[Premium-Rx] More Diversity Reception Approaches

[John H. Bryant]

Many thanks to Richard for uploading Capt. Lee's wonderful article on 
Diversity Reception. I remember the first time that I read it in 1964 or 
5.... I've lusted after such a set-up ever since and I've enjoyed this 
exchange.  I'm not sure that it is off-topic, either... Its about one way 
to use Premium Receivers.

Some of you might be interested in a very non-original article that I wrote 
some years ago about an audio switching arrangement that facilitates yet 
another type of Diversity Reception... "Receiver Diversity Reception."  The 
article is currently posted on the dxing.info site' Equipment page under 
"Audio Switching Network"  The URL of the entire equipment article 
collection is   http://www.dxing.info/equipment/

The audio switching network article describes a simple network of two 
switches and several connectors which allows you to interconnect the audio 
output of two receivers in various ways. When coupled with a pair of stereo 
headphones, it allows you to send the audio of either receiver to either 
'phone (only) or the audio of either receiver may be heard in both ears. 
Since this set-up takes the audio feed from either the headphone jack or 
the external speaker jack of the receivers, no mods are required, of course.

What makes the article relevant to this discussion string is my experience 
using the network to use two DIFFERENT receivers, simultaneously, in 
"binaural reception" of the same signal.  The binaural reception concept 
was first introduced to me by the famous Hildreath filter of twenty years 
ago, or so. The idea being that, if you have two different audio feeds each 
containing some of the same information (the wanted signal) and some 
different information... QRM, etc, that is more dominant in one than the 
other, our brains will focus on what is  identical in the two feeds and 
tend to ignore what is different. I've used this many times to good benefit 
in improving the intelligibility of very weak AM audio when DXing 
Trans-Pacific AM signals on the BCB or lower shortwaves.  What it feels 
like is that the "wanted signal" is in the center of your head and the 
unwanted stuff is way to the outside.

I find that this strategy works best using two quite different but good 
(premium) receivers... Especially if one is a modern digital rig like the 
Tentec 340 or one of the WJ's and the other is an excellent, but analog 
receiver. The two receivers, even when fed by a shared antenna, usually 
respond to a signal differently enough to create the binaural effect. 
Although the circuit and technology is laughably simple, there have been 
many circumstances where this approach has helped me enormously.  I should 
add that I also have used a Tentec 340 coupled to a Tentec 320 (the cheap 
black box) and I've had quite a bit of success binaurally, with 
them.  Though both are rather thoroughly digital, I suspect that it is the 
difference in algorithms and processors that generates the binaural effect 
there.

Where this simple circuit falls apart is in combining two versions of the 
same signal that are suffering from significantly different fading 
patterns... as in polarization or frequency diversity reception.  I've 
listened to the same feed from All India Radio on two different shortwave 
bands and had the binaural/spatial effect whipping back and forth between 
my ears like I'd had four too many of our Founder Greg Bailey's 
Margaritas!  That, of course is where the latter circuits in Capt. Lee's 
article really shine.

If you are interested in trying out "receiver diversity, binaural 
reception" the article is in the lower right of the dxing.info Equipment 
page. While you are there. there are several other good articles... I'd 
strongly recommend the two on impedance transformers for receiving 
antennas.  The longer of the two contains very new and (I think) 
groundbreaking work by the well-known Lowfer guru, Bill Bowers and Nick 
Hall-Patch of this list; I was just the scribe on that one. The shorter of 
the two articles covers fabrication of toroid-based transformers for those 
who have never "rolled their own." There are a couple of other articles 
there either by or featuring Pr-Rx list members. The first is a new 
addition to the equipment page called "Rack-mount Equipment Cases for 
DXers" by Pr-Rx member Guy Atkins. Its about 4.5 megs, but well-worth the 
download.  Also on the front page of the dxing.info site, 
http://www.dxing.info/ Guy Atkins has "DXing from the Upper Left: The 
Grayland DXpeditions in Sound and Pictures." This is a wonderful article 
with photos of a number of Pr-Rx list members. Unfortunately, the only 
camera there when list Founder Greg Bailey graced Grayland BROKE, so you 
will miss his "Aging Surfer" good looks.

Thanks again to both Greg and Jan Skirrow for alla their hard work in 
keeping this group somewhat organized and headed in similar directions!

John Bryant
Eastsound, WA

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