the New Intermediate Licence
This is the second of three articles written to help club Education leads plan for the new Foundation
This is the second of three articles written to help club Education leads plan for the new Foundation, Intermediate and Advanced Syllabi that come into effect this coming September.
I will use the words Foundation, Intermediate and Advanced as shorthand to mean their syllabi throughout this piece. I discussed the Foundation changes last month and this month turn to Intermediate. Some 30 teaching points have come ‘down’ to Intermediate from the old Advanced. There is new material too − look for entries in bold.
Has the RSGB ‘raised the bar’? Not overall – the total amount of radio knowledge to be acquired over all three licence levels has not changed. But by re-levelling − putting a little more theory into Foundation, and rather more into Intermediate −- Advanced becomes less daunting and more amateurs, the plan is, will progress to a Full licence.
Changes to Intermediate were necessary for another reason. Ofcom have long been unhappy with this level. Theory-wise, Intermediate is barely a step up from Foundation. Students can too easily pass at Intermediate, gaining access to more bands, higher power and the right to build and use transmitters.
So here we go. I have detailed all the changes (I hope; I may have missed some minor ones!)
Section 1: Licensing Conditions
Syllabus ref 1A4 gives the conditions whereby licences can be varied and revoked. The requirement to revalidate your details at least every five years has always been covered at Foundation, so students should know it.
Section 2: Technical Aspects
My commentary appears below and my specific comments, sub-section by sub-section, in Table 1.
Section 2E introduces the concept of ‘phase’ in AC waveforms. This is new. A rondeau or ‘round’ in music might help in teaching this. Do you remember these from primary school? One group of singers starts, and a line or two later another group starts. Both groups proceed, at the same speed, singing different parts of the song.
Section 2F Digital Signals, which was introduced at new Foundation, is now built on.
Section 2F1 made me stop and think: Nyquist’s rule, based on Shannon’s work, says that a digital sampling rate must be at least twice the bandwidth of the analogue ‘data’ to be sampled. CD-quality sound has a frequency response of 20kHz and a sampling rate 44kb/s, for example.
Resonance is covered in Section 2H1. Students must understand that at resonance capacitive and inductive reactance are equal and ‘opposite’. I modelled a 20m resonance in Excel - see Fig. 1. Xc and Xl lines crossing and will be theory enough for most students. Xl’s direct proportionality to frequency versus Xc’s inverse relationship with it is required knowledge.
Q is introduced in section 2H4, as an indication of selectivity. It is defined as bandwidth divided by frequency.
Section 2H5 is about filters. Response curves and filter sharpness, including cut-off frequencies, are covered. Students learn about crystals, classified as ‘electro-mechanical resonators’. (See Sections 10B and 10C.)
Section 2I5 deals with biasing. Semiconductors must be provided with the correct voltages and currents to function.
Section 2I7 takes us beyond transistors and introduces Integrated circuits and their substrate design and construction. Applications students can be examined on are amplifiers, oscillators, voltage regulators and digital processing chips.
Section 2J introduces students to different battery technologies.
Section 3: Transmitters
Modulation depth and Deviation are new. Students may be familiar with modulation depth from HF SSB operating but beware! Many Foundation students don’t operate HF and their only SSB experience could be from their course.
Deviation settings should be well-known from programming memories into radios. Wide and narrow deviation can be demonstrated with a 2m handie. Peak deviation can be explained in terms of channel steps and avoiding co-channel interference.
Section 3A3 includes a new recall point – that digital signals may use less bandwidth than any of (in order, high to low), FM, AM, SSB or CW.
Digital Synthesis DDS is introduced in Section 3C3. Students should recall that RF and AF (analogue) waveforms can be created by computers using a look-up table. Anybody who uses Excel seriously will know look-up tables.
Amplifier efficiency – but not classes of amplifier – now features in Intermediate. Section 3F1 requires students to understand amplifier (RF or AF) efficiency based on input (DC) power consumed. This topic may expose student weaknesses in calculating percentages.
Chirp appears, in Section 3G5. Are students likely to have experienced this, given the Foundation licence’s power restrictions? I doubt it, but if an Intermediate student were to homebrew a 50W CW transmitter with insufficient DC isolation between the keying stage and the PA, Chirp could rear its ugly head.
Section 3H2 requires students to understand block diagrams for crystal and direct conversion receivers.
Superhets are covered by Section 3I. Students will learn to ‘identify the tuned circuits in the circuit of an IF amplifier’.
Section 3M1 has more Digital Signals ‘recall’ points. Time and Frequency domains are central concepts to digital signalling. See Fig. 2, another Excel model, which shows amplitude against time for a10Hz waveform with the second and third harmonics added. This is a Time Domain plot. Because of the scale and easy numbers, the relative amplitudes are easy to pick out.
Now look at Fig. 3. This is a Frequency Domain display of the same waveform and shows the three component frequencies. This frequency resolving is what Fourier transformation does. Students are required to identify simple harmonic waves with one or two harmonics.
Automatic Gain Control (AGC) was already part of Intermediate. Section 3L1 now adds that AGC ‘can drive a signal meter’. How or why is not explained! Disabling AGC will prove this − the S-meter will simply stop working.
Section 4: Feeders and Antennas
Section 4G1 explains Dummy loads and the importance of resistors being as non-inductive as possible. Carbon resistors are good but the syllabus does not give examples.
Section 5: Propagation
The syllabus gives students a good picture of how propagation works.
Section 6: EMC
Section 6D2 requires students to understand common and differential mode currents. This is one of those things many of us nod sagely along to when it comes up without really understanding!
Consider an open feeder terminated by a resistive load and connected to an RF AC source. See Fig. 4. It’s a straightforward complete circuit and the instantaneous ‘up’ current (let’s say on the left) has to equal the ‘down’ current on the right. These are ‘differential’ currents.
Now make the load a dipole at resonance. The circuit, from the RF generator’s point of view, has not changed. This is the ultimate in balanced antenna systems.
Now let reality bite and add a bit of imbalance – perhaps the antenna slopes, say, Fig 5. This shows a new current flowing in the antenna system. This is quite unlike the differential current, because it flows in the same direction on both feeder wires.
Why both wires? Because they are so close together compared to the RF wavelength that the open feeder ‘looks like’ one wire. Say the instantaneous differential and common mode currents are 1000mA and 100mA respectively. The currents combine, so the up current will be 1100mA when the down current is 900mA.
The problem comes when amateurs talk of common mode currents in coax.
Open feeder looks like, and to RF is, two wires. Coax also looks like two conductors, but to RF it has three, Fig. 6. There is the inner conductor, the inside surface of the braid and the outside of the braid. The inner conductor and inside surface of the braid are so closely coupled that any currents in them are always equal and opposite.
Even with a balanced antenna current can easily flow down the outside of the coax. But the coax inner offers no additional path for an imbalance-generated current to flow. The current on the outside of the coax consequently has nothing to be ‘common’ with. It’s a nuisance, for sure (hence the use of choke baluns) but it is not, strictly speaking, a ‘common mode’ current.
I hope that helps. By exploring that, at least I understand it now!
Section 7: Operating practices and procedures
Section 7B1 covers some important international conventions such as no SSB on 10MHz, no contests on 10, 18 and 24MHz and satellite frequencies to be avoided for terrestrial QSOs.
Band Plans for 2m and 20m are provided in the exam. These may not be ‘real’ so students should forget what they know from operating and check the band plans supplied for the exam. Such easy marks should not be squandered.
Section 7F2 has more about receiving and transmitting Digital signals. Students must recall that different types (modes) of transmissions can be received using a computer and ‘a suitable interface’. See Figs. 7 and 8 for block diagrams (not the ‘official’ ones) of a simple SDR receiver and transmitter. When transmitting, voice distortion can be minimised by adjusting the operation of the Digital Audio Controller (DAC).
Section 8: Safety
These still are the easiest marks in the exam. Starting at question 40, students should ignore radio and electronics per se and just consider safety.
There is no 8A3, 5 or 7.
Section 9: Measurement and Construction
At Intermediate level, EMC includes elements of design and construction. Section 9D1 requires students to recall that metal sheeting such as a radio’s case is effective in preventing unwanted RF from radiating and is used in design and construction to isolate RF stages.
Section 10: Practical assessments
Wiring mains plugs has gone from the syllabus. I say no more.
10B Construction. This section of the article differs from above in that it details all that is required. Considering all the theory changes, the practical exercises – which have not increased – might seem to be less important. I don’t think they are; hands-on radio skills are still central to the Intermediate licence.
10B2 – Students may solder anything – no component types are specified! – to anything, even solder tags. Tutors (braver than me) could use this to introduce surface mount construction.
For Section 10B3 I offer the circuit in Fig. 9, which meets the literal requirement. The switch is not an on-off, so the LEDs will always be on if power is connected, and that makes me wonder if something less involved may have been intended.
I strongly recommend LEDs over bulbs. LEDs need resistors, as does the exercise, and have a more modern feel.
10B4 does not say ‘build’, even if is under ‘Construction’. Pre-made transistor switch boards with meter connections already in place could be used. Students can touch prominent contacts to demonstrate the circuit in operation. After reading base and collector currents they can calculate the gain.
10C Instrumentation and Measurement: Nothing to add here above what I have included in the table.
I said in my Foundation article that it must have been an enormous task to update the syllabus, and that goes a thousand-fold for Intermediate. I think the RSGB has done an amazing job. I sincerely mean that.
Yes, Foundation is more difficult (but not much).
Yes, Intermediate is (definitely) more difficult.
Yes, clubs have planning to do and changes to make. Some clubs, I’ve heard, are giving up running courses. I hope that does not turn out to be true.
All this needs to be seen in the ‘big picture’. Starting with new Foundation, and really built on by new Intermediate, students will be much better prepared both for ‘doing’ amateur radio and progressing to a Full licence.
This article was featured in the April 2019 issue of Practical wireless.