The following from long-time friend W4ZCB and maybe of
interest to some on the list. I'd forwarded Wayne's response
as I knew Harold ('ZCB) would be interested. Harold is one
of the designers of the original Signal One and the ETO line
of amplifiers.
Ken Kopp - K0PP
----- Original Message -----
I appreciate the response given by Wayne, but his response as given does
the
AOR 7030 somewhat of an injustice because of his unfamiliarity with it.
John Thorpe is the design engineer of the 7030, and he's in the middle
of
doing his follow on design right now. I saw the prototype when in
England
last month and it's gorgeous. The 7030 (over 10 years old now) and it's
successor are upscale receivers only which goes for something over
$1,000.00
The LO in the 7030 is indeed a PLL, but the design is unique and was
"invented" by Colin Horrabin G3SBI. It achieves a superior phase noise
characteristic by the use of a two tank VCO, which causes the phase
noise to
fall at the higher rate of some 30 dB per octave away from the carrier
instead of the 20 seen with a conventional single inductor oscillator.
When
Colin originally came up with the design, it was somewhat controversial
and
several folks were claiming that it couldn't perform as advertised,
despite
the fact that if they had built one, they could have measured it.
A mathematician named Tibor Hajder, a private contractor to the
Hungarian
Communications authority, proved Colins concept mathematically and
published
a paper in Applied Microwave and Wireless proving the concept. The
editor
of AM&W added the header to the article as "Occasionally, a paper is
published that is so timeless and important, it is referenced for
years.
This is such a paper."
I first met Colin over 10 years ago and we have visited many times and
have
mutually worked on several design facets of receivers. He measured a
mixer/filter I had built when he was still employed at Darsbury Labs
and had
access to the Queens finest test equipment to have a third order
intercept
in excess of +50 dBm which as far as either of us knows still holds the
record. A mixer this good REQUIRES a good LO or it's wasted. Colin is
also
the brilliant mind that brought us the "H"-mode mixer. This topology
removes
the mixer switching from the signal path and allows these kinds of
intercepts to be made. The "H" mode has been the last several ARRL
handbooks, the RSGB handbook, and is utilized in the Picastar
transceiver
which was featured in 20 contiguous issues of the RSGB's flagship pub
Radio
Communications. His twin tank oscillator is also featured in the
transceiver
named the CDG2000. (Colin is the C in there). It and the Picastar are
extremely popular homebrew projects that have been replicated all over
the
world.
Regards
W4ZCB
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