[minima] Re: New idears
- From: allison <ajp166@xxxxxxxxxxx>
- To: minima@xxxxxxxxxxxxx
- Date: Tue, 09 Jun 2015 19:00:40 -0400
On 06/09/2015 03:31 PM, beninturkye@xxxxxxxxx wrote:
Hello everybody,
I had some thoughts about this project, so i did some typing this
weekend. So find added to this email an html text file and 3 drawings,
download them and read it in your brauser.
Regards Ben PA9B
One of my transceivers is a 6M rig doing exactly that for TX and RX and
its quite good. I also have others using
the same techniques.
Version 3 tx can work, I've been running that for years, also radios
like Central electronics CS10 and Hallicrafters HT37.
With attention to the audio phase shift networks opposing sideband
rejection over 40 to approaching 50db is very doable.
However, the receiver design is conceived wrong and will not work. The
phase shifter for the RF after the preselector
is in the wrong place and will not work. It should be a zero degree
splitter for the RF in with the resulting audio having
the phase shift networks and that output going to a summing/difference
amplifer.
Look up the work of KK7B Rick Campbell, and Dan Tayloe and a few others
for examples of current work along these lines.
The critical work for TX or RX using that technique is phase and
amplitude errors degrade the opposing
sideband suppression. Distortion is also undesirable but modern opamps
can do that well at audio.
Generally speaking a good phasing (image reject) system has as many
parts as a good superhet with the
advantage of most of the work being done at baseband (audio).
Allison
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