Lee -
The T-4X has two four pole filters. As a result the unwanted sideband
and carrier suppression are marginal at best under current FCC "Purity
of Emissions" regulations. NOT significant for CW. The filters are 2.3
kHz at -6 dB and 6 kHz at -60 dB. All tubes, except for two transistors
in the PTO and one in the BAND oscillator.
The T-4XB has two six pole filters. They are 2.4 kHz at -6 dB and 4.08
kHz at -60 dB. Other changes are almost all cosmetic and ergonomic.
Black print above 'beltline', 'PTO in Use' indicator behind MAIN TUNING
knob skirt. Later models (~ 15000) switched from BJT to FET in PTO.
The T-4XC is considerably different in circuit topology, but essentially
the same block diagram. Several stages converted from tube to SS.
Earlier models passed only the PreMixer signal between RX and TX for
transceive, the C Line added the Carrier Oscillator / 3rd IF LO by
patching the CO to the receiver in transceive and disabling the 3rd IF
LO in the receiver. A few other cosmetic changes, controlling dial
lamps to indicate 'PTO in Use', plus Mic and Key jacks, VOX and ANTI-VOX
controls, separate CW and SSB Delay controls, all moved from the sides
to the back panel.
All functionally the same, compatible with R-4(any), AC-3 / AC-4 Power
supply.
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>
[email protected] wrote:
Friend of mine just got his Drake R-4B back from loan.
I will go through it for him and do a alignment.
He needs a TX now.
So what is the rundown on T-4X, T-4XB, T-4XC
What are the real differences?
All I have had is a C line.
He is into CW as much as SSB.
Thanks,
73,
Lee, KC9CDT
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