[amsat-bb] Re: Feedback on downlink on VO-52
rnutter at networkref.com
Tue Apr 1 07:12:03 PST 2008
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.
George Henry wrote:
> -----Original Message-----
>> From: Ronald Nutter <rnutter at networkref.com>
>> Sent: Mar 31, 2008 10:40 PM
>> To: AMSAT-BB <amsat-bb at amsat.org>
>> 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>.
> 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.
> George, KA3HSW
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