A great QRP (low power) ham radio story

A nice story with a big finish . . .

Today I saw a tweet pointing to a post on my friend Alan’s blog – announcing a local launch of a high altitude balloon by Bill, WB8ELK. With a couple of hours before the launch, I found and downloaded dl-fldigi, which is used to receive telemetry and report it to a central site for realtime display. dl-fldigi is a modified version of the digital mode application fldigi.

I caught my friend Kamal KA6MAL on IRC (Internet Chat), and he fired up his copy of fldigi to see what he could copy from his location in California. With the unmodified version of fldigi, he would be able to read along, but the telemetry wouldn’t be reported to the tracker.

The actual launch was a little late, but shortly after the balloon gained some altitude, I was able to receive the signal using both Domino and RTTY modes. As the balloon got well over Georgia heading East, I first lost the ability to copy Domino without errors, and then lost RTTY.  Even after this I was able to read a couple of transmissions of altitude in Hellschreiber mode. The telemetry transmissions were a sequence of CW, Domino, Hellschreiber, and RTTY every minute.

Reception was very difficult because there was an active RTTY contest, with signals all around and on top of the 14.102 MHz center frequency.  I’m also on the wrong side of a hill near my house for good reception from the east. I found out later that the balloon transmitter was only putting out 1/2 watt of power, so I’m pretty happy with what I did hear.

People listening for the balloon were able to receive the telemetry through the ascent phase and most of the descent, but the last signal reported was at an altitude of 8358 meters, just East of Raoul, Georgia. Here’s a look at the tracker map:

Balloon launched from Huntsville, to Georgia

After a while, it was certain that the balloon was on the ground, but the landing position wasn’t known with certainty. Then, Kamal said on chat that he was seeing the signal, and even managed to capture one perfect frame. Kamal lives in southern northern California. Now that’s QRP – over 2000 miles on half a watt! The actual landing location is about twenty miles further East than the last position on the tracker map shown above.

What a great way to spend an afternoon, and I know that Kamal is happy!

Bill said in email that the reported altitude after landing is about 60 feet above ground level, which sounds reasonable, considering that google maps shows a reforested pine timber grove at the landing site.

Bill does a lot of balloon flights, and they’re fun, even if all you’re doing is receiving telemetry. If you’re interested, keep an eye on this project – White Star Balloons – They’re about to attempt a transatlantic balloon flight, and will be transmitting telemetry on the 40m band.

UPDATE: Corrected the fact that Kamal lives in Northern CA. Also, here’s a screenshot he sent me of some of the Hellschreiber he received. He said the same thing in his email that I was marveling at while I was receiving Hell mode – the human mind has an astounding ability to pull meaning out of the noise when presented with the visual image. I could read the Hell images when there was no chance at all of receiving the other modes.

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About Steve

I'm Steve Conklin, AI4QR I'm employed by Canonical, Inc as a Linux Kernel Engineer. Interests include Linux, open source software and hardware, electronics and music, and amateur radio.
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3 Responses to A great QRP (low power) ham radio story

  1. Kamal A Mostafa says:

    Thanks for tipping me off about this WB8ELK2 balloon launch, Steve! Trying to pull in its weak beacon signal through the clatter of the RTTY contest presented an interesting challenge for sure. I was tickled pink that I was able to receive the final telemetry from the balloon after it landed and pass its location along to Bill WB8ELK.

    73 de KA6MAL -Kamal

  2. wb5rmg says:

    As usual, I was trying to do several things at the same time – and just left my program set for Domino. Watching the waterfall and observing the effect of the stronger signals up or down freq – I recognized that the receiver’s AGC was really the problem. When such a strong signal is within the passband, it reduces the gain. Seems I’ve seen reference to switching off the AGC and reducing the bandwidth, to prevent that loss of signal. I may have to learn my radio menus better enough to try that next time…
    Thanks /;^)

    • Steve says:

      That’s what I have to do when I’m running digital modes when there are strong stations in the audio passband that I’m not interested in. I turn off AGC and the use the DSP to filter down to the signal of interest. It works well. It would work even better if my rig had IF DSP filtering – I’m using a filter unit that goes into the audio path after the receiver. But it still can make a huge difference.

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