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XG1 Receiver Test Oscillator / S-Meter Calibrator

Ever wonder how well an HF receiver is really working--or how one receiver compares to another? One of the most important performance measurements is sensitivity. But measuring sensitivity (MDS or signal-to-noise ratio) usually requires an expensive, lab-grade signal generator.

The XG1 Receiver Test Oscillator is an inexpensive alternative. The XG1 is a fixed-frequency (7.040 MHz) signal source with highly-accurate 1 microvolt and 50 microvolt output levels. Thanks to its precision, low-level crystal oscillator, the XG1 achieves absolute output accuracy of better than ± 2 dB, and an extremely small unit-to-unit variation of typically ± 1 dB. This ensures that measurements made with different XG1s can be compared, which can be helpful when evaluating used equipment found at flea markets or on the web.

The 1-microvolt level can be used to determine a receiver's MDS (minimum discernable signal), as well as its overall receive gain. 50 microvolts is widely used as the standard "S9" reference, so this level can be used for S-meter calibration. Step-by-step procedures are included for receiver performance measurement and S-meter alignment.

Additional features of the XG1 include an on-board 3-Volt battery (standard coin cell), low-battery LED (yellow), power-on LED (green), and reverse-transmit warning LED (red). The unit is diode-protected against brief accidental

transmit, and has been tested at up to 10 watts for 2 seconds. However, the provided test procedures include warnings about disconnecting the key, mic, etc., so accidental transmit into the XG1 is very unlikely.

An output frequency of 7040 kHz was selected because nearly all multi-band HF transceivers, as well as many monoband transceivers, cover the 40 meter CW band. But the XG1 also provides reduced output levels at harmonics of 7040 kHz, so it can be used for receiver alignment and qualitative tests on 20, 15, and 10 meters.

Since the oscillator's output is only about 10 nanowatts, the unit requires no enclosure and no interstage shielding. Careful PC board layout and component selection ensure that RF leakage is virtually eliminated.

Like the other mini-modules, the XG1 is quite small: the PC board is just 1.5"W by 3.5"L. You can use a BNC male-to-male adapter such as our model BNC-MM to eliminate the coax cable and directly connect the XG1 to the back of a receiver or transceiver. Rubber feet are also included so the unit can be used on the workbench.


RF Output Level: 1 µV (-107 dBm) and 50 µV (-73 dBm) into 50 ohms

Output Accuracy: Typically Better than +/-2 dB at 25 deg. C

Frequency: 7040.0 kHz (+/-200 Hz at 25 deg.C before optional calibration)

Reverse Protection: 5 watts for 4 seconds,10 watts for 2 seconds (typical; not guaranteed)

Current Drain: About 2.5 mA from on-board 3-V,220 mA-hr battery (est. life 80 hours)


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