you are just balancing the TX audio across various voice level freqs. if you have the basci service manual it is in section 6.2.6. if not:
NOTE: Compensation alignment is only required after replacing (or servicing) the command board,
VOCON (vocoder/controller) board, RF board, or the VCO board.
Compensation alignment balances the modulation sensitivity of the VCO and reference modulation
(synthesizer low-frequency port) lines. The compensation algorithm is critical to the operation of
signaling schemes that have very-low-frequency components (for example, DPL) and could result in
distorted waveforms if improperly adjusted.
Compensation values are adjusted at the different test frequencies to achieve a flat VCO modulation
sensitivity with respect to the RF frequency and with respect to the low frequency response of the
synthesizer.
This test can be done with either the R-2670 Communication Analyzer or the 8901_ Series
Modulation Analyzer. The R-2670 analyzer is recommended.
1. Initial set up using the R-2670 Communication Analyzer:
- Connect a BNC cable between the “DEMOD OUT” port and the “VERT/SINAD DIST/DMM
COUNTER IN” port on the R-2670.
- Press the SPF key on the R-2670 to display the “SPECIAL FUNCTIONS MENU.” Move the
cursor to “High Pass,”and select 5 Hz via the soft key menu. Select 20 kHz for the “Low
Pass” setting.
- In the “RF Control” section of the R-2670, enter the frequency displayed on the RSS screen
(choose a test frequency from the list of frequencies displayed under Transmit Deviation
Balance [Compensation] in RSS). Move the cursor to the “B/W” setting and select “WIDE
+/- 100 kHz” via the soft key menu.
- Place the R-2670 cursor in the “Display” zone. Select “AC VOLTS” on the soft key menu.
Move the cursor to the “Range” setting and select “AUTO.”
2. Initial set up using the 8901_ Series Modulation Analyzer:
- Press the FM MEASUREMENT button. (The “Error 03-input level too low” indication is
normal until an input signal is applied.)
- Simultaneously press the Peak – and Peak + buttons. Both LEDs on the buttons should
light.
- Press the 15 kHz LP filter button.
3. From the SERVICE MENU, press F2 to select the TRANSMITTER ALIGNMENT MENU.
4. Press F5 to select the TRANSMIT DEVIATION BALANCE (COMPENSATION) alignment
screen (Figure 6-7).
5. Press Tab to select and start the alignment at the lowest frequency listed.
6. Press F3 (TOGGLE LOW TONE PTT) to key the radio. Wait approximately five seconds until
the frequency displayed on the analyzer stabilizes.
7. Measure and record the deviation value from the 8901_ analyzer or the ac voltage value from
the R-2670 analyzer.
8. Press F3 to dekey the radio.
9. Press F6 (TOGGLE HIGH TONE PTT) to key the radio. Wait approximately 5 seconds until
the voltage shown on R-2670 analyzer, or the deviation shown on the 8901_ analyzer,
stabilizes.
10. Use the Up and Down arrow keys on the computer keyboard to adjust the deviation to within
±1.5%) of the value recorded in step 6.
11. Press F6 to dekey the radio, and then press F6 again to verify the deviation setting.
12. Press F8 to program the new softpot value.
13. Repeat steps 4 through 10 to ensure the correct deviation balance value has been saved.
14. Repeat steps 4 through 11 for each of the remaining frequencies.
15. Press F10 once to return to the TRANSMITTER ALIGNMENT MENU, or press F10 twice to
return to the SERVICE MENU.
you may use any service monitor to perform this, though certainly the exact setup steps may vary from a R-2600 series. you just want to make the voltage level for higher tone freqs equal to the low tone freqs. perform the steps for EACH TX freq in order to make sure the unit has even deviation across teh voice and rf bands.
