QO-100 developments

I have been using a number of different antennas for the uplink on 2.4GHz.

As I am unable to achieve much more that 1.2W output from my SG Labs transverter, my tests have nearly all been done with 1W or less.

1W into the cable out to the 17.5dBi gain Huber Suhner flat plate antenna results in a signal that most QSO partners report as a just a bit too weak for comfortable copy (<10dB SNR in 2.5kHz?). Using my 2.3m EME dish with 13cm band septum polariser feed requires that I turn the power down to around 100 -150mW to reach beacon level. The septum polariser feed is probably not working so well at 2.4GHz. It was designed for 2320MHz. QSOs are easy with this set up, though. No PA required.

I have built a 4 turn helix to the W1GHZ online antenna book details. The match is as shown below. Excellent!

This shows almost 40dB return loss at 2.4GHz, although in practice keeping the spacing of the matching strip to the reflector is difficult and when set up for more testing, 20dB was about the practical limit. Once Dow Corning sealant was added to hold the helix in place, the RL had dropped to about 17dB. I judged this adequate for testing and with the helix temporarily taped above the LNB in the 1.1m offset dish, it was hard to get much a over 10dB below the beacon level, even at 1W into the feeder. The estimated (not measured)  cable loss to the feed was about 4dB. It was obvious from results that a bit better optimising was required.

With this set up I called and worked 3B8FA on the satellite. He was clearly having trouble copying me, so I completed the QSO using the EME dish!

Due to the kindness of one of my local amateurs I will be taking delivery of  a set of metalwork for one of the G0MJW dual band patch, dielectric lens feeds to try in the (near?) future.

One of the joys of this satellite is that I have already had QSOs with friends I haven’t worked on the radio for some time. Everyone seems to be having a go at working the satellite.

I worked Per, DC3ZB earlier today. The last time I saw Per was at Friedrichshafen a few years ago. Lots of time to chat and compare systems and news.

Sam