Sectio
4
Amplifier/Station Interconnections
See figure 5
Coaxial Cable Types & Connectors
Connect the transceiver RF output to the ALPHA 99 RF INPUT with 50 ohm coaxial
cable- RG-58C/U or equivalent. A 6 ft. cable is supplied for this purpose.
Coaxial cable from the 99 RF OUTPUT to antenna should be RG-8A/U, RG-213/U,
or equivalent high quality type with a PL-259 UHF-type plug on the amplifier end.
RG8X cable is not recommended.
T/R Control Cable
The Alpha 99 has a full break-in vacuum relay QSK system requiring only the normal
interconnection when used with a modern QSK transceiver. The Alpha 99 requires a
contact closure (short circuit) on transmit from its RELAY jack center pin to chassis.
This function is supplied by the transceiver, usually from a dedicated relay that is
normally open in receive and closed in transmit. Shielded wire should be used for the
T/R control cable. The Alpha 99 end must be fitted with a common phono (RCA-
type) plug and the other end with a connector suitable for the transceiver.
The T/R relay contact must close before application of RF drive. The Alpha 99
protection circuitry prevents “hot-switching” with RF drive applied. Modern
transceivers have the proper time delay between keyup and the start of the transmitted
signal to allow the Alpha 99 to follow the CW keying. If a T/R timing problem is
suspected, connect the CW keyer to the RELAY jack on the Alpha 99, and connect a
cable from KEY OUT on the amplifier to the keying input of the transmitter.
ALC
The use of ALC output on the rear of the 99 chassis is not normally needed or
recommended when the ALPHA 99 is used with modern transceivers. However, the
Alpha 99 does generate a negative ALC control voltage that can be fed back to most
transceivers if required, to minimize the possibility of overdriving the amplifier. This
external ALC voltage is available at the amplifier’s rear panel ALC jack via a common
phono connector. Alpha 99 grid current exceeding about 3mA will initiate ALC and
light the green GRID LED. About 5-10mA yields full ALC output-nominally -10 Vdc
- and the red GRID LED lights. If the exciter requires a lower ALC voltage, the Alpha
Manual Alpha 99 Rev 1.doc
22
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