Re: [K2] Sensitivity Spec

Posted by Don Wilhelm on Aug 16, 2017; 12:29am
URL: http://elecraft.85.s1.nabble.com/K2-Sensitivity-Spec-tp7633423p7633431.html

Steve,

Typically, the receiver is limited by the noise floor, so the MDS will
not change much whether the preamp is on or off.  While the preamp will
increase the strength of the signals, it also adds to the noise floor.

Generally a transverter will have a low noise preamp with plenty of
gain, so there is usually no advantage in running the transceiver with
the preamp on.  Use your ears while listening to a strong signal to see
if you can detect overload of the receiver preamp - if so turn it off,
but if there is no overload distortion, you can leave it on.

Typical MDS measurements are made at 500 Hz.
I typically do a quick test of the sensitivity of K2s that I repair.  A
-130dBm signal should be detectable above the receiver noise floor.  For
that test, I have observed that it makes little difference whether the
preamp is on or off.  So I would suggest you test whether strong signal
performance is better with the preamp on or off.  My wager is that you
will choose to leave it off unless your transverter(s) have negative
gain on RX.

73,
Don W3FPR

On 8/15/2017 4:10 PM, Steve Kavanagh via Elecraft wrote:
> I'm just trying to evaluate if I have the gain distribution right for a K2 used as an IF for a 10 GHz transverter, through a 2 m transverter mounted inside the QRP top.  The K2 manual gives a specification for the MDS but fails to define the bandwidth at which it is measured.  Sherwood's receiver table lists some measured values at 500 Hz bandwidth but fails to note whether the preamp is on or off for these measurements.  So I am not quite sure what the sensitivity should be.
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