Curt -
The "-*5" reading in the 10 tube version manual is a typo. Should be
"-0.5" VDC.
This NB is designed to remove very short, high amplitude noise.
Automotive ignition (spark plugs and leads) is the most common source of
this kind of noise. This is the ONLY type of noise that is effectively
"blanked" by the NB. Newer NB circuits often provide different settings
for wider pulses, but obviously if the pulse is too wide (most lightning
or power line "hash") the blanker removes so much of the desired signal
that it becomes unintelligible anyway.
The best way to check the NB is to set the AVC to "FAST", disconnect the
antenna and with a clip lead to the antenna jack center conductor drag
the lead across a grounded metal surface. A file is best, but lightly
scratching across a smooth surface will work almost as well. With the
NB "OFF" you should see the S-Meter jumping all over. Turning the NB
"ON" should cause the meter to quiet down considerably.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line & TR-4/C Service Supplement CDs
<www.k4oah.com>
Curt wrote:
The noise blanker on the R-4A I recently acquired doesn't work. That
is, switching into NB makes no difference, pulling V9 or V10 makes no
difference, replacing V9 and V10 makes no difference.
Measuring voltages shows all nominal except on V10, pin 2 measures 0.4
VDC rather than specified 5 VAC. Otherwise, the receiver functions
fine on all bands.
Anyone with ideas?
73, Curt KB5JO
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