Activities, Featured, General, Newsletter

Two Newbies at Dayton Hamvention

by Jamey, AC1DC and Abby, AB1BY

Abby, AB1BY and I were lucky enough to attend the Dayton Hamvention this year and see our club, the Nashua Area Radio Society accept the Club of the Year award. Here’s our recap of what it was like for each of us as first-time participants and Hamvention Newbies.

The Drive

On Tuesday evening I was picked up by Fred (AB1OC) and Anita (AB1QB) and we started our drive long drive through the night to Dayton.  It was only about 15 minutes into our ride when I realized I’d left my wallet at home. We turned back and I tore the house apart in a frantic rush as I looked for my wallet! No luck, so I went back to the truck and looked through my backpack… and there it was. Not the best start to the trip. We also had trouble with the navigation system and the mobile antenna was not tuning up! Our trip did not seem to be getting off to a good start. We did get everything working properly and we were still in good spirits as we were excited for what was to come. We arrived in Dayton on Wednesday morning and checked into our hotels and got a nap and shower.

Fondue!

We went out on Wednesday evening for Anita’s birthday dinner to the Melting Pot, a fondue place. I have never been to a fondue restaurant and ordering was quite a process – picking cheeses, meats, and desserts. Getting coached through the process, we had our meal ordered and it was fantastic!

Enjoying fondue at the Melting Pot!

Contest University/Booth Set Up

Thursday morning was the start of  Contest University at the Crowne Plaza in Dayton. I highly recommend this to anyone going out to Hamvention for the first (or any) time.

Dayton Hamvention
Contest University

I’m not sure of the exact number, but you can see from the picture there were quite a few people in attendance. The morning was made up of the 3 sessions in which you choose from 4 different topics to attend. There was quite a variety of topics! After the morning session of Contest University, I got my first view of Xenia, where Hamvention was being held, as we went to set up our booth for the next day. Our booth was in a great spot in the Tesla building with all the ARRL booths – prime location! The booth looked great and very professional when we were done thanks to a lot of work put in by Anita (AB1QB). We also got a chance to walk around the buildings a bit and look at the vendor booths as they set up. Fred and Anita took me over to the Heil booth and I got to meet Bob Heil (K9EID)! I also got to play with some fine Begali keys without the crowds and check out the AMSAT booth. AMSAT had a really cool display of module cubesats!

Dayton Hamvention AMSAT
AMSAT’s model CubeSat

After setting up I headed down to the Cincinnati Airport to pick up Abby (AB1BY). The fun was just beginning!

Abby Arrives

Since Abby had exams on Thursday morning she got to skip the drive and fly out to Dayton – actually Cincinnati, which is actually in Kentucky! This was her first time flying by herself and she was a little worried but had a direct flight from Boston so there wasn’t too much to worry about. She was excited to attend Hamvention but wasn’t really sure what to expect. I picked Abby up at the airport and drove back an hour to Dayton. We had a room in the Marriott and we were on the top floor where you needed your room key to make the elevator go to that floor. Abby was really feeling like a VIP. She also likes that there was also a lounge on our floor where you could get free cookies and drinks. Our room at the hotel was nice as well. Abby liked the view from our balcony. There’s a chalk outline on the pavement that says, “Don’t Let This Be You!”

“Don’t Let This Be You!”

Dayton Hamvention Begins

We woke up very early on Friday morning and had a quick bite at the hotel before heading over to the Xenia Fairgrounds for the first official day of Hamvention. We arrived a little late for our 8:30 am meeting as the traffic and crowds were huge! The NARS booth looked fantastic and we had a lot of people stopping by to check us out. Abby and I did some live-streaming on Facebook and took our audience on a virtual tour of the Tesla building. We also were stopped several times on our walk around the grounds by people who recognized Abby from some of our club videos. She was very tickled to be recognized and have people ask her for a photo with her.

Later in the morning, we headed over to our forum room for the club talk – ARRL Spotlight on Radio Clubs and Mentoring. We had a nice crowd and Fred (AB1OC), Anita (AB1QB), Dave (K1DLM), Scott (NE1RD), Abby (AB1BY) and myself (AC1DC) all spoke on different aspects of the club.

 

We spent the rest of the day hanging out at the NARS booth and checking out the grounds around Xenia. We loved the fairground food. I got to have a corndog on a stick and Abby tried out the cheesecake on a stick.

AB1BY enjoying cheesecake on a stick

Speaking of food! On Friday night we went to the Top Band Dinner and listened to a talk by Ted Rappaport (N9NB). The food was great and Ted kept us all entertained with his talk.

Crowds and Forums

Lines as long as the eye can see

Saturday morning was another early start for us. We thought it was packed on Friday. Saturday it was mobbed! Huge crowds and the NARS booth was hopping! Luckily we had a large contingent of NARS members to handle the crowds.

Saturday, we also got our first taste of attending the forums. Abby attended the Youth Forum presented by Carole Perry (WB2MGP) and a host of other speakers, including Tamitha Skov (WX6WW)! Abby enjoyed the variety of topics presented from the speakers from around the world. She had a great time seeing and meeting other amateurs that love the hobby. She also won a raffle for $100 from DX Engineering – she has yet to use it!

While Abby was at the Youth Forum I attended the Summits on the Air forum presented by Keith Schlottman (KR7RK) with Craig (N1SFT), Brian (W1BP) and Jerry (K1OKD). This was held in one of the smaller venues on the fairgrounds and it was a full house. Keith did a great job explaining the basics of how SOTA works and he had some really nice pictures of different SOTA activations. I realized how lucky we are here in New England as he mentioned some “summits” or high points had a Wendy’s across the street!

Abby was busy on the forum circuit as she then attended the Young Ladies Radio League (YLRL) forum presented by Marily Melhorn (AF7BI) and Anna Manna (WB1ARU). Abby really enjoyed the presentation and how welcoming everyone was. They also had time at the end to “mingle” which Abby also loved!

Club Of The Year Awards Dinner

Saturday night was the night for the Awards Dinner. We had a lovely meal with other members of the NARS Executive Committee as we anxiously awaited the announcement and Fred’s (AB1OC) acceptance speech.

Club Of The Year
Fred (AB1OC) accepting Club of the Year Award

Fred did not disappoint with a very nice speech. Fred is always very willing to give credit to others even when he deserves the credit. He took the crowd through the club’s journey starting back four years ago up to the present. As we sat and listened to Fred talk so passionately about the club it really hit home how much this club has accomplished in such a short time. It really has been a huge group effort under the leadership of a very passionate leader.

 

After dinner, we all took turns with pictures of the award and with other dignitaries in attendance.

Heading Home

We got a little later start on Sunday and things were winding down at Hamvention. We greeted more people at the NARS booth and attended the ending raffles (with no luck) and the public announcement of all the award winners from the night before. We then packed up the truck and started the long drive home. We were back in Nashua early Monday morning and Abby didn’t miss school – she was thrilled…

We both realize how lucky we are to have attended Hamvention and meet so many people there, to be associated with the best club and to have made so many close friends in the club over the years. This was truly an amazing trip for both of us – something we’ll have memories of for a lifetime – and we want to thank everyone who made this such a wonderful experience.

Education and Training, Featured, General, Newsletter

Skywarn Training Report

Late spring brings with it the start of a new severe weather season. As we saw this week in the Dayton area, severe thunderstorms and tornadoes can cause damage and threaten life. The Hara Arena, the former site of Hamvention was destroyed by a tornado.

National Weather Service forecasters track storms carefully using radar and automated weather observations, but their forecasts can be aided by Skywarn reports from trained observers. These eye-witness observations can validate radar data and help forecasters make decisions on whether to issue additional warnings.

I recently attended a Skywarn training session conducted by the Norton, MA National Weather Service office. The class was held at the Milford, MA Fire Department and lasted about two and a half hours.

Rob Macedo (KD1CY), the Norton office’s Skywarn amateur radio coordinator, taught the class with the assistance of an NWS forecaster. Rob started the training with an overview of how often southern New England has severe thunderstorms and tornadoes. He discussed a few of the tornadoes that have occurred in New England, and the role that Skywarn spotters played by informing NWS forecasters of conditions on the ground.

Rob taught that moisture, instability, and lift are the ingredients needed to form a thunderstorm. He also told us about the stages of a thunderstorm, thunderstorm types, and cloud identification.

The instructors spent quite a bit of time on thunderstorm types and cloud identification. Properly identifying clouds is key to spotters providing accurate reports to the forecasters.

The NWS forecaster concluded the training with a discussion on challenges of weather spotting in New England and the criteria for reporting weather phenomena.

This was the fifth time I’ve taken the course over the last 20 years. I was impressed by how the training materials use videos and photographs from New England to help prospective spotters better understand what they’ll see here. My first training I took in the late 1990s was done with a slide projector showing photographs of perfect examples of thunderstorms in the mid-west, things we’d never see here.

Skywarn training is a wonderful opportunity for any weather-lover, and a great way to fulfill our obligation to use amateur radio to benefit the public. Learn more about local Skywarn programs at the NWS Norton office, and at the WX1BOX website.

Brian, W1BP

CW and QRP, Featured, General, Homebrewing, Newsletter

The RockMite Part 3: The Oscillator

In the first RockMite article, I described the receiver of the radio. I identified the place in the receiver that accepted the output of the oscillator (marked B going into pin 6 of the mixer) but skipped describing the actual oscillator. In this article, we’ll examine the oscillator and how it drives both the receiver and the transmitter.

The RockMite Overall

As a reminder, here is the whole schematic for the RockMite.

Schematic for the RockMite transceiver (from QRPMe.com)

Figure 1. The Schematic for the RockMite Transceiver

The part of the schematic we need to analyze for this article is near the word “Transmitter” in the big schematic. I’ve cut it down in the next figure (and removed some of the distracting elements).

Figure 2. The RockMite Oscillator

Colpitts Oscillator

The RockMite has within it a Colpitts oscillator. The transistor Q4 is the amplifier and the two capacitors C10 and C11 form the voltage divider. This design employs a crystal (Y2) that is band-dependent, of course, as are C10, C11, and C12. The output of C12 leads to another layer of transistor amplification that enlarges the voltage swing.

Note point B between R13 and R14. This signal leads to the input of the mixer U1 and serves as the beat frequency oscillator (BFO) that detects the received signal.

Silicon Tuning Diodes

Before I can describe the rest of the circuit I need to introduce a part that I thought was almost magical when I learned about it. The part number for these devices is MVAM109 (in the center of Figure 2). The symbol looks like a cross between a diode and a capacitor. Indeed this is exactly what this part is: a diode and a capacitor combined in a very special way. The varactor (tuning) diode acts like a capacitor, but the capacitance depends on the reverse voltage across the diode. I’ve included a plot from the Motorola data sheet below.

Figure 3. Capacitance versus reverse voltage

You can see that as the reverse voltage goes up the capacitance exhibited by the part goes down. Change the voltage and you change the capacitance. We use this in the part of the circuit described in the next section.

Tuning One of Two Frequencies

The oscillator uses Y2 (a crystal) to help determine the frequency. But, the frequency can be altered by adding or subtracting capacitance. MVAM109 (D6) will be the device that changes the capacitance.

Examine the circuit beginning with Q2 (2N7000). When the transistor is turned on there is a completed circuit between the source and drain (S and D in the diagram). In this case, the source is connected to ground. So, when the transistor is turned on the point in the circuit after D is brought down to zero volts.

Check out R9, a 4.7K Ohm resistor that connects to the drain of Q2, and to a Zener diode D5 (which is also band dependent, as it turns out). The Zener is used as a voltage regulator. Say the Zener is a 3.9-volt model. Since we are connected (through R9) to V+, the voltage at the point where D5 connects to R9 will be limited to 3.9 volts (or whatever the Zener is rated) and R9 is the current limiting resistor. This is assuming the transistor switch Q2 is open (not conducting).

In this situation we have D6 being reverse-biased to the voltage determined by the Zener diode. That much reverse bias will cause the varactor to exhibit some amount of capacitance.

If the switch Q2 is closed (and it conducts) then that point in the circuit is brought down to zero volts and the varactor is no longer reverse biased (or to a voltage below what the D5 part would supply) and we get a completely different capacitance.

The gate of Q2 is controlled by the UI PIC from a line called “Shift”, and it is used to switch between these two frequencies (by turning Q2 on or off). This is how the RockMite offers two different crystal-controlled frequencies with the push of a button.

Next Time

We have already gone through three-quarters of the schematic of the RockMite. Next time, in the last installment, I will walk through the transmitter and the filtering used by the radio.

Links

The RockMite Part 1: The Receiver

The RockMite Part 2: The UI

Scott, NE1RD

Radio Amateurs Developing Skills Worldwide