[TowerTalk] 1 or 2 dB

[Jim Brown]

On 5/19/2022 11:38 AM, Jim Brown wrote:
> Combining the outputs of the two receivers to a single (mono) channel is 
> problematic, because the phase relationships at audio have a good chance 
> of cancelling.

I should add that when diversity reception is used with wireless 
microphones for broadcasting, entertainment, and worship, the outputs of 
the two receivers are "voted" for best signal to noise ratio, just as 
multiple receive sites are voted in VHF/UHF repeater systems. When I 
lived in Chicago, I was part of a team maintaining one of several such 
2M systems. The transmitter was on a tall building in the Loop, 
receivers were at opposite ends of the metro area.

Here in the Santa Cruz Mountains, there's a very innovative system with 
6-8 sites (a variable because wildland fires have destroyed several 
sites), each of which receives and transmits the voted combination. The 
transmitters are synchronized; cancellation is minimized because the 
mountainous terrain combines with inverse square law causes arrivals at 
any RX location from multiple transmitters to be nearly equal.

http://www.wb6ece.org/technical-info.html

73, Jim K9YC