SECTION 3 - CONNECTION TO THE TRANSCEIVER
ALPHA 86
interconnections to the station transceiver are shown in figures 2 and 3 on page 7.
3.1 Coax Types & Connectors
Connect the transceiver RF output to the
ALPHA 86
RF input with 50 ohm coaxial cable-type RG-58C/U
or equivalent Coaxial cable used between the
ALPHA'S
RF output and antenna should be type RG-8A/U,
RG-213/U, or equivalent high quality type. Type RG-8X cable is
not
recommended. Suggested connectors
are Amphenol 83-1SP male UHF type (with reducing fitting type UG-175 for use with RG-58C/U).
32
T/R Switching
For transmit/receive switching the
ALPHA 86
requires a relay contact closure on transmit across its
RELAY jack (center pin to chassis). This control function is supplied by the transceiver, usually from a
dedicated relay that is normally open in receive and closes in transmit.
The relay contact must close before RF drive is applied. The
ALPHA 86
protective circuitry will not
allow the amplifier to "hot switch" with RF drive applied. Attempting to force a hot switch will cause
protective circuitry to lock out the receive to transmit change over. If this happens the "T/R" fault LED will
illuminate. It may be reset by removing drive, unkeying the transceiver, and switching the
ALPHA
from
operate (OPR) to standby (STBY) and back to operate (OPR).
A few (mostly older model) transceivers may generate an RF transient (spike) when keyed. This spike
may activate the
ALPHA 86
's excessive grid current protection, in which case modification of the transceiver
will be necessary. For specific instructions contact the ETO customer service department.
Figure 2 should be used with late model transceivers such as those listed below, and will allow the full
capabilities of the
ALPHA 86,
including break-in (QSK) operation, to be enjoyed. Suitable transceivers
include at least these (as of 9/90):
*
Kenwood TS-9405, TS-950S/D, TS440S, and later production versions of the TS-930S and TS-4305
Icom IC-735, IC-751, IC-751 A, IC-761, IC-765, and IC-781
Yaesu FT-757, FT-767, FT-1, and FT-1000
Figure 3 shows a switching arrangement that may be used to facilitate changing from conventional SSB/
VOX or PTT to CW break-in operation with older transceivers that have inappropriate T/R sequencing. The
desired mode of operation is selected by the external DPDT switch. QSK-capable transmitters of older design
may also require connection per Figure 3.
For transceivers or transmitters not mentioned above, try connection per Figure 2 first. If T/R faults
occur, try Figure 3.
33 ALC
The
ALPHA 86
generates a grid-current-derived, negative-going (from zero) DC control voltage that can
be fed back to most transceivers to avoid overdrive. To take advantage of ALC, connection must be made to
the
ALPHA 86
rear panel ALC jack.
Any grid current excursion above approximately 70 mA will "trigger" the ALC. At about 100 mA, ALC
output is nominally -10 VDC. If the transceiver requires less voltage a 100 kohm potentiometer may be
connected across the center pin of the ALC jack to chassis. The potentiometer wiper will provide an adjust
able "feed" to the transceiver. While driving the amplifier the potentiometer can be adjusted to limit trans
ceiver output to keep the amplifier grid current less than 100 mA.
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