REXON PA-85V User manual

VHF POWER AMPLIFIER
PA-85V
User Manual

Multifunction display bar operating modes
Mode Color Type Blink Function
Power
measurement
Green Bar-gra h No Measure out ut ower, 10Watt
increments
Power setting
dis lay
Green Bar-gra h Yes Indicates actual ower limit
(25,45,65,85 Watt)
SWR
measurement
Green Dot No* Shows VSWR
Error indicator Red Dot(s) No Indicates error condition
* Blinks on under/overrange
Pushbuttons function
Name Function
RX LNA Toggles o eration of receiver re-
am lifier (LNA)
TX PA Toggles o eration of transmit ower
am lifier
SSB ON Toggles SSB mode
SET POWER Dis lays/changes transmit ower limit
SHOW SWR Enables SWR dis lay

Turning amplifier on and off
Transmit ower am lifier and receiver ream lifier functions are inde endent on
each other. They can be toggled on/off by ressing res ective ushbuttons: RX LNA
and TX PA. When function is enabled, LED associated with ushbutton is lit.
Am lifier is com letely off, when both LEDs are dark.
Changing power level
Transmit ower am lifier is equi ed with Automatic Level Control loo (ALC).
Preset ower is adjustable is 4 ste s: 25W,45W,65W,85W. First ress of SET
POWER button enters ower setting mode. Multifunction dis lay bar blinks, showing
reset ower level. First ress of SET POWER button, doesn't change the level, but
dis lays actual setting. Subsequent ressing of SET POWER button change ower
setting. Am lifier exits ower setting mode if SET POWER button is not ressed
again within 2 seconds.
Automatic Level Control is of saturated nonlinear ty e, only suitable for FM
modulation. While using am lifier with AM/SSB modulations, set ALC threshold to
maximum ower (85W), then adjust transceiver ower to yield a ro riate ower
dis layed on bargra h. For AM modulation, carrier ower should not exceed 20-25W,
to accomodate modulation eaks without distortion.
In case of SSB modulation, observe bargra h which is of PEP ty e, kee ing 80W
LED lit only ocassionally.
Turning SSB mode on off
The SSB ON button toggles SSB mode on/off, actual state indicated by associated
LED. When SSB mode is enabled, carrier sensing algorithm, time delays, ower
meter bar behaviour are changed to address modulation ro erties. There is no
difference in ower am lifier biasing itself, since this modern desing is inherently
linear, unlike elder bi olar transistor based designs.

Measuring VSWR
This useful function allows to accurately measure am lifier load VSWR. To enable
VSWR measurement, ress SHOW SWR button while transmitting. This mode will
ersist as long as am lifier is in transmit mode. Dis lay returns to normal o eration
( ower measurement) after releasing transceiver PTT button.
Actual VSWR is re resented as single „moving dot”. Lowest reading is 1.20, below
this value res ective LED starts blinking, indicating underrange. Highest reading is
1.90, crossing 2.00 will cause res ective LED blinking, indicating overrange.
Built in VSWR meter is of good quality, com ensating for detector nonlinearities,
what makes measurement result fairly inde endent on out ut ower. It also offers
exce tional directivity, with residual VSWR reading in order of 1.10.
Error signalling
To signal error in am lifier o eration, multifunction dis lay bar LEDs change color
to red. A erance of any error denies ower am lifier transmit o eration.
Error LED Meaning Amplifier reaction
HIGH SWR Excessive VSWR (over 2.1)
detected. Ty ically caused by
faulty antenna.
Deny transmitting, resume
after PTT release
OVERDRIVE Excessive in ut ower (>7Watt) Deny transmitting, resume
after PTT release
DC VOLTAGE DC su ly voltage out of
ermissible range (10.5V to 14.8V)
Deny transmitting, resume
after PTT release and voltage
restored
HIGH TEMP Chassis tem erature over 60 ºC Deny transmitting, resume
after cooling down
PA FAIL Am lifier electrical failure Deny transmitting, resume
after PTT release

Specifications: Power amplifier
Parameter Min. Typ. Max. Remarks
Frequency
range
138 MHz 174 MHz
Maximum
out ut ower
80Watt 85Watt 90Watt ALC limited
In ut ower
range
1 Watt 7 Watt Between carrier detect and
overdrive thresholds
In ut ower for
full out ut
3 Watt 5 Watt Frequency de endent
By ass ower 50 Watt
Harmonics
su ression
65dBc
Modulation AM, FM, SSB
Circuit ty e Twin MOSFET, PUSH-PULL
Specifications: Receiver preamplifier
In-band gain 18dB 21dB 24dB 138 MHz - 174 MHz
Out-of-band
gain
19dB @ 108 MHz
8 dB @ 88 MHz
-50 dB @ 30 MHz
Noise figure 2.4 dB 3 dB
Specifications: General
DC su ly
voltage
10.5 V 12.6 V 14.8 V O eration at low end of range
may not yield s ecified
maximum ower
Transmit
su ly current
10 A 13 A Transmitting at maximum
ower. Frequency de endent.
Standby su ly
current
20 mA All functions OFF
35 mA TX PA enabled
80 mA RX LNA enabled
88 mA TX PA and RX LNA enabled
RF connector UHF (SO-239)
Weight 1.15 kG
Dimensions H=50mm, W=125mm, L=210mm