TopBand: 1000MP RX

[wb6tza@compuall.net]

re the "poorer than should be" RX performance on 160..

dont forget the "TUNED" mode for the front end inserts deliberate reduction
in front end gain for the 1.8-7.5 mhz front end amp.  I have measured this
reduction at about 10db, and Yaesu concurs that is correct...  to see this,
tune to a signal at 2.000, 3.500, 7.000 as you tune across the exact .0000
freq, the RX switches from Tuned to Flat (the GEN light comes on), and you
will see a fairly large change in S meter reading, and hear a SMALL change
in S/N, about the same amount as noted when selecting IPO.  this does NOT
apply above 10 MHz, a different tuned amplifier is used.

IF you use bandpass filters (Dunestar, etc) in front of your beverage
preamps, or can insert one, it then should be tolerable to set the RX to
FLAT to recover the lost gain for 160,80,40.

for those who hear a lot of "crossmodulation" of CW signals, dont forget to
disable the noise blanker before deciding the RX is being overloaded.   the
noise blanker listens for noise pulses INSIDE the 6 KHZ AM filter width,
so, any strong signal inside that window will tear up the blanker
operation, and sound like crossmodulation.

73
robin critchell, wa6cdr/xz1n top band

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