External Audio Control; Internal & External Modulation Summing - Aeroflex NAV 2000R Operation Manual

ADDRESS 0: A read of address 0 of U3 (output Y0) reads in the status word of the RF Modulator Module.
High bits in this status word indicate error conditions as described in the Table below.
Data Bit
0
1
2
3
4
5
6
7
A write to address 0 of U3 writes the MSB byte of the word, which sets the attenuation of variable
attenuator (U7), which controls percent modulation. A write to address 1 of U3 writes the LSB byte of the
percent modulation word to the percent modulation variable attenuator.
ADDRESS 2 & 3: Writes to addresses 2 and 3 of U3 write the MSB and LSB of the RF Fine tune level
attenuator (U8), respectively. Use of this feature is reserved for future releases.
ADDRESS 4: Latches the byte that controls the programmable step attenuator into the attenuator driver
U10.
ADDRESS 5: Latches a byte that controls the DISCRETE features of the module U11. Setting bit 0 of
U11 high will enable external modulation to be AC coupled, and when cleared low, DC coupling. Setting
bit 1 of U11 high enables external modulation and turns it off if cleared low. Setting bit 6 of U11 selects
LOW BAND operation of the leveling loop.
To transfer data to and from the RF modulator module, the bus request line is held low. The bus grant
line returns an active low bus grant signal after a short time indicating that the module is ready for reads
or writes to its valid addresses. The bus grant is open collector as it is for all modules in the NAV 2000R.
CR9 enables the acceptance and release times to have two different time constants. C46 allows high
speed edges to bypass R4.

4.5.7 EXTERNAL AUDIO CONTROL

External modulation can be turned ON or OFF. The External Modulation jack, J3, is normally calibrated
for a signal with AC component of 1V peak. DC coupling is not used within the NAV 2000R.
Since external and internal modulation are summed, an external signal may be added to the internally
generated modulating signals. However, the circuitry which indicates modulating level high/low will only
indicate that their sum is high or low. During the External Modulation Mode, EMM, all internal audio is
turned off. Adjusting an external modulating signals until the modulating high/low indicators show that the
modulating signal is of an acceptable level will cause the output to match the selected modulation level.
4.5.8 INTERNAL & EXTERNAL MODULATION SUMMING
During the five primary MODES which are selectable by means of the five MODE buttons, internal and
external audio can be summed. The internal and external modulating signals are summed in one of the
op amps of U12. The output of the summing amplifier, U12 pin 7, is the input to the Audio High/Low
Indication circuit and the % modulation Level Set Attenuator. However, as previously mentioned, the
modulating high/indication circuitry will only indicate whether or not the peak of the modulating signal is
within a small percentage of a calibrated level, which is the level at which internal audio is maintained.
Therefore, a summed internal plus external signal is not monitored by this circuitry.
NAV 2000R SIGNAL GENERATOR - REV. 0 – JULY 26, 2007 - PG 4-17
Aeroflex Operation Manual
Description
Internal or External Modulating Audio too high
Internal or External Modulating Audio too low
RF output level unleveled and too high
RF output level unleveled and too low
Peak of detected audio for 50% modulation of a single tone too high
Peak of detected audio for 50% modulation of a single tone too low
N/A
N/A