I am using seperate antennas and feedlines. For the time being, I am using a Channel Master antenna to turn the antennas. I have a pvc pipe rig setup with the antennas at an angle of 25 degrees due to the clutter in the neighborhood I have to clear to see the sats. I hope to have a tower in the future but with being laid off from my job, cant really have any expenditures right now.
I have the cat interface for the IC910H but havent looked into how to set it up yet.
Ron KA4KYI
George Henry wrote:
-----Original Message-----
From: Ronald Nutter [email protected] Sent: Mar 31, 2008 10:40 PM To: AMSAT-BB [email protected] Subject: [amsat-bb] Feedback on downlink on VO-52
Thanks to the help of several on this listserv, I was able to get a contact on VO-52 until I lost coordination on keeping the rotor turned and the IC910H tweaked the right way on the VFO's. I had problems finding my downlink because of what I think is desensing on the 2M downlink.
Can I resolve this by putting a filter on the 2M receive to stop the desensing like I would on the UHF receive on the FM birds ? If not, is there another way to fix the problem ?
Thanks to W0EOZ for putting up with me while I was trying to figure things out. Hopefully my next contacts will last a bit longer <G>.
Ron KA4KYI
Are you using separate 2 meter and 70 cm antennas with separate feedlines, or diplexing onto a single feedline to a single antenna? First thing to do is reduce your uplink power as much as possible while still being heard. If you are diplexing to a single feedline, you only have about 60dB or so of isolation, so too much uplink power can exceed that. You should be able to work VO-52 with 25 watts or less...
I have never experienced desense on 2 meters from my 70 cm uplink... only the reverse, which can be cured with separate feedlines and antennas, ample separation between the antennas, and the diplexer-as-filter trick found at http://www.amsat.org/amsat-new/articles/Mode-J/
And I strongly recommend buying or building a CAT interface and letting your tracking program take care of tuning the radio (and turning the rotors, if you buy or build a rotor interface as well). The demo version of SatPC32 is fully functional except for saving your station parameters, and can be downloaded from <www.dk1tb.de/indexeng.htm>. If you like it, register it: all proceeds go directly to AMSAT. A CAT interface PC board with the harder-to-find chips included is available from <www.farcircuits.net> and only costs about $20 to build. The FOD-Track rotor control PC board is also available from Far Circuits, and will cost $45 - $50 to build. The LVB Tracker is available thru the AMSAT store, and has the advantage of being able to operate without a computer attached... nice for mobile ops!
Go for the radio control first: that'll free you up to deal with the rotors manually, and they demand far less attention than tuning does.
73, George, KA3HSW