EXTRA! Intermediate Licence Book

A companion page to Intermediate Licence Book, including: Updates, amendments, corrections, further information, component suppliers and web addresses.

All about the book and how to get your copy

Corrections, updates, further information and web sites		The RSGB is currently shipping a corrected 4th edition of the Intermediate Licence book which incorporates the changes made to licensing and the exam syllabus in 2006 & 2007.  If you have a previous edition below are the major changes made and links to the replacement licensing pages.  These are not the only changes included in the 4th edition but those that may have an impact on success in the examination. Following UK amateur radio licence changes in December 2006 and the Intermediate Licence syllabus will change with effect of the 1st April 2007. If you using an edition of the Intermediate book that does not contain the changes you are advised to substitute these pages: Intermediate Licence Update (pdf) Throughout the book any reference to BR68/I should now refer to the new ‘lifetime’ Licence Document, a sample of which is available from the OfCom website. Throughout the book, the term ‘voltage’ should now be read as ‘potential difference’. Page 2:  When applying for your Intermediate Licence and paying the appropriate fee. From December 2006 a new system was introduced where on-line applications enable you to obtain your new Licence free of charge. You can apply by post if you wish, but there is a charge for paper applications. You can make your application as soon as the paperwork has been returned to RSGB Headquarters and entered into the OfCom database. This may take a few days. Page 4: The risks from inhaling solder fume have been re-emphasised; when inhaled, rosin based solder flux fume can lead to occupational asthma or can make existing asthmatic conditions worse. Pages 17-20: Should be replaced with the new pages on this site Pages 22 and 23 refer to keeping a Log. Whilst there is no longer a legal requirement to keep a Log, being able to check up on contacts you have made in the past is a very good reason for keeping one. If you receive a QSL card from another station for a contact you made a year or two before, how will you be able to verify that the contact took place without some kind of record? Contesting is one area of operating where logging your contacts is absolutely essential. You will need to record the contact details and the relevant information exchanged in order to submit an entry. Page 29: The required knowledge relating to tuned circuits has been extended. The book already states that the resonant frequency of a tuned circuit depends on the values of the capacitor and the inductor but students are now expected top know that changing the value of either component will have an effect on the resonant frequency. At this level you are not expected to know how the resonant frequency is affected by such a change, or to do any calculation; that is for the Advanced level. Page 36: The topic of oscillators needs a few more words. The book has already covered transistors being used in RF oscillator circuits with the transistors maintaining oscillations in crystals and tuned circuits. You should note that transistors can also be used to maintain oscillations in ‘other frequency selective circuits’ to generate audio frequencies. At this level you do not need to know what those circuits are but you are expected to know that transistors can be used in this way. It is also worth noting as you might find AF oscillator circuits in projects that you build. Pages 43-45: Should be replaced with the new pages on this site Page 54:  The relationship between wavelength, feedpoint impedance, voltage and current has been clarified; The feedpoint impedance of an antenna is not fixed, it is related to the dimensions of the antenna and the wavelength of the signal you are feeding it with. You should recall adjusting an antenna during your Foundation Licence assessment. As you changed the length of the antenna to suit the wavelength of the signal you were using the feedpoint impedance of the antenna was also changing. When the length of the antenna was correct the feedpoint impedance was close to the 50Ω that the transmitter was designed to use. Taking this a little further, you should be able to see that if you apply an RF potential difference across the antenna feedpoint impedance, some RF current will flow in the antenna. Following what we have already learned about Ohm’s law in DC circuits it should be no surprise to find that the RF current (Amps) flowing in the antenna is related to the feedpoint impedance (Ohms) and the potential difference of the applied signal (Volts). In general, you will get maximum radiation from the antenna when you have maximum RF current flowing in the antenna and you will only get maximum current flowing when the feedpoint has the correct impedance. Ohm’s law cannot be applied here, there are other formulas that link the feedpoint impedance, the RF potential difference and the RF current but you do not need to know them and you certainly will not be asked to carry out any calculations using them. Page 63: The following should be added: Dummy Loads (5g.3) A dummy load is a screened resistor, intended to be connected to the output of a transmitter in place of the feeder and antenna for test purposes. These tests could be when setting up a newly constructed transmitter, or when carrying out your EMC detective work. Amateur radio transmitters expect to transfer energy into a 50Ω load, so the resistor must be 50Ω, able to handle the full output power of the transmitter and screened so it does not radiate. The 50Ω resistor must be non-inductive. That means its construction must not include a coil or of wire. Higher power resistors are often made by winding resistance wire on a ceramic rod.  That construction is not suitable for a dummy load because the winding will be inductive.  At radio frequencies an inductor will provide additional opposition to the flow of current and will no longer appear to be 50Ω. Instead, a dummy load should be made from a resistor, or a number of resistors, of carbon composition. An outer metal screen acts as a screen to minimise radiation and some have fins to help get rid of the heat – rather like a central heating radiator. For EMC detective work the dummy load is particularly useful for testing your transmitter without radiating to see if any RF is escaping down the power supply leads or any other leads connected to the transmitter. Pages 70-71:  References to log keeping. It should now be noted that although log keeping is not a requirement of your licence, the recording of all your transmissions is part of good radio housekeeping and if the matter becomes a formal complaint to the authorities, i.e. OfCom, they will require logs to be kept as a first action in identifying the cause. page 72: The practice question number 7 is no longer valid as the Schedule does not specify modes of transmission

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