WEBVTT NOTE Integrated Circuits, Ferrites, and Connectors 1 00:00:00.000 --> 00:00:01.903 Integrated circuits. 2 00:00:01.903 --> 00:00:07.183 Question. What is meant by the term MMIC? 3 00:00:08.083 --> 00:00:13.283 Answer. Monolithic Microwave Integrated Circuit. 4 00:00:13.883 --> 00:00:23.742 A complete microwave amplifier or mixer on one chip, typically in a tiny package with 50-ohm input and output. 5 00:00:23.742 --> 00:00:35.483 MMICs are why microwave amateur work became approachable, a stage that once needed careful hand tuning is now a part you solder in. 6 00:00:35.483 --> 00:00:44.867 Question. Which of the following is an advantage of CMOS integrated circuits compared to TTL integrated circuits? 7 00:00:45.767 --> 00:00:49.127 Answer. Low power consumption. 8 00:00:49.727 --> 00:01:02.127 CMOS draws current essentially only when switching. That is why it dominates everything battery-powered, and why TTL survives only in legacy designs. 9 00:01:02.127 --> 00:01:08.535 Question. What kind of device is an integrated circuit operational amplifier? 10 00:01:09.435 --> 00:01:12.155 Answer. Analog. 11 00:01:12.755 --> 00:01:32.083 An op-amp is the archetypal analogue IC: a high-gain differential amplifier whose behaviour is set by external feedback components. Worth holding against MMIC and CMOS as the analogue member of the set. Ferrites. 12 00:01:32.083 --> 00:01:39.152 Question. What determines the performance of a ferrite core at different frequencies? 13 00:01:40.052 --> 00:01:46.132 Answer. The composition, or "mix," of materials used. 14 00:01:46.732 --> 00:02:03.853 Ferrite is not one material. Each mix is optimised for a frequency range, and using the wrong one is a common and invisible mistake, a mix intended for 100 MHz does very little at 3.5 MHz. 15 00:02:03.853 --> 00:02:15.692 Mix 31 for HF common-mode chokes, mix 43 for VHF; the numbers are worth knowing because the cores are otherwise indistinguishable. 16 00:02:15.692 --> 00:02:24.792 Question. How does a ferrite bead or core reduce common-mode RF current on the shield of a coaxial cable? 17 00:02:25.692 --> 00:02:31.132 Answer. By creating an impedance in the current's path. 18 00:02:31.732 --> 00:02:39.421 Impedance, not absorption. The choke makes the path unattractive to common-mode current, so less flows. 19 00:02:39.421 --> 00:02:51.812 It does nothing to the differential signal inside the coax, because that current's outbound and return paths are equal and opposite and the ferrite sees no net field. 20 00:02:51.812 --> 00:03:10.809 Question. What is an advantage of using a ferrite core toroidal inductor? A. Large values of inductance may be obtained. B. The magnetic properties of the core may be optimized for a specific range of frequencies. C. 21 00:03:10.809 --> 00:03:18.372 Most of the magnetic field is contained in the core. D. All these choices are correct. 22 00:03:19.272 --> 00:03:22.792 Answer. All these choices are correct. 23 00:03:23.392 --> 00:03:40.329 Self-shielding is the one people undervalue. A toroid's magnetic field is almost entirely inside the core, so a toroidal inductor neither radiates into its neighbours nor picks up from them. 24 00:03:40.329 --> 00:03:55.038 That is why they are used in tight RF layouts where a solenoid coil would need a can around it. RF connectors. The frequency limit is the specification that matters. 25 00:03:55.038 --> 00:04:10.104 Connector, BNC (50 ohm); Limit, about 4 GHz; Notes, bayonet, quick, test-bench standard. Connector, Type N; Limit, useful to 10 GHz; Notes, moisture-resistant, threaded. 26 00:04:10.104 --> 00:04:22.851 Connector, SMA; Limit, several GHz; Notes, small, threaded. Connector, RCA phono; Limit, low frequency or DC; Notes, audio and control, not RF. 27 00:04:22.851 --> 00:04:30.072 Connector, PL-259 / UHF; Limit, a few hundred MHz; Notes, not constant-impedance. 28 00:04:30.072 --> 00:04:35.365 Question. Which of the following describes a type N connector? 29 00:04:36.265 --> 00:04:43.185 Answer. A moisture-resistant RF connector useful to 10 GHz. 30 00:04:43.785 --> 00:04:51.179 Type N is the outdoor choice, the weather resistance is designed in rather than achieved with tape. 31 00:04:51.179 --> 00:05:00.825 Question. Which of these connector types is commonly used for low frequency or dc signal connections to a transceiver? 32 00:05:01.725 --> 00:05:05.171 Answer. RCA Phono. 33 00:05:05.771 --> 00:05:21.251 Cheap, unshielded to any real standard, and entirely adequate for audio and control lines. Not an RF connector, despite appearing on the back of radios. LEDs, once more. 34 00:05:21.251 --> 00:05:26.108 Question. How is an LED biased when emitting light? 35 00:05:27.008 --> 00:05:29.928 Answer. Forward biased. 36 00:05:30.528 --> 00:05:48.334 Same as the Technician answer, stated in the bias vocabulary rather than the current vocabulary. Check yourself. You fit a ferrite choke on a coax and the interference is unchanged. Name two likely causes. 37 00:05:48.334 --> 00:05:57.454 Which connector for an outdoor 70 cm feed line junction? Why does a toroidal inductor need no shield can? 38 00:06:03.454 --> 00:06:18.180 Wrong mix for the frequency, or the problem is differential rather than common-mode, a choke only addresses common-mode current. Type N, moisture-resistant and good to 10 GHz. 39 00:06:18.180 --> 00:06:25.922 A toroid is self-shielding: its magnetic field is contained almost entirely within the core.