Topband: CY9C

[Don Moman VE6JY]

We ran both phone and CW, both with amps (~1 kw) simultaneously on 160m
during the RAC contests.  Also did that on all the other bands too. SSB was
1845 and CW was 1825 (we never op on a multiple of a 10 khz MW IMD
product). Separation was perhaps a wavelength.  No special filters or
anything were used. Interference was minimal, often more due to mixing
products from all the other combinations of transmitters.   I felt the
radios (we used all ICOM 756PROx) with their clean outputs were
instrumental in accomplishing this.  I'm not sure more modern radios would
allow that.

On Sat, Sep 7, 2024 at 2:06 PM Jim Brown <jim at audiosystemsgroup.com> wrote:

> On 9/7/2024 11:17 AM, Rudy Bakalov wrote:
> > How does this work? IF this is indeed the case, this would be a great
> solution for multi-op contest stations.
>
> Very careful design of both RX and TX antennas and their matching
> networks, physical separation of RX and TX antennas, combined with very
> careful design of very narrow-band pass and reject filters for RX, and
> combiner networks for TX that prevent each TX from seeing the other.
> Combining networks for TV and FM broadcast transmitters have been in
> common use in major cities for more than half a century at sites like
> the Empire State Building, the World Trade Center, Chicago's Hancock
> Building and Sears Tower, and mountaintop sites in the West.
>
> Very complex design of both the system and individual components. As one
> of my old EE profs would say, "non-trivial!"  Uses everything I learned
> in EE 60+ years, and at a much higher level than I ever did anything. :)
>
> 73, Jim K9YC
>
>
>
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