Tag Archives: Antennas

Featured, General, Newsletter, On The Air, Space

Making Contacts Through LEO Satellites

I’ve been having a lot of fun this past week learning to operate using satellites. It is amazing how many LEO satellites are operational right now!

LEO Satellites - Antennas
Satellite Antennas

We built an improved portable LEO satellite station a little while back and used it for the first time during a Technician License Class that we taught earlier this spring.

We decided to set up the station in our back yard about a week ago. The idea was to spend some more time learning to operate the station and to improve our satellite operating skills.

The past week has been a productive one. Here are some stats for our satellite operations during the last 7 days –

  • Contacts Made: 78
  • Modes Used: SSB Phone, FM Phone, CW and Packet (APRS FM)
  • Satellites Worked – 9 Total plus the ISS: AO-7, AO-85, ARISS (International Space Station), FO-29, SO-50, XW-2A, XW-2B, XW-2C, XW-2D, and XW-2F
  • States Worked: 23
  • Grids Worked: 49

The week began with a visit from Curtis, N1CMD who has quite a bit of experience with Digital Packet operation via the digipeater on the ISS. After some experimentation, Curtis helped me to find a setup using a SignaLink Sound Card and a second, windows computer that works well for Packet QSOs. I tested the setup using the terrestrial APRS network to get all of the hardware and software working correctly. The combination was then used to make a first packet contact using the ISS.

Operational LEO Satellites

The LEO satellites which are currently operational support a mix of split band modes. All of the satellites that we’ve worked so far use either 2M/70cm or 70cm/2M up and downlinks. The satellites support a variety of operating modes including via single channel FM, linear transponders, and APRS packet systems. Operating skills such as proper adjustment of up and downlink frequencies, Tx power management and setup of the digital packet system have been at least partially mastered this past week.

There are a great bunch of folks who are regulars on the satellites and we have made some new friends in our short time operating through satellites. The single channel FM satellites are usually too busy to support rag-chewing. The linear transponder satellites (there are many of these) support several conversations at the same time and we have had some nice rag-chew sessions on these birds.

There is also a good bit of DX to be had via satellites. This past week we have worked Patrick, FJ/N2IEN in Saint Barthelemy; Chris, 9Y4D in Trinidad and Tobago; Burt, FG8OJ in Guadeloupe; Fausto, HC9VF in Ecuador; and several stations in Canada.

We are planning to set up our portable satellite station at Field Day this year. Curtis will be the main operator/station master for our satellite station. If you are interested in learning more about satellite operations, please let Curtis or I know and we’ll help you to learn more during Field Day 2017.

Fred, AB1OC

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

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