Topband: New MFJ 259C available
w9ac at arrl.net
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.
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