Swann CUBIC ASTRO 102 BX Service Manual page 168

Cubic Astro 102BXA Transceiver
Conducted By Paul K. Pagei,' N1FB
American made? Yes, indeed! The Astro
102BXA (formerly Swan/ Astro) is built by a
tenured engineering firm, Cubic Corporation,
of Oceanside, California. The manufacturer
once stated that "75 of our engineers were in-
volved in the design of the Astro." Those who
subscribe to the "buy American" doctrine
should be pleased with this product.
If your buying urge is stimulated by the
presence of dazzling geegaws, this rig may not
be for you. But if truly functional and impor-
tant operating features inspire you, the
102BXA might be what you've been waiting
for. It has what the operator needs, and
nothing more.
Coverage is from 160 through 10 meters in
six bands. This transceiver is completely tran-
sistorized (inclusive of ICs and diodes). Twin
PTOs are included to pro vide split-band opera-
tion when desired. Other features are variabie
agc time constant, passband tuning, and
separate controls for rf and i-f gain. It also has
RIT, selectable break-in delay or full QSK,
noise blanker and speech processor. The panel
meter indicates forward and renected power in
watts, ale level and the relative strength of in-
coming signais.
A large red di git al display provides readout
of thc operating frequency to six places, such
as 21,025.3 kHz. An eight-Ievel LED string
shows the status of the passband tuning from
0,6 to 2.7 kHz. Thcre is also a noteh filter that
is adjustable from the front panel of the
transceivcr.
The passband-tuning control scts the i-f
bandwidth with cilher a high-pass or low-pass
cutofL Clockwise rotation of the control at-
tenuates low-frequency audio, while counter-
c10ckwise rotation reduees the high-frequency
response. The LEDs mentioned earlil'r indicate
the effeetive audio pass band of the receiver. I
learned that the control l1eeds to be set for ap-
proximatcly 1.0 kHz or highl'r when Ihe sharp
'Assistant Technical Editor
48 Q5T~
cw accessory filter (300 Hz) is being used,
Otherwise, no cw beat note is hcard.
The microphone impedance is specified as
47,000 ohms, A key jack is located on the rear
panel of the transceiver, but the PTT line (ac-
cessible at the mike jack) can also be used as a
keying-control \inl'.
Other connection points on the rear apron of
the equipment are EXTRELAY, EXT MODULATION,
EXT LO, ANTENNA, GND and EXT SPEAKER. There
is a built-in speaker, plus provision for an ex-
ternalone. Thc EXT MODULATION jack provides
an interface for AFSK, and the MIC GAIN con-
trol on the front panel is used in that mode to
control the level.
The speech-processor action is determined
automatically by the setting of the MIC GAIN.
There is no separate external adjustment for
the processor. Similarly, the noise blanker is
factory-adjusted. It has no external threshold
control. Carrier-level control during cw opera-
tion is provided by Ihe MIC GAtN con trol.
I am mystified by the presence of a
SOFTIHARD keying switch Qn the transcciver
front panel. The keying waveform in the
"hard" position is what we at AR RL consider
objectionable in terms of clicks (see Fig. 3).
The "soft" position yields an excellent
waveform, closely approaching the desired
5-ms rise and fall times that result in c1ick-free
keying. That panel switch might have beeW'put
to
better use as a CARRIER LOCK control, which
has not been included in the design. This makes
tune-up difficult unil'ss the kever has a "carrier
hold" switch.
Other fealures that arcn't present in the
Astro 102BXA arc' a cryslal calibrator or
WWV band-switch position. Fortunately, the
40-meter coveragc is from 7.0 to 7.5 MHz,
whieh permits reeepIion of Canada's CHU
lime/slandard station in some areas of lhe
country.
Thc intern al swilehing kat ure for an extcr-
nal amplifier is compatible wilh thc' manufac-
turer's Astro 1200Z and 1500Z amplifiers. Uno
fortunately, the internal solid-stale switching
circuit is limited to a maximum of
+
200 V and
200 mA. Therefore, most amplifiers of dif-
ferent manufacture can't be switched by the
Astro 102BXA - at least nol directly. I had 10
interface the transceiver with my Heath SB-22)
by means of an external relay that was actuatcd
I
by the solid-state switch in the Astro. A 12- V
dl' relay can be used (low-current coil), and
power for it can be borrowed from Ihe
+
12· V
bus in the transçeiver. If an external relay is
used, it wil! negate the use of full QSK since
many control relays will not follow the cw
speeds that are used by most operators.
I was impressed with the skirt selectivity of
the i-f system. The variabie passband tuning of
the receiver complements the i-f filters to
reduce wideband noise and enhance the effec-
tive selectivity. In fact, acceptable cw selectivi-
ty can be had wh en using the ssb i-f filter by ad·
Fig. 1 - Worst-case spectra I display ol the
Cubic Astro 102BXA. Vertical divisions are
each 10 dB; tlorizontal divisions are eactl 10
MHz. Output power is approximately 100 watts
at a IreQuency of 26 MHz. Spurious emisslons
are at least
49
dB down Irom peak lundamen·
tal output. Ttle Astro 102BXA complies wittl
current Fee' specilicalions lor spectral purity.