Tag Archives: Antennas

CW and QRP, Education and Training, General, Homebrewing, Youth Activities

My Name Is Patrick…

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By Dennis Marandos – K1LGQ

The excitement for warm time operations is just heating up and getting out is easier now than it was a while ago. And judging from what I have already heard on the air, the rivalry for band space is getting hotter and harder to find. Let me tell you about an episode I experienced in Nashua one warm, sunny day when the adrenaline was kicking in and the sun was shining brightly. In the back of my mind-set was the sheer fact that I am radio-active, have a valid license, am getting on the air is what I love so what could possibly go wrong?

I arrived at the local city greenery named Greeley Park (after Horace Greeley) in Nashua, NH and scouted for some tall, white pines for a wire antenna. Here in the northeast, pine trees are like blades of grass…they’re everywhere. Another friend of mine, we’ll call him Mike, and I spotted a pine tree at the edge of the 150-yard field and I took aim with my trust surgical-rubber sling-shot, bought at the local Wal-Mart emporium, and on the second try landed a nice 95 foot shot into the coniferous tower. With my mighty homebrew antenna, called the ‘Gusher,’ the tentacle was placed into combat readiness within fifteen minutes after arriving at the park. We mountain men of the northeast don’t waste any time in being prepared.

The yellow card table was unfolded, the collapsible chair was pushed into the ground for stability, and the tools of the day were unraveled. The NorCal 40a, a 40-meter homebrew transceiver, was attached dutifully to the MFJ-971 antenna tuner, which was then gingerly appended to the Gusher antenna, which culminated with a fully charged jolt of volts from the 7aH gel-cell battery. The log book was strategically placed to the right side, (I am left handed so all papers need to be in front of the writing hand and to the right. Smudges…you know.) Retractable Cross pen in hand, MFJ-24 hour clock blinking away, Vibroplex Bug (Original #2636801) adjusted, antenna swaying in the breeze—what’s left?

Contest time and the calls were loud and clear. My first contact was WA4CMI. Great, we’re getting out! Second QSO was with CH3Y (Canada), a special call for an event I’m still not sure about, dealing with the police department? I wonder if I can get a QSL or an acknowledgment from them…? My third contact was N2HMN in New Jersey, followed by KA3P in Pittsburgh, PA. It seems the RF was flowing to the north and south. The vertical long wire (a sloper) was still hanging in the tree pouring out two watts of pure, unadulterated New Hampshire power across the country…around the world. (I always like to think big.) Then another contact with K1TJ in Morristown, VA, followed by N2VPK in NY, WA4KAC in MD, W1XH in MA, K3AS in PA, N2YIY in PA, KF2HC in NJ, N1RXT on Mt. Monadnock, NH, N2SMH in NJ, AA6UL/4 in VA, W3BNB in MD, AA3LY in PA, WB3GCK in DL, K9UT in IN, KC1GS on Wachusett MT, MA, K8DSS in OH, AF3V in PA, W3GES in PA, K3TKS in MD, WK8S in MI, VE3FAO in Ont., VE3LCW in Ont., and K8JJC in MI. It was pretty exciting hearing and working all these good people on 40 meters and I wanted to thank each and everyone one of them…even the dupes.

Now, what could have gone wrong during such a brilliant contest in the park such as this? During the Saturday sunshine, while in Nashua’s public park, were also 35 to 50 fifteen to nineteen-year-old teenagers who were reenacting Dungeons and Dragons. Their crusade was to run, jump, whoop and yell it up. Okay, they were over THERE, and I was over HERE, about 150 yards apart; and we were worlds away from each other. WRONG! They wanted my space also. They wanted to “play” where I was and to see if I would notice them. Actually, they were the curious ones for many came to my table and asked, “Whatcha doin’?” while snapping their gum and starring at the QRP rig. Boys and girls who were holding duct-tape swords, mock malls and hammers in their hands, wanting to know why I was using Morse code and not a microphone. One brave young man, who looked like he needed a bath, said he had a radio too. My ears perked up and I asked him what his call was. He couldn’t remember but he was on channel 19 along with his divorced mother. “Oh,” I said and turned back to my CW.

After everyone had seen what they wanted to see, they left to conquer the world. Thank goodness for me, for now it is peace and quiet time. Well, not really. Standing in front of me, for minutes…not moving, was Patrick, a five year old boy who had no one to play with and deemed me his friend. HE WOULD NOT GO AWAY. He was inquisitive and pulled on the long wire which was connected to the MFJ-971, of which I said politely, “Please don’t touch anything.” He said okay, until he saw the cable from my gel-cell and wanted to know why it was red and black. I said politely, “Please don’t touch anything.” This appeased him until he saw inside my Xerox paper box filled with field strength meters, a frequency meter, coax, et al, something more interesting. Patrick wanted to see what else was inside and proceeded to empty, one piece at a time, the entire contents of what was there. “Wow, what are you doing?”…ran through my mind, but I looked at him and said politely, “Please don’t touch anything.” I, at this time, mentioned that his father was looking for him, or perhaps his mother wanted him too. Patrick said his mother wasn’t there in the park but that his father wanted him to play with that nice man in the corner of the field…me. My eye lit open and I said nicely, “Why don’t you go play with your friends.” He said he wanted to stay and watch me. Patrick then spied the Oreo cookies I had in my Tupperware container in my Xerox catch-all radio box. He said that they must taste good because he has had them before. I offered two cookies to him and said make sure your dad gives you permission to eat them. Patrick ran away with smiles on his face and a kick in his gait.

Patrick ran back ten minutes later, mouth all loaded with black cookie crumbs and said that they were so good he was wondering if there might be more. Again, he got another two cookies and off he went. That was the end of Patrick, until he came back for the third handout. I said, “I am sorry Patrick, but you ate them all and now you’ll have to leave here and not come back till I have over fifty contacts.” He didn’t understand what I meant but HE LEFT! Nice kid, but what a time to pick to be an inquisitive five year old!

Did I have a good time? YES! I can’t wait for the next QRP contest in the park, and I know a lot of us are waiting for the good times to continue. I have always said that amateur radio has to be instant gratification and that’s why I love it so much. This has got to be the best fraternity I’ve even been in and I love all you guys. You dudes are great and I want to work you all. And…Patrick, too!

Antennas, Featured, General, Homebrewing, Newsletter

20m Vertical Dipole

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My main antenna is a full wave 40m delta loop which also matches well across 20m. While the match is good the pattern is not ideal for DX. EZNEC predicts numerous nodes and nulls and a high take off angle. I have been looking for a better 20m DX antenna while I wait to get a beam up.

At the Club’s (N1FD) recent VE session a Radio Wavz 20m Dipole was described as having good DX performance when mounted as a vertical.  At $39 including a 1:1 choke balun, I decided to try it.

I shot a rope over a branch at 65′, attached and sealed the coax, and hauled the dipole up. The coax needs to come away from the vertical at roughly 45° to minimize the coupling to the lower antenna wire.

Vertical Dipole - The Balun is hung at a right angle
Figure 1 The Balun is hung at a right angle

A paracord is attached to Balun in the opposite direction from the coax to oppose the pull of the coax and is needed to keep the antenna wire vertical as shown in Figure 1.

I used a water bottle to weigh down the lower wire which allows the antenna to move with the tree to avoid damage during high winds.  Figure-2 shows the Delta Loop and to its right the Vertical Dipole. It is difficult to see the Vertical, the green water bottle can be seen just below the center of the figure.

Delta Loop and Vertical Dipole (right)
Figure-2 Delta Loop and Vertical Dipole (right)

After the initial installation, the first step was to measure the VSWR. This can be done using the radio’s VSWR meter or an antenna analyzer. If the antenna had to be brought down to adjust its length I wanted to do it before I secured the cables and finished the installation.

The antenna analyzer measured a <1.8:1 VSWR from 13.4 MHz to 14.35 MHz. A good match over 1 MHz of bandwidth is very good. The resonate point with a 1.2:1 VSWR was at 13.9 MHz. The antenna was long which is normal “out of the package” without any tuning. With a little shortening, the match was <1.5:1 across the entire 20m band and less than 1.2:1 at band center. This is better than EZNEC predicted. The VSWR measurement includes 100′ of LMR-400 which will improve the apparent match a little. I suspect most of the improvement is from the interaction with the angled coax. It is also possible the balun isn’t a perfect 1:1 as described by Radio Wavz. The antenna has a very good match across the full band and does not need a tuner.

The vertical dipole’s noise floor was S3 (-106 dBm 3 kHz BW) which is good. I had assumed it would be much higher because it was a vertical. It is only an S unit higher than the Delta loop which measured S2 (-111 dBm 3 kHz BW).

EZNEC shows a low 10-45 degree take off angle and no NVIS capability with the top of the vertical dipole at 65′ as seen in Figure 3.

Vertical Dipole EZNEC Analysis at 65' height over poor ground
Figure 3 EZNEC Analysis at 65′ height over poor ground

Based on EZNEC it should be better for DX than for local communications.  In practice, this is the case.

For the first test, I tuned into the afternoon 20m Net. Most of the stations are within 400 miles of my QTH. The Delta Loop had a 10 dB to 20 dB SNR (signal to noise ratio) advantage at this range. An Agilent spectrum analyzer was used for these measurements.  Tuning the band I found Vancouver BC, WA, OR, CA, and Ireland. Only Ireland could be heard with the Loop. I have never heard any 20m stations in the Pacific NW  while using the loop.

The next test was to use the RBN (Reverse Beacon Network) to measure the antennas DX performance. For those unfamiliar with RBN, there are roughly 140 stations worldwide that are connected to CW Skimmers. Using CW you send a series of CQs and your call sign. If you are detected you are added to a Spot Collector which is accessible on a website or via telnet.

I transmitted on 14,037.5 when using the Loop and 14,038.5 when using the Vertical Dipole.  By using two frequencies I could tell which antenna the Spot was reporting. Also, most of the RBN stations will not respond to a second call too soon after reporting the first intercept. With a quick QSY, I could transmit on the opposite antenna without waiting. Figure 3 is a sample of the RBN Spots.

RBN Spots
Figure 3 RBN Spots

I plotted the distance to the Spots versus the reported SNR. This can be seen in Figure-4. The number of RBN nodes is limited and some of the nodes listed on the RBN website might not be available, especially during this weekends SSB contest.   Also, the band conditions will impact the range and number of stations reached.

Delta Loop vs. Vertical Dipole - SNR versus Range
Figure-4 SNR versus Range

Note that where two data points (Red and Blue) are at the same range and therefore directly above each other both antennas were spotted by the same station.   If the Spot could hear the Loop it always heard the Vertical Dipole but there were many times the Spot heard the Vertical Dipole and not the Loop.

KM3T is only 3.1 miles from my QTH. As seen in the RBN screen capture and on the plot the SNR with the Vertical is 55 dB and only 45 dB with the loop. The plot also shows an SNR=9 dB data point for the Vertical near the Y axis and no matching Blue data point for the Loop. This station was 70 miles away in MA. Both of these data points rely on ground waves and the Vertical Dipole has an advantage when compared with the Loop.

Overall beyond 1000 miles the Vertical Dipole clearly performs better than the Delta Loop and will definitely add DX to a log.

In summary when mounted high the vertical dipole retains the low take off angle of a 1/4 wave ground mounted vertical. It does not need ground radials and ground losses are reduced. It can be placed above obstructions such as a barn or house. It only needs one high support and it does not require a tuner.

It isn’t a hex beam or a yagi due to the impact of ground losses on the gain, but at $40, no tower required, it is a great antenna. It is very stealthy as well.

Hamilton, K1HMS

General, Homebrewing, Newsletter, On The Air

A Good Day To Be Doing Radio

It’s snowing at my QTH. A lot. If your QTH is within 30 miles of mine, then it’s bad for you too. Normally, I don’t mind the snow blowing. But in this instance it’s not supposed to taper off until 11 pm — meaning I…you…we…us — will likely have to go outside multiple times just to keep pace with it. Additionally, not only am I doing the driveway but the decks and sunroom roof. On days like this, I look forward to the days of being too old for it to be considered unreasonable for me to do it myself. For now, I am cursed with youth. Damn youth. So while I await my impending fate, I decided to get some fun stuff done. If you have some time, I’ve enumerated three projects I’ve been working on. Get some coffee, and enjoy!

Project 1:

The first item on my list for a while is to get my ADS-B (Automatic Dependent Surveillance Broadcast) receiver going. For those of you unfamiliar with this, I won’t delve too deeply into it, but I’ll try to provide useful information. ADS-B / Mode S is data transmitted on 1090 MHz, which is downlinked from airborne platforms communicating their telemetry such as latitude, longitude, altitude, speed, heading, ICAO number, and flight numbers (as long as they have an ADS-B transmitter on board, which most do). If you’re familiar with the website FlightAware, users who collect their own ADS-B data, can create an account with FlightAware and upload their data to feed the system helping to provide a robust and complete air-picture. There are references and links all over the web on how to achieve this, so I won’t enumerate them here but know they are out there and an easy Google search away.

To intercept these signals/broadcasts, one needs a receiver and an antenna. Of course. The receiver is easy. I bought an RTL-SDR dongle (which I saw someone brought in during the Xmas Yankee Swap — AWESOME gift) which came with two stock antennas all for $24.95. This software-defined radio is a neat little gadget. I also download the RTL-SDR library package and GnuRadio in order to actually play around with its functionality. The dongle comes with an SMA connector, so to attach any coax, you’ll need an SMA-male to an F-female connector. (Aside: The other Sunday, I intercepted some broadcast radio stations and was able to demodulate them. The structure of the signal looked just like that from the Wikipedia article about FM transmissions!! The one down side about these dongles, however, is that the lowest frequency they can reach is 24 MHz, which isn’t great for HF work. I was hoping to intercept my own transmissions from the shack, but no dice on this.)

Ham Radio Projects - RTL-SDR dongle
RTL-SDR dongle

The next bit was the antenna. Since ADS-B signals are vertically polarized, one has to of course use vertical antennas. I tried two different designs for this. The first was a colinear coaxial antenna whose plans you can view from the link. I did this a while back and found it a bit cumbersome, additionally, I wasn’t able to collect a ton of data. Many others using this antenna’s praises and I think the fault is the author for not correctly constructing it.

I then found another inexpensive design called the cantenna. This was by far the easiest of the constructions.

Ham Radio Projects - A Cantenna
Cantenna

The theory behind it was that one would take a quarter-wavelength piece of bare copper wire (from inside a spare coax lying around) which at 1090 MHz is about 69mm, and then the cutoff part of a soda can would act as the ground-plane (completing the other quarter-wavelength of the antenna). As seen from the picture, there is an F-female to an F-female connector which connects the bare copper wire to RG-6 coax cable (which is running through the PVC in the picture). And because the RG-6 was only $6.99 at Home Depot, I picked up 15 ft. for use with this antenna. You probably do not want to use coax much longer than this (and ideally shorter is better) at these frequencies due to losses in the coax.

Lastly, was to get the right software. There are a ton of software options. My ultimate goal is to run this on a RaspberryPi, setup somewhere outside, where I can open up a TCP port and pipe the data through so I can look at it from any machine connected to my LAN. To this end, I found the dump1090 distribution was an excellent choice. This dude wrote some excellent code, well-commented, and compiled in a jiffy.

With everything in place, I let her rip and began to integrate data. After about an hour, on Sunday evening, I was able to get the following results (after post-processing the data in MATLAB — eventually I’ll move this over to Python to run on the RPi)

ADS-B Flights above my QTH
ADS-B Flights above my QTH

The legend is as follows: The blue square is my QTH. The upper right square is the Lawrence Municipal Airport in North Andover, MA while the lower right square is Logan Airport. Everything else is color-coded by flight number. Even after an hour, I was able to get quite a few hits. Though not shown in this image, the farthest I’ve been able to see is 78 nmi! I’m going for the horizon limit folks!!

Project 2:

Get on the radio! Oh, man, have I been looking forward to this. Ok, so part of this is my fault. My shack isn’t complete yet. I do not have a great system of running my feed lines into my home. That’s for the Spring. For now, I have to open and close my basement window and pull the coax through. It kind of sucks. But, nevertheless, only temporary.

Other excuses: work is long and arduous now, need to hang out with my W1FEY (that’s my wife’s unofficial call-sign — I like to think I’m clever), and been doing a lot of work for the club in the form of bringing you rock-solid programming and figuring out the High-Altitude Balloon project.

Now that the excuses have been enumerated and judged, it’s time to put them aside and do some operating. I love trying to work DX. I’m not great at it, but I’m learning. Plus, every time I hop on the ol’ ICOM-7300, I have an excuse to learn how to use DXLab a little better. In fact today, I fired up the SpotCollector for the first time. I’m no expert, but I’m vectored the right way 🙂

I found that 17 and 20m worked out particularly well today. 40m was good, but I didn’t work anyone on there, and 80m was pure static during the late morning or early afternoon. (Maybe that’s just me). I only got to make 4 QSO’s but that’s 4 more than I had this morning ladies and gentlemen. They were:

I was going to work more, but then W1FEY CQ’d for me in the shack and told me to look outside. When I did, it was about time to suit up.

Project 3:

Before braving the elements, however, I wanted to use an antenna analyzer to check out my SWR’s for my Buckmaster 7-band OCF dipole. I love this antenna. I had decided that the 3 kW version was right for me since at some point I wanted to add an amp. And I did…inherited an Ameritron AL-80B from a friend’s dad who is a Silent Key.

Anyway, I noticed that 6 and 10m were conspicuously bad. As a result, I had asked Greg (W1TEN) if I could borrow his analyzer. Being the gracious gentlemen that he is, he loaned me his RigExpert AA-54. Really neat gadget and the cool thing (maybe this is standard but it was cool for me) is that with a simple USB connection, one can get results on your machine and save data for later use.

In the next set of pics, I’ll show my results for the 7 bands that the Buckmaster covers: 80, 40, 20, 17, 12, 10, 6: (It might be a bit hard to see)

80m SWR values
80m SWR values
40m SWR values
40m SWR values
20m SWR values
20m SWR values
17m SWR values
17m SWR values
12m SWR values
12m SWR values
10m SWR values
10m SWR values
6m SWR values
6m SWR values

What’s immediately obvious is that 10m is beginning to get wonky and 6m is completely gone. At least this begins to explain why I can’t hear anything on these bands. I did a bit of research online asking if anyone else encountered the same issues and some people seem to suggest that there will be a few bands that your SWR will not be ideal. With that said, however, it does seem most people have fantastic luck with these particular antennas, and so it could be user error. Perhaps something when I initially put it up? But if you’ve read this far, then maybe you have some suggestions for me…

Epilogue:

Well, thanks for reading. I hope you enjoyed a break from the snow and my somewhat lively banter kept you mildly entertained. Any comments, concerns, and questions welcomed.

Brian, AB1ZO

Radio Amateurs Developing Skills Worldwide