5.8 GHz Helical Feed for the 90cm dish

Yesterday was day 2 where we were repairing the broken Azimuth rotator and making a small 90cm dish ready to track UNITEC-1 on 5.84 GHz. Actually, we already fixed the rotator on Monday but we ended up mounting it 180° off and we decided to fix it properly instead of just correcting it in software.

Fixing the orientation of the Azimuth rotoator was very quick – it took only 17 minutes to get up to the mast, lift the antenna construction, change the orientation of the rotator and fasten the nuts and bolts again. We had the practice from yesterday.

Next item on the agenda was to make a small helix with two turns to feed the 90cm dish so that we can use this smaller dish for tracking UNITEC-1 in the beginning of the interplanetary cruise. We found some online helical antenna calculator to generate the design but that was more than 1 GHz off and it took a lot of tweaking and tuning to get it close to 5.8 GHz. Here are the results, photos and videos.

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OZ7IGY beacon with GNU Radio, USRP and WBX

I was playing with GNU Radio, the USRP and the WBX daughterboard tonight preparing for the tests of the 5.7/5.8 GHz receiver setup tomorrow. For some reason that I can not remember, I have decided to tune in to 432.471 MHz – the UHF frequency of the OZ7IGY beacon, which is located approximately 50 km (24 mi) from me.

I knew I could receive it even when I am inside using my FT-817 but I didn’t really expect to receive it with the USRP+WBX. Well, I was wrong. Already with the lousy multi-band whip I could hear it. It wasn’t strong but I could hear it. I decided to try with the Arrow antenna and voila, suddenly I could receive it with 40+ dB SNR!

Watch in high definition on YouTube or get the 80 MByte .mov file.

The software was a slightly modified version of the simple CW receiver I posted yesterday, implemented in GNU Radio Companion. The modification consisted of adding a waterfall display after the band pass filter. I have included the GNU Radio flow graph at the end of the video, the one below is without the waterfall display:

So, what do you think, how does the CW sound in a so simple software defined radio?