WSPR Station

Project 5 of 7 for October, 2020 – projects to keep sane during Covid-19 Lockdown

Status: Completed and on the air as of June, 2021

WSPR has been played with for so long it has gone through may iterations. As of May, 2022, the latest attempt is to use a TAPR WSPR board on a Raspberry Pi. This runs 200 mW on one designated band. In our case, 10 meters. Watch for progress. Continue reading below to learn about earlier attempts.

The object of building a WSPR station is to be able to see signals first hand real time that are coming into this qth. A band to operate on can be chosen more quickly and more efficiently. WSPR per se is explained here:

While it would be great to have a WSPR transmitter as well as receiver that is not feasible at the remote site or at home. The radiated signal from WSPR would cause interference to other services. A reasonable alternative exists and that is to receive only. Stations decoded will be posted to which shows a map of where those stations are located.

Hardware and software is about as simple as it can get. All parts are already in place and just need to be connected and configured. A computer that is already on site can run the WSJT-X software. An antenna that is already on site, the DXEngineering RF-PR-1B Active Magnetic Loop, can provide a signal on multiple bands. A receiver that will work well is the SDRPlay. The new model RSPdx is on site and is an excellent choice because of it’s additional bandpass filter on the low bands. It will enable monitoring of 630 meters all the way up to 10 meters. Virtual audio channel software will need to be installed to provide a software connection between the SDRPlay and the WSPR decoder. Virtual com port software will be needed for cat control to change frequencies. Power budget will be low because the pc and the receive loop already run 24 hours a day. The SDRPlay is the only additional power draw and it is insignificant. It plugs into a usb port on the pc and draws power from the pc.

Updates to follow as the project is implemented. Example display of is below.

It’s working! Check it out at Running on 30 meters alone provides this result.

All it needed was to reload SDRUno with the latest version, vspn port emulator software, and vb basic virtual audio cable software. A YouTube instruction video by the SDRPlay technical department helped a lot.

Final step will be to open up all bands, not just 30 meters. That works but the whole WSPR operation is not at all stable. This project is not done. It is stable so long as it is not disturbed but accessing the pc with remote desktop. That disturbance stops the WSPR operation.

It has been stable for more than a day by starting the applications on site and not using remote desktop. This is not a solution because we need remote desktop to reach other applications. Work in progress.

Currently working on an antenna on the house back in Denver to become the beacon antenna. How long before the HOA notices?

Update – June, 2021: Relocated to the site of the remote base, using Hustler 6BTV vertical antenna and Yaesu FT-817 transceiver. Running 1 watt on 80,40,30,20,15,10, and 6 meters. The computer is an Intel NUC i3 running Windows 10 and WSJT-X 2.4.1. Here is a typical example of performance. The best spot is Iceland hearing W0QL with it’s 1 watt and a vertical.

Above is an example of 30 meters early one evening. One watt and a vertical is amazing.

630 Meters for 2020

Project 3 of 7 for 2020

Upgrading from last year’s 630 meter station is underway. The antenna will be reused. A new station transceiver was added during the year and can provide the 630m signals on the XVTR port. The biggest addition will be a linear amplifier to improve the transmitted signal. Actually, it’s a non-linear amplifier because the WSJT-X digital modes do not require the amp to be linear. A non-linear amp is just fine. The amp decided on is the K5DNL.

Two Hundred Watts? Yes, it’s legal because with a 2.5% efficient antenna the radiated power is a perfectly legal 5 watts.

On 630 meters, or 474.2 KHz, the antenna’s phase is very important. The rf current and voltage need to be in the same phase for the best radiation. An oscilloscope is used to make the phase measurement, with current on one channel and voltage on the other. When the sine waves line up the phase is perfect. K5DNL has available the hardware to sample the current and voltage to feed to the scope. Ken calls it the Scopematch. One was obtained along with the amplifier for this project. The scope in the shack here is the Hantek DSO5102P dual channel oscilloscope.

A big jump ahead happened when the decision was made to reconfigure batteries and build a 24 volt system temporarily. The amp runs on 24 volts. The main batteries for the permanent 24v system are on order but are still off shore.

Status: A temporary 24 volt supply has been set up and the project is awaiting time to complete it.

Amplifier and Inverter

Project 1 of 7 for 2020

This project has been completed. See “1.5 KW Amplifier Off Grid”

A new amplifier is on order and installation parts are arriving. The good ole SG-500 gave up the ghost and besides it didn’t have 6 meters. Good excuse to look around for a new amp. Deciding on which amplifier to chose was a tough decision because many fabulous new amps are on the market today with 6 meters and great new features. The decision was made easier because one amp looks like it was designed from the ground up to integrate with the Flex. It is the 4O3A PowerGenius XL, or just PGXL for short. Good experience with another 4O3A product (the Antenna Genius) is a strong selling point. A PGXL is on order from Flex.

Going from the 500 watt SG-500 to the 1500 watt PGXL requires some power improvements. A new amp cannot be run on 12 volts. It was decided to add a separate set of batteries, an inverter, and to go to 24 volts and stay off-grid. The existing 12 volt off grid solar system will stay in place untouched for use by the existing 12 volt equipment. The hope was to go all the way to 48 volts for efficiency but no solar controller could be located that would provide low temperature foldback. Foldback is important because it reduces charge current when the temperature is below freezing. The Morningstar ProStar 30 currently in use on the 12 volt system does provide foldback and it works for either 12 volts or 24 volts. Thus the decision was made to run at 24 volts to make sure the batteries are protected in the winter. It takes big wire to carry the 200 amp current needed. The inverter manufacturer recommends this 1/0 cable to run between the batteries and the inverter.

Deciding on an inverter was also a tough decision because there are a lot of fabulous looking inverters on the market. Hybrid means the inverter is combined with a solar controller (charger) in one cabinet. The new so-called hybrid inverters would simplify things but none could be found with temperature foldback. Two more must-have features limited the choice greatly. First, the inverter must have FCC Part 15 Class B certification or equivalent. Inverters are notorius for generating RFI and presumably an FCC certification will fix that. No China inverters have certification. The other must-have is pure sine wave output. That’s pretty easy to find. Output voltage is also important because the amp can’t run full output power on 120 vac. It must have “220”. That number is in quotes because it is has become a generic term to describe 230 volts in some countries and 240 volts in the United States. Since the amp was made in Europe it will be quite happy with 230 volts. There is no neutral wire on European circuits. No 120 volt appliances can be run from this inverter. The inverter that was decided upon and is on order is the Victron Phoenix Inverter Smart 3000.

. A week later the inverter has arrived and is unboxed, looking like a work of art. It is 24 volts in and 230 volts 3000 watts out.

Victron recommends using 1/0 wire for this model between the battery and the inverter. That is the largest wire ever used at W0QL and a new crimper had to be obtained along with terminal lugs for 1/0.

A closeup look at the crimps with heat shrink tubing installed.

Mounting the inverter was a piece of cake.

Lugs are easy to reach.

The very first cable attached was the green wire ground. This wire runs directly to the copper ground bar which is bonded to the ground ring around the shed.

The 1/0 cables were bolted and strapped in. One more stage is finished and ready for the next equipment to arrive: the batteries, the BMS, and the AC power parts. A 250 amp fuse is midway down the battery cables. At the lower right is the terminal block for the cables from the BMS. One thought is to replace the terminal block with current shunt from another Victron Coulomb counter battery monitor. No decision has been made. The batteries will go in that big bare spot on the floor.

Current status: Amplifier shipped last week, has arrived in UPS facility in Denver, awaiting delivery Monday or Tuesday, September 22, 2020. Batteries are still off shore or in Customs.

Amplifier arrived but no place to plug it in yet. Batteries have still not arrived in the States.

A decision was made today to temporarily borrow half of the cells currently in use for the 12 volt system and rewire them for 24 volts until the permanent batteries come in. On the floor is the borrowed temporary 24 volt battery pack. This pack provides 100 AH which is enough for testing at moderate RF power levels. It is being charged by four 12 volt solar panels connected in series-parallel to provide 24 volts nominal. BMS? A 24 volt 8s 100 Amp BMS was found in the junk box and put to work.

With this pack the inverter powers up perfectly and provides it’s default voltage of 230 volts AC.

The amplifier is on site for testing but not in it’s permanent place yet.

It is rather massive and needs a little more space cleared out before it can be completed. Initial tests are amazing. Antenna and feed from the transceiver are the only connections to the Flex 6600. All control, CAT, PTT, and ALC signals are over the LAN. Upon firing it up the amp found the radio automatically. Like people say, the operation is so slick it just acts like a bigger front end for the radio. No tweaking or peaking needed nor bandchanging. The amp follows the band on the radio transparently. The operation is just amazing. Testing with the temporary battery the amp was given 10 watts RF input. Output was 350 watts. The inverter reported a drain of 1000 watts. With no way of measuring the battery drain it looks like another Coulomb counter is in the future. The inverter can display instantaneous battery load but not the capacity remaining. This is a learning experience.

This project has been completed. See “1.5 KW Amplifier Off Grid”

Maestro Arrives

Flexradio says the Maestro manufacturing has been held up for several months due to a shortage of parts caused by Covid-19. This unit was snatched up from the online swapmeet and it’s a beauty.

Shown above in it’s travelling mode. All it needs is a wifi connection. It has an internal battery that will run quite a few hours. Portable operation gets a lot simpler with this device. A mic or a paddle is all it needs to get on the air. Back at the shack it looks equally at home with a paddle and a microphone.

The Maestro is an option that is not essential because all operations can be done with a pc or a laptop alone but this is for those of us who still like knobs. The knobs on the Maestro have an expensive-radio feel. It’s a pleasure to operate with this option.

160 Meters Using Tower As Vertical Antenna

An omega-matching system was added to the tower when it was on the ground in the hopes the tower could be made into a 160 meter vertical antenna. The concept was suggested by Bill, N0CU and illustrated in ON4UN’s Low Band-DXing, Fifth Edition on p 9-68.

PVC pipes were attached to the tower with stainless steel clamps and 8 ga aluminum wire was connected at the top.

Today was the first chance to see if could be tuned. Two large variable capacitors were mounted temporarily, one in parallel with the tower and the other in series with the feedline. It is held up by Velcro strips and connected with clip-leads.

The results were amazing with the capacitors set at half way on the first try. This is what it looks like on the RigExpert AA-55 antenna analyzer.

With a little tweaking the match could probably be made perfect. It is quite useable right now with no other adjustment. Upon re-reading some of the technical articles on gamma matching a tower some new (or missed) information came to light. The main point is the resistance of the match is determined solely by the gamma apparatus connection height and distance from the tower. Resistance cannot be changed by the matching unit. If this proves out we are stuck with 66.5 ohms.

Next the clip-leads were carefully removed without touching the capacitor settings. A Banggood tester was connected to the capacitors and readings were taken to determine a ballpark figure for required capacitance.

The Banggood shows one capacitor is 82pF and the other is 116pF. Capacitors to achieve these values but with higher voltage ratings will be obtained. Next step is to mount them more permanently in a NEMA box and attach the box to the tower. Getting ready for winter and the fabulous upcoming 160 meter DX season will be fun this year.

A new box with two variable capacitors is ready to be installed and adjusted. The capacitors are capable of handling a peak voltage of 3KV. That should be right on the edge of being ok.

Update 9/6/2020: New box with room for two 3KV variable capacitors has been installed and tuned up.

The results are below 2:1 swr but not down to 1:1 which was the goal, of course. Moving the gamma tap point location would probably be necessary but too much work to accomplish. One article mentioned moving the gamma wire closer or farther from the tower down at the matching unit level. That will be given a try later this month. Here is an analyzer view of the match. This was taken at the shack end of the coax.

The SWR of 1.27 is lower than we measured at the base of the tower due to the coax loss. At the tower the swr was slightly higher at 1.45 and the resistance was up to 72 ohms.

See a separate posting for the updates.

Cushcraft A3S Modified For 17, 15, 10 Meters

An attempt to use a tri-band yagi on the 17m WARC band instead of the 20 meter band for which it was designed is successful. This project proved that an A3S will work on 17 meters without any modifications to the traps and only needs changing the length of the tip pieces. Today the balun was installed and the antenna went up after final tuning. It works quite well upon initial testing based on one contact.

The antenna farm as it stands today buried in a lot of smoke from a distant fire. The modified A3S is on the right.

First contact was with Estonia on 17 meters. Yay. Here are the analyzer screenshots for each band giving a first look at how well the modified A3S measures.

Ten meters was not modified so one would expect this band to look good and it does. The Cushcraft dimensions were used unaltered. Below 2:1 SWR for the entire band. That’s an admirable accomplishment for such a large band. SWR for FT8 is 1.21. Great. Ready for Sunspot Cycle 25.

Likewise, 15 meters was kept according to the original Cushcraft instruction manual dimensions. It works well as expected, SWR of 1.37 at the FT8 frequency and below 2:1 for the entire CW portion. SSB will be a problem with this antenna. Fortunately most SSB will be stateside rather than DX and that should be ok.

The 17 meter band is the nut that was sought after and it has paid off. SWR below 1.2 for the entire band and 1.14 at the FT8 frequency. Ahhhhhh. Good feeling. It is now proven that a A3S can be modified for 17, 15, and 10 successfully.

The tips were removed on the driven element and reflector and replaced with much shorter pieces of about 12″ each. The director had the tips removed and no replacement tips were needed. On the driven element and on the reflector tuning for resonance on 17m with the replacement pieces was all that was required. Note that the reflector was tuned 5% lower than the driven element per accepted yagi design. The standard trap resonance of 20 MHz is such that 17m does not interfere or cause any interactions and works perfectly. This is a winner.

Currently the antenna bearing is fixed on Europe because there is no rotator installed. Next upgrade project will be to add the rotator.

Balun for Modified A3S

1:1 Balun Made Using Four Mix 52 Cores With 5 Windings of RG-58

Baluns, it turns out, are not all that simple. An important goal of a balun is to prevent common mode current on the feedline coax. Incidentally it is supposed to convert from the balanced antenna to the unbalanced coax. In the words of Bill Leonard, N0CU, “Only recently has the importance of Zcm been understood.” Mr. Leonard presented talks on baluns to the 285Tech Club, Conifer Colorado. His slides are here:

Mr. Leonard stated in the presentation that coax is a better choice for conductor than solid wire. The reason concerns the impedance of the conductor. With coax the impedance stays at 50 ohms from beginning to end. With solid wire the impedance could be something other than 50 ohms and may influence the effectiveness of the balun.

If common mode currents radiate from the feedline coax it will act like a vertical antenna and that radiation will alter the yagi antenna’s pattern. The balanced to unbalanced conversion is apparently very easy to accomplish and almost any style or type of balun can do that. The common mode rejection part is not so easy. After lots of reading on the subject from the ARRL Antenna Book to articles on the web and YouTube, this is what has been decided upon. Five turns of coax thru a stack of 4 cores of mix 52 toroids. Here is how that combination was determined. First the requirements. The balun must function well from 17 meters to 10 meters. “Function well” is defined as having a high common mode rejection ratio and be non-reactive in the frequency range being used. It must have only resistance and no reactance. A typical problem in many baluns is they function well up through 20 meters then fall off above that. Commerical baluns are not a solution. Why not a commercial balun? No manufacturer publishes specifications of either common mode rejection or reactance. One does not know what one is getting from a commercial manufacturer other than glowing product claims. That problem could be easily overcome if there was a way to measure a balun. Measuring HF Balun Performance by Ron Skelton, QEX, Nov-Dec, 2010 explains the issues involved.

Mr. Skelton discusses that a balun is a 3 port device and thus needs a three port VNA to adequately perform measurements. A nanoVNA like at W0QL is only two ports. Some examples of using a two port VNA have been shot down as only testing the differential mode. Switching the leads around and repeating the tests will work but the results must be run through a complicated algebraic process to get an answer. Depending on the measurements taken by others is the obvious next step. ARRL Antenna Book 24th Edition contains graphs and pictures of practical transmitting chokes on page 24.50. (Earlier editions have the same information).

Antenna Book 24th Edition

In the chart above notice that all baluns fall off above about 14 MHz except one. That one is 3 turns on a stack of 7 cores. Not ready to build a stack of 7 cores the search continued. Another deal killer is the lack of mention of reactance. Next a chart was found by G3TXQ, Steve Hunt (SK). His charts include reactance as well as common mode rejection ratio.

G3TXQ (this link works intermittently)

In this chart we are looking for a balun that will work in the 18 to 30 MHz range and have resistance higher than reactance. Two meet that bill. First is 12 turns on one core. Second is a more manageable 5 turns on 4 cores. That is our choice and is the balun pictured at the top this posting. Mr. Hunt explains in his articles why the mix is 52. Mix 31 is for the lowest bands like 80 meters. Mix 43 is ok for the mid bands. Mix 61 is primarily used for the upper bands and vhf. Mix 52 is rather rare but a perfect match for 17 meters through 10 meters. These charts visualize baluns are not broadband as some literature states. They are optimized for certain bands.

The one big problem remaining is how to measure the performance of baluns . Please post a response if you have a solution for measuring balun common mode rejection ratio, Zcm, or any other parameter important to common mode current.

This has been my path of determining how to construction a balun for a modified Cushcraft A3S. Next will be a follow up on how well it works.

Followup 8/19/2020: The balun is installed and the antenna is up in the air. Contacts are being made and the antenna analyzer measurements look good. As for the performance of the balun the pattern of spots of our station is the only indicator available. If the pattern is what would be expected from a 3-element yagi then the balun is doing it’s job of keeping current off the outside of the coax.

The only spots from DX are from Europe. That’s a good indication that the beam is working because it’s pointing toward Europe. Also that’s a good indication the balun is working.

Colorado’s First Derecho Wipes Out Two Antennas

A derecho (pronounced dare-h-o) is a strong wind not accompanied by a thunderstorm. Apparently they occur in the Midwest regularly but none had ever been recorded in Colorado before last week. One went through the state and took out two elements on the big 203BA 20 meter beam. It also folded over one of the 43 foot antennas. Reports were the wind was 87 mph.

Elements came loose from the reflector. Damage is limited to the small diameter tip tubing.
The reflector shouldn’t be so short. Good excuse to replace the single band antenna with a tri-band beam since the antenna has to come down for repair anyway.
The 43 foot vertical is on the right hand side of this security camera image. This is the second antenna damaged. Good excuse to replace it with a better quality antenna from DXEngineering. The other antennas survived.
A Cushcraft A3S tri-band beam with a 40 meter add on kit is being put together to replace the 203BA.
Assembly is completed and ready for swapping out when the tilt-over tower is lowered this week.

Things were going great when this picture was taken, except the elements seemed to sag a little more than expected. Once the tower was lowered and the new antenna was attached the sag became a real issue.

What was causing this? Opening a trap revealed a very loose screw. Upon trying to tighten the screw it became clear that it had been stripped out. Opening a second trap revealed the same thing. Searching the web and YouTube turned up many similar experiences. Each trap could be rebuilt with larger screws but there are 14 traps. That’s a lot of work just to be able to use a brand new beam. The antenna was returned as defective.
The dip was not where it should be which indicated something is wrong in the antenna–a loose connection or a short somewhere. Dimensions were verified. Loose screws in the traps are a good bet. Despite the terrible image quality the dip can be made out above the band where it should have been below when it’s on the ground. The frequency of the dip is at 14420 kHz.

A week later a New-Old-Stock Cushcraft A3S was found on eBay, made before the company was bought by MFJ, and it was purchased quickly. Assembling the genuine Cushcraft felt like better qualtiy from the get-go. What’s more the elements don’t sag nearly as much. Expected reliability is much higher with this replacement antenna.

The elements don’t sag!
Now the dip is where it should be when it’s still on the ground, about 200 kHz lower than it will be when up in the air. Much improved. Ready to be raised.

Up in the air now.

The dip sure didn’t move as much as expected, from 13.830 to 13.914 mHz. Two hundred kHz was expected, which would have put the dip at 14.030. Although the dip is outside of the band the SWR at 14.074 is quite respectable at 1.48. Next time the tower is down the antenna will be adjusted to move the dip up into the band. Meanwhile here’s a look at 15 and 10 meters.
Dip is way outside the band and the SWR at the FT8 frequency is 2.0. How bad is 2.0? It is mainly a concern to the transmitter which likes to see SWR below 2.0. How bad is it for effective radiated power?

dB = log10(1-x) where x is the loss in per centage. A rule of thumb for 2.0 SWR is 10 per cent loss. Therefore log10(1-.1) or log10(.9) is .45 dB. Loss of output from a 2.0 SWR is .45 dB. That’s a loss that can be lived with.

In testing the antenna many, many FT8 qso’s were made easily. This is the best performing 15 meter antenna at this station. (Yay!) Ten meters is not as rosy.

Dipping outside the band above the band is a surprise. SWR at the FT8 frequency is 2.65. The transceiver we are using begins to reduce output at 2.0 but does not totally shutdown until SWR reaches 3.0. Several FT8 qso’s were accomplished during the testing but probably would have been more if the dip was closer to 28.074 MHz. Using the transceiver’s internal tuner was not tried. Again, next time the tower is down for maintenance the antenna will be adjusted. It sure is pretty to look at. The 160 meter gamma match support poles can be seen on the side of the tower. They are the four white things sticking out.

Post script, 8/19/2020: A bad trap was found and repaired. One winding had shorted. Next, the A3S was modified to change the 20 meter band to 17 meters. It was then mounted on the small 30 ft. tower and works well. On the big 60 ft. tower the original Hygain 203BA was repaired and reinstalled. It works well, too, and all bands 20 through 10 now have a good yagi antenna. The A3S turned out to be more of an adventure than expected.

RSPdx and SDRConsole

Next up in the quest for the perfect FT8 decoder is the SDRplay model RSPdx.  This is SDRPlay’s latest receiver.  Several software packages are capable of running this SDR including the one that comes with it, SDRuno.  Most popular is probably SDRConsole and it has the advantage of coming with a built-in server for remote access which is a requirement.  The RSPdx antenna input is connected to an external splitter and continues on to an active receive loop, the DXEngineering RF-PRO-1B.  The other output of the splitter is connected to the IC-7610 RX-IN jack.  A direct comparison of the number of FT8 decodes was made by running two copies of WSJT-X simultaneously.  The 7610 wins by a mile.  Here are screen snaps of the same pass for the two radios.  First, from the 7610.

2020-03-31 screen

Next, from the RSPdx.


Observing the decodes for pass 193730, the top image has 32 stations and the bottom 19. In this one pass the winner is clearly the IC-7610. The RSPdx might not be optimized considering it was just installed today.  Next step is to try to optimize the RSPdx.


Trying to find a way to optimize the RSPdx performance it was found by turning the SDRConsole gains up and the agc off the same number of stations can be decoded on each radio.  Gain has to be reduced to the WSJT-X application so it won’t be overdriven.  The number of decodes are the same on both receivers now and the SNR (signal to noise ratio) is within a few dB.  On RSPdx both the RF gain and the IF gain are set to max.  Even with the gains set wide open SDRConsole is not showing any signs of overload.  This result might indicate the signals from the active antenna, which are attenuated when they go through a splitter, are very weak.  Still the IC-7610 has no problem with the levels and the RSPdx perhaps shouldn’t either.  At least a way was found to make the performances equal.  It would be interesting to remove the splitter however that would produce meaningless results since the two receivers would then be on different antennas.  The new Flex radio should arrive soon and that will provide a third radio for comparison.