![]() ![]() They have a +/- 2.5 ppm frequency stability with a +/- 3 ppm mechanical trim adjust on top. These Vectron oscillators have decent specifications for such a low cost and small package. These are available for $6 (for two) on eBay from the seller "rfextra." They appear to have a custom part number, but the datasheet for the "OSC Series" of oscillators from Vectron covers this model. The clock oscillator used here is a Vectron T-1115-10M0 miniature 10 MHz TXCO. ![]() If this is not sufficient, the 33 ohm series resistor can be replaced with a low-impedance coupling capacitor (0.01 ♟). For a 50 ohm line, with a 50 ohm load at the end of that line, the 50 ohm load will receive a 2.5 volt peak-to-peak square wave. The reflected signal will be dissipated in the series 33 ohm resistor plus the internal resistance of the 7SZ04 driver (approximately 17 ohms). A 33 ohm resistor is shown as a series element in each output.įor a 50 ohm line, with a high impedance load at the end of that line, the mismatched load will create a reflection. Each output is 5 volt CMOS that can drive a 50 ohm line that is terminated with either a high impedance load or 50 ohms. The master oscillator module contains a 10 MHz clock oscillator and three 7SZ04 buffered line output drivers (Digi-Key Part: NC7SZ04M5XCT-ND). Also, the 1024 MHz second local oscillator for my version of the spectrum analyzer will be done using a Mini-Circuits KSN-1024A+ fixed oscillator and it requires a 10 MHz reference input. ![]() The Analog Devices AD9851 may be a better "drop in" choice. The overall phase noise will also be slightyly increased by using the multiplier, but should be well within spec. Since the DDS is programmed to output a 10.7 MHz signal, the minimum internal clock frequency is 21.4 MHz (Nyquist), so the 40 MHz should work out quite well. The recommended Analog Devices AD9850 DDS has an (undocumented) internal 4x multiplier which can be used to convert the 10 MHz external clock into a 40 MHz internal clock. The MSA software has a setting for changing the clock oscillator frequency, and it looks like 10 MHz will work, but this hasn't been tested yet. The main difference here is using a 10 MHz Temperature Compensated Clock Oscillator (TCXO) instead of the recommended 64 MHz clock oscillator. ![]() The original MSA oscillator design is SLIM-MO-64. This is my version of the master clock oscillator for Scotty Sprowls' Modularized Spectrum Analyzer (MSA) project. Scotty's Spectrum Analyzer - Master Clock Oscillator ![]()
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