[Elecraft] Diversity Reception

[Jim Brown]

On Mon,8/3/2015 8:41 PM, Edward R Cole wrote:
> However it is not always bad for the two diversity channels to be 
> combined for best signal.  The example is digital signals which the 
> human brain cannot process.  The example was given of using two 
> antennas of differing polarity for HF. 

Combining, yes -- into different inputs of the analysis system. Again, 
when signals combine IN THE SAME SIGNAL CHANNEL (emphasis added) 
differences in the time/phase response of the two signal paths can cause 
destructive interference which degrades decoding.

OTOH, in a sophisticated decoding system, there's certainly nothing 
wrong with bring both signals in on separate inputs, then combining 
them, or choosing the best signal, or even processing the signals to 
enhance readability. But ONLY combining them on a single electrical 
channel is a bad idea.

One of my neighbors (near Santa Cruz) has a VERY interesting UHF 
repeater system. It's multi-site(five sites going on six),voted (meaning 
that the RX with the best signal is transmitted), and simulcast (all 
sites transmit at the same time). To make this work, Bboth audio and RF 
are synchronized to the Hz using a GPS reference and some really 
innovative use of low cost audio and networking gear. If you're 
interested, look at wb6ece.org, especially the Technical Info page, 
where there's video and audio of a talk that KA6SQG did at Pacificon 
about his system (WB6ECE is his dad's call). The audio is not well 
recorded, so you'll need headphones for good copy.

73, Jim K9YC