Friday, October 9, 2009

Pensive but philosophical three days on

Well, it's now three days since the exam and, although I am still filled with apprehension about the results, I am trying to get into a mindset where I am not expecting anything.

I have been able to remember almost all the questions from Section A, and the answers that I gave, and I realise that it's very tight. I know I got some right, I think I got some others right, and there are others I'm not sure about. Plus there are a number which I know I got wrong.

The main conclusion that I've drawn is that, in Section A at least, it's so close that I couldn't possibly call the result. I may fail by just a question or two. I was disappointed that I got three out of the four measurements questions wrong. The propagation section was tougher than I thought and there's at least one question there which I'm not confident about. In the first ten questions, I am certain about only five - that's just half. I am puzzled about a question about what the purpose of a capacitor in a transformer was. I put down "to reduce hum" and am not confident. Also, there was the diagram of an audio amplifier asking what two capacitors and a resistor were for. They looked a bit like a pi network or low pass filter so I gave the answer "to limit the AF bandwidth". Another possible answer related to RF feedback so I assumed that to be wrong.

The first question in the whole test asked what a radio wave was:

a) an electromagnetic field
b) an electric field
c) a magnetic field
d) an electro-somethingorother field. (Can't remember the fourth answer).

I gave a) an electromagnetic field

In feeders and antennas, I think I was right in answering that the characteristic impedance of a quarter wave electrical feeder was determined by its dimensions and the spacing of the conductors rather than the other options which were: its length, the power used and something else, maybe the SWR.

Also, a feeder open at the far end would show low impedance at the near end. I looked that up when I got home and discovered I got it right.

An FM transmitter amplifier works in Class C because? Well I answered that it was rich in harmonics. An FM transmitter uses frequency multiplication which requires harmonics, so I might be right on that one.

There were three separate questions about band plans and power etc, two in Section B and one in Section A. To my absolute disgust, I found that I only got one right. 15 metres is 21.000 to 21.450. I was asked what the maximum power was on 1.9 MHz. I said 100 watts but the answer is 10 watts. I was asked what mode was 29.520-29.700 reserved for. Having initally given the correct answer - FM - I then doubted myself and opted for QRP instead. Again this was simply down to me not knowing my stuff well enough. Plus, in an exam situation where you have no books or internet or notes to refer to, self doubt creeps in when there is the slightest suspicion about a wrong answer.

There was a question, I'm not sure whether it was in propagation in Section A or not, about what the frequency 14.100 was reserved for. I answered beacons, which I believe is correct.

The end result of all my investigations since the exam is nothing but anxiety. And that's because I didn't give enough correct answers to give myself a comfort zone. I got two simple answers wrong - one was the graph for the current through an inductor, the other about AM being a carrier plus two sidebands. (I said carrier plus one sideband. Where the hell did I get that idea? Silly mistake which might have cost me the whole bloody exam.)

Another question in Section A was about the intermediate frequency of a CW transmitter, or something like that, maybe the difference between the oscillator frequency and the IF. There were four possible answers: 10MHz, 0.8kHz, 455kHz or 1Hz. I thought 10Mhz and 1Hz looked like completely spurious answers and I knew in all the superhet receiver questions that 455kHz was always mentioned so I went for that.

My little "Man United's New Players" mnemonic helped me answer a question which asked about what value a 1000 uF capacitor had. The answer was 1 nF. Great!

In the safety part of Section C, the first question asked how to wire a plug. The second question asked something like what was most likely to give you an electric shock in a circuit, and the answer was capacitor. The third question asked the purpose of a fuse in the plug of a transceiver. The most legitimate answer looked to me to be that it protected the transceiver from voltage or current overload, something like that.

There was a question about a HF transmitter interfering with a TV which was tuned to certain frequencies (I think one was an 800 mhz band). The most appropriate action, in my opinion, was to fit a high pass filter to the downlead of the TV antenna.

The first question in Section C was about the primary purpose or issue of concern with regard to Electromagnetic Compatibility. One answer was the protection of human health from emissions, but to be honest the more likely answer to me was the prevention of spurious emissions, so that's the one I gave.

If I can remember any more questions I will note them here. Hopefully that will provide some assistance to people who intend to sit the next exam. I might well be sitting it with you!! . . .


  1. Best of luck Anthony... hope you passed.
    Also I had a laugh at that MUNP mnemonic... I would have to try harder to remember that than the actual milli-micro-nano-pico it's supposed to help you with.

  2. Thanks Gerry.

    Yes mnemonics work for some people and not for others. I suppose it depends whether you support Man U or not!!


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