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ARRL General Class Study Guide
I found a copy of the Technician class exam question pool which seems to
be from the ARRL study guide. It is in a great format with the answers along the margin so you can hide them easily. But the only list of questions I can find for the General class has the answers immediately above the questions so it is hard to hide them. Anyone know of similar question pool lists for the General and Extra classes? -- Rick C |
ARRL General Class Study Guide
In article , rickman wrote:
I found a copy of the Technician class exam question pool which seems to be from the ARRL study guide. It is in a great format with the answers along the margin so you can hide them easily. But the only list of questions I can find for the General class has the answers immediately above the questions so it is hard to hide them. Anyone know of similar question pool lists for the General and Extra classes? http://www.arrl.org/files/file/Gener...CLM_8th_ed.pdf http://www.arrl.org/files/file/Extra...Studyguide.pdf |
ARRL General Class Study Guide
On 8/29/2016 4:23 PM, Dave Platt wrote:
In article , rickman wrote: I found a copy of the Technician class exam question pool which seems to be from the ARRL study guide. It is in a great format with the answers along the margin so you can hide them easily. But the only list of questions I can find for the General class has the answers immediately above the questions so it is hard to hide them. Anyone know of similar question pool lists for the General and Extra classes? http://www.arrl.org/files/file/Gener...CLM_8th_ed.pdf http://www.arrl.org/files/file/Extra...Studyguide.pdf Hey, thanks. I followed every link I could find on their site and didn't find these. Great! I'm thinking I'll just study and get all three and not have to bother with going back to take them one at a time. -- Rick C |
ARRL General Class Study Guide
In article , rickman wrote:
Hey, thanks. I followed every link I could find on their site and didn't find these. Great! I'm thinking I'll just study and get all three and not have to bother with going back to take them one at a time. Not a bad idea! Most of the VE groups will let you take all three tests for a single fee (assuming that you keep passing). That being said: I'm not a fan of "study just the test questions, and cram the answers" approach to getting a ham license. A lot of people do get their Technician licenses that way, but they tend to be somewhat lost afterwards - they often don't understand the "why" behind the answer. This may be OK for a Technician who just wants to communicate with family and friends on a pre-programmed radio, but it doesn't work so well at the General and Extra levels. Even at the Tech level, a fair number of people who get their ticket after a one-day Ham Cram session never seem to get on the air. For the Amateur and Extra licenses, at least, I'd recommend getting the ARRL license manuals and actually reading through them at least once (you might be able to get current copies of the current manuals through a public library, or from someone who has recently passed the exams). If you've got a solid understanding of radio and electronics theory already, this may not be necessary, at least for the questions in these areas. There's still a fair bit of material in the General and Extra exams which relates to legal issues e.g. third-party communication, power levels, emission modes vs. frequency bands, RF exposure, etc., where you tend to need a combination of "understand the background of the topic" and "memorize the specific details of what's in the current regulations, which may not make any real sense but are Just So." |
ARRL General Class Study Guide
On 8/30/2016 1:08 PM, Dave Platt wrote:
In article , rickman wrote: Hey, thanks. I followed every link I could find on their site and didn't find these. Great! I'm thinking I'll just study and get all three and not have to bother with going back to take them one at a time. Not a bad idea! Most of the VE groups will let you take all three tests for a single fee (assuming that you keep passing). That being said: I'm not a fan of "study just the test questions, and cram the answers" approach to getting a ham license. A lot of people do get their Technician licenses that way, but they tend to be somewhat lost afterwards - they often don't understand the "why" behind the answer. This may be OK for a Technician who just wants to communicate with family and friends on a pre-programmed radio, but it doesn't work so well at the General and Extra levels. Even at the Tech level, a fair number of people who get their ticket after a one-day Ham Cram session never seem to get on the air. For the Amateur and Extra licenses, at least, I'd recommend getting the ARRL license manuals and actually reading through them at least once (you might be able to get current copies of the current manuals through a public library, or from someone who has recently passed the exams). If you've got a solid understanding of radio and electronics theory already, this may not be necessary, at least for the questions in these areas. There's still a fair bit of material in the General and Extra exams which relates to legal issues e.g. third-party communication, power levels, emission modes vs. frequency bands, RF exposure, etc., where you tend to need a combination of "understand the background of the topic" and "memorize the specific details of what's in the current regulations, which may not make any real sense but are Just So." I'm an EE, so I have a lot of electronics background even if I'm not really an RF guy. I'm going through the ARRL review for the General license now. One question that is stumping me is about FM bandwidth. Here is the question. What is the total bandwidth of an FM phone transmission having 5 kHz deviation and 3 kHz modulating frequency? The correct answer is 16 kHz, (3 kHz + 8 kHz) * 2. But I don't get why. The only page I've found so far that tries to explain refers to "heterodyning" the carrier, the audio bandwidth and the maximum deviation, Df. Df is not really a signal, it is just a parameter describing the RF signal. Further, there is no hetreodyning. Am I just getting hung up on terminology? As to cramming the questions, I'm not sure I will ever use the license to transmit. I think I'm just getting it to be able to say I have it. I might learn Morse code as well, just for street creds. Mostly I want to build receivers. -- Rick C |
ARRL General Class Study Guide
In article , rickman wrote:
What is the total bandwidth of an FM phone transmission having 5 kHz deviation and 3 kHz modulating frequency? The correct answer is 16 kHz, (3 kHz + 8 kHz) * 2. But I don't get why. The only page I've found so far that tries to explain refers to "heterodyning" the carrier, the audio bandwidth and the maximum deviation, Df. Df is not really a signal, it is just a parameter describing the RF signal. Further, there is no hetreodyning. Am I just getting hung up on terminology? A bit, but your concern is reasonable - for FM you aren't heterodyning, and the rules are a bit different. FM modulation is mathematically more complex than AM/SSB. AM and SSB involve multiplication of two sines (the carrier and the content) and you end up with precisely two sidebands per content-tone (at carrier+tone and carrier-tone). So, the bandwidth is easy to determine... it's twice that of the highest frequency in the content signal (for AM) and half that for SSB. FM is trickier. If you work out the formula for the instantaneous value of the RF carrier (given an information signal of a given frequency and maximum carrier deviation) you end up with a "sine of a sine" equation, and this is *not* as "well behaved". In principle, the actual occupied bandwidth of an FM-modulated carrier is *infinite*. If you FM a carrier with a 1 kHz tone, the resulting RF spectrum contains discrete sidebands at 1 kHz offsets from the carrier frequency, in both directions, going out "forever". Fortunately for us all, the amplitudes of these sidebands drop off very sharply once you get out beyond the maximum instantaneous deviation of the carrier. The actual amplitudes of the sidebands are the results of the Bessel functions. So, we don't have to treat the occupied bandwidth as literally infinite... we just treat it as the portion of the spectrum that has enough energy in it that would interact with other transmissions. What we tend to use (for most audio-modulated FM) is what's known as Carson's rule (or rule-of-thumb). Add together the peak deviation, and the bandwidth of the modulating signal, and that's the amount of spectrum you need on each side of the carrier. So, you double this number to get "occupied bandwidth". So - a voice-audio signal of DC - 3 kHz, modulating an FM carrier by up to +/-5 kHz, requires 2*(3+5) KHz of bandwidth, or 16k. Running FM voice channels on 20 kHz separations is thus practical. In areas where hams use 15 kHz channelization, it's best practice to keep peak deviation down to 3.5 kHz or so. |
ARRL General Class Study Guide
On 8/30/2016 3:30 PM, Dave Platt wrote:
In article , rickman wrote: What is the total bandwidth of an FM phone transmission having 5 kHz deviation and 3 kHz modulating frequency? The correct answer is 16 kHz, (3 kHz + 8 kHz) * 2. But I don't get why. The only page I've found so far that tries to explain refers to "heterodyning" the carrier, the audio bandwidth and the maximum deviation, Df. Df is not really a signal, it is just a parameter describing the RF signal. Further, there is no hetreodyning. Am I just getting hung up on terminology? A bit, but your concern is reasonable - for FM you aren't heterodyning, and the rules are a bit different. FM modulation is mathematically more complex than AM/SSB. AM and SSB involve multiplication of two sines (the carrier and the content) and you end up with precisely two sidebands per content-tone (at carrier+tone and carrier-tone). So, the bandwidth is easy to determine... it's twice that of the highest frequency in the content signal (for AM) and half that for SSB. FM is trickier. If you work out the formula for the instantaneous value of the RF carrier (given an information signal of a given frequency and maximum carrier deviation) you end up with a "sine of a sine" equation, and this is *not* as "well behaved". In principle, the actual occupied bandwidth of an FM-modulated carrier is *infinite*. If you FM a carrier with a 1 kHz tone, the resulting RF spectrum contains discrete sidebands at 1 kHz offsets from the carrier frequency, in both directions, going out "forever". Fortunately for us all, the amplitudes of these sidebands drop off very sharply once you get out beyond the maximum instantaneous deviation of the carrier. The actual amplitudes of the sidebands are the results of the Bessel functions. So, we don't have to treat the occupied bandwidth as literally infinite... we just treat it as the portion of the spectrum that has enough energy in it that would interact with other transmissions. What we tend to use (for most audio-modulated FM) is what's known as Carson's rule (or rule-of-thumb). Add together the peak deviation, and the bandwidth of the modulating signal, and that's the amount of spectrum you need on each side of the carrier. So, you double this number to get "occupied bandwidth". So - a voice-audio signal of DC - 3 kHz, modulating an FM carrier by up to +/-5 kHz, requires 2*(3+5) KHz of bandwidth, or 16k. Running FM voice channels on 20 kHz separations is thus practical. In areas where hams use 15 kHz channelization, it's best practice to keep peak deviation down to 3.5 kHz or so. Thanks, I've never derived the equation for an FM signal, so I wasn't aware it was that complex. Now that you have explained the basis of it, I don't need to actually go through the math, I'll believe Carson. While I've got your attention, what is the basis for the 150 Hz bandwidth for CW signals? What data rate (or symbol rate) is assumed? I'm working on a WWVB decoder and would like to figure out the bandwidth needed to detect the signal edges reasonably well (for various values of "reasonable"). I expect these are similar since they are both pulse width encoded. -- Rick C |
ARRL General Class Study Guide
On 8/30/2016 4:01 PM, Ralph Mowery wrote:
In article , says... In article , rickman wrote: What is the total bandwidth of an FM phone transmission having 5 kHz deviation and 3 kHz modulating frequency? The correct answer is 16 kHz, (3 kHz + 8 kHz) * 2. But I don't get why. The only page I've found so far that tries to explain refers to "heterodyning" the carrier, the audio bandwidth and the maximum deviation, Df. Df is not really a signal, it is just a parameter describing the RF signal. Further, there is no hetreodyning. Am I just getting hung up on terminology? A bit, but your concern is reasonable - for FM you aren't heterodyning, and the rules are a bit different. FM modulation is mathematically more complex than AM/SSB. AM and SSB involve multiplication of two sines (the carrier and the content) and you end up with precisely two sidebands per content-tone (at carrier+tone and carrier-tone). So, the bandwidth is easy to determine... it's twice that of the highest frequency in the content signal (for AM) and half that for SSB. FM is trickier. If you work out the formula for the instantaneous value of the RF carrier (given an information signal of a given frequency and maximum carrier deviation) you end up with a "sine of a sine" equation, and this is *not* as "well behaved". In principle, the actual occupied bandwidth of an FM-modulated carrier is *infinite*. If you FM a carrier with a 1 kHz tone, the resulting RF spectrum contains discrete sidebands at 1 kHz offsets from the carrier frequency, in both directions, going out "forever". Fortunately for us all, the amplitudes of these sidebands drop off very sharply once you get out beyond the maximum instantaneous deviation of the carrier. The actual amplitudes of the sidebands are the results of the Bessel functions. So, we don't have to treat the occupied bandwidth as literally infinite... we just treat it as the portion of the spectrum that has enough energy in it that would interact with other transmissions. What we tend to use (for most audio-modulated FM) is what's known as Carson's rule (or rule-of-thumb). Add together the peak deviation, and the bandwidth of the modulating signal, and that's the amount of spectrum you need on each side of the carrier. So, you double this number to get "occupied bandwidth". So - a voice-audio signal of DC - 3 kHz, modulating an FM carrier by up to +/-5 kHz, requires 2*(3+5) KHz of bandwidth, or 16k. Running FM voice channels on 20 kHz separations is thus practical. In areas where hams use 15 kHz channelization, it's best practice to keep peak deviation down to 3.5 kHz or so. Well put Dave for a short answer. The FM is infinite just as the light from a flashlight may be distance wise,but as you get far enough away it is not detectable by most instruments. As most of the power is in the first 8 kHz each side of the center of the 5 khz deviated by 3 kHz audio, it was just decided to call that the bandwidth and is good enough for most receivers with the correct filters. The 15 kHz spacing comes from years ago. I may be wrong on the spacing of comercial FM being 60 kHz, but think it was at one time. I know it was 30 kHz at one time and the deviation was set at 15 kHz. Then as the bands got more occupied and the stability of the equipment improved the comercial stuff just went to 5 kHz deviationa and cut the bandwidth in half to 15 kHz. I was not aware that FM broadcast radio was ever spaced at 60 kHz. My understanding is the bandwidth is most of the 200 kHz channel spacing which is a bit too close to prevent interference on adjacent channels in many cases. Typically they don't assign adjacent channels in overlapping areas. As hams are not reqired to keep the spacing or deviation some areas did go to 20 kHz spacing and 5 kHz deviation. Other areas went to 15 kHz spacing and kept the 5 kHz deviation. If the rigs are not very well up todate and the frequency and deviation set correctly there can be problems with the 15 kHz spacing. -- Rick C |
ARRL General Class Study Guide
In article , says...
On 8/30/2016 4:01 PM, Ralph Mowery wrote: In article , says... The 15 kHz spacing comes from years ago. I may be wrong on the spacing of comercial FM being 60 kHz, but think it was at one time. I know it was 30 kHz at one time and the deviation was set at 15 kHz. Then as the bands got more occupied and the stability of the equipment improved the comercial stuff just went to 5 kHz deviationa and cut the bandwidth in half to 15 kHz. I was not aware that FM broadcast radio was ever spaced at 60 kHz. My understanding is the bandwidth is most of the 200 kHz channel spacing which is a bit too close to prevent interference on adjacent channels in many cases. Typically they don't assign adjacent channels in overlapping areas. I should have been clearer. I was thinking of the comercial two way radios like the public service of police and taxi cabss. Not the FM broadcast stations. The FM broadcast stations are deviating much wider than the 5 and 15 kHz we were talking about. --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus |
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