Vega DSP-223 Technical Manual Download Page 10

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Vega

DSP-223

3.2 Radio TX Level Adjust Procedure

Due to the large range of input requirements for the radios that can be connected to the DSP-223, there
is not a prescribed way of setting the Radio TX levels. Radio TX test points (TP-5 & TP-6) on the front
panel of the DSP-223 provide a location to measure the actual value being placed onto the radio TX
inputs. The Radio TX gain potentiometer (R7) can be used to adjust these levels. Note if the unit is
placed into single ended mode with jumpers J14, 15, 22, and 23 the Radio TX+ should be measured with
respect to ground. The user also has the option of placing J26 into the “A” position to decrease the
output of the TX line by a factor of 10. The final adjustment should allow for undistorted audio to be
transmitted for the full range of transmission levels at the desired deviation. Soldering JP6 together will
increase the radio TX output adjustment range.

3.3 Radio RX Level Adjust Procedure

The Radio RX level input to the DSP-223’s ADC can be measured by connecting an Oscilloscope or
Meter to the ground and Radio RX test jack (TP-3) on the front of the unit. The maximum expected
receive level should be set so that the measurement at the test points is approximately 3.4 volts peak-to-
peak or 1.2 volts RMS. This insures that the receive audio from the radio will not overdrive the input
circuitry of the DSP-223. The usage of Table 1 can help facilitate this by following the directions for
setting the Line RX levels. If the radio will not be generating a level above 0dBm, the 5-7 columns of the
table can be used with a known input value to set the maximum level seen by the ADC. If the radio max
level output will be below 0 dBm the Radio RX (R98) gain can be set higher to accommodate this.

3.4 Line TX Level Adjust Procedure

The Line TX level is the last item that should be adjusted.  With the unit connected to the 600 Ohm line,
connect an oscilloscope, meter reading true RMS, or a meter with an output in dBm to the Line TX test
points (TP-7 & TP-8) on the front of the DSP-223. There are three ways to generate the required test
tone for setting the levels. The easiest is to “double click” the IC PTT button on the front panel. A 1-
minute 0dBm test tone will be sent on the Line and Radio TX lines. Pressing the IC PTT button again
during the tone output will turn off the output. The second option, with the receive levels already set and
a console capable of generating DTMF tones onto the Line RX pair, press “*0#8”.  A 15 second, 1kHz,
0dBm tone will be placed on the TX line pair. The third method to generate the tone is to move the test
jumper, J11 to the “B” position. As long as the test jumper is in the “B” position, a 0dBm 1kHz tone will be
placed on the TX line pair.  This does require opening the case.  Adjust the Line TX Potentiometer (R12)
until the measured voltage is 2.2 Volts peak-to-peak, 0.77 volts RMS, or 0dBm. Soldering JP7 together
will increase the Line TX output adjustment range.

3.5 CTCSS Level (Continuous Tone coded Squelch)

The CTCSS Level can be measured by connecting an oscilloscope or RMS meter to the ground and
CTCSS test point (TP-13) on the front of the DSP-223. With the radio connected to the CTCSS output,
have the remote console key up so that CTCSS is present. Adjust the CTCSS Potentiometer (R149) until
the level is as desired.

3.6 DSP –223 Detection Frequencies

The DSP-223 has been factory-tuned to the following frequencies. The user of the DSP-223 has no
ability to change the detection frequencies as they are coded into the software. However any actual
function or output can be made to work with any existing programmed frequency. Please consult the
factory for special requirements for frequency selections.

Guard tone/PTT Tone:

2175 Hz

MON Function Tone:

2050 Hz

Frequency Select Function Tones (where used)

F1:

1950 Hz

F5:

1550 Hz

F9:

1150 Hz

F13: