SXHAM1 – CHEAPO18 flight for EssexHAM/TXFactor/RSGB – 31/05/15

I was approached by Pete M0PSX to do a HAB launch for a promotional video by the RSGB.
The launch took place from the EssexHAM field event at Shoebury East Beach on Sunday the 31st of May.
There were a few other radio amateurs present operating on HF and 2m, as well as a couple of guys flying drones.
Footage was captured by a group called TX Factor, who are doing a piece for the RSGB promoting youth and interesting new activities in amateur radio.

We launched a Cheapo Micro tracker under a 100g Pawan balloon, then tracked the flight from the event using a couple of RTL-SDR’s with a yagi and a 2m/70cms magmount.






Video and photos credit Pete M0PSX

Footage from TX Factor to follow.

ECC1 – Pi in the sky test flight 24/05/2015

On Sunday the 24th May 2015, I carried out a test flight of the Pi in the sky high altitude balloon tracker for our local council. There are currently over 10 schools constructing payloads around this tracker which should be launching in the next couple of months. A couple of my experimental trackers also hitched a ride on the flight to test out, as well as another backup tracker.

I was joined by Will to help with the launch, tracking and recovery. After a quick stop for breakfast and to check the predictions one last time, we met Steve up at the Elsworth launch site at Cambridge. Steve was also trialling out live streaming the launch over 4G, which turned out to be very successful.

Shortly after arriving, we powered up all of the payloads, ensured they had a GPS fix and were transmitting correctly, then joined them together with the 3ft rocketman parachute to form a train.

Balloon — 5m — Parachute —– 10m —– ECC1 — 5m — CHEAPO – 2m – CS4

We then began filling the Hwoyee 1200g balloon with about 3.6m³ of helium. The lift was checked by attaching a 2500g weight to the balloon and filling until it achieved neutral buoyancy. The balloon was then sealed off at the neck and joined to the train using cable ties and duct tape.


Image credit Steve Randall

Image credit Steve Randall

After Steve coordinated with local air traffic control and the rocketry club in the next field, it was time to launch. The wind was picking up a little bit, so the launch was a little more violent than usual. Will and I ran along with the payloads to match the speed of the wind, and then released them when the balloon was straight above us.

We then shot off in the chase car to wait in a car park in Royston until the burst. This ensured we had good 3G/4G signal to run predictions and fast access to the main roads once we had a predicted landing site.

Unfortunately shortly after launch ECC1’s signal dropped to a single carrier (as opposed to the normal alternating frequency of RTTY), this was a pretty solid indication that the tracker had crashed. We continued receiving updates from SPARK and CHEAPO for the duration of the ascent. When the balloon eventually burst at 32759m altitude, we waited for a few more updates of the descent from CHEAPO before heading out to the predicted landing site. SPARK once again however failed to report the burst or descent, and carried on “floating” at a roughly steady altitude.

Alt Graph


Once we arrived at our predicted landing site the flight had landed, and the signals from all 3 payloads were visible and audible, however too weak to decode. After 15 minutes or so of trying different antennas and tweaking decoder settings, we decided to head out further west in pursuit of a stronger signal. Around this point we saw a bunch of updates appear on the tracker from Steve, and headed to the new location.

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We were greeted by Steve and his cameraman, who had already had time to locate the payload and set up their live stream before we arrived. The payloads were sitting happily on the ground, with the parachute caught up a tree dangling most of the balloon remnants below it. After a couple of tugs the parachute joined all 3 payloads in their successful recovery.


Keen to investigate what happened to ECC1, we headed back to Essex to carry out some debugging. On recovery neither of the OK or WARN LED’s were lit on the board. The camera LED was however still flashing, and had stored images of the entire flight on its SD card. Voltage readings were normal. On closer inspection I found that the SDA wire for the BMP180 sensor had broken at the solder joint to the PITS PCB. After soldering this back on and simulating the breakage, the PITS tracker program once again crashed and dropped to a single carrier. I also found that the micro SD card was very lose in the low profile micro SD adapter I was using. It could easily be pulled out by dragging your finger across it (despite remaining in the “locked” position), More hot glue required.

I’ve reported these findings back to Dave Akerman and he is hoping to release a software patch by the end of the week. I think it would then be wise to carry out a small repeat test flight (perhaps on a 100g pawan) just for a little more confidence.

A recording of Steve’s entire live stream can be found here, along with all of the pictures of the flight recovered from the SD card here.


UKHASnet WiFi node using ESP8266

Since the UKHAS conference in August I have been playing with some UKHASnet nodes, which are “A simple wireless network aimed for use with low power licence exempt wireless modules”.
The system was developed by members of the UKHAS community, but is not specifically aimed at ballooning (however can be used for it).
I have 2 LPC810 based nodes designed by James Coxon, and an AVR node from Phil Crump. After I had these set up, I loaded Phil’s code onto an old Cheapo v3 PCB and bug soldered a RFM69 onto the back. This made a pretty effective GPS node and after some tinkering I had positions being uploaded to


The system relies on packets being repeated between nodes, before hitting a “gateway” node which is connected to the internet. This may be a node connected to a PC, or a raspberry pi with an RFM69 radio. After seeing the ESP8266 popping up in various places, I decided to order a couple of modules and design a PCB for a simple AVR based wifi node.


The PCB was very quick to put together and Phil’s repeater code had it working almost straight away.


I put together a library for sending HTTP POST requests to the ukhasnet server from an ESP8266 via AT commands. I updated my ESP chip with this firmware ( from /   Mirror) to reduce the speed down to 9600 baud. The chip does indeed work with WPA2 (which I was not expecting, possibly down to the firmware update)

The node has been running now for about 72 hours with no apparent problems 🙂

The ESP8266 Library, repeater/gateway code (credit to Phil) and PCB files are up at

The basic upload sketch looks something like this:

#include "ESP8266.h"
#include "wifiConfig.h" //this is where you need to set your SSID and Password
#define DST_IP "" //
#define WIFI_EN 7 //CH_PD

ESP8266 esp8266 = ESP8266();

void setup()
  Serial.begin(9600); //Open serial communications 
  esp8266.initialise(Serial, WIFI_EN); //Pass it over to the ESP8266 class, along with the pin number to enable the module (CH_PD)
  while (!esp8266.resetModule()); //reset module until it is ready
  esp8266.tryConnectWifi(SSID, PASS);//connect to the wifi
  esp8266.singleConnectionMode(); //set the single connection mode

void loop()
  esp8266.uploadPacket(DST_IP, "your_data");

JOTA HAB launch

On the 18th and 19th of October I joined Steve Smith (G0TDJ) and Pete Sipple (M0PSX) at the Jamboree On The Air scout event in Basildon. We carried out two launches, a cheapo payload under a 100g pawan on Saturday, followed by Steve launching VAYU under a 36″ foil on Sunday.

My flight made it almost across the north sea before ditching in the water just short of the Netherlands.

DA13891_25 (Small)



Steve’s flight on the other hand entered a very nice float after being launched from the top of the climbing tower and made its way towards Sweden before running out of power.

JOTA1+2 B0TOg3mIUAEESu9.png large


Steve has done an excellent write up of the launch over on his blog:

As has Pete on the EssexHAM site:

RFM22B temperature cycling tests

I recently ran a test to investigate why the rfm22b often fails at low temperatures, with some interesting results.

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The radio module was set up in a test chamber and cycled from +20 to -50 degrees Celsius and repeated 5 times. The board was powered and the output frequency monitored and logged using an SDR.


The above results were surprising, as I was expecting the rfm22b to drop out around -40, however it carried on transmitting just fine all the way to -50. However as the temperature rose back out to ambient the module stopped transmitting as the temperature passed about -10. This happened consistently 4 out of the 5 times tested. I believe this is caused by dew forming on the crystal and pulling the frequency way out. You can see the frequency clearly shoot off to the side in this screen capture:



You can see in the graph below how the temperature affected the frequency, and where the module dropped out. I have also put together a time lapse of the SDR output to illustrate the drifting.


Test data spreadsheet: rfm22b_test_data.xlsm