Hello, my name is Mark (W5TSU). I started amateur radio as KD5AMB (tech) on 02/21/2007 and I hold a general class license. (Working on my Extra.)

I love electronics. This website is my way of keeping notes for my self and sharing what I learned with others. You will also find documents to things I own or things I have owned and used. If you want to ask questions you can email me at w5tsu @ grennan.com.

Besides amateur radio I also build and fly radio controlled aircraft (http://torks.org), write software (http://xastir.org) and make pen and ink watercolor art. (http://grennan.com) But this site is about my ham work.

AM broadcast band filter

For the W5TSU.net:8030 receiver I build a broadcast band filter. This should front end overload and intermod created by these stations and allow for better Ham band receiption. I also wanted to learn how to build my own coils.

I found a design at the vk3il blog. This filter was modeled with the ELSIE (free version). It is a 7-pole Chebychev filter with cutoff frequencies of 1.7MHz.


I started by winding some coils from 22, 26 and 30 awg magnet wire. I use a MingHe model LC100-A meter to masure these coils. I found holding the coils with my fingers didn’t make a sizeable different in the coil. What did make a difference was how tight the coile was wound and the lingth of the wire used. The size of the winding did make some difference but not as much as the amount of wire and how stable the winds where.

To make my coils I used a thick wall plastic tube. I put a hole with a T pin in the tube and put the 22awg wire through the hole. The wound the wire around the tube. Testing told me less then 20 turns would produce a coil with less then 2uh.

As I wound the wire I would use the LC meter to learn the value. When the value reached the 1.6 or 1.4uh needed I would put another hole in the tube and push the other end of the wire through it. I then secured the coil in place with some heat scrink.

Here are some pictures of the process and the results on the radio.

Coil tube. Whole made with T pin

Coil Measure.

AM broadcast bandfilter

Band before filter

Band with filter

I used 470pf instead of the 560pf caps. The result is a higher cut off frequency. It is 2.9MHz not 1.7MHz. I’ll correct this when I get the correct caps.

APRS Transmitter

I’m working on the design of a APRS Tracker transmitter. The dream is a self contained radio transmitter, modem, and controler with a bluetool connection to a tablet running Xastir.

There are lots of designs and APRS Trackers. Some are almost what I’m looking for. Many are out of date or the designer is dormant. The bigest example is MicroModem. Wounderful design from 2014 but the deveoper is… In his how words… “Long Time, No See”.

The AP510 AVRT5 is exactly what I’m wanting but it has some very bad review.

I purchases a Mobilinkd. It has everything but… GPS for “off line” tracking and Open Source Hardware. Mobilinkd is made to work with APRSdroid. You Android phone or tablet provides the GPS information and the tracking logic. Connects to the modem via BlueTooth and has cable for almost every kind of radio. This is nice buy I ask myself why it is needed at all when APRSDroid also works as a sound card TNC. All you need is a radio with VOX or a VOX curcit to key the radio.

Then there is Tracksoar. This is a very small tracker with gps and radio. It’s all opensource and open hardware. This project is very alive and perfect for a balloon project. But, receive and bluetooth are missing.

Some of these designs use a resistor network and for data pins to output a 16bit sign wave. Others use the pulse width modulation (PWM) out of one pin and a low pass filter. PWM works good and because I uses less data pins this is preferred.

For my build I’m breadboarding with a Arduino Nano, a HC-05 bluetooth and a NMEA compatible GPS. The radio output will be SA818V or DRA818V. The transciver is 1W. (https://www.youtube.com/watch?v=vetZwme2lhk)

W5TSU started in 1951

This is my grandfather’s ham license from 1952. My mother told me stories of her and her father lessioning to the radio and him teaching her morse code. My mother tough me my name in code when I was five.

Image of W5TSU License 1952

New WSPR station

I’m fascinated by the WSPR (http://wsprnet.org) network and found out you can build a transmitter station with an Raspberry Pi.

So, because I have a few Raspbery Pi comptuers setting about doing nothing, it’s time to put one to work. The code for this is at (https://github.com/JamesP6000/WsprryPi). WSPR net has some documentation on it (http://wsprnet.org/drupal/node/5353). The output from the RaspPi is a square wave so lots of filter is needed. (http://www.gqrp.com/harmonic_filters.pdf). A kit is avaible at (http://www.kitsandparts.com/univbpfilter.php).

I also have a HackRF. I’m thinking I could use it to receive WSPR stations on a schedule. May take some work.



Start here:

I have a new radio. I picked up a KiwiSDR (http://kiwisdr.com/) receiver from Seeed. (https://www.seeedstudio.com/KiwiSDR-Kit-p-2725.html).

The KiwiSDR was developed by the Funkamateur John Seamons ZL / KF6VO, is a branch of the OpenWebSDR project and realy started life as a kickstarter project.

This is the best HF (10kz-30mz) receiver I own. With the propagation so bad (its 2017) hams are using web based SDR receivers to make contacts. I share my SDR because I use other’s SDRs. Check out the list at (http://sdr.hu).

There a a couple of web based SDR servers out. The first I found was WebSDR.org. This is a sound card based SDR. Meaning, It receives left and right chanles as the quaditure IQ data from the sound card. This limits the band width the software can receive. To receive RF, most people use a down converter like the SoftRock (fivedash.com) tuned to the band they want to receive and feed the output the the sound card. With multipule receivers and sound cards WdbSDR can supply multipule bands to the web. Also you could downconvert any band.

I have two softrock receivers and the software for the WebSDR and I’m working on them. The KiwiSDR is up and running now. Why? Because it came out of the box working. It’s 100% plug and play.

I think I like the KiwiSDR more than the Websdr because it is fully open source. Both the hardware (https://github.com/jks-prv/KiwiSDR_PCB/tree/master/KiwiSDR) and software (https://github.com/jks-prv/Beagle_SDR_GPS) are avaible. So you could build your own or modify it for your needs. The web interface is written in Python. All you realy need to do is plug it in (power, antenna, network) and connect to it with a browser (Not IE). It boots into you’re wired network via DHCP.

I’ll be looping the my house to make a wire loop antenna for it. For now is has a 100 foot long wire attached.

Technical data:

  • Frequency range: 10KHz - 30MHz
  • Operating modes: AM, AMn, LSB, USB, CW, CWn, NBFM
  • Bandwidth filter: Adjustable between 50Hz - 10KHz
  • 30MHz low pass filter
  • 14bit ADC with 65MHz clock frequency
  • SMA RF antenna connection
  • 3.3V SMA connector for GPS active antenna

There are several places to purchase the KiwiSDR if you are intersted.

You can purchase a KiwiSDR here. SeeedStudio


I’ve added a new SDR. The FlyDog SDR is use the KiwiSDR software with new hardware arunning on a RasberryPi 3.

Tradition is… Amature Radio Operators don’t get along with each other’s projects. Witness APRS.

As the KiwiSDR source code is open source and itself boarrowed from OpenWebRX, it could be considered fair game to fork.The KiwiSDR developers don’t quite see it that way. John Seamons (ZL/KF6VO), the leader of the KiwiSDR project has announced that despite the clones KiwiSDR development will remain 100% open source with any future updates also being available to the cloners should they choose to implement them. He also mentioned to us that the clones will also be able to contribute to the TDoA service and can be listed on the KiwiSDR (http://kiwisdr.com/public/) directory. However, the reverse proxy feature will be limited only for official products. (Research needed here.)