[amsat-bb] Duplexer to Dual-Band Vertical

[Paul Stoetzer]

Even at 100 watts output and 60 dB of isolation (the rated isolation of off
the shelf diplexers, though as you mention, they may be better), the
maximum amount of transmit power that might possibly get back into the
radio is -10 dBm or 100 uW (100 watts = 50 dBm - 60 dB of isolation = -10
dBm). That won't do any damage. Cheap off-the-shelf ATSC tuners are rated
to handle something around -5 dBm for those living very close to extremely
powerful television transmitters.

73,

Paul, N8HM

On Tue, Feb 11, 2020 at 10:13 AM Mike Thompson via AMSAT-BB <
amsat-bb at amsat.org> wrote:

> It’s not ideal, but there are plenty of worse things that one can do. Last
> time I tested some off the shelf diplexers on my former employer’s VNA, I
> found them to have 80-90db of isolation. That’s not bad.
>
> On Tue, Feb 11, 2020 at 7:08 AM VA3ASE via AMSAT-BB <amsat-bb at amsat.org>
> wrote:
>
> > Good morning,
> >
> > I was chatting with a friend about his experimentation with amateur
> > satellites and have been pondering if his setup is "safe" for his radio.
> He
> > is running an FT-847 through a duplexer (diplexer if you want to be
> > pedantic) and into a dual-band vertical base antenna on his roof.
> > Definitely not an ideal setup, but meant to be temporary until time and
> > better weather allow. He has managed to make some FM contacts on AO-92
> with
> > it.
> >
> > My concern is him using a duplexer in this manner while running full
> > duplex. I suppose this is similar to what people must do if using an Elk
> > antenna. I just worry about there being enough isolation between the
> ports
> > and damaging his transceiver. Are there others using similar setups or is
> > this something to avoid?
> >
> > 73,
> > Alex VA3ASE
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> _______________________________________________
> Sent via AMSAT-BB at amsat.org. AMSAT-NA makes this open forum available
> to all interested persons worldwide without requiring membership. Opinions
> expressed
> are solely those of the author, and do not reflect the official views of
> AMSAT-NA.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
>