Established in 1990, Fadong Power Co., Ltd. is a professional China comb generator manufacturer and supplier of in the emergency power supply industry. We not only specialize in manufacturing different kinds of generators, but also in motors, engines, diesels, gearmotors and other power supply products. We also have more than 100 series of equipment to support and check our products, such as VPI equipment, auto painting lines, auto testing systems and CAD systems. We warmly welcome every customer to cooperate with us on the basis of mutual benefit, and hope to be your faithful friend and best partner. Our custom comb generators has obtained the certifications of ISO9001-2000, GS/TUV, CE, VL, EPA, QHS, SON, CAP and SRS.

The most commonly used semiconductor device for comb generation has historically been the step recovery diode (SRD). While SRDs have proven very useful in this application, they do have limitations, most prominently the introduction of undesired phase noise and a very limited range of input frequency and power. This new family of comb generators utilizes a different circuit to generate harmonics, a device called a nonlinear transmission line (NLTL). NLTLs employ a completely different physical mechanism for frequency multiplication. The significant technical advantages of NLTL-based comb generators relative to SRD-based comb generators include:
Low Phase Noise – better phase noise performance improves overall multiplier module performance. The poor phase noise performance of SRD comb generators often limits multiplier phase noise performance.
Wide Range of Input Frequency – flexibility of input frequency allows changes in input frequency or a single device to be used in multiple applications.
Low Input Power – relaxes power requirements on amplifiers. This simplifies multiplier design by reducing supply voltages and improving amplifier performance.
High Power in High Frequency Harmonics – NLTLs generate faster transitions that have more frequency content, producing more power in higher frequency harmonics. NLTLs also enable higher frequency inputs, increasing the power in each harmonic and increasing harmonic spacing, which simplifies filter design. This allows the use of multiplier-based frequency sources at higher frequencies than was previously possible with SRD-based comb generators.

The schematic for the 1 MHz and 10 MHz crystal oscillators are identical in terms of all the DC components, they only differ in the reactive parts, both use a 2N708 transistor. The 1 MHz circuit has about 50 mA of collector current, way too high whereas the 10 MHz circuit has about 5 mA of Ic which is right in the center of it's speced range. The VBE and VBC on the 1 MHz oscillator differ from those on the working 10 MHz oscillator. Replacement of the 2N708 is next.
After replacing Q1, a 2N708, the 1 MHz combs were there but with the trimmer cap fully open the frequency was too low. By installing the Jameco crystal the frequency could be brought right on. Note that the spec on frequency is +/- 0.01% or 50 kHz at 500 MHz and the actual performance is maybe 10 times better, but these are just raw crystal oscillators and are sensitive to temperature and to warm up as the three (1, 10 and 100 MHz) oscillators are switched on. Warm up may take up to an hour each time you switch in a newoscillator. The amplitude of the combs is typically 10 times higher than the spec, so for the 1 MHz combs up to 500 MHz they are around -70 dBm vs. a spec of -80 dBm. The Jameco crystal has a few dB more output than the factory Bliley crystal.

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