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Amateur Radio Info & Exams - Components 2 - ICs and Connectors

Digital ICs

Digital ICs range from simple gates, to complex microprocessors


In days of old, memory used to be accessed sequentially, by clocking data around a chain of registers. A "shift register", mentioned in a question, is a device, which when clocked moved data through the memory array. The more modern form is "Random Access Memory", RAM. There are also two types, Read-Write Memory, RWM; and Read Only Memory, ROM. RWN is normally "dynamic", but a few computers, such as the MicroBee used static RAM, so your programme was reserved even if power failed. Somehow, RWM become known as RAM, in contrast to the ROM which contained the BASIC, or boot up software for CP/M systems. This is despite most ROM technically also being randomly accessible.

Variations on ROM are PROM, programmable ROM (write once, read many times); EPROM, erasable PROM, erased by exposing the device to intense UV light via the quartz window on the top, which should be covered by a sticker (often with a version number); and the latest EEPROM or E-squared-PROM (E²PROM), electrically erasable programmable read only memory.

In microcontrollers, in addition to the processor, there may be some "bootstrap" ROM; EEPROM or PROM, depending of whether you wish to update the programme or have it fixed; and RAM. EEPROM versions are often used by hobbyists, and for development work.

Non-volatile means that memory is preserved, even when power is lost.


A MMIC is a Monolithic Microwave Integrated Circuit, an IC designed to work at microwave frequencies.

Sub-D Connectors

Serial and parallel data, and VGA (analogue) computer video, among other PC connections used a D shaped connector with multiple pins. The first letter is a D, the second is the size of the housing, then a dash, and the number of pins. For the smaller sizes there are normally 2 rows, but the high-density (HD) version has 3. Examples are DE-9 and DB-25, both used for RS-232C serial data; and DE-15HD used for VGA. The DA-15 pin versions were used for joysticks, and there were or are various other uses for D connectors, including multi-channel audio, and a drive and image scanner interface called SCSI (in some cases using DC-37).


USB, or Universal Serial Bus is an interconnection system for PCs. Some modern transceiver include these for connection of a PC, and may include one to connect a keyboard. For others, a USB to serial port interface is needed, with CAT being a variation on the Serial standard.


DIN stands for Deutsches Institut für Normung (German Institute for Standardisation), and they have standards for all manner of things, even Parker style pen refills; and DIN-476, now ISO 216, the A-series paper standard.

The DIN 41524 and related standards, replaced by IEC 60130-9 specifies a round connector with a 13.2 mm shell. More popular in the past, for audio and control signals, these have multiple pins. The most popular has 5 pins arranged in a 180 degree arc, with a diameter 7 mm. The earliest PCs used this standard for keyboards, as did MIDI. Some CBs use these instead of the proper microphone connectors with the threaded locking ring.

There are however non-standard versions with retaining rings.

RF Connectors

These consist of a central pin, and an outer housing connected to the coax shield.

The PL-259 is a ohm plug which connects to a SO-239 socket. Actually, these codes related to specific versions, but generically it applies to all related units. These have a characteristic impedance of something like 30 ohms, so they cause reflections in the feedline. They are used at HF, and up to around 150 MHz, according to the examiner. However, they are used on US versions of some radios at 70 cm (US versions of the FT-857D, the European one used an N socket), and some Aussie UHF CBs.

Two gentlemen, Neill and Concelman, developed a series of constant impedance connectors which bear their initials.

The C-connector, alluded to in one of the spoilers, is a fairly large bayonet connector, more substantial than an N-connector, and which could easily handle a kilowatt. They are used in avionics (aircraft electronics and communications) and military systems.

The N is a threaded connector, available in 50 and 75 ohm versions. While there are advertised as "moisture resistant", like any coaxial termination, you still need to apply self-amalgamating (mastic) tape, then black electrical tape, then grey electrical tape, over these terminations if installed permanently. The grey looks like galvanising, and discourages birds. They are mechanically stable, and maintain their quoted impedance through the connection, so may be good up to 10 GHz.

BNC and TNC, bayonet and threaded connectors developed by the two blokes above, are medium sized connectors, with the threaded version being more mechanically stable, and therefore having a higher frequency rating.

SMA is a smaller threaded connector, good for quite a few gigahertz. There are also even smaller connectors, of similar appearance, including the SMC connector.

For confusion value (but not on the exam), there are also large "7-16 DIN" RF connectors, typically used with Heliax. And the D-connectors above? DIN 41652.

Audio Connectors

The RCA Phono is a mid-1930s connector designed for occasional disconnection audio signals in phonograph (record) players, primarily for use during servicing, including when a radio and record player was included in one device. They have a long pin carrying the signal, which means connects before the shield, resulting in loud buzzes if plugged into powered systems. Professional versions have a retracting shield, which makes contact first, when consumer gear must be connected to professional systems. RCAs are however fairly mechanically stable, so better than 3.5 mm connectors.

Serious audio gear uses jack plugs / phone plugs / 6.5 mm plugs / ¼" plugs (actually 6.35 mm) for unbalanced audio, or Cannon / XLR ones for balanced audio. There is however the potentially confusing 3 way 6.5 mm version, where the tip and sleeve can be left and right unbalanced, send and return unbalanced for connecting effects units, or balanced mono audio.

LEDs and LCDs

Light Emitting Diodes emit light when the diode junction is forward biased, such that current flows through them. They can be a single indicator, or grouped to form 7-segment or other displays. Newer high current version are useful for illumination.

Liquid Crystal Displays use a material which changes polarisation when a very small current is applied to them. Most often they are configured so that the background is light grey, and the numerals, etc, are dark grey. They require external illumination to be visible, or may include a backlight.

Relevant Questions

These are actual questions from the General exam pool.

What determines the performance of a ferrite core at different frequencies?
A. Its conductivity
B. Its thickness
C. The composition, or "mix," of materials used
D. The ratio of outer diameter to inner diameter

This is the "mix" or materials used, answer C.

What is meant by the term MMIC?
A. Multi Megabyte Integrated Circuit
B. Monolithic Microwave Integrated Circuit
C. Military Manufactured Integrated Circuit
D. Mode Modulated Integrated Circuit

Monolithic Microwave Integrated Circuit, answer B.

Which of the following is an advantage of CMOS integrated circuits compared to TTL integrated circuits?
A. Low power consumption
B. High power handling capability
C. Better suited for RF amplification
D. Better suited for power supply regulation

CMOS ICs have low power consumption, and are suitable for battery powered devices, answer A.

Another upside is that they often don't need to be supplied via a regulator, and many will operate over the 10 to 6 volt range of a discharging 9 volt battery, or the 10 to 15 volts found in an automotive system.

What is meant by the term ROM?
A. Resistor Operated Memory
B. Read Only Memory
C. Random Operational Memory
D. Resistant to Overload Memory

This is Read Only Memory, used to hold the permanent programming in some radios. answer B.

What is meant when memory is characterized as non-volatile?
A. It is resistant to radiation damage
B. It is resistant to high temperatures
C. The stored information is maintained even if power is removed
D. The stored information cannot be changed once written

This is memory which is not lost when power is removed. Things like settings on a HT or mobile radio are stored in this sort of memory. It is answer C.

What kind of device is an integrated circuit operational amplifier?
A. Digital
C. Programmable Logic
D. Analog

An operational amplifier (op-amp) IC is an analogue device, answer D.

Which of the following describes a type N connector?
A. A moisture-resistant RF connector useful to 10 GHz
B. A small bayonet connector used for data circuits
C. A threaded connector used for hydraulic systems
D. An audio connector used in surround-sound installations

N connectors are fairly large, and are claimed to be moisture resistant. They work at up to 10 GHz, so answer A.

All connections should be properly waterproofed if outside for any significant period of time.

How is an LED biased when emitting light?
A. Beyond cutoff
B. At the Zener voltage
C. Reverse Biased
D. Forward Biased

The emission of light requires forward current flow, meaning it must be forward biased, answer D.

Which of the following is a characteristic of a liquid crystal display?
A. It utilizes ambient or back lighting
B. It offers a wide dynamic range
C. It consumes relatively high power
D. It has relatively short lifetime

An LCD itself is not light emitting, so needs either ambient light (room light or sunlight) or back-lighting, answer A.

Back-lighting can be old-style lamps, LEDs, or electroluminescent.

How does a ferrite bead or core reduce common-mode RF current on the shield of a coaxial cable?
A. By creating an impedance in the current’s path
B. It converts common-mode current to differential mode
C. By creating an out-of-phase current to cancel the common-mode current
D. Ferrites expel magnetic fields

They cause an inductive reactance to RF current flow, aka an impedance, answer A.

What is a type SMA connector?
A. A large bayonet connector usable at power levels in excess of 1 KW
B. A small threaded connector suitable for signals up to several GHz
C. A connector designed for serial multiple access signals
D. A type of push-on connector intended for high voltage applications

These are quite small, and are threaded. They are also good for (at least) several GHz, Answer B.

I have used these at 100 watts on 6 metres, but kilowatt, even at HF, would be "pushing it".

Which of these connector types is commonly used for audio signals in Amateur Radio stations?
A. PL-259
C. RCA Phono
D. Type N

The examiner is looking for the RCA / phono connector, the only one commonly used for audio, answer C.

They are certainly used in consumer electronics for audio and some video signals; in ham radio, yeah, nah, maybe. Perhaps a few external soundcard devices use it, or the recorder output on top-of-the-line radios. I have seen this connector used as the RF socket on a crappy CB.

Which of these connector types is commonly used for RF connections at frequencies up to 150 MHz?
A. Octal
B. RJ-11
C. PL-259
D. DB-25

The only RF connector here is the PL-259, answer C.

While not an ideal connector, they are used at the frequency mentioned.

The Octal socket consists of a fairly large 8 pin valve (tube) socket as the socket. The plug fits this. They are used in things like connecting external RF amplifiers and speakers to the Kenwood TS-830S discussed previously. They can handle large currents and voltages, but care needs to be taken te ensure the user is not exposed to dangerous voltages, as the contacts may be almost flush with the face of the socket, which is not an issue within equipment, but is on a back panel.

If you skipped ahead, you should return to Electrical Principles 1 now.

On to: Circuits 1 - Power supplies and Schematics

You can find links to lots more on the Learning Material page.

Written by Julian Sortland, VK2YJS & AG6LE, April 2022.

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