Jim -
It is normal for there to be a 'small' difference between power output
and receiver sensitivity in the various TRANSCEIVE switch positions.
First, the INJ cable MUST be a low capacitance coax or mic cable. Cable
impedance, loss, shielding, etc. are NOT important, only the
'capacitance per foot'.
The original cables were all 38" long, tip to tip.
Original Drake INJ and CAR OSC Cables = 19 pF/ft = .160" o.d. (foam poly)
RG-62 = 93R = 13.5 pF/ft = 0.240" o.d.
RG-59 = 75R = 14.8 pF/ft = 0.242" o.d.
RG-6 = 75R = 16.2 pF/ft = 0.270" o.d.
RG-174= 50R = 30.8 pF/ft = 0.110" o.d.
Mic Cable (Belden 8410) = Hi-Z = 33 pf/ft = 0.160" o.d. (foam poly)
Mic Cable (Belden 8421) = Hi-Z = 16 pf/ft = 0.180" o.d. (foam poly)
R/S Audio Patch Cable = 28 pF/ft = 0.165" o.d. (poly)
The best choice is the Belden 8421 Audio cable from their "Brilliance"
line. It looks just like the other cables, and is very flexible. The
RG-62 is OK, but it is 50% larger and far less flexible. RG-62 is also
prone to shorting if bent over too small a radius, and is susceptible to
heat damage when soldering connectors. The best "feature" of RG-62 is
that it is often FREE, since there have been many miles of it pulled out
of old computer networks. Belden 8421 has been available by the foot
from someone on the list in the recent past.
The CAR OSC cable in the C-Line should be the same cable, although it
isn't quite as critical.
The proper cables will minimize the difference, however it may still
require a touch-up of the RF TUNE and GAIN controls as well as the
PRESELECTOR control in the receiver. Especially in CW, the GAIN control
must be advanced further. The ALC masks this in TUNE, but the GAIN
control is more critical in CW. It also helps to do the PreMixer
alignment steps with the two cabled together using the correct cables.
It does sound like your GAIN control is on the low side. Typically, on
40M in TUNE, you should get full output (typically 130W, limited by ALC)
before 12 o'clock. CW shouldn't require more than about 1 o'clock for
full output. These are two different controls on the same shaft. In
TUNE one section is an AF gain control adjusting the level of a 1 kHz
audio tone into the Balanced Modulator, similar to whistling into the
microphone. In CW, the other section controls a DC current applied to
the diodes in the Balanced Modulator to un-balance it and allow the
Carrier Oscillator to come through to be amplified and mixed to generate
the CW signal.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>
Jim Bo wrote:
My T-4XC has different Pout depending on the position of the
"transceive" switch and in the CW Mode.
With transceive swith set on "separate"
Gain is at 2:30
Plate current is 300 ma
Pout is 100 watts
With transceive switch set on "rcvr"
Gain is at 2:30
Plate current is 320 ma
Pout is 117 watt
When transceive switch is on "xmtr"
Gain is at 2:30
Plate current is 140 ma
Pout is 19 watts
When transceive switch is on "xmtr"
Gain is at 5:00 (fully clockwise)
Palte current is 320 ma
Pout is 117 watts
What is pecular is that Pout when seperate compared to Pout when xmtr
supposedly uses the same oscillator signal for drive.
I did not see anything in the manual that looks like there is an
alignment step for this.
Comments?
Thanks
Jim
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