Richard Knoppow wrote:
Jim's on the right track. I'd check the Carrier Oscillator as
described in the manual in Section VIII, Para. B, 1-4. It should
require very little adjustment, unless someone has been "fixing" it!
Then go back to Section IV, Para. C to rebalance the Carrier Oscillator.
The amplified D104 works fine, _as long as you don't turn up the
preamp in the base up too high_ . Best to set the GAIN control on
the transmitter to about 10 - 11 O'clock, and then adjust the preamp
gain for about 150 - 200 mA ON PEAKS, depending upon your voice
characteristics.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line& TR-4/C Service Supplement CDs
<www.k4oah.com>
Curt -
There seems no good reason to use an amplified microphone on a
transmitter like a Drake T-4B or C. The microphone input is arranged
with a series resistor that should present essentially an open circuit
to whatever is connected. While this resistor will reduce the input
from dynamic mics a bit its not much since they also have output
impedances which are very high.
One thing to settle is the frequency response of the microphone
itself. If there is any way to wire around the amplifier so that the
microphone is connected directly to the transmitter input it will
settle some questions. Also, there may be some filtering in the
amplifier. I am not familiar with the amp in the D-104 although its
undoubtedly on one of the sites, like BAMA or Nostalgia Air who have
old schematics.
Richard -
Contrary to popular belief, the "amplified base" for the D104 was not
developed for the CB trade! Newer transmitters with solid state AF
preamps (Low input Z) were hitting the market, and the amp was viewed as
a good way to allow the microphone to drive varying input loads,
including Lo-Z, without causing the frequency response to wander all
over the map. Of course it didn't take long for the CB crowd to turn up
the gain for more "skip" to take advantage of the "Power Mike"!
The amplifier is pretty flat, and is mainly an impedance matching
device. There is at least one website where someone has produced
another amp, with varying input impedance, along with curves allowing
you to tailor the old D-104 to just about any shape you desire.....
If not THE longest selling cycle for a single product, virtually
unchanged from 1930 to just a few years ago..........
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line& TR-4/C Service Supplement CDs
<www.k4oah.com>
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