[Elecraft] K2 receive sensitivity

[N2EY at aol.com]

In a message dated 1/17/07 6:37:02 AM Eastern Standard Time, 
d.cutter at ntlworld.com writes:


> The G2DAF receiver did it for me when he demonstrated gain and s/noise 
> ratios.    If I remember rightly he had no gain in the front end, only matching 
> to the antenna and input filters; all the gain was in the IF.

Depends on what version he built. The last version used a push-pull RF 
amplifier and mixers, all low-noise triodes.

There *was* some gain in that front end. The RF amplifier had just enough to 
make up for the losses in the tuned circuits, and the two mixers had some 
gain, but not a lot. They were primarily designed for dynamic range and low noise, 
not gain.

The result was that there wasn't much gain ahead of the selectivity.

Another example is the fabled Squires Sanders SS-1R receiver, which used 
balanced 7360 mixers and no RF stage. But it cost $700 back in the early 1960s!

IMHO, the trend started with a 1957 QST article by W1DX called "What's Wrong 
With Our Present Receivers?".  There was also QST articles called "The Miser's 
Dream" in 1965, and "An Experimental Receiver of 75 Meter DX Work", in 1971, 
which showed receivers using those basic principles.

73 de Jim, N2EY