It is recommended that the board be placed in an enclosure of some type, preferably of metal construction. The board mounting holes mate to a (5.6" × 4.3" × 1.8") Bud Industries or DigiKey part number #CU-387 plastic enclosure and may be used from an economy standpoint. The modulator IC gets very warm during normal operation so using a metal standoff here will help sink heat away from it.
Environmental Details
Temperature – 0 to +30°C (32–86°F)
Humidity – +10 to 95% non-condensing
Electrical Details
Input Voltage Requirements
+9 to +15VDC (400 mA @ 12VDC). Input is polarity protected but not fuse protected. External 1 amp slo-blo fuse is required by user for safe operation.
Frequency Range
100 MHz to 2450 MHz
Symbol Rate
Select SR from 1.00 to 9.99 MS/s in 0.01 steps (design optimized for 2–6 MS/s). There are 12 preset configurable combinations.
Note: Symbol rates >8.00 MS/s show increased 12 MHz sidebands on each side, approximately 35 dB down from center carrier, because I/Q low pass anti-aliasing filters are optimized for 2–6 MS/s.
FEC Combinations
1/2, 2/3, 3/4, 5/6, and 7/8 for DVB-S and DVB-T protocol.
Signal Quality
EVM (Error Vector Magnitude)
2.4% — measured with Agilent EXA N9010A Signal Analyzer (≤3% acceptable for commercial broadcast).
EVM is the percentage away from the ideal symbol landing spot in the signal constellation. Includes combined effects of transmitter and receiver CNR/SNR.
MER (Modulation Error Ratio)
32 dB
Minimum recommended: 12–13 dB for QPSK, 27 dB for 64-QAM (including 3–4 dB headroom). Calculated as: 10LOG(average symbol power / average error power).
RF Output
| Parameter | Value |
|---|---|
| Frequency Range | 100 MHz to 2450 MHz |
| Frequency Resolution | 100 Hz |
| Frequency Accuracy | ±2 kHz |
| Frequency Stability | ±100 PPM |
| Output Impedance | 50 ohms |
| Output Level @ 100 MHz | −34 dBm to +13 dBm in 1 dB steps |
| Output Level @ 1280 MHz | −35 dBm to +12 dBm in 1 dB steps |
| Output Level @ 2450 MHz | −39 dBm to +8 dBm in 1 dB steps |
| Spectral Regrowth (settings 00–35) | −60 dBc |
| Spectral Regrowth (settings 36–47) | −50 dBc |
| Software-Controlled RF Level | 00 to 47 in 1 dB steps (00 = minimum) |
CAUTION: DO NOT ATTEMPT TO TRANSMIT A SIGNAL OUTSIDE THE ALLOWED HAM FREQUENCIES.
Since all unwanted frequencies are above the fundamental, a simple low pass filter may be all that is needed. If operation is planned for the 70cm band (420–450 MHz), a third harmonic at ~1290 MHz will be present about 26 dB below the fundamental. DO NOT use an interdigital filter here — that type passes the third harmonic with almost no added loss. Low pass filters should be placed between the DATV-Express board and power amplifier, not after the PA.
Connector Details
- J1 — USB2 type "B" connector — standard USB2 to/from host computer
- J2 — RF output connector — SMA female
- J3 — DC power connector — female DC connector, 2.54mm center pin (Switchcraft #760 or equal)
- J4 — Data I/O connector (see table)
- J6 — Expansion connector (see table)
Data I/O Connector J4 Pin-out
| Pin | Function |
|---|---|
| 1 | +5.2 VDC through 50Ω ¼W resistor |
| 2 | Tx disable input (GND to turn Xmit OFF; floats to +3.3V through 100Ω for Xmit ON) |
| 3 | Key (no pin) |
| 4 | FX2 OK output (LED5)* |
| 5 | I2C activity output (LED1)* |
| 6 | Symbol Rate output (LED2)* |
| 7 | PLL Locked output (LED3)* |
| 8 | I2C bus SDA — reserved for future expansion |
| 9 | I2C bus SCL — reserved for future expansion |
| 10 | Ground |
| 11 | Analog input 1 — forward/reverse power signals via dual directional coupler |
| 12 | Analog input 2 — forward/reverse power signals via dual directional coupler |
Expansion Connector J6 Pin-out
| Pin | Function |
|---|---|
| 1 | Ground |
| 2 | Key (no pin) |
| 3 | FPGA I/O pin 97 (Symbol rate clock – test point) |
| 4 | FPGA I/O pin 96 (pulse+ for data overruns – test point) |
| 5 | FPGA I/O pin 95 |
| 6 | FPGA differential −output pin 72 |
| 7 | FPGA differential +output pin 71 |
| 8 | FPGA differential −input pin 70 |
| 9 | FPGA differential +input pin 69 |
| 10 | FPGA I/O pin 67 |
You can download a PDF version of this specification from the Downloads page.