[Elecraft] Orion added to Elecraft rig RX comparison page

Fri Dec 5 02:15:00 2003

Dave;
The BDR test that the ARRL performs measures the 1 dB compression point of
the receiver.  The test procedure is to inject an inband signal that is 20
dB above the MDS and measure its output level as the signal power of the out
of band signal is increased.  The 1 dB compression point occurs when the
inband signal decreases by 1 dB.  The BDR is the 1 dB compression point
minus the MDS.

This measurement does not take into account reciprocal mixing from the LO
phase noise.  If you look at the output audio when you make this
measurement, you will first see the noise floor increase and then the inband
signal starts decreasing.  In some receivers, the phase noise completely
covers up the inband signal before its level is reduced.  This type of
measurement is useful if you are listening to a strong signal and are
concerned about its level being reduced by a strong nearby signal.

The DR3 measurements does include phase noise since that test procedure
measures the total power in the audio output.  The K2's DR3 measurements are
phase noise limited.  If the K2 had a perfect local oscillator, the K2 would
achieve a DR3 of 101 dB in both the 5 kHz and 20 kHz measurements (this can
be computed from the IP3 measurements).  This measurement is more relevant
if you are interested in copying a weak signal and are concerned about
nearby strong transmitters driving the signal into the noise.

So the basic rule for these measurements are to look at DR3 if you are
interested in the effect on weak signals and look at BDR if you are
interested in the effect on strong signals.

-John

----- Original Message ----- 
From: <[email protected]>
To: <[email protected]>; <[email protected]>
Cc: <[email protected]>; <[email protected]>
Sent: Tuesday, December 02, 2003 9:32 AM
Subject: RE: [Elecraft] Orion added to Elecraft rig RX comparison page

I notice that the K2 phase noise at 4 KHz offset the LO is -124 dBc. The BDR
at 5 kHz is 135 dB. Shouldn't the phase noise dominate and determine the BDR
at this offset? I am making the assumption (perhaps incorrectly) that if the
phase noise at 5 kHz offset is -124 dBc then a signal at +124 dB above the
desired received signal will mix to produce noise of 0 dB (referenced to the
received signal). Note that I am assuming the phase noise at 5 kHz offset is
the same as at 4 kHz offset.

   Dave WX7G