to expand...

Not talking about 2 meters or cm bands

rabbiporkchop · Jun 8, 2017

WA4GCH said: ↑

No it is a POOR BEAM ......

At 40 meters 2 phased base antennas makes SENSE
AT 11 METERS ON A CAR JUST LIKE ON 6 why bother ......

Lots of wires little in return .....
Click to expand...

It's nice to cancel out signals coming in from the sides and make it easier to hear front to rear. It makes a drastic difference in what you're capable of hearing straight ahead of you and to the rear.

Log in or Sign up

Forums

Tuning dual antennas...and etc ?'s

M8R-1kbf631 Bobtail Member

Trucking Jobs in 30 seconds

Wait, employers can't reach you!

WA4GCH Road Train Member

Attached Files:

oldphotos_112.jpg

oldphotos_114.jpg

M8R-1kbf631 Bobtail Member

WA4GCH Road Train Member

Dieseldowg Bobtail Member

rabbiporkchop Road Train Member

Trucking Jobs in 30 seconds

Wait, employers can't reach you!

Log in or Sign up

Useful Searches

Tuning dual antennas...and etc ?'s

M8R-1kbf631 Bobtail Member

Wait, employers can't reach you!

WA4GCH Road Train Member

Attached Files:

oldphotos_112.jpg

oldphotos_114.jpg

M8R-1kbf631 Bobtail Member

WA4GCH Road Train Member

Dieseldowg Bobtail Member

rabbiporkchop Road Train Member

Wait, employers can't reach you!