The antenna arrived in a sturdy box, and all of the parts were in good shape. The paper manual is adequate and includes diagrams that were helpful for assembly. It took me about an hour to put it together. Once assembled and tightened, it is a sturdy antenna. It’s worth reading the manual closely before attempting assembly, and again afterwards to understand the instructions for tuning the SWR.
Installing and Testing the Antenna
I installed the antenna on 28-foot heavy duty fiberglass telescoping mast from Max Gain Systems. The mast is located next to a long chain link fence, which may have interacted with the antenna and made tuning it a bit challenging initially. Once attached to the mast, I used a Comet antenna analyzer, and attempted to tune the antenna for the lower end of 40 meters for CW and digital modes. For my first test, with the antenna mast lowered, the SWR was just above 3:1. I believe that was partially due to close proximity of the metal fence. Also, the manual specifies that the antenna works best with a metal mast, likely to serve as a counterpoise. I attached about 25 feet of copper wire to the antenna ground as a counterpoise, and made some more tuning adjustments. After that, and when I raised the antenna to 25 feet, the SWR was down to 1.6:1. Close enough, since I have an antenna tuner in the shack.
I tested the antenna for 30 days using FT8, WSPR, CW and SSB. The first contact I made on FT8 was in Washington State… a very promising start! Using FT8, I was easily able to work stations all over North America, as well as some DX stations in Europe, Australia and Japan. I also tested the antenna using WSPR for 24 hours, and my signals were received across North America and in Europe. I used the antenna for all of my 40 meter phone and CW contacts during Winter Field Day, and I was able to make a lot of contacts across the U.S. and Canada. The antenna performs better than I expected it would. However, it is not a good for receiving when compared against my end-fed halfwave antenna. I made comparisons several days, and the wire antenna was always noticeably better for receiving.
Pros: 1. It actually works! When I first looked at the antenna, I was skeptical. After testing it for 30 days, I realize there are some use cases where this antenna is a good choice. 2. This antenna would probably good for someone with HOA restrictions, as it is small enough to be hidden. However, keep in mind that my testing was with the antenna mounted at 25 feet and in the clear. 3. Because the antenna is compact and can be raised quickly, it would also be a good choice for portable operations or emergency communications. Cons: 1. The antenna is only for the 40 meter band. If you have space for several antennas, that’s probably not an issue. 2. The antenna can be somewhat finicky with SWR. It made several trips up and down a ladder, and lowered the mast a few times, to get it adjusted. I also had to retune the antenna after one particularly cold, windy, rainy day.
The antenna retails for $160. Would I have bought this antenna on my own? Probably not. During the podcast, each reviewer was asked to give a “signal report” between 55 and 59 as an overall rating of the antenna. My report was solidly in the middle with a 57. It is definitely strange looking, but the appearance and compact size belie an antenna that actually performs fairly well, as long as you don’t expect miracles. I will most likely take the antenna down from the mast to install an off-center-fed dipole, and see if one of my ham friends living in a HOA community would like to give the Isotron a try.
This was a great ham radio experience for me. I had a lot of fun building, testing and using the antenna. I also enjoyed being included on the 100 Watts and a Wire podcast, and Christian Cudnick, K0STH, is a great host.
I wanted to incorporate some of my most recent ham radio activities into a new QSL card. I reached out to my friend Jeff, K1NSS, and gave him a basic idea about what I wanted. I wanted my DX hound buddy Luke the Catahoula featured in the card. As usual, he worked his magic and came up with a fantastic design that captured my vision, and then some! What do you think? This version will be going to the printer soon.
WSPR (pronounced “whisper), which stands for “Weak Signal Propagation Reporter,” is a fantastic digital signal for assessing band conditions and evaluating antenna performance. It’s also great for detecting band openings. WSPR mode implements a protocol designed for probing potential propagation paths with low-power transmissions. The protocol was designed, and a program written initially, by Joe Taylor, K1JT. WSPR is included in the WSJT-X software, along with several other weak signal digital modes (FT8, FT4, etc.) for amateur radio. WSJT-X can be used to transmit and receive WSPR signals.
There may be times when you don’t want to tie up your HF transceiver for WSPR signals, and you really don’t need the power that’s available in most HF transceivers for WSPR. With a decent antenna, you can transmit and decode signals over very long distances with very low power. Because of the encoding of the WSPR signal, a 200 mW signal has the same DX capability as a 1 KW SSB transmitter, or CW at 80W.
You can search the Internet for information on how to build your own transmitter, and there are also some kits for sale. There are also a couple of relatively inexpensive and small WSPR transmitters that are easy to configure and use. I have been using the WSPRlite Classic, made by SOTABEAMS, and two WSPR Desktop Transmitters, made by ZachTek. There are some common features between the two, but there are also quite a few differences. Both transmit a 200 mW signal using 5V (USB) input for power, and both use software for configuring your callsign, location, etc. They can also be powered from a USB power bank.
The first WSPR transmitter I started using is the WSPRlite, which costs around $140. It is very small and light, and therefore great for portable operations. The unit contains internal filters for 20m and 30m, but SOTABEAMS also sells filter kits to expand the capability to include 630m, 160m, 80m, 60m, and 40m. I have not purchased or used any of the filter kits.
A unique feature from SOTABEAMS that comes with the WSPRlite is the DXplorer web site.
The WSPRlite instructions, configuration app, USB drivers, and firmware updates are available on DXplorer. Following the detailed instructions from the website, configuring the WSPRlite is a relatively easy process that involves installing USB drivers and configuration software, connecting to the computer through a USB port, selecting the appropriate COM port, entering data for a few settings, and saving the settings to the device. Once configured, the WSPRlite is ready to transmit. The trickiest part to begin transmitting is pressing a button 2 seconds after the start of an even numbered minute (i.e. 14:58:02, 10:20:02, etc.) to begin transmission. The time must be set accurately for the transmitted signals to be decoded.
The configuration application also provides a link to dxplorer.net, where you can view statistics and maps depicting the WSPR signals transmitted from the WSPRlite. There are several different ways to view the data, including a metric call DX10. According to SOTABEAMS:
We use the WSPR data to generate a special metric, DX10. We recalculate your DX10 range (km) every two minutes. DX10 is a great system performance indicator. The best HF system will give the longest DX10 ranges. … Within seconds of your two-minute WSPR transmit period ending, you can see where you have been heard.
The DXplorer website is where the WSPRlite really shines. It’s easy to use and provides lots of useful informaton.
WSPR Desktop Transmitter
The WSPR Desktop Transmitter from ZachTek also costs $140, and is slightly larger and heavier than the WSPRlite, but has several additional features. The unit includes a GPS receiver and antenna, which can automatically set the location (grid) and control the timing of the transmissions. Once initially configured, this makes operation nearly automatic. Additionally, the latest firmware and software supports Type 3 WSPR Messages. A Type 3 message can transmit a more exact location using six figure Maidenhead reports instead of the regular four figure report, which is especially useful if you use the transmitter in a mobile or portable application with it functioning as tracker.
I am using two transmitters, each designed for operation on different bands. The “Mid” model transmits on 40m, 30m, 20m and 17m. The “High” model transmits 15m, 12m, 10m and 6m.
Note: ZachTek now sells three updated models for this transmitter: – “Low” for 2190m and 630m – “Mid-Plus” for 160m, 80m, 40m, 30m, and 20m – “High-Plus” for 17m,15m, 12m, 10m and 6m You can purchase multiple units at a discount ($254 for a Mid-Plus and High Plus, or $359 for all three models).
The WSPR Desktop Transmitter also uses an app for configuration. The documentation web page has links to the configuration software, a quick start guide, and lots of additional details about the transmitter. A USB driver might be required to connect to the computer, and there is a link on ZachTek’s download page. Similar to the WSPRlite, once the device connected to the computer with the micro USB cable, you can determine COM port using Windows Device Manager. You set the serial port (for my computer, COM13) on the Serial Port tab, and click open. After a moment the software will be connected to the device.
After the connection is open, the next tab to click is WSPR Beacon. This is where you will enter your callsign, and select the bands. With the GPS antenna connected and placed near a window, you should start seeing the GPS signal quality and a position lock. Once the position is locked, the Maidenhead grid information will fill in automatically. When initially powered up, it might take several minutes to start seeing the satellite positions and get a position lock.
Once the WSPR configuration is complete, click on the Save Settings button, then click on the Boot Configuration tab. In this tab, you can configure the transmitter to start up in WSPR beacon mode. When power is applied, once it achieves a GPS position lock, the unit will automatically start transmitting WSPR beacons, cycling through the bands that were set in the WSPR Beacon tab.
There is also a Signal Generator mode so the transmitter can be used as a piece of test equipment in your shack. It can output a 23dBm sine wave from 2kHz to 50MHz, depending on model. I have not tested or used this feature.
The WSPR Desktop Transmitter does not include access the DXplorer website like the WSPRlite, but you could still use DXplorer standard mode to view statistics for signals transmitted from either device. You can also view maps and data for WSPR signal on the WSPRnet.org website. You can get a free account to access all of the features on WSPRnet.
The Weak Signal Propagation Reporter Network is a group of amateur radio operators using K1JT’s MEPT_JT digital mode to probe radio frequency propagation conditions using very low power (QRP/QRPp) transmissions. The software is open source, and the data collected are available to the public through this site.
The Map tab opens a configurable map for a visual representation of where your WSPR signals are being decoded.
Scroll down in the map to configure the view. There are several settings that you can use to tailor the information displayed on the map.
Click on the Database tab at the top of the web page to display a sorted list of spots. This view can also be configured.
The WSPRlite and WSPR Desktop Transmitter both performed very well. There are some difference in features and operation. For the price, the WSPR Desktop Transmitter offers a few more features and once configured it operates automatically every time it’s powered up. The WSPRlite is very small and easy to carry, and the DXplorer website offers excellent statistics for those tracking propagation conditions or comparing antennas. You can’t go wrong with either option, and your choice would depend upon your operating preferences.
The first balloon, which carried a payload with a SPOT Trace GPS tracker and a GoPro camera, was designed climb to an altitude of 70,000 – 100, 000 feet before bursting and falling back to earth. A parachute was attached to the payload so it could return to ground intact for retrieval by a chase crew. We expected the payload to land approximately 50 miles east of the launch site, but the balloon traveled much farther than anticipated. The chase teams scrambled and the payload was successfully retrieved approximately 150 miles from the launch site. The camera captured some amazing images while the balloon was in the stratosphere. Some of the best pictures are featured in the linked news stories.
This post focuses primarily on the second “pico” balloon, which carried only a LightAPRS-WAPRS and WSPR tracker as the payload, and was designed to reach an altitude of approximately 50,000 – 60,000 feet and achieve neutral buoyancy to travel for a much longer period of time. The LightAPRS-W, which is very small, was powered by two small PowerFilm 4.8V solar panels with two 5F 3V supercapacitors. With this power source, the tracker transmits APRS on VHF at .5 to 1 Watt, and WSPR on HF at 10 mW (1/100th of a Watt!).
We spent several days configuring and testing the tracker, using the configuration and programming instructions provided by QRP Labs on GitHub, and following some helpful suggestions in the Tips & Tricks for Pico Balloons wiki. The tracker also had two light wire antennas for APRS (19.4 inches) and 20 meter WSPR (16.6 feet), and a counterpoise (16.6 feet) attached.
Once assembled, the tracker was easy to configure with an Arduino IDE to load the APRS callsign (K4KNS-11), WSPR callsign (K4KNS), and a few other settings. It’s best to pay very close attention to the instructions and comments in the configuration file! After the loading the configuration, we placed the tracker in the sun to test and listen for APRS and WSPR signals. We were able to confirm that the tracker was transmitting good APRS and WSPR signals. Due to the very low power of the VHF and HF transmitters, we could only confirm local reception. With the tracker stationary and in full sunlight, we noted that the LightAPRS-W transmitted an APRS packet approximately every 5 minutes, and a WSPR signal every 4-6 minutes.
It’s one thing to have a good test under controlled conditions, but quite another to achieve success under field conditions. On the day of the launch, the weather was marginal, but within acceptable parameters for a launch. We double checked to ensure the tracker was powered up and transmitting, and tied it to the balloon.
We had a good launch. The balloon, with the tracker hanging 16.6 feet below the balloon (to accommodate the counterpoise) and trailing a 16.6 foot HF antenna, quickly rose to an altitude above any potential obstructions and began its journey. Within moments, we saw the first APRS positions appear on aprs.fi. A few moments later, using the WSPR Watch iPad app, we saw that the WSPR signal was being received across the U.S.!
It was all going so well! We continued to watch the balloon tracking eastward and climbing, following the same track as the high-altitude balloon that had been launched about a half hour earlier. Then, after about an hour of flight, both the APRS and WSPR signal went off the air. At that time the balloon was 55 miles east of the launch site at an altitude of 37,500 feet.
We’re not sure exactly why the signals were lost, but we do not believe the balloon went down in that location. We are speculating that the tracker may have been damaged due to the high wind speeds on lost power. It is unknown how much farther the balloon might have traveled. Despite the relatively short flight, we did collect some good data for the students at Savannah River Academy to evaluate. We also proved to ourselves that we could successfully launch a balloon and track it with APRS, and that a very weak WSPR signal transmitted from high altitude could be received by stations thousands of miles away!
Using aprs.fi’s data export tool, we were able to export a KMZ file with the balloon’s tracking data, and use Google Earth to view the full track and altitude changes.
This was an amazing experience! We captured many lessons learned, and we intend to build another more hardened version of the tracker so we can launch another balloon and hopefully track it over a much longer distance and time.