Topband: We need better preamps for 160 because FT8 activity

[Charles Morrison]

George, Jim,
Where can we find George's work for these items ??
-Charlie N1RR

On Wed, May 24, 2023 at 5:06 AM Jim Brown <jim at audiosystemsgroup.com> wrote:

> George's work on this system is first class engineering, and has
> revolutionized TopBand expeditions, allowing simultaneous use of the two
> best small signal modes, CW and FT8, by expeditions transmitting high
> power. He developed the system so that the expedition wouldn't miss the
> one or two "magic" nights during a 2-3 week trip that generated most of
> the QSOs.
>
> But that's a minor achievement in comparison to his Radio In A Box, that
> greatly reduces the difficulty of activating islands and other locations
> with extremely challenging access. Again, engineering at the highest
> possible level. He's been field-testing both systems for contests from
> his island in C6 for years, and is currently sailing through Oceania on
> another field test. Radio in A Box could have turned that recently very
> disappointing trip to a very challenging island into a howling success!
>
> George is one of those geniuses who live among us and have done so much
> to advance the state of the art. I'd like to start a movement to
> nominate him for the greatest award the ARRL and world ham radio has to
> offer for technical achievement!
>
> 73, Jim K9YC
>
> On 5/23/2023 11:25 PM, GEORGE WALLNER wrote:
> > I have built, for DXpedition use,  a very selective RX front-end for 160
> > m for simultaneously operating CW and FT8 on shared TX and RX antennas
> > with 800 feet of separation. The LC filter had 8 dB loss at 1825 kHz and
> > it was about 10 dB down from that at 1840 kHz (-8dB at 1825 and -18dB at
> > 1840). That is a 10 dB difference, which should be enough to prevent a
> > good preamp from saturating.
> >
> >
> > (I also built a XTAL filter that was 40 dB down, but only had a 2.5 kHz
> > bandwidth -- OK for a DXpedition that can nominate its RX frequency.)
>
> _________________
> Searchable Archives: http://www.contesting.com/_topband - Topband
> Reflector
>


-- 

-Charlie N1RR

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