Noise Chase

For a long time there have been multiple signals on this remote base that appear to be digital hash and not legitimate radio signals. On the water fall they look like noise from switching power supplies. Considerable work has been done trying to get these signals chased down. Over the last year each switching power supply has been replaced with a linear supply or the switching power supply has been mounted in a metal box with ferrite chokes on the leads. Since the noise continued, looking elsewhere was necessary. The next suspects are the solar controllers considering they switch power on and off rapidly just like a switching power supply and considering they are about the only devices that haven’t been investigated. Searching the web turned up numerous reports that solar controllers are major contributors of rfi. The controllers used at the remote site* are specifically selected because of their FCC Class B certifications. They aren’t supposed to be generating rfi. That’s why they haven’t been investigated earlier. Today’s testing was very revealing. The controllers are generating tremendous rfi. Later it was discovered the interference occurred only in the mode where the batteries are fully charged. The controllers are in a state of “high voltage disconnect” to avoid overcharging the LifePO4 batteries. When the system is in a charge state there is no interference. Below is a picture of a water fall on 17 meters on a sunny day when the solar system is generating full capacity in a “high voltage disconnect” status.

Obviously those big wide bands of yellow-green are not supposed to be there. They are digital hash caused by something. Their huge signal strength indicates the source is probably local. Next picture is with one of the four controllers turned off. Observe the band on the right and the band in the center have disappeared as the waterfall continues to scroll down. Two bands on the left are still present.

Next, another of the controllers is turned off revealing an amazingly rfi free band. What a stunning difference. Apparently the other two controllers are not generating hash, for some reason yet to be determined.

Toroid chokes on the controller wires should be an easy fix. A hand full of Mix 31 ferrite toroid chokes was placed on the wires that come in and out of the controllers and no noticeable change occurred. Paraphrasing the captain of the boat in the movie Jaws, “We’re going to need a bigger choke”. Upon more Web scouring back home, an article was found that discussed a rarely mentioned bit of information about ferrite chokes.

“Ferrite material choking performance degrades in the presence of strong DC current. For this reason, it is better to pass both DC wires from the solar panels through the same snap on ferrite as this will eliminate the DC bias in the core.”

The chokes had been placed on individual wires in the initial test. About 15 amps of DC was present on those wires. Is this DC current enough to degrade the performance of the chokes? On the next trip to the site, both wires will be placed through the cores and the results will be reported here.

*The controllers used at the remote site are Morningstar PWM ProStar PS-30 and Morningstar MPPT ProStar PS-MPPT-25M.

Chokes On Both Wires Together

Next site visit and the first thing noticed is that different controllers are causing interference than the ones that caused it last time. Here is the first picture upon walking in the door without any testing.

Two lines of digital hash coming down the waterfall are from two of the four controllers, but not the same ones as last time. Next picture is after turning off three controllers and at the 7 second mark placing a choke on both wires of the 4th controller.

The choke clears up a good amount of noise but not nearly all of it. More chokes were added and there was almost no more improvement. Chokes don’t seem to be the answer.

Next topic is why only two controllers at a time cause interference. What is the difference? PWM and MPPT controllers are both contributing equally. It was soon noticed that the interference is coming from the controllers where the batteries are fully charged. When a battery is not fully charged and the controller is working hard there is no interference. When a battery reaches it charged state and the controller stops charging, it starts generating the digital hash. Solutions come to mind both elegant and crude. An elegant solution would be to monitor the modbus data output and watch for the fully charged messages. Use a microcontroller like an Arduino to turnoff the controller. That sounds like a lot of coding and debugging and time spent. Turning to the crude solution, that would be a relay on the solar input cables driven by a voltage sensor on the battery. When the battery reaches full voltage the relay would open and effectively turn off the controller. Call this solution the Rube Goldberg, band-aid, patchwork-quilt solution but voltage sensors and relays are now on order from China. The interference will have to be lived with for a month until the parts arrive.

While waiting for the parts from China an article surfaced that suggested trying 4 turns of both wires through one toroid of mix 31. That was tried and it did not reduce the noise noticeably.

In an act of desperation bypass relays were inserted in the solar panel input leads so each of the panels could be cut off completely if they were causing interference. This is the method referred to above as “Rube Goldberg”. The difference is the relays are controlled remotely from home over the Internet instead of by an Arduino monitoring the modbus or instead of a voltage detector. So far it works perfectly. Case closed. For now.

Lithium Batteries In a Non-Heated Environment.

When LifePO4 batteries are located in an unheated outdoor equipment shed in climates like Colorado their winter temperature can fall below freezing quite often. LifePO4 batteries will be damaged if they are charged when they are colder than freezing. A couple of uninviting options exist. First, the shed can be insulated and heated, which could be a lot of work and expensive. Second, the batteries could just not be charged until the temperature warms up. Even on a sunny day that typically means around noon and leaves only time for a partial charge on short winter days. A third option appears to be the least painful and that is to provide some external source of heat directly to the batteries through the use of heaters. There doesn’t seem to be any product marketed specifically as a LifePO4 battery heater. Researching alternatives, one possibility is the silicone heaters used to warm the bed of 3D printers. It is flat, comes in various shapes, voltages, power ratings, and it is inexpensive. A sampling was ordered and tried out. Finally selected is a 20 watt 12 volt heater shown below.

These pads fit nicely between alternating cells so each cell is adjacent to one heater. Leads are brought out and connected in parallel with wire nuts. Each heater draws 1.5 amps and in the lineup below 4 heaters draw 6 amps.

Getting this far was the easy part. Figuring out how to power the heaters is the next challenge. It was quickly learned that using the batteries themselves was a net negative. Heaters use too much power. The batteries don’t get fully charged before the sun goes down. An external set of batteries was tried but that just shifted the problem. After a few days the external batteries don’t have enough charge to run the heaters. Another failure was the use of timers to only turn on the heaters right before the sun came up. A new idea was needed. Time for …

Innovation

While the batteries are too cold to charge and the heaters are running, the solar cells are sitting idle wasting generated power. Why not use that solar power to run the heaters? Duh. This idea was tried and has been working successfully for several cold winter months. Power was tapped where the solar panels go into the solar controllers. The tap is the small red and black wires in the picture below.

Raw voltage from the panels is typically 20 volts and that might burn out the heaters. A 10 amp buck converter was inserted in the line to keep the voltage at 12 volts, one buck converter for each of the battery banks. A metal box limits the rfi emitted from the digital buck converters.

W1711 thermostats round out the installation. These little guys are set for 5 degrees Celsius which allows some margin to make sure the batteries are kept above freezing when the sun is up. When the sun isn’t up there is no concern because there is no solar power available to damage the batteries. What happens when there is solar power but the batteries haven’t warmed up above freezing? The Morningstar controllers were specifically chosen because of their feature called “low temperature fold back”. Even when there is solar generation, if the batteries are below freezing the Morningstar controller will refuse to charge the battery.

-0-

Impedances and SWR’s of Typical 43 Foot Vertical Antenna

To determine what tuners will work with a 43 footer the impedances need to be known for each band so tuners can be utilized that can handle those impedances.

For an interesting read on radials for vertical antennas see an extensive article by Al Christman, K3LC. http://ncjweb.com/bonus-content/k3lcmaxgainradials.pdf

The vertical tested here is a DX Engineering DXE-MBVE-5A 43 foot vertical. Radials are four pieces of welded wire fencing each 25 feet long laid flat and terminated on a DX Engineering DXE-RADP-3 radial plate. The fencing is 48 inches wide. A RigExpert model AA-55 was used to make the measurements. Each band was tested, 160 meters through 10 meters, except 12 meters. Here are the results including the (poor) snapshots of the AA-55 screens.

160 Meters

|Z| = 506.9 ohms (notice the R component is only 11.8 ohms)

SWR = infinity

80 Meters

|Z| = 216.6

SWR = infinity

60 Meters

|Z| = 58.6 ohms

SWR = 3.5

The 60 meter frequency of 5357 kHz is very close to the resonance of a 43 foot vertical. A dip at 5957 confirms the expectation.

A quarter wave vertical with a perfect ground system should have an impedance of 36 ohms. For curiosity the AA-55 was adjusted to the antenna’s resonance at 5957. Here is what this antenna measures:

|Z| = 45.7 ohms

SWR = 1.10

This reading of 45.7 ohms indicates a ground loss of 9.7 ohms (45.7 – 36 = 9.7) or approximately 10 ohms. This value agrees with the amateur literature for a typical ground system. One example is Phil Salas, AD5X’s presentation on The 43-Foot Vertical : “Assume 10 ohms of ground loss — Probably a much better ground than most hams have”. The efficiency calculation in the AD5X presentation should match the vertical in today’s test very closely. AD5X calculates 78%. For every 100 watts delivered to the antenna 78 watts is radiated.

An idea for improving this blog post would be to test a 43 Footer over a better radial system for comparison.

40 Meters

|Z| = 131.9 ohms

SWR = 4.8

30 Meters

|Z| = 636 ohms

SWR = 12.77

20 Meters

|Z| = 227.7 ohms

SWR = 17.03

17 Meters

|Z| = 102.7 ohms

SWR = 2.93

Notice another dip. This one at 17180 is the third harmonic of the fundamental frequency of 5957 kHz.

15 Meters

|Z| = 385.3 ohms

SWR = 7.8

10 Meters

|Z| = 61.2 ohms

SWR = 1.23

Conclusion

Matching 30 meters should be the most difficult at 636 ohms but that’s well within the range of most automatic tuners. An additional challenge should be 160 and 80 meters with their infinite swr’s. One of many good tuners to use as an example is the MFJ 998RT. It is specified to handle impedances from 12 to 1600 ohms and swr’s up to 32:1. In practice with this model of tuner installed on this 43 foot vertical it matches beautifully on 80 thru 10 but not on 160, maybe because the R component is only 11.8 ohms on 160. Optional coil and relay kits are available to add 160 meters. No matching problems have been noticed on 30 or 80.

A note of caution. Just because an antenna matches does not guarantee it is getting out possibly due to objects nearby or due to radiation patterns on each band. It may match perfectly at 10 meters but all of the energy is straight up to the clouds, with only a little radiation at low angles.

On the other hand antennas with a poor match still can make contacts with even a small amount of power being radiated, although inefficiently.

Insolation Monitor Project

Insolation is a big word meaning how much sunshine is there? That’s an interesting bit of information when one is trying to keep batteries charged with solar panels. It’s just a cross check to see if the charge amperage is consistent with the amount of sunshine each day.

The project consists of a photo cell and an Arduino-emulation device called a ESP32. The hardware looks like this. Very minimalist. The breadboard is just to hold the ESP32 in place. A USB cable brings in 5 volt power. The round disc is the photocell.

The ESP32 connects to the Internet over wifi and uploads data every 10 seconds using the protocol MQTT, “the standard for IoT messaging” . Data consist of the resistance of the photo cell. A server processes the data and provides a web page GUI. The server is called a broker and in this case the broker is provided free for personal use by Adafruit. The ESP32 is also a product of Adafruit. The ESP32 cost $20 at Microcenter.

Below is a screenshot of the GUI page, putting it all together.

Ideas for the next version: Mount the ESP32 inside a solar powered yard light and eliminate the USB cable. Disconnect the light and power the ESP32 instead.

For a closer look the link is here:

https://www.amazon.com/gp/product/B07ZSC6TNB/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1

This solar powered led yard light was chosen at random and it was chosen for it’s reasonable price. When it arrived it looked like this:

Opening it up revealed a pleasant surprise which had not been mentioned in the sales description. It has an actual 18650 lifepo4 battery. Perfect. This battery should power a ESP32 for many hours. The ESP32 draws 100ma at 5 volts which is one half watt. The 18650 is rated at 4.4 watt-hours (4.4 watts for an hour). That would be 4.4/.5 or 8.8 hours. In reality that time would be extended by the ESP32 going into sleep mode when it’s not sending data. It would never need to send data constantly for 8.8 hours.

Unfortunately the controller board that comes with the unit will have to be discarded because it doesn’t have the features needed for the ESP32.

Will the ESP32 fit inside the waterproof cabinet? Looks like it will.

In fact, a LORA board will fit very nicely, too, and that can come in useful for the next project, building a LORA network.

Reading up on how to power a ESP32 from a solar yard light has revealed some challenges but also solutions. First, the cell voltage is 3.7 as can be seen in one the pictures above. The ESP32 needs either 5 volts or 3.3 volts, neither of which is close to 3.7 volts. What is needed is either a boost converter to get up to 5 volts or a buck converter to get down to 3.3 volts. The battery voltage of 3.7 is nominal. The voltage can vary from 4.7 to 3.2. When it’s 3.7 or above the buck converter works fine but when the voltage drops below 3.7 the buck converter shuts down. That rules out the 3.3 volt option. Looking at the 5 volt option, there is a possible solution. Connect a standard charge controller between the solar panel and the battery such as the TP4056 Charging Module 5V Micro USB 1A 18650 Lithium Battery Charging Board with Protection (5 pieces for $5.95 on Amazon) which looks like this. It’s output will vary with the voltage of the battery.

Boost converters exist ($7.29 for 5 pieces on Amazon) that will provide a constant output of 5 volts with an input as low as 1 volt or as high as 5 volts and look like this.

The concept is the charging module will regulate the solar input to keep the battery properly charged. As the battery charges and discharges the output voltage will vary. The boost converter will take that varying voltage as input and it will output a constant 5 volts.

Moving on to the next step, those parts will be ordered today. Total additional cost $2.86 per unit.

The Short Vertical Antenna by Jerry Sevick, W2FMI(SK)

A very short antenna had about the same power gain and radiation pattern as a full half-wave antenna.

“My first interest in the short vertical antenna began when my thesis advisor at Harvard, Professor R.W.P. King, developed the full theory of the short antenna. In it he disclosed that a very short antenna had about the same power gain and radiation pattern as a full half-wave antenna. The main difference was that the resistive component, the radiation resistance, was very small in comparison. In turn, the short antenna has a very high capacitive reactance, which has to be cancelled by various loading techniques.

The theoretical results show that the power gain (when compared to an isotropic radiator) for a very short antenna, even one that is less than 1 foot high on 40 meters, is 1.5. This increases slowly to 1.513 for an 11-foot vertical. These gains are to be compared to about 1.62 for a resonant 1/4-wave vertical. This difference amounts to less than 0.4 dB or 0.07 S unit, based on 6 dB per S unit.

Base loading,[ as shown in Figure 2-3 above ], yields the lowest value. Top hat loading yielded the largest value of radiation resistance for a particular height. A top hat is also considered the most low-Q loading element. The reduction in height due to top hat loading (with a conducting wire around the perimeter) is approximately equal to twice the diameter of the top hat. A four-spoked wheel approximates, to a good degree, a solid disk. Doubling to eight spokes only improves the loading by about 9 per cent. Thus, a few radials on the top of a vertical, which are electrically connected by a perimeter conductor, are very effective.

The data were obtained by essentially cancelling out the reactance and measuring the resistive value with a simple impedance bridge. Because I used an extensive ground system together with base loading coils with Qs approaching 900, the resistance measured was actually that of the antenna itself. At the radial point the input resistance approaches the theoretical value of 35 ohms which strongly indicates low earth loss and reliable data.”

Summarized from a book by Dr. Jerry Sevick, The Short Vertical Antenna and Ground Radial, CQ Communications, 2003.

Fact checking Dr. Sevick there is a book published by ARRL written by Robert J. Zavrel, Jr. called Antenna Physics: An Introduction. From pp B.2: “A short vertical’s value will be about 6 ohms for a 1/8 wave physical height. For a perfectly top loaded 1/8 wave vertical, value becomes about 24 ohms…a fourfold increase in radiation resistance when compared to an unloaded simple vertical of the same physical height” These values agree very closely with those in Figure 2-3 above.

The above excerpts have been field tested in a 160 meter vertical antenna constructed in 2018. This vertical has been very successful and is still in use today. It has eight radials, each 100 ft long made of 4-ft wide welded wire fencing laid flat on the ground. The vertical element is made of 43 ft tall aluminum tubing tapered to average 1.5 inches in diameter. The top hat is made up from 6 102″ CB whip antennas with hookup wire connecting the tips.

Inside the box is a matching coil which is tapped with a coax feedline at the 50 ohm point. This setup is good up to about 300 watts. It needs to be hardened before it will get up the legal limit.

1.5 KW Amplifier Off Grid

Running a full kilowatt from battery power has it’s challenges. This note steps through the design and installation of the amplifier, inverter, battery bank, and solar panels. First, the amplifier. It is a Flexradio 4O3A PGXL. To reach 1500 Watts output it requires 220 Volts AC. It does not run on DC. Here it is waiting for some AC while sitting next to the Flexradio 6600 exciter .

The next item is the inverter which provides the AC. A Victron Energy model Phoenix Inverter Smart 24/3000 has been chosen. It provides 3000 watts at 230 volts when connected to a 24 volt battery. This inverter was chosen because it has RFI certification, a reputation for meeting specifications, and it was less expensive than some others.

Next component is the 24 volt battery bank. LiFePO4 lithium ion batteries were chosen, of course. The capacity of each cell is 180 AH. Sixteen cells are connected in parallel/series to provide 24 volts DC with a capacity of 360 AH. Aren’t they pretty?

Finally, the solar panels. This array is four 100 watt panels wired in series/parallel to provide enough voltage and current to charge the batteries.

It really works! This is the control panel on the amplifier. Notice the output power is shown in the upper left corner, 1512 watts. Id is the current on the drains of the LDMOS finals, 43 amps. It is also nice to notice that under the load of a full kilowatt the inverter is holding the AC at 228 volts. With no load the voltage is 230 volts which means only a 2 volt drop at full output.

A clamp-on ammeter on one lead of the AC shows 9.3 amps of current.

One concern during the design phase was whether the AC connector on the amplifier was heavy enough. It is only a type C13 which is a 10 amp connector. Today’s measurement of 9.3 amps and the fact that the connector stayed perfectly cool to the touch is reassuring.

Next a look at some of the “glue” holding the stages together. The batteries are protected by a BMS. BMS stands for Battery Management System. It’s the big red thing. It will cut off the power if the voltage is too low or too high and it will try to keep the cells balanced. Electrically it goes between the negative terminal of the battery and the negative lead to the inverter. One small red wire goes to each cell to keep track of the state of the cell.

To the left of the BMS is the shunt resistor for a Victron battery monitor. A battery monitor is not required but makes it easy to keep track of the battery’s state-of-charge remotely. The black thing in the upper left corner is a terminal block. A copper strap connects between the terminal block and the shunt resistor. These items together make up the negative leg of the circuit.

In the positive leg there is only one component. That is a 250 amp fuse. Victron specified big 1/0 cable for the inverter DC power, and specified the 250 amp fuse.

One other piece of glue is the AC circuit breaker. A GFCI breaker is connected between the inverter and the amplifier to protect the inverter from overload and to protect humans from electrocution. It is 16 amp 240 volts. Don’t hunt for this unit in the 2020 NEC code. It is not a product designed for the U.S. market. It is designed for the 230 volt standard in Asia and Europe. This project is using European standards rather than U.S. The main difference is this is not “split phase” as in the U.S. which means there is no third wire on the 220 volt circuit. Why is it done this way? Because with the U.S “split phase” wiring a second inverter would be required to get the third wire, approximately doubling the cost. There is no safety or any other reason not to use the European standard. This system is entirely off grid and therefore NEC code is not required. Safety is a big concern and all European standards have been adhered to for safety.

Some observations

Sizing and the capacity of the components is a big part of any design. Today’s numbers provide some insight. The amplifier was drawing 9.3 amps AC at 228 volts. That’s 2120 watts (watts instead of VA because power factor is assumed to be 1 due to automatic PF correction, so watts and VA are equal). The amplifier was producing 1514 rf watts which is an efficiency of 71%. This calculates to 92 amps DC from the batteries (unfortunately no dc reading was taken). Looking next at state-of-charge (SOC), good practice for LifePO4 batteries is to limit depletion to 20 per cent SOC. That is, operate with SOC between 20% and 90% which provides 70% of rated capacity. Usable capacity would therefore be .70 X 360 AH or 252 AH ( or 6678 watts at 26.5 volts). Under a constant load of 92 amps the batteries would be expected to last 2.7 hours. With a 50 per cent duty cycle mode like FT8 the batteries should run at least 5 hours. There are no plans to operate at 1500 watts on FT8. This is just a worse case example.

Concerns would include whether the 4-panel solar array (400 watts) is adequate to maintain this large battery. That would not be the best way to look at it. Consider instead whether the array is adequate to provide typical amplifier operation. If the amplifier is operated two hours a day at 50 per cent duty cycle that would use 92 amps ( or 2438 watts at 26.5 volts). The panels generate about 2 kw on a good day (400 watts X 5 hours of sunshine). That is close to the 2.438 kw of typical usage. Good to go. On cloudy days the batteries are oversized so they will have capacity to operate for more than one day without sunshine. Winter is close and some hard numbers will soon be available. If needed the existing PWM charge controller could be replaced with a MPPT controller for 30 per cent more output. After a few weeks of operation in November the batteries have recharged to 90% every day when there was sunshine. As of late December during the solstice all is still functioning well.

A lot of effort and expense went into this project but it is proving that running a kilowatt from batteries off the grid is possible.

November 22, 2020 – The amplifier has a problem. It is refusing to transmit on all bands except 160 and only puts out 500 watts on 160. This problem started after receiving a message that SWR was too high and the amp should be shut down. The amp was quickly shutdown but has not worked correctly since. It was connected to the A3S antenna on either 15 or 17 meters when the failure occurred. Possibly the amp was putting out too much power for the A3S and a trap shorted out. Apparently the amp’s protection circuits failed. A ticket has been opened with Flexradio but Covid and Thanksgiving have delayed the response.

December 12, 2020 – Amplifier is fixed and back in the shack. Flexradio’s warranty tech support is amazing. They requested a remote test and determined from the results that it needed new finals. The amp was shipped to Austin, repaired at no charge, and shipped back in two weeks time. What a quick turnaround. Kudos to Flexradio.

The finals are MRF1K50H LDMOS transistors each rated at 1.5 kW dissipation. Mouser has these listed for $900 each in single quantities.

Update – June, 2021: The amplifier system made it through the entire winter without any power problems and all worked as designed. To avoid destroying any more final transistors FRStack3 was installed. FRStack reduces the exciters output power when an amplifier is placed in operate mode, protecting the finals. It is performing that function well. Lesson learned.

Adding a Web Controlled Rotator to A3S

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

Status: All work is completed.

A new Yaesu G-450ADC rotator was ordered from GigaParts. Still needed are the rotor plate, the cable, and the interface to make it remote controlled. Cable and interface are on order from DXEngineering and HRO. This project has hit a snag. Rotor plate is special order and has a November ship date. It has not even been ordered and by the time it gets here the weather could be too wintry to install it.

Universal Towers saved the day. An order was placed directly with them today and they promised a much earlier delivery date.

“The rest of the story” is this tower is decrepit. It was used 10 years to hold up wireless Internet antennas on a windy hill. It has two blow outs from being overloaded. Even though the blowouts have been repaired the concern now is it might not be able to keep the A3S in the air. Torque is the tower killer when wind makes a beam twist. An overloaded tower can fail from that twisting motion. When this tower is down for the rotor installation a torque arm will be attached in an attempt to reduce the twisting motion.

Remote Controlling The Rotator

All parts have arrived. The Yeasu G-450 rotator is the new DC version which makes absolutely no detectable difference in the operation but it makes lightning protection easier. Relays had to be used on the AC rotator because the AC voltage was too high for the 26vac/31vdc MOV’s on hand. Perfect for the 20 volts DC the new version uses. Modifying the controller for access over the Internet looks like this:

Actually the controller is not modified. A few wires are tacked onto existing terminals inside. Wires are brought out through an existing hole. The controller could be easily restored to original. In the picture above, the green thing at the bottom is the remote interface from RemoteRig.com model RCU-1216:

http://www.remoterig.com/wp/?page_id=840

The interface talks to the RemoteRig 1216H Webswitch and will get mounted inside the controller. A Webswitch already exists at the remote site to provide remote access of the first rotator on the taller tower. That missed getting written up. That’s why this is being written up now. The unit has the capability of two rotators so all that was needed was this interface to the Webswitch. The installation just needs some hookup wire and a solder iron.

There is no brake release button on Yaesu control boxes so a brake release connection is not needed. Only the Pot potentiometer connection and the two motor activation buttons are needed. A data pair and a power pair connect back to the Webswitch.

For this rotator the two jumpers, P5 and P6, are opened up to accomodate the voltage on the Yaesu rotator for direction indication potentiometer. Voltage maxes at 1.3 volts on the pot. Next attach a little Blue Tack or 3M gray stickem to hold the interface in place.

Stick it to the inside of the cabinet and you’re done. It should look something like this:

Coming out of an existing hole in the back are two pairs of wires. One is for 12 volts DC. The other is the 1-wire data pair (1-wire really means 1-wire and ground). Next step is to install and test at the site.

Today the rotor plate was mounted and the rotator is mounted to the plate. A short piece of aluminum tubing was cut to go from the rotator to the mast. A hole was drilled for a bolt to keep the mast from twisting and slipping.

The tower was raised a few feet to see if it is too heavy with the rotator. It is noticeably heavier and harder to lift but not impossible. None of the gin components complained. The rotator only weighs 7 pounds and the wire is probably 2 more pounds. Another 9 pounds is apparently not overdoing it. Next the cables will be extended where needed for slack and they will be dressed. The bolt will be installed. The rotator connector will have a waterproof boot installed. The balun will be reworked to provide enough slack for turning the antenna (the balun is near the center of the picture with cable ties holding it to the tower leg). The rotator cable will be run through the cable entrance at the shed and MOV lightning protection will be provided. Inside the shed the controller will be connected to the RemoteRig Webswitch and all will be tested. It will be really nice to be able to turn this beam in the direction of the signals as they change.

Today, the balun was rebuilt by replacing the RG-58 windings with LMR-400. It is still 5 turns through a stack of 4 Mix 52 ferrite toroid cores. It looks like it can handle a lot more power now. Only the common mode current is flowing through the toroid.

Proving the balun is working is a matter of observing the signal pattern on pskreporter. In this case it is a nice flashlight beam shape in Europe indicating the balun is doing it’s job. It’s job is to keep common mode currents from generating stray radiation which distorts the pattern. No pattern distortion, the balun is working.

The rotator mounting is completed and the cables are dressed. Ready to raise the tower.

Back up in the air the rotator turns the beam perfectly with no issues. As for remote control, a relay is being used to switch between the two rotators. The other rotor turns the 203BA 20 meter beam on the big tower. One rotor at a time is accessible over the Internet.

This project is completed.

160 Meters 4 Square Receive Antenna

Project 6 of 7 for October, 2020 – projects to keep sane during Covid-19 Lockdown

Status: Completed

For the virtual Dayton Hamvention this year Contest University had some wonderful online presentations. One was especially interesting to someone who still has countries needed on 160, W3LPL –  “Effective Low Band Receiving Antennas”. A video is still available on YouTube. Frank Donovan, W3LPL, listed receive antennas from the smallest to the largest along with ranking their effectiveness. The best of size, cost, and effectiveness looks like the 4 square high impedance active antenna. DXEngineering offers one in a bundle with all possible parts needed, DXE-RFS-SYS-4S. One is on order.

In Frank’s excellent presentation only one antenna performs better and that is twice as big and only has 1.5 dB Receiving Directivity Factor (RDF) improvement. The Hi-Z 4square appears to be the best bang for buck.

As of today grounds rods to mount the antennas have been made. A 1000′ roll of direct-bury CAT-5 cable is on hand to run power and control signals. A location has been selected about 500 feet north of the transmit antennas. A scheme to reduce the number of control wires so direction can be switched remotely has been invented. This receive antenna should coordinate nicely with the omega-matched tower transmit antenna upgrade this year.

One concern is how far apart to put the verticals for the best performance. The DXEngineering user guide says 135′ or one quarter-wave is optimum for 160. Other references says 80′ or 88′. An email was sent to Frank, W3LPL, to get the word from the master himself.

Hi Mark,
Optimum 4-square spacing for 160M receive is 67 feet.  Wider spacing produces higher signal levels but also higher side lobe levels.


Much more important is maximizing the spacing from resonant 160 metertransmitting verticals, towers more than 90 feet tall power lines andhomes or buildings that may contain RFI sources.   I would try for at least one thousand foot spacing.
Good luck!


73FrankW3LPL

Five hundred feet is do-able but 1000? Hmmm. We’ll see with a site visit tomorrow.

Cable was pulled from the shack to the 4-square site today which is 1000′ away. One thousand feet seems like no problem after today’s site visit. The site is very close to the Field Day site for 2019.

https://w0qlremotebase.wordpress.com/2019/06/07/field-day-2019/

One cable is quad-shielded RG-6 and the other is direct burial CAT-5. One of the CAT-5 pairs will be used for direction control. The other three pairs will be grouped to provide power. Resistance of a single 24 gauge wire 1000′ long is 26 ohms at room temperature. Three wires grouped together will cut the resistance to about 9 ohms (8.77 to be exact). With 1 amp of current the voltage drop would be 9 volts (E=I X R). To provide 12 volts to a device the supply voltage will need to be 21 volts. Fortunately the battery voltage for the new inverter will be 24 volts. A linear buck converter (LM-317 voltage regulator) can be installed at the 4-square end and provide a regulated 12 volts. Per the instruction manual:

The DXE-RFS-3 phasing unit uses and distributes the voltage to power the active antenna elements.
For all four active elements, a nominal +12-15 Vdc at 250 mA current is required.

At only 1/4 of an amp load the voltage drop would only be 1/4 as much or 2.25 volts. If a 13.35 supply was used the voltage at the 4-square would be 11 volts. That might work but might be unreliable. Using a 24 volt supply and a buck converter is a more reliable choice.

Today the ground rods were driven for mounting the verticals. They were measured out to be within 1″ accuracy, using the 67′ side lengths recommended by W3LPL. The sides are precisely east- west and north- south. That makes Europe at 45 degrees the default direction.

Status: 4-square arrived today (some assembly required). The Quad Shield RG-6 cable has been measured out as accurately as possible and cut to length at home for the delay lines.

Next the excellent quality Snap-N-Seal connectors provided by DXEngineering were crimped on.

Tomorrow the cables will be taken to the remote site and connected. The verticals will be installed on the ground rods.

Installed, here is one of the verticals:

This is the hub at the center of the four verticals. The three delay lines are coiled up and strapped to the post. The gray box on the far side contains the voltage regulator (buck converter). The black box in the foreground is the DXEngineering control box.

Inside the gray box is a LM317 voltage regulator or buck converter. It converts the 24 volts input to a 12 volt output. A LM317 is used instead of a LM2596 because the LM317 is linear technology (analog) and does not generate digital hash like the LM2596. This method was chosen to carry 12 volts over a 1000 feet of CAT5 to overcome it’s inherent cable loss. In the picture below the blue/white pair carries the BCD data to switch the relays that control the direction.

Testing to see if the design works in the field shows good results. The gold thing is a 50 ohm resistor which simulates the load of the relay controller. (E = I X R, E = .25A X 50 ohm, E = 12.5 volts).

With the weeds looking very much like vertical antennas a wide shot of the 4 square doesn’t show much. It blends in quite well.

Performance is extremely directional as expected. A station to the northeast that comes in S9 completely disappears when the relays are switched to null it out. Come on winter and 160 season. It will be fun to use this.

Next, FT8 signals on this antenna were compared to the same signals on the 160 meter transmit verticals. Signals are stronger on the transmit antennas but there is no way to null out unwanted signals. A preamp is under consideration to bring up the gain where it will be even with the transmit verticals. The loss in 1000 feet of RG6 may need to be compensated for.

Status: completed (but always looking for improvements). To try to get a little more gain on 160 the jumpers were put in place to peak the response on that band. Gain is still low but it is working as designed.

January, 2021 update: Performance is amazing. A YouTube demonstration should be produced. A preamp was added at the 4 square to overcome the loss in the 1000’ of coax.

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: https://en.wikipedia.org/wiki/WSPR_(amateur_radio_software)

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 WSPRnet.org 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 WSPRnet.org is below.

It’s working! Check it out at wsprnet.org. 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.