Antennas in parallel...

if identical and equidistant, using 50Ω cable, then 25Ω

This assumes that both antenna are perfectly decoupled. If there is coupling between the antennas, the impedance will be different.

Thanks gentlemen.
Perfectly decoupled means the radiation from one does not affect / is received by the other ? Or is it about geometrical phasing and on the same plane being identical antennas ?

Antennas cannot be connected "in parallel".
Antennas are radiators and the parameters of a pair or more antennas depend on their mutual location in space, positioning and objects around.

Connecting their feeder cables "in parallel" makes the situation moe complex. Google "antenna arrays" to learn more.

Antenna arrays are in parallel. There is arrays with dozens in parallel, and they work great with high gains.
Some antennas may be phased, out of phase, depending on its disposition, but still in parallel.
Mixed parallel/series work too as far as I have learned..

hello all ,
About parallel with 2 antenna yagi
Assume if I have with ones were workinng on 2100 Mhz(tx) with impendance 75ohm and another ones is 1900 Mhz(RX) with same impedance.
I have question that those 2 yagi in parallel .
If i don't use matching Impedance circuit ? just connected that 2 yagi antenna.
but if using matching circuit can you tell me example simple circuit diagram or maybe how to calculated.

Thank's again

Yes, right.



They are not "in parallel". Antenna array feed is with power splitters that connect each antenna with controlled impedance (50 Ohm at all ports).

If we assume that your feed cable is 75 ohms, then at the junction of the cables from your aerials, each aerial must look like 150 ohms. So you feed each aerial which at its working frequency will transform 75 ohms to 150.
Dipoles are 75 ohms. The 50 ohm figure comes from high power feeders which is the impedance where you can transmit the most power for the minimum use of materials. Many European companies use 60 ohms as a compromise (Rhodes and Schwartz).
Frank

Thanks, Volker.

A massive parallel etched antenna attached; does not have power splitters.

Another array ----> https://www.cemworks.com/wp-content/...p_fed_PAA1.png
And another ----> http://www.hardhack.org.au/files/col...side_array.gif

How is their impedance kept reasonably high with so many in parallel ?

Each radiator is fed via a quarter wave transformer, this is repeated for groups . . . You can see the lines thinning at certain nodes to get the impedance back into range.
Frank

It does. In the picture, you can see that quarter wavelength impedance transformers.

agreed !

Externet, every one of those T intersections IS a power splitter ( divider)

and along with what Frank said ....
That keeps all the impedances in check for each section


Dave