[GreenKeys] Space diversity receive antenna

[Duncan Brown]

Harold,

In the heyday of RTTY (1940s-1980s?) space diversity was standard for 
long distance/ intercontinental HF RTTY, like RCA Global & military.  
Most systems combined the two receivers in real-time rather than trying 
to switch them.  The Navy even used triple diversity with three antennas 
and three receivers. The Army CV-116 and the Navy URA-8 & -17 are good 
examples of military units. Collins made a diversity FSK converter for 
commercial service. I believe that the Dovetron MPC-1000 series were set 
up for paring two units for diversity operation.

Most (if not all) of the receivers at KPH/KFS would have been set up for 
diversity.

There seems to still be some frequency diversity RTTY on the HF bands.  
You can often hear what sounds like the same digital signal being sent a 
few hundred KHz apart.  (Frequency diversity makes more sense shipboard, 
where you don't have a lot of room for antennas.)

have fun,

Duncan
K2OEQ



On 1/4/2025 12:29 PM, Harold Hallikainen via GreenKeys wrote:
> I'm really having a problem with QSB. A received signal (20 meters) goes
> from great to down in the noise over several seconds. As an experiment, I
> transmitted both mark and space tones from here in Tucson AZ and received
> them on the KFS SDR in Half Moon Bay CA. I then ran the recorded audio
> into the DSP TU and output the levels of the mark and space filters. The
> results are at
> https://w6iwi.org/script/csvgraph.html?CsvUrl=https%3A%2F%2Fw6iwi.org%2Frtty%2FTuNotes%2Fms220517a.csv
> .
>
> This reminds me of a TV station where I lived in San Luis Obispo CA that
> had a long microwave feed. They put two receive dishes on their tower and
> had a carrier operated relay in the receiver start a slow astable
> multivibrator that switched the receiver input between the two receive
> dishes. The switching would stop when a good signal became present.
>
> So, how about applying this to RTTY? I am using a 30 foot vertical for
> transmit and receive. I could put up a 20 meters dipole about 50 feet
> away. During receive, I could switch between these two antennae.
>
> Is this worth trying? I could use signal strength indicated by the
> receiver. Or I could use something from the terminal unit (such as switch
> during mark hold).
>
> Is anyone using space diversity? Comments?
>
> Thanks!
>
> Harold
> https://w6iwi.org
>
>
>
>
>
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