Tuning help? - Satellites Forum at eHam.net

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eHam.net Forum : Satellites : Tuning help?

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Tuning help?	Reply
by VA7CPC on October 13, 2009	Mail this to a friend!
I'm just getting started on satellites with my local ham club. We are using hand-held Yagis and two rigs. I may have blown some FM QSO's today, by not having my receiver tuned correctly. A question: ----- Without using computer software with real-time update to my rig, how can I keep the receiver tuned to the center frequency of the Doppler-shifted signal? ----- I remember, in the days before digital tuning, there were FM broadcast receivers that had a 'center-channel' indicator. My FT-817 doesn't have that feature. I can watch the S-meter (although I wasn't doing that -- my bad), but with the antennas waving around, I can't tell if a reduction in signal strength is caused by being off-channel, or a mis-aimed antenna. Any hints? Thanks -- Charles

RE: Tuning help?	Reply
by KA1DBE on October 16, 2009	Mail this to a friend!
I always start 10 khz high and then work down through the pass. Doppler is much more pronounced on 70 centimeters than it is on 2 meters. You should just be able to park your 2 meter rig on the uplink frequency and leave it. The "Work Satellite with your handheld" article shows a good example of doppler effect. Good luck and 73's, Jeff

KHz steps	Reply
by KJ4KKI on October 27, 2009	Mail this to a friend!
I understand starting 10 KHz above the freq. and doing 5 KHz step downs until 10 KHz below. My problem is I can never remember the math. If the freq. is 430.500, is + 5 KHz 430.550 or 431.000? Likewise, for the subtraction... 430.725 - 5 = 430.720 or 430.220? If you could point me in the right direction, it'd be a lot more helpful than digging out the book again. Thanks, Steve

RE: KHz steps	Reply
by KB2FCV on October 28, 2009	Mail this to a friend!
If the center frequency is 435.300, starting 10khz up you would be at 435.310. When you drop 5khz you are at 435.305. Then you're at 435.300(center), 435.295 and finally near the end of the pass 435.290. You can program these in your memories or just keep it in VFO mode. Another thing to keep in mind, if you don't have a computer nearby to know where the frequency is.. by around the middle of the pass you should be at the center frequency. I just keep an eye on my watch. As you get more used to it you'll know when it's time to change by ear.

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