Re: 80dB now but still needs improvement at 1KHz [OT]

Cursitor Doom <cd@notformail.com> wrote:

On Fri, 8 Nov 2024 12:41:18 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
 

Jan Panteltje <alien@comet.invalid> wrote:
>
[...] >
https://panteltje.nl/pub/audio_90_degrees_phase_shifter_circuit_diagram_
IMG_6958.JPG
>

Thst is a 90 degrees phase shifter over the speech audio range for
generating I and Q signals for SSB modulation. design is not mine, used
trimpots to test it :-)

>
After reading through some back issues of 'Rad Com', I had been thinking
along similar lines for generating SSB.  I was also intrigued by the
Weaver method and wondered if modern multi-stage filters between the
inverted and non-inverted audio sidebands  could reduce the audio notch
effect and allow a wider frequency response.
>
I let my licence lapse many years ago and had been thinking about taking
it out again before the call-sign got issued to someone else.  The
problem is that they need to see my certificate to prove I passed the
Radio Amateurs' Exam and I don't know where to find it.

 
You'd ace it. It's been dumbed down so much over the years you'd have
to be some kind of imbecile not to pass. I'm not sure if they still
have it in two parts: technical and legal. However, the legal bit is
pretty Janet & John as well.

The Rad Com magazines from the 1960s include reprints of recently set
exam papers, some of the questions are quite mathematical.  In those
days it was recognised that radio was just another branch of electrical
engineeing, so you were expected to be able to do calculations on A.C.
networks and understand PI tank circuits.

--
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk