AmateurRadio.com

As I mentioned in the earlier Field Day 2010 report, the CUARC group built two antennas for the event.  In this post I will describe the first one of these, an off-centre fed dipole.

The common place for the feed point of the off-centre fed dipole is at a 1/3 : 2/3 split in the arms. This has the advantage of providing low SWR (with a 4:1 balun) at even harmonic frequencies, such as 20m and 10m for an antenna cut for the fundamental frequency of 40m (around 66ft). Whereas a centre-fed dipole will only have the odd harmonics which for a 40m (7MHz) dipole is 15m (21MHz).
Rather than use the traditional off-centre length split of 1/3 : 2/3 for our Field Day antenna, it was decided to follow the design proposed by Richard Formato, K1POO, in two technical correspondences published in QST ^1,2 and followed up with further article with by Dale Gaudier, ³. In this design the feed point is moved closer to the 1/6 point on the short arm, the advantage being stated in the articles that you should get a 200Ω feedpoint there and so a low SWR on 40m, 20m, 15m and 10m bands when using a 4:1 balun, with no need for an antenna tuner unit.  The emphasis on the 15m band is intentional as a low SWR on that band is not usually possible with an off-centre fed dipole with the feed at 1/3 : 2/3 and a 4:1 balun.  Four bands on one 69 foot wire antenna with no tuner looked very attractive for Field Day.

The antenna was cut carefully prior to Field Day and the end insulators were added.  When cutting the antenna the length measurement included the ‘pig-tail’ connections that I have on the 4:1 balun. The diagram below shows the arrangement of the antenna.

On the day the antenna was installed between two trees at about 35ft off the ground. While the second antenna was being constructed (to be featured in a later post) its SWR was measured with my Autek RF-1 antenna analyzer.  The results were taken by Maria, VA3MMI and Gil, VE3JRY and are tabulated below.

_______________________________________________

Band (m)    2:1 VSWR Range (MHz)          Minimum VSWR
40                                                                      3.1 : 1 (at 7.38 MHz)
20                       13.29 – 14.65                            1.4 : 1
15                       21.20 – 22.31                            1.5 : 1
10                      27.78 – 29.25                            1.7 : 1
_______________________________________________

The overall results were very pleasing, although the 40m band was a little disappointing. This higher than expected SWR on 40m was also encountered by Dale, M0AOP/K4DG, and was reported ³ by him to be due to the severe imbalance in the antenna, so requiring a choke balun to remove the stray RF on the coax.  We did not try a choke balun, since we were unlikely to operate on 40m, that was another station’s band of operation.  However we had an antenna tuner unit if we needed to try and tame the SWR. It was very good to see the SWR profile observed in reference 3  was repeatable.

On Sunday morning Maria, VA3MMI, returned with a portable analyzer borrowed from work and did a sweep analysis.  The response is below and markers have been inserted to show the minimum SWR associated with the bands. Thanks goes to Maria for the measurement and the plot.

It would be interesting to remeasure the SWR response again with a choke balun in place.  I expect the SWR will drop below 2:1 within the 40m band as found by the author of reference 3.  If this does happen then four bands and no tuner needed makes this antenna one for serious consideration on HF. Even without a low SWR on 40m the antenna offers three bands and it performed well on 15m and 10m for us on Field Day.

As a final note, I should reiterate the warning by Dean Straw, N6BV, at the end of reference 1 where he warns about using the antenna on 30m, 17m or 24m, as a very high SWR could damage the balun at the feedpoint.

References

1. “Improved Feed for the Off-Centre-Fed Dipole” R. A. Formato, K1POO, Technical Correspondance, QST, May 1996 p76.

2. “Off-Centre-Fed Dipole Comments, Part 2″, R. A. Formato, K1POO, Technical Correspondance, QST, October 1996 pp72-73.

3. “Choke the OCFD” D Gaudier, M0AOP/K4DG, Technical Correspondance, QST, September 1997, pp82-83.

Note: all three of the above papers are collected together in “More Wire Antenna Classics Volume 2″ ARRL, (1999).

The Field Day photographs above are from the Ottawa Valley Mobile Radio Club’s photo gallery.

Alan Steele, VA3STL, is a regular contributor to AmateurRadio.com and writes from Ottawa, Ontario. Contact him at [email protected].

Various QRP related email reflectors and lists are full of chatter about the Flight Of the BumbleBees (FOBB). Comments about the CW being too fast and the weather being too hot at this time of year make it sound like a broken event. IMHO it is far from being broken! It is probably the premier QRP event of the year. And I say, if it ain’t broke… yep, you guessed it, don’t fix it.

Sunday the bands were full of QRP ops, both home based and portable, so the activity really did make a BUZZ despite band conditions that have not been all that helpful to hf qrp contacts.  The weather was HOT, but hey, find some shade, altitude or water and go for it. Historically this is the time of year for this event and as others have commented, it keeps our activity up during the summer time when vacations and mowing the grass take their toll on ham radio activity.

As far as fast cw, I’m not fast (not even close hi hi), but it sure is fun listening to the buzz on the bands rather than QRN and a high noise level with only a few weak signals. Certainly I am not a hard core contester. My cw skills are still in need of practice, but isn’t that what events like this provide? I often have to listen multiple times to get the callsign and info but that repetition and practice pushes my speed and confidence level up every time I try. After listening to a fast op several times I have the info I need and then I jump in and have fun making a contact at speeds faster than my comfort zone. Most of us slow guys can send faster than we can receive, right? Come on in, the water is fine, and FUN!

My XYL, Connie and I drove over to Honeymoon Island State Park on the Gulf Coast in Dunedin, Florida. This is a very pretty beach, not overly crowded most of the time and has been one of the top rated beaches in the US for several years. The weather cooperated, there was no sign of the BP oil spill that has run so many tourists to other locations, and we snagged a primo spot to operate right next to the water.The only negative, if you call it that, was that the view was sometimes distracting, but sure was enjoyable.

My trusty Sierra and Buddistick provided plenty of action so I never switched over to my mini-bac Delta Loop backup antenna. I also stuck to 20m the whole contest since 40m has been in such poor condition here in Florida lately.

One of the great things about these events is the leveling of the playing field. It is fun to contact the guys that write the articles, create the websites and design the equipment that we use for our hobby. My score was modest at 26 QSO’s, 18 Bumblebees and 17 states and provinces but it was one fantastic day of activity for me! Being able to connect with the big guns of QRP was a thrill too!

For me, one of the highlights was when W8DIZ rode over to meet me as I was setting up my site. Diz lives about 3.5 miles from Honeymoon island and is a regular bicycle visitor of this great beach location. I’ve been a customer of his toroid and kit business and have benefited from the info he has shared, not to mention being one of the movers and shakers of the Famous Flying Pigs QRP group. Diz I was honored that you took time out from a busy family day to swing by and say HI! Thanks for the help getting our screen house up too!

Thanks to Adventure Radio Society and the guys that put this event on for all of us. We appreciate the effort it takes and you deserve the very best of 73′s from all of us.

72,

Kelly K4UPG  BB #10

Kelly McClelland, K4UPG, is a regular contributor to AmateurRadio.com and writes from Florida, USA. Contact him at [email protected].

AmateurRadio.com is offering a free prize drawing!

With the help of our generous sponsor, KB3IFH QSL Cards, we’re holding a drawing for 1,000 free full-color photo QSL cards. This is a US$100 value.
Enter now to win!

Read the rest of this post

Matt Thomas, W1MST, is the managing editor of AmateurRadio.com. Contact him at [email protected].

Readers who follow this blog regularly (all five of you in straight jackets) have probably noticed that I haven't blogged much recently.  I'm still alive, in good health, and pumping RF into the atmosphere.  In fact, I've emitted more RF into the atmosphere these last few weeks than I have in quite awhile.  Six meters has been hopping and I re-joined the local amateur radio club to participate in Field Day.  I think I may be getting my radio artisan mojo back that I thought I was losing much of the previous year.

In my Blogger drafts area I have 98 articles that I've started but haven't completed or I've completed but just haven't felt like they should see the light of day.  Some are just titles of quick, fleeting ideas I had for an article but just haven't had the time or inclination to further develop.  Several are April Fool's joke articles.  And then there are the rant or soapbox articles.  I hope to polish some of these draft articles in the coming weeks and months and slim down my drafts area.  Hopefully I don't release any clunker articles in the process.

The web animation I did a few weeks ago with virtual radio artisans Bob and Jane was done on a bit of a whim.  I'm working on a second web animation on a different topic with most of the dialog again coming from online amateur radio forums.  I'm entitling this series of web animations Off Frequency.  I intend to add more characters and other sources of dialog, focusing on this strange hobby we all love and the often strange people within in. We'll see where this goes.

On an aside, I have to give a shout out to KE9V for his Cornbread Road podcast.  I'm hooked on the story and I'm impressed with the production quality of the podcast, and I'm not much of a podcast aficionado.  If you haven't been following Cornbread Road, I strongly suggest you check it out.
Anthony Good, K3NG, is a regular contributor to AmateurRadio.com and writes from Pennsylvania, USA. Contact him at [email protected].

I operated a contest yesterday that I’d only ever done before as as DX, The RSGB IOTA contest. In this contest, any station can work any other station, but if you work an island (as defined by the organizers [note that the link goes to a PDF file]) it is worth more points (15, instead of 3 for a non-island contact) and each island you work counts as a multiplier, increasing your score. The contest has some interesting rules regarding hours of operations (you can submit as a “12 hour” or “24 hour” contestant) and some categories that are different from many other contests. (e.g., “Island DXpedition”). I decided that I’d try to operate in the 12-hour, low-power assisted  mixed category as “world” station. That means that my operating time was 12 hours or less, I used 100 watts to transmit, I used the packet cluster to help locate stations, operated both phone and CW, and I was not located on a island.

Unlike many other contests which typically start either in the evening or mid-afternoon for me, this one started at 8AM local (Eastern Daylight Time), and, not being a “morning person”, I didn’t get on the air until around 11:30 AM, and was a little disappointed to find out that the band conditions didn’t seem to be as good as I’d hoped. I started off on 20m phone and made a handful of contacts in the first 20 minutes. I realized that if 15m was open, if I wanted to work anyone outside the US it would have to be early in the afternoon. I switched over to 15m and found … nothing. Well, almost nothing. I did manage to work two stations in about 10 minutes, one on phone and one on CW. Clearly 15m was not going to be a productive band.

I moved back to 20m and worked stations steadily, thought not terribly quickly using Search & Pounce to find stations. I worked a few dozen stations on phone, then another dozen or so on CW and moved back to phone. After another hour of S&P, I was lucky enough to find a clear frequency to call CQ to try to “run” stations. (During most contests, it’s pretty tough to find and keep a frequency, especially for a small station like mine.) I called CQ for a couple of minutes and got one reply from a station in Poland, then about a minute later got a reply from my friend David, K2DSL, who is located nearby. We chatted briefly, then I moved on to work other stations. All of a sudden, a number of stations all started calling me. It turned out that David had “spotted” me on the packet cluster. When that happens many stations will tune to the spot frequency to work whoever is there. For someone like me being spotted is terrific because it significantly increases the rate at which  I can work stations. Prior to being spotted, I’d operated for around 4 hours and had made around 100 contacts, for a rate of around 25/hr. One hour after being spotted I’d worked an additional 65 stations, almost tripling my rate. I finally gave up the frequency after about 90 minutes, making 75 QSOs during that time which comes to around 50/hr. (The final 20 minutes or so of that period was considerably slower). In any case I had a great time and it was a lot of fun being the person that was being called, rather than having to hunt.

After time out for dinner (we were out with friends), I got back on the air at around 11:30PM. The only band that was open at the time was 40m, and because of atmospheric noise due to all the thunderstorms in and around the east coast, the band was very noisy. It was very slow going making contacts, and I suspect that some of the ones that I made then will turn out to be incorrect, since I had a particularly difficult time getting the details of the contest exchange. (For this contest, you gave a serial number, starting at one, and, if located on an island, the island identifier). I gave up after about 90 minutes, with a total of 210 contacts in my log. I thought that it was a pretty decent effort for the seven hours that I operated. Here’s my score summary:

        Band  Mode  QSOs     Pts  Sec
           7  CW      10     138    9
           7  LSB     22     246   13
          14  CW      45     399   13
          14  USB    130     990   27
          21  CW       2      18    1
          21  USB      1       3    0
       Total  Both   210    1794   63

            Score : 113,022

David Kozinn, K2DBK, is a regular contributor to AmateurRadio.com and writes from New Jersey, USA. Contact him at [email protected].

The whims of Cycle 24 presents a challenge for my low power, low profile station. Likewise, the difference between a vertical antenna and a horizontal wire antenna, is most notable during the summer from my location. The difference is becoming evident in terms of logged contacts during an event between summer and winter.

Polarization?
My production slopes toward the negative or dwells at the bottom in the summer. Winter conditions are favorable for my vertical antenna system and its low take-off angle. Additionally, I recently read W1ZR’s article on Antenna Polarization — What Does it Mean and When is it Important?

I’m curious if my vertically polarized signal takes a beating during the summer? I had a dickens of a time during the IARU HF World Championship against horizontal antenna systems. I logged a stunning 7 contacts in 5 hours of operation on the high bands. Perhaps, my doublet is better at focusing radio frequency energy, during the summer when it is really critical given conditions?

Shackadelic Update.
I thought again about a QSL card and Fred, KI6QDH inspired my approach given time budget and resources. Likewise, neither Global QSL or Cheap QSL, are sponsoring my recommendation. However, I chose Global QSL as my bureau manager for DX contacts and Cheap QSL for their thrifty price per unit (10 cents per card) for 100 cards.

Why our stateside bureau(s) are not moving into the space of domestic QSLing is something to think about given today’s austerity. The cost of confirming a domestic contact would fall dramatically when factoring bulk mailings.

I would gladly trade a little more patience for the price of one pound bulk mail. Would staff at the bureau(s) be willing to help out in driving down cost?

TS850S.
I have a few payments left and the shack relaxation zone will sport a used Kenwood TS850S in the near future. My FT100 will move into a pelican case for portable operations especially for 6m during the summer.

73 from the shack relaxation zone.

Scot Morrison, KA3DRR, is a regular contributor to AmateurRadio.com and writes from California, USA.

Since becoming licensed in the Fall of 2007, I’ve participated in every ARRL Field Day event since becoming licensed (2008, 2009 and 2010) and can honestly say I’ve had fun each and every year.

Let me explain, my three field day weekends mention above are not my only field day weekends. As a child I attended at least one FD with my Uncle, K5SOR perhaps more…But one I remember really well.

Anyway, in 2008 I was honored to have the opportunity to spend my first field day as a licensed ham with my Uncle. He and I went down to his childhood home of Cleveland, Texas and participated with the SHARK (Sam Houston Amateur Radio Club). Many of my Uncles friends belong to this club and just about all have been licensed for over 50 years. The 2008 FD event with the SHARK club was a lot of fun. We operated as N5AF, a 1A station in STX.

Last year in 2009 I spent Field Day weekend with my local club here in Denver. We operated as W0TX, a 6A station in CO. We setup out near Hudson, CO at an old AT&T site. The site is literally in the middle of nowhere.   It was hot, it was dusty and dry.  The Rocky Mountains just west of Denver teased us with every glance.  But…it was fun. 

As I began thinking about what I wanted to do for Field Day 2010, the thought of a hot, dusty location just didn’t appeal to me.  After all, I live in one of the most beautiful states in the lower 48.  I kept thinking of all the advantages to having Field Day in the mountains.  First, the daytime temps could be anywhere from 10-20 degrees cooler than those down in the city.  Second, the elevation difference sure wouldn’t hurt from an operating position.  Third, the smell of pine is just incredible.  It was decided….my third Field Day….Field Day 2010 would be in the mountains. 

I discussed the idea with a few friends and back in the March/April timeframe all thought it was a great idea and everyone was in.  At that time there would be three operators.  Our number one goal was to have fun.  We weren’t out to win anything…just have fun and prove to ourselves we could pull something like this off.  We stayed in touch via email and every couple of weeks we would update logistics and add more to the overall planning checklist.  We would keep things simple and operate as a class 1 station.  The decision of power was yet to be determined.

As we got closer and closer to Field Day weekend, more and more issues began popping up for the three of us.  It was pretty clear we would only be able to operate on Saturday as we all started having scheduling issues with Sunday.  But that was OK.  We planned to operate for 6 hours or so and break down our operation and be back home before dark.  Remember, our number one goal was to have fun. 

Just a few days prior to Field Day I got the call.  One friend had to bail on the plans.  And then there were two.  But….no sooner as I even thought that….the second friend sent me an email saying he would be unavailable.  And then there was one…..ME!  Well I wasn’t going to let this ruin my plans and I wasn’t going to change my plans either.  I wanted to operate Field Day in the mountains….I wanted to have fun and I wanted to smell pine trees while doing all this. 

Now my wife is THE BEST wife a ham can have.  She supports me and my hobby and all that goes along with it.  She agreed to go with me.  Give her a picnic lunch, a comfy chair and a good book and she’s very happy.  We’ve gone on picnics before where I take my Yaesu FT-817 and Buddipole and she takes a book and we’re both happy doing what we enjoy for 2-3 hours.  I figured the same could be true for Field Day. 

All was set, the car was loaded and it was time to head up the hill.  We have a favorite little park just up from Evergreen, Colorado.  It’s a great site because there is almost no one there and it sits up overlooking the town of Evergreen.  We arrived just before 11 AM local time (1700 UTC) and I had an hour to get my station setup.  Field Day would start at High Noon. 

My wife the day before encouraged me to leave the generator at home and try operating “green” for field day.  Now understand, we’re not tree huggers or anything like that.  By the way….there is nothing wrong with being a tree hugger.  Yes we care about the environment and we do our part to make a difference.  I have batteries and I have solar panels.  What else do I need? 

So we arrived and I began setting up.  The forecast was calling for a beautiful day.  Of course, I checked the forecast the day before and didn’t bother checking again that morning.  Like other places….In Colorado, wait 5 minutes…the weather is sure to change and change it did.  We quickly had our meal just before noon and I was setup.  About 5 minutes before noon the clouds began to roll in.  Hmmmmm, solar panels not working.  No worries….this will blow over and as long as it doesn’t rain……

I managed to work about 5 stations and then I felt it.  Yep….one single, tiny little rain drop.  But you know….where there’s one.  Possibly the one piece of equipment I did not take with me (other than a portable sun) was a canopy.  So the rain drops turned from one to many and so the gear needed to be packed away.  Saint Maximilan Kolbe (the Patron Saint of ham radio operators) was truly looking out for me because no sooner did I close the back of the Ford Escape, the bottom fell out.  It rained and it rained some more.   Knowing the weather would not clear up for the next few hours, we decided to start heading back to Denver.  I finished out my Field Day fun for Saturday afternoon and even a few hours on Sunday morning from a local park with just my buddipole and my Yaesu FT-897. 

So….do I have a favorite Field Day weekend from the three?  Well…certainly nothing will ever top sharing field day with my Uncle.  But I still managed to have fun and as with the two years previous, I did learn a few things.  As for Field Day 2011, I’m not sure where or how it will turn out.  Field Day in the Rocky Mountains???  It will happen some day.

Until next time,

73 de KD0BIK

Jerry

Jerry Taylor, KD0BIK, is a regular contributor to AmateurRadio.com and writes from Colorado, USA. He is the host of the Practical Amateur Radio Podcast. Contact him at [email protected].