[Elecraft] Diversity modes

[Bill Frantz]

There are some other uses of diversity modes which aren't common 
in amateur practice, but might be interesting for special applications.

Pro-audio radio microphones use diversity receivers to minimize 
signal loss as the microphones move. I believe, and Jim or Joe 
will correct me if I am wrong, they transmit using FM. By 
measuring the degree of quieting on the two receivers, the 
combiner can decide which signal is better and route that signal 
to the audio mixing board. Since the audio volume represented by 
a FM signal is mostly independent of signal strength, good 
quality audio gets to the board even as the system changes 
receivers. This kind of system might be useful for amateur 
weak-signal FM work.

The other interesting diversity mode I know of is the way the 
costal commercial communication radio stations worked in the 
1930's and later. They were using CW to send messages across the 
oceans. Each station transmitted on 3 separate bands. The 
receivers listened to all 3 bands and routed the "best" signal 
to the operator. (I don't know how they determined the best 
signal using 1930s technology.) Obviously a two channel version 
could be assembled using a K3 with a sub-receiver.

A system where you can automatically determine which receiver 
has the better signal, could be useful for RTTY. Measuring the 
difference in signal strength of the mark and space signals 
compared with the signal strength half way between them might be 
a useful technique.

73 Bill AE6JV

On 8/8/15 at 4:37 AM, ve3iay at storm.ca (Richard Ferch) wrote:

>In Diversity mode, the lower VFO B display works just like it 
>does with a single receiver - it tells you where the 
>transmitter will be when SPLIT is on, but it has no connection 
>with either receiver. Do not make the mistake of thinking it 
>tells you where the subRX is - that is only true in 
>non-diversity mode.
>
>Normal non-diversity dual receive is usable in all modes, 
>including phone modes, although the level of activity and the 
>likelihood of split operation might be low enough in AM and FM 
>that it might not be economically worthwhile to add subRX 
>filters for these modes.
>
>Diversity mode is very useful in CW. It is not useful in 
>digital modes (unless someone can write software to emulate 
>what the human brain does with the inputs from two ears). I 
>don't know how useful it would turn out to be in wider 
>bandwidth modes like SSB, AM and FM - never tried.
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