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Dealing with doppler for newb...


Randon Loeb
 

So far have 2 contacts under my belt on AO-91. Just an HT and a tape measure yagi. Getting the hang of it so now there's some mental bandwidth during the pass to deal with the doppler changes...I've just left it on center freq for now.

All I know right now is as per some of the guides, I programmed 7 channels per satellite into my radio. #4 is the center, then the uhf goes up or down by 5khz for three clicks...you get the idea hopefully. At first I figured KISS and just used that center channel and hope for the best, not worry about turning the knob during the pass.

Now I think I can manage turning the knob during the pass, but how do I know when/if to adjust for doppler? I assume there's theory/formula, and then some rules of thumb?  Set a timer? By sound?

Thanks
Randy KN4YRM el96vc


David Spoelstra
 

My two bits. First off, seven steps is way too many. Five is more than enough. See:
from the work-sat site.

As far as when to step, that's why you should be using a full-duplex setup. With full-duplex, it's really obvious when to step because you can *hear* it. You can have a full-duplex setup very inexpensively. I've used two Baofeng UV-5Rs. I got a two-pack on Amazon for $46.

-David, N9KT


On Sun, Oct 18, 2020 at 12:58 AM Randon Loeb <randonloeb18@...> wrote:
So far have 2 contacts under my belt on AO-91. Just an HT and a tape measure yagi. Getting the hang of it so now there's some mental bandwidth during the pass to deal with the doppler changes...I've just left it on center freq for now.

All I know right now is as per some of the guides, I programmed 7 channels per satellite into my radio. #4 is the center, then the uhf goes up or down by 5khz for three clicks...you get the idea hopefully. At first I figured KISS and just used that center channel and hope for the best, not worry about turning the knob during the pass.

Now I think I can manage turning the knob during the pass, but how do I know when/if to adjust for doppler? I assume there's theory/formula, and then some rules of thumb?  Set a timer? By sound?

Thanks
Randy KN4YRM el96vc


David Spoelstra
 

Since you are looking for tips, I'd give you one other. Work some birds at 1am or 2am local. There will be very few other people on so you will be able to clearly hear your downlink. You'll also be able to ask the other hams how your signals sound versus working the bird at noon local when everyone is transmitting on top of each other.

I just worked PO-101 at 3am local and there were only two other hams on and I had most of the pass to play with changing my TX frequencies and hearing how they sound.

-David, N9KT EM69


On Sun, Oct 18, 2020 at 2:36 AM David Spoelstra via groups.io <davids=mediamachine.com@groups.io> wrote:
My two bits. First off, seven steps is way too many. Five is more than enough. See:
from the work-sat site.

As far as when to step, that's why you should be using a full-duplex setup. With full-duplex, it's really obvious when to step because you can *hear* it. You can have a full-duplex setup very inexpensively. I've used two Baofeng UV-5Rs. I got a two-pack on Amazon for $46.

-David, N9KT


On Sun, Oct 18, 2020 at 12:58 AM Randon Loeb <randonloeb18@...> wrote:
So far have 2 contacts under my belt on AO-91. Just an HT and a tape measure yagi. Getting the hang of it so now there's some mental bandwidth during the pass to deal with the doppler changes...I've just left it on center freq for now.

All I know right now is as per some of the guides, I programmed 7 channels per satellite into my radio. #4 is the center, then the uhf goes up or down by 5khz for three clicks...you get the idea hopefully. At first I figured KISS and just used that center channel and hope for the best, not worry about turning the knob during the pass.

Now I think I can manage turning the knob during the pass, but how do I know when/if to adjust for doppler? I assume there's theory/formula, and then some rules of thumb?  Set a timer? By sound?

Thanks
Randy KN4YRM el96vc


Brad Smith
 

Work SO-50, because you have to tune Doppler on the downlink, or the sound will go away. This will teach you when to tune. Then transfer what you learned to the other birds, while tuning the uplink.

Brad KC9UQR 

Sent from Brad’s iPad

On Oct 17, 2020, at 11:58 PM, Randon Loeb <randonloeb18@...> wrote:

So far have 2 contacts under my belt on AO-91. Just an HT and a tape measure yagi. Getting the hang of it so now there's some mental bandwidth during the pass to deal with the doppler changes...I've just left it on center freq for now.

All I know right now is as per some of the guides, I programmed 7 channels per satellite into my radio. #4 is the center, then the uhf goes up or down by 5khz for three clicks...you get the idea hopefully. At first I figured KISS and just used that center channel and hope for the best, not worry about turning the knob during the pass.

Now I think I can manage turning the knob during the pass, but how do I know when/if to adjust for doppler? I assume there's theory/formula, and then some rules of thumb?  Set a timer? By sound?

Thanks
Randy KN4YRM el96vc


 

This is a great idea, but I want to point out something between the two situations. With SO-50, you are adjusting the downlink frequency, with AO-91, it's the uplink that you need to worry about. The downlink should start high on SO-50 as it's racing towards you because it's wave are being scrunched together and you'll hear it start high. So tune from high to low on the downlink throughout the pass, but on the uplink for AO-91, go low to high. That's always the case for an uplink from a ground station. That's because your the one correcting for Doppler. You have to transmit low so when it's scrunched together, it will sound correct to the satellite. This took me a while to figure out.

73s,
Loren
K7IW


On Sun, Oct 18, 2020, 06:08 Brad Smith via groups.io <corlissbs=aol.com@groups.io> wrote:
Work SO-50, because you have to tune Doppler on the downlink, or the sound will go away. This will teach you when to tune. Then transfer what you learned to the other birds, while tuning the uplink.

Brad KC9UQR 

Sent from Brad’s iPad

On Oct 17, 2020, at 11:58 PM, Randon Loeb <randonloeb18@...> wrote:

So far have 2 contacts under my belt on AO-91. Just an HT and a tape measure yagi. Getting the hang of it so now there's some mental bandwidth during the pass to deal with the doppler changes...I've just left it on center freq for now.

All I know right now is as per some of the guides, I programmed 7 channels per satellite into my radio. #4 is the center, then the uhf goes up or down by 5khz for three clicks...you get the idea hopefully. At first I figured KISS and just used that center channel and hope for the best, not worry about turning the knob during the pass.

Now I think I can manage turning the knob during the pass, but how do I know when/if to adjust for doppler? I assume there's theory/formula, and then some rules of thumb?  Set a timer? By sound?

Thanks
Randy KN4YRM el96vc


Howard
 

That really had me puzzled, the reversed doppler adjustment, so thanks for the explanation!

Howard AE0Z