Vco Crossover Frequency; Table 17 Transmit Deviation Limit Reference - Motorola FLASHpot Handie-Talkie MTX Series Service Manual

VCO Crossover
Frequency
Transceiver Board
Identification
VHF Radios
24

Table 17 Transmit Deviation Limit Reference

Channel Spacing
20 KHz
12.5 KHz
4. Press F6 to dekey the radio, and press F8 to program the softpot
value.
5. Press F10 to return to the TRANSMIT menu.
NOTE: This procedure is only required after the field
repair of a VHF or UHF VCO.
In order for a phase-locked-loop to tune very wide bandwidths, both
negative and positive control voltages (Vcntl) are required. This
procedure sets the crossover frequency at which the negative Vcntl
(or –Vee) switches from zero to negative.
VHF transceiver board NUD7070 and NUD7085 ("C" and later) kits
include new VCO varactors, and are factory aligned with a new
transmit VCO crossover frequency of 164.850MHz.
Since the transmit crossover frequency has changed, whenever
transmit VCO crossover alignment (an RSS function) is performed,
circuit board identification will be important. The "C" kits can be
identified by the circuit board number 5511Y02 or 5511Y32 visible on
side 2 of the board, located along the circuit board edge just next to
crystal filter FL1. All future VHF transceiver boards will be in the
"5511Y" series.
Anytime a controller board or transceiver board is replaced in a radio,
it will be necessary to perform the RSS transmit VCO crossover
alignment, and check the transmit VCO crossover frequency. The RSS
screen for this alignment will show a "current value" box
with a frequency already assigned, placed inside the box. When
performing transmit VCO crossover alignment, first check the
transceiver circuit board number. In a VHF radio:
• If the board number is any "5511Y" series number, other than
5511Y01 or 5511Y31, the transmit VCO crossover frequency in the
"current value" box should be 164.850MHz. If it is not, change it
to 164.850MHz.
• If the board number is 5511Y01, 5511Y31 or any other number
not in the 5511Y series, the transmit VCO crossover frequency in
the "current value" box should be 161.50500MHz. If it is not,
change it to 161.50500MHz.
Deviation (kHz)
3.40 - 3.60
2.20 - 2.30