Hi Joe,
Dishes are not commonly used in ham or other applications with frequencies as low as 70cm. It takes a pretty large dish before you really start seeing benefits on 70cm, and a dish so large would be difficult to turn fast enough to keep pointed towards a LEO satellite. Such an apparatus is generally only used for EME, or perhaps a HEO satellite application may reveal itself in the future. A 15m dish wouldn't be very practical to stick very high in the air for terrestrial work. Yagis are the antennas of choice for 70cm satellite operation, although you can get away with other types and even omnis. I guess you could stick a quarter wave 70cm antenna at your dish's focal point, but I wouldn't expect exceptional performance. Your dish would be best used for receiving or transmitting to satellites in the 23cm or 13cm and up. When P3E is launched, your Winegard dish will be very useful in receiving it with its 13cm (S band) downlink. You can fashion a 5 turn helix feed to place at the focal point and typically a downconverter would be placed behind or under it like on the arm of the dish. However, P3E will require a SSB radio, of which I don't think the T90 can do. Still, AO-51 is occaisionally in S band down mode and transmits FM. Also it has an L band uplink mode in which your dish would be useful for with an approriate feed.
Your T90 by itself with an appropriate antenna can work three voice satellites; AO-51, AO-27 and SO-50. A quarter wave whip eye poker can work AO-51 and AO-27 on high passes. The AL800 I've talked about before is an inexpensive, compact telescoping antenna which has done well on satellite passes above 7 degrees or so. A yagi is your best choice. You can buy an Arrow handheld yagi and get the one with the minidiplexer which lets you connect separate 2m and 70cm antenna leads to the one connector on your radio. A much cheaper homebrew version can be constructed by plans on the internet, try googling for XE1MEX. You can also homebrew the diplexer as well.
AO51 is in L band uplink mode today, and next week will be digital only, but it will return to VHF uplink/UHF downlink mode on Monday the 24th (or Sunday night on the first pass that hits Florida). AO27 you should be able to hear. It is only turned on for voice for 6 minutes at a time during ascending passes while it's over the middle third of the northern hemisphere. In other words, if you're listening for AO27 and you don't hear it right away, wait a couple of minutes, it will switch on and you'll hear packet for about 20 seconds.
Now, when you mention sound card with a computer, I'm assuming you're interested in the digital modes? AO-51 has a BBS which runs at 9600 baud most of the time, although sometimes it's scheduled for 38k4 (like all of next week!). 9600 baud can be done with a soundcard, but you have to tap the audio from your radios discriminator. Most "data ready" radios have this via a connector on the back, but HT's are not like this. You'd have to open up the radio and make the tap yourself! However, you can do 1200 baud via the speaker mic jack on the HT no problem. This is good for PCSAT-1 (when it's in daylight and operational), PCSAT2 although some of its packets are 9600, ISS (the space station) and maybe some others; not sure.
AGWPE is a program which you can use your computer's sound card to do packet with. You will need to construct a device which will allow your computers COM port to trigger your radio's PTT. I built one out of an optocoupler/optoisolator and it works fine; cheap and simple to do and keeps your radio isolated from the computer provided you're wiring the mic and speaker leads via audio isolation transformers as well. Not required to do I suppose, but it's a good idea to, preventing ground loops and the sort. If you want to operate AO-51 digital or even the other pacsats, you will need to download WiSP (Windows Satellite Program). WiSP can work with AGWPE but it's pretty tricky from what I understand. You have to create virtual com ports for the two programs to talk to each other, etc. It's something I've never tried and I'd have to refer you to the AMSAT-BB archives for exacts, but something tells me the taking apart of your HT and soldering wires inside of it will turn you off of trying to work AO51 with a digital mode! AGWPE is fine on its own with ISS and the two PCSATs although you might want to run it with APRS like UI-VIEW as many are using APRS on these satellites to chat, send posits and what not.
So, give the voice sats a try. AO-27 will probably be quite busy this weekend with the holiday and good weather for many. See if you can't hear it on a good, high pass. If you can hear it, don't be afraid to uplink through it too. We're all excited to hear new callsigns on the birds and you'll probably get a pileup, especially if you're in a rare grid. Hope this helps!
73,
Mark VO1ONE
