Extra Class question of the day: stay in band

February 7, 2012 By Leave a Comment

When using a transceiver that displays the carrier frequency of phone signals, the highest frequency at which a properly adjusted USB emission will be totally within the band is 3 kHz below the upper band edge. (E1A01) So, with your transceiver displaying the carrier frequency of phone signals, you hear a DX station’s CQ on 14.349 MHz USB. Is it legal to return the call using upper sideband on the same frequency? No, the sidebands will extend beyond the band edge. (E1A03)

The reason for this is that the USB signal extends from the carrier frequency, which is the frequency that the transceiver is displaying, up 3 kHz. When you set the transceiver to 14.349 kHz, the upper sideband will extend up to 14.352 MHz, and because the amateur radio band stops at 14.350 MHz, some of the transmission will fall outside the band.

A similar thing happens, but in reverse, when you operate lower sideband, or LSB. When using a transceiver that displays the carrier frequency of phone signals,the lowest frequency at which a properly adjusted LSB emission will be totally within the band is 3 kHz above the lower band edge. (E1A02) With your transceiver displaying the carrier frequency of phone signals, you hear a DX station calling CQ on 3.601 MHz LSB. Is it legal to return the call using lower sideband on the same frequency? No, my sidebands will extend beyond the edge of the phone band segment. (E1A04)

The lower sideband will extend down 3 kHz from the carrier frequency. So, when your transceiver is set to 3.601 Mhz, your signal will extend down to 3.598 MHz, which is outside the phone band.

Filed Under: Extra Class Question of the Day, Rules, Regulations, Enforcement

Extra Class question of the day: antenna gain

February 3, 2012 By Leave a Comment

Antenna gain is one of the most misunderstood topics in amateur radio. There are several reasons for this, including:

  • Antennas don’t really have gain in the same way that an amplifier has gain. When you use a linear amplifier, you get more power out than you put in. Since transmitting antennas are passive devices, there’s no way to get more power out than you put in.
  • It’s not easy to measure antenna gain. There is no antenna gain meter that you can simply hook up to an antenna to measure its gain.

So, what is antenna gain? According to question E9A08, antenna gain is the ratio relating the radiated signal strength of an antenna in the direction of maximum radiation to that of a reference antenna. What this means is that when you talk about antenna gain, you have to know what kind of antenna you’re comparing it to.

When talking about antenna gain, antenna engineers often refer to the “isotropic antenna.” An  isotropic antenna is a theoretical antenna used as a reference for antenna gain. (E9A01) An isotropic antenna is an antenna that has no gain in any direction. (E9A03) That is to say it radiates the power input to it equally well in all directions.

Let’s take a look at a practical example. I often say that the 1/2-wavelength dipole antenna is the most basic amateur radio antenna. Well, the dipole actually has some gain over isotropic antenna. The reason for this is that it is directional. The signal strength transmitted broadside to the antenna will be greater than the signal strength transmitted off the ends of the antenna.

The gain of a 1/2-wavelength dipole in free space have compared to an isotropic antenna is 2.15 dB. (E9A02) Sometimes, you’ll see this value as 2.15 dBi, where dBi denotes that  and isotropic antenna is being used for this comparison.

Since the isotropic antenna is a theoretical antenna, some think it’s better to compare an antenna to a dipole antenna. An antenna will have a gain 3.85 dB compared to a 1/2-wavelength dipole when it has 6 dB gain over an isotropic antenna. (E9A13) You obtain this value by simply subtracting 2.15 dB from the 6 dB figure:

Gain over  a dipole = gain over an isotropic antenna – 2.15 dB =
6 dBi – 2.15 dBi = 3.85 dBd

Sometimes, the gain over a dipole is denoted as dBd.

Similarly, an antenna has a gain of 9.85 dB compared to a 1/2-wavelength dipole when it has 12 dB gain over an isotropic antenna. (E9A14):

Gain over  a dipole = gain over an isotropic antenna – 2.15 dB =
12 dBi – 2.15 dBi  = 9.85 dBd

Filed Under: antennas, Extra Class Question of the Day

Extra Class question of the day: contesting

February 2, 2012 By 1 Comment

E2C01 asks, “Which of the following is true about contest operating?” The correct answer is “Operators are permitted to make contacts even if they do not submit a log.” This is a fun way to get your feet wet in contesting and helps the operators participating in the contest to achieve higher scores.

Having said that, you should submit a log, even if you only make a handful of contacts. At WA2HOM, we participated in the CQWW SSB contest last fall. We only operated for a short time, as we can only operate when the museum is open. Even so, we recently received a certificate for being the highest scorer in the single transmitter, multi-operator category in the 8th call district. As it turns out, we were the only entry in this category, but so what? We’re champions!

Now, let’s look at the wrong answers:

  • Interference to other amateurs is unavoidable and therefore acceptable. It’s bad practice–as well as illegal–to cause harmful interference whenever you’re operating, even during contests.
  • It is mandatory to transmit the call sign of the station being worked as part of every transmission to that station. Part 97 requires only that you identify your station, at least once every ten minutes during a contact and at the end of a contact. Even during normal operation, you don’t have to give the callsign of the station being worked.
  • Every contest requires a signal report in the exchange. Many contests no longer require a signal report in the exchange.The reason for this is that the signal reports exchanged are rarely true signal reports. That being the case, why bother to exchange them?
Filed Under: Contests, Extra Class Question of the Day

Extra Class question of the day: resonance

January 31, 2012 By 1 Comment

Yesterday, the National Committee of Volunteer Examiner Coordinators (NCVEC) question pool committee released the latest version of the Extra Class question pool, and I’m pleased to announce that I will be writing an Extra Class study guide. I’m planning on having it ready to release it at the Dayton Hamvention.

In conjunction with that, I’m also planning to do an “Extra Class Question of the Day” here on my blog. In reality, the “question of the day” will cover more than one question, as so many of them are related. As in my study guides, the correct answer will be highlighted, and the question will be marked with the pool question number.

Today’s question of the day is about resonance. Resonance is one of the coolest things in electronics. Resonant circuits are actually what makes radio, as we know it, possible.

What is resonance? Well, a circuit is said to be resonant when the inductive reactance and capacitive reactance are equal to one another. That is to say, when

2πfL = 1/2πfC

where L is the inductance in henries and C is the capacitance in farads.

For a given L and a given C, this happens at only one frequency:

f = 1/2π√(LC)

This frequency is called the resonant frequency. Resonance in an electrical circuit is the frequency at which the capacitive reactance equals the inductive reactance.(E5A02)

Let’s calculate a few resonant frequencies, using questions from the Extra question pool as examples:

The resonant frequency of a series RLC circuit if R is 22 ohms, L is 50 microhenrys and C is 40 picofarads is 3.56 MHz. (E5A14)

f = 1/2π√(LC) = 1/6.28x√(50×10-6 x 40×10-12) = 1/2.8×10-7 = 3.56 MHz

Notice that it really doesn’t matter what the value of the resistance is. The resonant frequency would be the same is R = 220 ? or 2.2 M?.

The resonant frequency of a series RLC circuit if R is 56 ohms, L is 40 microhenrys and C is 200 picofarads is 1.78 MHz. (E5A15)

f = 1/2π√(LC) = 1/6.28x√(40×10-6 x 200×10-12) = 1/5.6×10-7 = 1.78 MHz

The resonant frequency of a parallel RLC circuit if R is 33 ohms, L is 50 microhenrys and C is 10 picofarads is 7.12 MHz. (E5A16)

f = 1/2π√(LC) = 1/6.28x√(50×10-6 x 10×10-12) = 1/1.4×10-7 = 7.12 MHz

The resonant frequency of a parallel RLC circuit if R is 47 ohms, L is 25 microhenrys and C is 10 picofarads is 10.1 MHz. (E5A17)

f = 1/2π√(LC) = 1/6.28x√(25×10-6 x 10×10-12) = 1/9.9×10-7 = 10.1 MHz

Filed Under: Classes/Testing/Licensing, Extra Class Question of the Day

ARRL News – January 25, 2012

January 25, 2012 By 2 Comments

We’ve criticized the ARRL website here on KB6NU.Com from time to time, but there’s a lot of good stuff there, too. In particular, they regularly post timely news items. Here are three items I found particularly interesting:

  • FCC denies Anchorage VEC’s waiver request. In July 2011, the Anchorage VEC asked the FCC to permit individuals who have previously held an Amateur Radio license grant issued by the Commission — but which has expired and is beyond the two year grace period for renewal — to receive credit for elements previously passed, and thus a new license grant, without additional examination.
    I’m not altogether sure why this VEC would request this waiver. In fact, I’ve suggested that maybe it would be a good idea to regularly re-test ham radio operators.
  • Minutes of ARRL Board’s winter meeting posted. The ARRL board held their annual winter meeting the weekend of January 13-14, 2012. The  minutes from that meeting have now been posted. These are always interesting and worth perusing.
    One item of interest is that the board has approved electronic voting for division elections. I wonder how that would have affected, if at all, the two elections that I participated in.
  • LOTW to support CQ awards. The ARRL and CQ magazine have agreed that QSLs recorded in Logbook of the World can now be used to apply for CQ-sponsored operating awards. These are the first non-ARRL awards to be supported by LoTW. The first CQ award that you will be able to apply for via LOTW is the WPX award.
Filed Under: ARRL, Classes/Testing/Licensing

Last weekend a busy one for KB6NU

January 17, 2012 By 6 Comments
KB6NU teaching the Jan. 14, 2012 One-Day Tech Class

Me making a point (apparently about SWR) at Saturday's One-Day Tech Class

Last weekend was pretty busy for me, ham radio-wise. It started bright and early Saturday morning with the latest One-Day Tech Class. There were twelve students in the class, and all twelve passed!

This class was a bit odd in that most of them signed up during the week before the class. So few had signed up by Saturday, January 7th, that I was even thinking that I might cancel the class.

On Sunday, January 8, I sent out a reminder to my mailing list, and after that, the class quickly filled up. Many of them were engineering students from the University of Michigan, who are part of a project that sends up weather balloons. They use amateur radio to track the balloons and to find the payloads once they’ve returned to Earth.

Hamfest not so festive
Sunday morning, I was up even earlier to attend the Hazel Park ARC hamfest. Since I was selling some junk, errrrr good stuff, I wanted to get there by 8 am. So, I was up and out of the house by 6:45 am. I needn’t have rushed, though.

Attendance was way down, and while I did sell a little over $100 worth of books and other stuff, I was hoping that I’d sell more. In particular, I thought I’d sell a few of my new “Hams Obey Ohm’s Law” stickers. I didn’t sell a single one, however. One friend of mine offered to purchase one, but I just gave him one.

I think clubs have to think twice about when they schedule these things. Holding them so early on Sunday mornings almost guarantee that only the old farts will show up for these things. And the old farts are a dwindling audience.

No propagation, no glory
Sunday night, I tried to participate in the monthly Run for the Bacon (RTFB). This low-pressure QRP contest, run by the Flying Pigs is usually a fun event. Sunday night, however, the band had gone way long by 9 pm EST, when the contest started. I managed one contact with a station in Idaho, but no one else could hear me.

To be honest, I don’t really know how much power I was running. Instead of hooking up the KX-1, I just cranked down the power on the IC-746PRO until the power out meter was showing just a single bar. I really gotta get that wattmeter kit finished.

Filed Under: Classes/Testing/Licensing, Hamfests

150 freshmen to get tickets at Cal Poly

November 7, 2011 By Leave a Comment

From a Cal Poly press release:

A record 150 electrical engineering freshman students from Cal Poly will take their FCC amateur radio technician-class license exam this November in the largest amateur radio licensing event ever held in San Luis Obispo County.

Hosted by the Cal Poly Amateur Radio Club (CPARC), this session may be the largest Amateur Radio License Testing Session ever held at the collegiate level. These 150 potential amateur radio operators will join over 700,000 other hams in the U.S. in providing volunteer and emergency communications support for everything from local bike rides and parades to global disaster relief, including the 2011 earthquake and tsunami in Japan.

Dennis Derickson (AC0P), Cal Poly Electrical Engineering (EE) department chair, conceived the Freshman Licensing Initiative which gives every EE 111 student a chance to get their radio license. As part of the EE 111 curriculum, this test session will be administered during the 50-minute class period and count as one of the midterm exams for the freshmen students.

“CPARC members have been hosting review sessions to help students prepare to pass their exam and get introductory knowledge on a wide variety of electrical engineering topics,” said CPARC member Javen O’Neal. “Getting an amateur radio license is the first step towards many career opportunities in the communications industry, from engineering UAVs and integrating Wi-Fi on the Amazon Kindle, to creating 4G cell phone networks and designing communication subsystems on DirecTV satellites.”

CPARC members learn about radios by retuning filters on radios, building directional antennas for transmitter hunts, and putting together an emergency vehicle tracking network for Wildflower Triathlon using two dozen radios and GPS units, digital repeaters, and internet gateways.

Founded in 1947, the Cal Poly Amateur Radio Club has a long tradition of communications service on campus and in the San Luis Obispo community. The club maintains Emergency Communications Station No. 16 on the Cal Poly Campus for the San Luis Obispo Emergency Communications Council (SLOECC) which is equipped with emergency power and radio equipment to support various public safety agencies in the event of a disaster. More information about the club can be found at www.w6bhz.org.

Cal Poly Amateur Radio Club

Filed Under: Classes/Testing/Licensing, Clubs

Ham Radio Licensees Top 700,00 in the U.S.

October 4, 2011 By 1 Comment

Whenever I mention to a friend or relative that I am a ham radio operator, the most frequent response I get is, “I didn’t know that they still do that.” My response has always been, “Well, it might surprise you to know that there are nearly 700,000 licensed radio amateurs in the U.S.”

Now, I can drop “nearly” from my reply. According to the statistics at AH0A.Org, the number of licensed radio amateurs topped the 700,000 number for the first time in September. Elwood, WB0OEW, who sent me this factoid, notes, “Also note the number of Techs continues to fall, evidently they are upgrading because there are record numbers of Generals and Extras now too.”

My question is, “Where are all these hams and what are they doing?” I suppose there has been a small uptick in the activity on the HF bands, but VHF and UHF activity is still pretty sparse, at least here in Southeast Michigan.

How is it where you are? Are you noting any increase in activity on the bands/modes that you operate?

Filed Under: Classes/Testing/Licensing, Operating

What Happened?

September 21, 2011 By 2 Comments

A reader writes:

I wanted to send you a note because you are in close contact with new Techs, and I’m wondering what your thoughts are. [If you look at the statistics (see figure below from www.ah0a.org), there is a]] very distinct decline in the number of new Techs that began exactly with the release of the last question pool. Is this a cause-and-effect thing or just coincidence?

Tech Licenses

The number of new Tech licenses seems to have declined since the release of the latest question pool.

I’m kind of at a loss to explain this. Looking at the charts for General and Extra, it doesn’t appear that this phenomenon can be explained by more hams upgrading. Does anyone have a possible explanation for the lack of growth in the number of Techs?

Filed Under: Classes/Testing/Licensing

Yesterday’s Tech Class: Disappointing

September 18, 2011 By 4 Comments

Yesterday, I held another in  a series of one-day Tech classes. While five students will soon get ham licenses, the results were disappointing.

First, I was disappointed that several of the students phoned or e-mailed at the last minute that they wouldn’t be able to attend.  They all had good excuses, but it was still disappointing.  I’d had this problem in the past, and this time, I required students to send in their donations prior to the class, thinking that would motivate them to show up, but that didn’t work quite as well as I’d hoped.  Perhaps the donation of $10 was too little.

Next, I was disappointed that four of the nine that did show up failed the test. As with previous classes, I think that I can point to the lack of preparation as the reason these folks failed. Even though I stress that preparation is required, it was clear that several of them failed to do that. One of them noted, “I just picked up the study guide less than 48 hours ago.” She missed passing by two questions.

Another contacted me Friday afternoon about signing up for the class, and even though I told her that I was concerned that she was getting started very late on this, she decided to try it. She was one of the ones that failed.

Scott, W1BIC, who assisted me yesterday, said that I should be more forceful when telling prospective students about the need to study. Scott said that rather than saying that studying beforehand will “greatly enhance the chances of passing the test,” I should tell them that if they don’t study or don’t take any practice tests, coming to the class will be a waste of time. I think I just might do that next time. Another thought that just hit me is that perhaps I could come up with some kind of questionnaire that would identify those that are likely to pass with little preparation and those that will need more extensive preparation.

After the exam, Scott and the VE team all consoled me, pointing out that five students will soon get their Tech licenses. That is a good point, but I can do better.

Filed Under: Classes/Testing/Licensing
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