Topband: New MFJ 259C available

Paul Christensen w9ac at
Wed Mar 5 14:03:07 EST 2014

> Where is a selectivity spec or a description??
> 73 Tom


Apart from the N2PK analyzer, I don't know any published selectivity spec. 
The detector minimum res. bandwidth of the N2PK unit is 7 Hz and produces 
+4dBm into 50 ohms.

FWIW, RigExpert put together a comparison of analyzers based on measurement 
topology.  For sure, it's a biased piece -- especially when the MFJ product 
is discussed.  So, keep that in mind.

The plot below shows how well the N2PK analyzer can selectivly ignore a 
large multi-volt base voltage from three nearby AMBC stations located 2 
miles to the south.  Two of the AM stations are Non-D in the daytime.  One 
is 15KW, the other is 5KW.  Note that the T is resonated to 1420 kHz, right 
where the stations transmit (look for 1320, 1460, and 1530 kHz).  The 
attached plot shows total RF immunity on the X trace.  On the R trace, small 
"blips" do show - each representing the local AMBC stations.  However, even 
these can be easily ime-averaged away in the software.

Paul, W9AC 

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