[GreenKeys] CV-483

[Roy Morgan]

On May 27, 2008, at 7:35 PM, Bob McConnell wrote:

> ...t the basic idea the Navy taught me about diversity was to  
> receive the same signal on two frequencies.... The R-1051B was the  
> most common HF receiver of that era in the tin-can service.


As mentioned:

Frequency diversity:  receive two or more frequencies carrying the  
same information. Combine and/or choose the stronger one.

Space Diversity:  Use two or more antennas on the same frequency,  
preferably 500 or more feet apart.  You can't do that on a destroyer  
("tin can"), which may be about 300-500 feet long.  They may have been  
able to do it on carriers (800 to 1200 feet long) with the side  
mounted vertical antennas commonly used on them.

The combine/choose function could be carried out between two receivers  
by letting the one with the stronger signal "turn down the gain" on  
the one with the weaker signal (tie the AGC lines together).  Or it  
could be done at the decoded signal level by using the stronger of two  
signals in a comparator, as in the URA-8 or similar.

I would guess that there is polarization diversity, where  
horizontally- and vertically-polarized antennas are used, possibly at  
the same location or even the same antenna structure.  Maybe the  
cubical quad antenna acts this way.

Roy


Roy Morgan
k1lky at earthlink.net
Lovettsville, VA 20180