Topband: Diversity-capable transceivers

[Tom W8JI]

Barry,

It is more than just second receiver quality. For maximum diversity effect, 
the receivers must use a common time base for both channels. They do not 
have to be phase synced (unless blended into mono), a person's brain will 
learn around that. The channels should not drift phase when on a given 
frequency, and if phase changes with tuning, it should be very gradual.

This can be checked by running a common oscillator or carrier signal into 
both channels and listening in mono. Another test is observing background 
noise with a single antenna common to both channels. Listening in mono can 
be as simple as laying the headphones on the desk. There should be no beat 
warble or no fading and peaking on a carrier, and when the band is swept on 
noise any change in apparent audio level with frequency change should be 
very gradual.  Ideally there should be no changes at all.

My R4C's, because I used one receiver's oscillators to run both channels, 
were perfect. The K3's I have are imperfect, they have a gradual phase 
change between channels with frequency.

My FT1000D was terrible, as was the Orion I had. They gave some diversity 
effect, but were so far unsynced they did not give the deep noise digging 
the K3 or R4C system would.

If you never use a system that is phase locked, you might not realize the 
difference. The channel audio phase relationship has to be stable without 
drift to get the real enhancement.