Satgen65 More - Simple Pacsat Hardware by GM4IHJ 25th June 90 Activity this last week has concentrated on the developement of two pieces of hardware. The first is for Uosat3 9600 bps reception and consists of a Microwave Modules 434/28 converter, recrystalled to 101.85 MHz to give a 27.67 output from the 435.07 Uosat3 input. Four values of switched capacitance in series with this new Xtal, allow its frequency to be shifted through 4 by 2.8 KHz steps at 407.4 MHz, providing inter channel tuning between the 10 KHz channel steps of the CB Rx used as IF. The CB has a broad 12 KHz ceramic filter replacing the normal 6 KHz filter in its 455 KHz IF. Additional mods now under consideration are a centre tuning meter, and , or AFC. At present the scope eye diagrams are adequate for tuning, but not everyone else will be able to afford a scope. The second piece of hardware is a new DIY aerial for Dove S Band reception on 2401.22 plus or minus 50 KHz doppler. Initial tests on a 2 metre dish were a flop. S9 one moment , S0 the next. Equally hopeless, the heavy awkward large quad helix was just too cumbersome for good tracking of fast moving Dove. The new aerial looks like a medium size pair of binoculars and to add to this illusion it fits nicely on a very manoueverable camera tripod complete with pan tilt head. The helixes are of welding wire , wound on plastic tube supports. The reflector is Aluminum foil on plywood backing board, and the helixes are parallel connected through matching coax to an N type plug which carries the 2400/144 converter. With this aerial smooth tracking is at last possible for at least half of any orbit in range of Scotland. The aerial points out of a large open window in the roof and has a relatively clear view on all bearings from west through north to east. Dove is a very strong signal at times and once doppler track charts had been checked was easy to follow. Unfortunately however there is a fault on the modulator of Dove's 2401 beacon such that the phase modulation is nothing like the desired 180 degrees. The next step here is to try to rig AFC, so that the modulation problem can be further explored. Meanwhile Amsat NA Controllers are already trying Digital Signal Processing on this difficult signal to investigate whether they can achieve demodulation effectively enough to allow investigation and correction of Doves computer problem, which presently prevents use of its 2m transmitter. As a further test of the simple aerial described above , it was pointed at Oscar 13 as it passed through Apogee sending Mode S beacon and transponder traffic. The beacon was good S2 copy , and so were CW signals from I7LIT but though voice signals could be heard they could not be read. This latter is hardly surprising however noting that Oscar 13 is 40 times further from the earth than Dove , hence there is approx 33 dB of path loss. So do not expect too much from Oscar 13 if you decide to build a simple aerial with no pre amp to listen to Dove, but be aware you can test on AO13 whilst you wait for Dove to come around , noting that AO13 has very little doppler shift on its signal and once you have found it , no aerial training is required. 73 de John GM4IHJ@GB7MAC .