Bob -
Correct! I think Drake just overlooked the R-4 being parallel resonant when the "B" manual was
done. Probably lost in the day-to-day business staying IN business! :-)
Just for completeness, the 2-A/B are parallel, the 2-C is series.
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>
Bob Loving wrote:
Hi, Garey, et.al.:
Your explanation of the various crystals for the 4-line made me grab my Drake 4-line manuals and
look through them. The circuits for all of the crystal oscillators in the receivers, except the
R-4, and the transmitters are virtually, if not, identical. Those would use the series resonant
crystals.
The R-4 manual states "Only parallel resonant third overtone crystals designed for a Miller
oscillator should be used." From the circuit it is fairly obvious that parallel resonance is
required. I have used parallel resonant crystals in some of the 4-line radios and, yes, the dial
and/or skirt has to be repositioned if those crystals are active if calibration is desired (handy
if you are at a band edge).
The T-4X manual cautions, "When ordering, be sure to specify whether the crystal you are ordering
is for a T-4X or R-4. They are not the same!" (the exclamation point is Drake's).
Curiously, Drake has in the T-4XB manual (page 25) this statement: "R-4, R-4A, R-4B and T-4X,
T-4XB crystals operate in the series mode and are interchangeable." Note that the R-4 is included
in the list. I wonder if Drake decided after the R-4/T-4X that carrying two crystals for the same
band but different resonances didn't make a lot of economic sense.
In any case, as Garey implies, each crystal has two resonances and the circuit defines in which
mode it will operate.
73,
Bob K9JU
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