Stefan's Radio Blog

Working on HAM Radio Apps

Even though my year started with a business trip I found some time to work on my HAM radio apps. Last year I was busy with some other hobby so these apps were a little bit left behind.

APRS Windows Phone has got a fix of the faulty beacon counter. After some intensive testing during my business trip its now released in version I am currently working on a sound modem to support beaconing over a radio transmitter. So far I have got the modulator and NRZI working, next steps are to implement HDLC and AX.25 framing.

HF Propagation has problems with data provided by N0NBH now in a slightly modified format. The current parser sometimes can not digest the data properly. That prevents to display the complete data set. The parser is fixed now and I am working on the display part: Windows 8 is not any longer actively supported, for Windows 10 I want to introduce something like a "Gadget View".

APRS for Windows Phone - published

For Christmas I have published a new version of my APRS app for Windows phone. It comes with only a few changes and no major new features:

  • fixed reported speed
  • fixed wrong colors for some APRS symbols
  • added manual mode for position reporting
  • removed dynamic advertising and replaced it with a link to my blog
In the next version, planned for January 2017 I want to fix an newly introduced bug with the beacon counter and some other potential problems caused by my latest changes. Further down the road I want to support Bluetooth and a sound modem, so that APRS tracking can be used without connection to the internet. Please see also my roadmap for the app here.

60m band in Switzerland

I found this today on the USKA's news page: Beginning with 1st of Januar the 60m band will available for HAM radio operators ins Switzerland. Allowed power is 15 Watts EIRP.

This is the IARU band plan for region 1:

5351.5 - 5354.0 khz
CW, Narrow band modes, digimodes
5354.0 - 5366.0 khz
All modes, USB recommended for voice operations
5366.0 - 5366.5 khz
Weak signal narrow band modes

Before Mars

Prequel to National Geographic channel's "MARS": Two young girls are moving into a new town. In the attic of their  house they find an old HAM radio transceiver. With the help of an old man they can finally make a contact with the ISS. The 30 minutes video can be found here on YouTube.

If you want to contact the ISS yourself start with listening. The AMSAT-UK provides a short guide to the beginner on their website, more information is available on the ISS fan club website. National Geographic created also a Guide To HAM Radio.

ICOM 736 Repair

This year my ICOM 736 had some problems. The first issue was a failure in the CAT interface. At some point I noticed that my computer log could not communicate with the ICOM transceiver anymore. It happend to be at the same time when I updated my OS to Windows 10. So I was put on the wrong track when I started my troubleshooting since in the past I had a lot of problems with Serial-to-USB adapters. I thought the new OS might be incompatible with the adapter I am using. But finally it became clear that the new OS did not cause the communication problem.

So I had to dive into the schematics which I found on the internet when searching for a ICOM 736 service manual. The CAT interface is located on the PCB inside the front panel. So I had to open the transceiver and to take it quite a bit apart:

Some measurements quickly revealed, that the driver transistor for the CAT interface was defective. Since I had no SMD transistor at hand I replaced it with one universal type in a TO-92 housing from my junk box:

After carefully reassembling the transceiver the CAT interface was working fine again. But a few weeks later another problem turned up: Receiving SSB and CW was not possible, the audio sounded like I had some IF filter problems or the band pass tuning was set to narrow. Receiving AM and FM worked fine. So I could not use the ICOM 736 anymore and was left alone with my Elecraft K2.

Yesterday when I tried to participate in the SSB part of CQ WW contest I finally was so annoyed by operating SSB with only 10 Watts output of my K2 that I took my ICOM 736 and tried to repair it. Luckily the problem was easy to find - a ribbon cable connector for the band pass tuning potentiometer had some contact problems. So within half an hour the ICOM 736 was fixed and I could easily made some more contacts in the contest.