On Thu, 07 Oct 2010 14:58:38 -0400, Bob wrote:

Hi,

A bit off topic, but I figure you folks are the true theorists out
there, and would probably know about this.

Am thinking about purchasing a shortwave defined radio receiver from
WinRadio (http://www.winradio.com/home/g33ddc.htm).

Here is copy from part of their spec sheet:

"The receiver's robust front-end is equipped with an
ultra-high-linearity amplifier which results in exceptional
strong-signal performance. This already robust front-end is further
enhanced with a user-selectable preselector that can operate either in a
fully automatic or user-configurable mode. As many as 119 different
filter combinations can be constructed by the user (91 bandpass, 14
low-pass and 14 high-pass). The front-end employs 34 subminiature
electromechanical relays (rather than often used but distortion-prone
semiconductor switches) to ensure high dynamic range."

Was really surprised to see: The front-end employs 34 subminiature
electromechanical relays (rather than often used but distortion-prone
semiconductor switches) to ensure high dynamic range.

I am retired now, so haven't kept up withese things, or the state of the
art nowadays, but are they still using electromechanical relays for
front ends feeding a 16 bit A to D ?

Haven't semiconductor switches, caught up with reed relays for this
application by now, or do they "still" provide a lower "on" resistance,
etc. ?

Any thoughts would be most appreciated.

Thanks,
Bob
Really good relays are available at very low cost today. Like less
than a dollar each! Between the Low Pass filter and the inboard
antenna tuner my TenTec Jupiter there are about 30 relays.

Other than overrall circuit size and switching speed I see no
advantage for semiconductors as compared to relays.

As far as "Why Ham Radio instead of internet?" :
I worked Japan last night (not my first time) on PSK-31/20 Meters with
40 watts and off the side of the Beam. The feeling was not unlike my
first Ham Radio contact 50 years ago....

It is my kind of getting high!
John Ferrell W8CCW