Tag: wspr

Solar Powered WSPR Transmitter

A while ago I completed the QRP labs WSPR transmitter, you can read about that project in this article. I wondered how easy it would be to set this up in the garden, solar and battery powered.

The QRP labs unit transmits around 200mW, and the idea was to have this running 24×7 transmitting around 80% of the time and band hopping. I have the multi-band option, with BP filters for 3.5, 5, 7, 14 and 21 MHz.

Searching eBay I found a low costs solar charge controller and solar panel. I also needed a voltage regulator to drop the 12v to 5v for the QRP labs unit.

The items I selected are not “high quality” it was more proof of concept. The charge controller is in fact so high quality even China didn’t put their name on it.

The charge controller is marked as follows.

10A Advance Pulse Width Modulation (PWM) Charge controller:

  • Automatic 12v/24v recognition (need 2 panels to run 24v systems)
  • Fully 4 stage PWM charge management
  • Day/night recognition
  • Dual mosfet reverse current protection
  • Protection from over-charging, deep-discharging and reverse connection from both solar panel and battery
  • Protection from short circuit and over current
  • LED indicator to show charging/fault/battery status/load status etc
  • LED digital display to show the load work mode and status
  • Self-consumption: 10mA or less
  • Working temperature: -35C to 60C
  • Working Humidity : 10% to 90% RH
  • Size: 14 x 7.5 x 3cm
  • Weight: 180 g
  • Terminals for wire up to 6mm2

The solar panel is marked 10w

The QRP labs kit was connected to the GPS module, battery and a random bit of wire and placed in a plastic bag. I left it running 24×7 for 8 days and then checked the battery voltage.

The voltage showed 12.7 volts, I consider that to be a success.

MF WSPR Reception

Following on from the previous post, WSPR reception continues mostly 24×7 with a focus on MF. As previously described the setup has been operating for a couple of weeks now, and its a good time to review the WSPR spots.

Best DX Spotted

472 KHz

Call Grid Pwr km az
 WA4SZE  EM65 0.2 6826 45
 AA1A  FN42pb 5 5281 53
 EB8ARZ/1  IL18uk 0.2 2915 24
 EA7HPM  IM67xj 0.2 1650 15
 EA5DOM  IM98xn 1 1446 1
 HF7A  JO91oq 0.2 1308 277
 EA4GHB  IN80hu 1 1222 12
 LA8AV  JO59cs 0.2 1105 219
 EA3AER  JN12kd 1 1066 350

52 unique calls received, you can download the complete list online.

Setup includes WSJT-X band hopping (via CAT) Wellbrook loop antenna, Elad SDR receiver.

WSPR Reception 24×7

WSPR reception 24×7 has always been something I have wanted to try. The problem is trying to find a transceiver, computer, antenna combination that will allow this with minimum fuss.

472 KHz Reception



You won’t need a very high spec computer, but if you are leaving it on 24×7 low noise and power consumption will be high on the priority list. A laptop is one option, although they often have fans and may not be noise free, so you may want to consider one of the new breeds of “minicomputer”. Low power consumption, and low noise with many running on 12v. I opted for a second-hand minicomputer, silent running and powered from 12v. It uses the Intel Celeron J1900 with 4 cores and I added a 128G SSD so it boots in 3 to 5 seconds. These are good value and should provide a reliable machine, with a very small desktop footprint.


If you looking to cover multiple bands then you need a broadband receive antenna and this typically doesn’t work well on a simple unmatched G5RV or doublet antenna. I completed some receiving tests using my doublet and a Wellbrook and found the loop outperformed the wire antenna significantly below 5 MHz. You can read more about receiving loop antenna on this page. George M1GEO has provided a very interesting article and instructions on how to build a low-cost Wellgood loop on this page. The Wellbrook loop I use seems especially good at 136 and 472 KHz, providing some interesting spots on these bands. The antenna is shared with my online SDR providing connectivity to the ELAD and Kiwi via a 2 port antenna splitter.


I use the ELAD SDR, as its very low power consumption, and I can CAT control the band changes to suit the time of day.  The radio is connected via USB to the PC running Joe Taylor WSJT-X program.

The transceiver draws around 500 mA on receive and the Mini PC  around 600mA at 12V. I have used a 12v SMPS designed as a computer power supply, its rated at 5A and runs cold.


In the last 24 Hrs

Receiver antenna and band changes biased towards MF and LF

Typically adding 1,000 spots per day

150 spots on 472 KHz and 23 on 136 KHz

I hope to add TX soon, using 200mW from the Ultimate 3S beacon transmitter


QRP labs Ultimate 3S Part 2

Welcome to Part 2, the project started in Part 1 and this covered the initial build and setup of the Ultimate 3S. Changes to the TXM are possible but require you to manually change the LPF and input a new frequency via the software.

QRP labs have developed a relay switched LPF kit, and Part 2 covers the assembly and operating of this unit.

Building this kit twill allows you to increase the bands from 1 to 6. The relay kit has space for 5 further LPF, and you can continue to use the 1 from the original kit giving you a total of 6 band operation.

LPF are available for all bands from 136 Khz to 50 MHz.

I chose to order and make up the following 3.5 MHz, 5 MHz, 7 MHz, 10 MHz and 21 MHz. The process of assembling the  LPF is very easy, the circuit is standard and simply requires different values of capacitor or inductor to achieve the correct roll off characteristics. The  Low Pass Filter kit is based on the G-QRP technical notes, a design by Ed Wetherhold W3NQN. Ed has published an interesting article on band pass filters published in QST dated 1998.

Winding the toroids without doubt takes the longest, and with 15 to wind I spaced it out over the course of the day. Here you can see the 5 MHz and 10 MHz (left) LPF assembled and ready for installation.

The winding of the toroids for the LPF was interspaced with adding the relays to the band switching relay kit.


The kit uses Panasonic TX2-5V relays, the kit includes 6. One is to mount on the Ultimate 3S main board.

Here you can see the kit is completed, and awaits LPF. Its important to note the highest frequency LPF must be fitted in position 1. The positions are numbered 1 to 5, with position zero being on the main Ultimate 3S board.


The next stage is to mount the relay LPF on top of the main Ultimate 3S, the system has been designed to stack on top of each other, providing a very neat solution. In this example I have 3 LPF fitted, with room for a further 2. Its seems logical that you should arrange the LPF in band sequence, I don’t think this is strictly necessary but it helps the planning and programming later.


The completed item is installed, working from right to left 21, 10, 7, 5 and 3.5 Mhz. I also installed a SMA socket onto the relay board, as the RF is now routed from here after the expansion. RF can be coupled in one of 3 ways, the board has options for SMA upright, SMA side mount and pin connections. The SMA upright doesn’t provide enough clearance with the LPF directly above it, so you could try a right angled SMA socket. I didnt have one so opted for the SMA mounted on its side.

The RF is now routed to the side angled SMA, here you can see the modular design with the GPS module to the top.

QRP labs to stock cases for the completed project, and I have recently ordered one to provide the finishing touch.



Further thoughts and lessons learned.

I need to investigate why the o/p power has dropped on 14 MHz, as a single band unit I was getting 250 mW, but this has recently dropped to 100mW. I suspect this may have something to do with the LPF arrangement, as all RF must now pass via the LPF placed in position 1. This shouldn’t present an issue as LPF 1 should pass anything below 21 MHz, but without a spectrum analyser or a Vector Network Analyser I haven’t been able to investigate further at this stage. Other bands have an o/p between 200 and 300 mW.

Its worth mentioning again you need to take out the original U3S board and add a relay and diode before LPF zero. This isn’t required unless you have added the LPF relay kit.

You will need to cut jumpers previously installed on the U3S, you need to cut W0 – W1 and W2 – W3.

Configuration in the menu system for multi band operation is a little fiddly, but once you understand the steps needed its easy enough to follow.

You will need to change the menu option  TxS to increase the amount of transmit slots from the default 3 to 6 in order to make use of the enhanced LPF.

Typical display options explained. starting from top left

1] is the sequence number, this indicates its the second mode option (zero then one)

1 This indicates it will select LPF 1 (check this corresponds to the correct frequency LPF) For example number 5 here would select the LPF in slot 5

021,096,125 is the frequency for TXM. You can find a complete list of freq in part 1 of the ultimate 3S construction.

JO01 is my locator, shown when in txm

23 is my power in dBm

93 is the symbol number (WSPR is 162 for a complete message)

0 is the tone currently being sent.

If you want to add additional tx sequences, then this can be done by editing the menu system, just ensure you have the correct frequency and LPF slot set.

This is covered in great detail in the firmware manual.

Ultimate 3S QRSS/WSPR project (Part 1)

Welcome to Part 1, this covers the initial build of the U3S, Part 2 covers the addition of the LPF relay board.

Some month ago I purchased a Ultimate 3S QRP transmitter from QRP Labs. The latest version is the ultimate 3S and it comes with a number of options.

Over the christmas holidays I decided to make the project, inspired by Dave G7UVW and George M1GEO activity on QRSS over the holidays. I have used WSPR before from home, but really wanted a QRP transmitter that I could leave on over night, without running the main radio. The answer is one of these kits, as they are very low power consumption, and flexible enough to run multiple modes / bands.

The transmitter can be configured to run on any band between 2200m to 2m (136 KHz to 144 MHz)  with a suitable low pass filter. I have linked a table showing actual TX frequencies online.

I had purchased the Ultimate 3SSi5351A synthesiser module, Low Pass Filter for 14 MHz and the QLG1 GPS unit. Other kits / options are available, and the project is modular so you can pick and choose the options that work for you.

I found the instructions really easy to follow, and coupled with the pictures component identification was easy. I did use a magnifying glass to check some of the component values, and the “quality” of my solder joints. Starting with the GPS module, and then the synthesiser I found the build easy to complete. I then moved onto the main 3S transmitter, this again has various options, but I decided to get the basic version running with one transistor before considering other higher power options.

I found having an LC meter helped when winding the torriods, but the values didn’t seem to be too critical so this was more of a confidence check.

You can see the completed LPF on the left, very compact and the instructions suggest this is good for 10w.


Here you can see the completed main board, with synthesiser and LPF installed. You can see on the bottom of the board the single transistor installed, with space for more.

The instructions suggest a stable 5v power supply is required for the single transistor version, and looking around the junk box I found an obsolete USB blackberry phone charger. This seemed ideal, so off came the USB plug, replaced with some wire and heat shrink. This also provided a current limited supply, with the USB charger rated at 1A being more than adequate for the TXM.

Once built, assembled and powered the kit goes into diagnostic mode (assuming no blue smoke). Mine powered up and worked without any further modifications, but any issues are likely to be mine as the kit is very well designed.

This provide the initial indication all is well, next you need to adjust the display contrast and the the PA bias.

The instructions suggest you should expect around 250mW on 10 MHz, with the power falling away as you move higher in frequency.


I found I could achieve 250mW with ease on 14 MHz as can be seem here on my QRP power meter.

The next stage was to get it on air, this took a little longer than expected, as getting a GPS fix indoors required some careful positioning of the patch antenna. I also found the menu system a little difficult to navigate, its not actually difficult but you have so many options its a little overwhelming to start.

I think the priority should be getting the GPS feed configure, once this is correct the display shows a heart beat. The default option is this is not configured in the software, and so even connecting up the GPS unit will not start this process. The next is frequency correction. If you have the GPS unit fitted this can be completed automatically, but you still need to setup the calibration time, and frequency correction steps in the menu.

Calibration completed showing 27.004.382 (4.382 Hz correction) and the hart beat symbol for GPS lock.

On my first attempt I had not set this up correctly, and while it was slowly correcting the frequency the number of iterations would have been extremely high before I had anything like an aligned txm.




I found the FAQ helpful, as this told you the specific steps to take and values to input.  I set the operating frequency to 14.0971 and after a few calibration cycles it worked!

Here you can see the unit is transmitting WSPR from JO01. The first spot I received was from KK1D at 5474 KM, not bad for 250 mW.


Its always nice when you build something and it works 🙂

Other suggested frequencies

Update 17/1

The TXM has continued to work flawlessly without issue. Ive move the antenna over to a dedicated 1/4 ground mounted roach pole with 4 radials. The power has been checked again and its 250 mW, the best spot I have is from 6500 KM away into Asiatic Russia to the East, and West around the same distance into the USA.

How far does 1mW go ?

Do you remember playing as a kid with the short range 49 MHz walkie-talkies ?


49 MHz Walkie – Talkies

We used to play with these often as a kid, and the range was shorter than your voice ! With an output between 5 and 50 mW these could often struggle to communicate more than a few meters.

Still the fun we had trying to extend the range.

The Elad FDM-DUO has a 0 dBm o/p on the rear that will provide 1mW out from 100 khz to 156 MHz


The Elad uses a SMA female connector on its rear, and using a ebay special connector I routed this into my ATU and doublet antenna matched for 7 MHz. I wanted to run WSPR at 1mW and see what decodes I could achieve.

Over the course of the next couple of days I ran the Elad both at night and during the day. It was hard to achieve any decodes at night, but in the day I was decoded on many occasions from stations in the range of 50 to 770 KM.

Best DX was 2 spots by Denmark based station 5P1B at 770 KM.

The following statistics provided by WSPR.net database


 Stations who decoded M0TAZ v Signal @ 1mWsignal m0taz

Stations who decoded M0TAZ v Distance @ 1mW

decoded m0taz


You can download the free WSPR software provided by K1JT online. WSPR reports are uploaded and databased online.

73 Dave M0TAZ