Discussion in 'Satellite and Space Communications' started by N8HM, Sep 30, 2018.
Also, the ISS repeater just is the standard Kenwood crossband repeater and is easily workable.
I didn't know the others have AFC and was just tuning to stay within 5kHz anyway so this one shouldn't be more difficult.
Interesting responses It will be fun learning how to operate the new bird!
I tune during the passes of AO-91/92. I guess I do it more out of habit than anything.
Yep. I guess what I was trying to state with my original statement was that tuning will be required during the pass just like SO-50 except it's for the uplink. Out of curiousity, why doesn't Cliff have AFC?
Same here. I've always tuned for Doppler on the higher frequency on all satellites except the 2-meter packet birds. It never occurred to me that one might not have to.
To be honest, I assumed I was observing this fairly often: the op I'm calling doesn't respond right after I tune for Doppler and call him. I'm getting into the bird, but I figured he didn't tune yet so he wasn't getting back into the bird. Now it seems that isn't likely to be the situation ...
Maybe it's just me, but I don't really find tuning the linears to be that similar to tuning the FM birds. On the linears, I tune the UHF link continuously to correct the pitch of my (or the other op's) voice, while on the FM birds I tune only at a few discrete points in the pass based on the current elevation of the satellite, not based on any aural feedback from the downlink.
I've used the ISS Detector app on my phone to display the real-time Doppler effect values during the pass often enough that I no longer depend on the readout to know when I need to change frequencies. When Fox-1C is operational, I'll need to learn the new tuning points based on the satellite's orbit and the uplink's frequency offset from the nominal multiple of 5 kHz that I use for the "center" frequency.
I could definitely see operating L/V mode without the benefit of AFC could be challenging near TCA if one doesn't have the Doppler readout to cue the very quick frequency changes that would be needed.
73, Ryan AI6DO
It might be a confusing explanation, that's why I asked that it just be said that it's not there rather than to elaborate on it in a news item. Might be a good subject for another video though, hmmm...
I'll see if I can keep it reasonably short, to avoid a bunch of followup questions.
Recall that Fox-1A was "hard of hearing" upon launch, and we weren't sure what the cause might be. Also recall that Fox-1Cliff and Fox-1D were actually the second and third Fox-1 to be produced, basically both at the same time and hot on the heels of Fox-1A, with work starting in January 2015. Fox-1A launched in October 2015 just a few months before Cliff/D were completed, as they were to be delivered/integrated for launch which at the time was set for March 2016.
That left very little time to consider whether the 1A problem might also be there for Cliff/D, and whether anything could be done. Not knowing the cause of the problem left us to speculate possible causes, although the broken antenna was at the top of my list but that didn't really mean anything when you're still investigating and basically guessing for Cliff/D. AFC was a candidate that we discussed because it was new and an unknown in the sense of no experience on orbit. Could there be a radar, or strong birdie, or some signal strong enough to be pulling the AFC way off so it couldn't capture "real" amateur signals? Could AFC have a bug that was just completely missed in design/testing?
It's hard to make a determination with no data and no time. Of the last minute changes that would be possible for Cliff/D, and even as the receivers were in the last stages of their build, disabling AFC was something that we determined could be done and having the two sats on the same launch would give a good opportunity for side-by-side comparison to help evaluate that as a possible cause of 1A's problem. By the time we had narrowed down the possibilities to experiment with, I had one day to decide in order to avoid delaying Cliff/D.
I elected to disable Cliff because Fox-1D has the HERCI experiment and my gut said that the AFC was not the problem, so having it would help the University of Iowa in commanding the experiment given their relative "inexperience" with ham satellites and the Doppler shift at 70cm. All the rest of you guys could work Cliff just fine since you're good at it, hihi.
And then the Cliff/D launches got delayed, and then we determined that the antenna was the very likely cause of Fox-1A's hearing problem, and then Fox-1B launched before Cliff or D and proved out the antenna theory, but of course Cliff and D were completed and sealed long before we knew any of that. And then D launched and added more proof to the antenna problem, and now it's Cliff's turn.
"And now you know the rest of the story."
Perfect explanation! Thank you for sharing it with us. Those of us that are used to tuning during a pass should be able to quickly adapt to it and those that aren't used to it will quickly learn. Each satellite has it's own personality and I'm cure that Cliff will also have a delightful personality. W4AQT and I can't wait to access it. I truly feel that AMSAT-NA spends our membership monies wisely and we are proud to be members.
Well, I didn't mean they might be similar in what you are listening/responding to when tuning, I meant the step adjustments might be similar. In other words, the new bird without AFC might be similar to linears in the one aspect of a need for more frequent 'touches to the dial'. One might still use the 'discrete points' method, but the question is, how many will there be? BUT, point taken that one's 'ear passband' might be more narrow than the FM receiver's passband, so adjustments will likely not need to be AS frequent as a linear bird. Basically, I'm wondering how many more adjustments will be needed, if any, compared to the birds that have AFC. (Of course, not having 2.5 kHz steps or a linear VFO will affect the rate and the number of steps possible.)
Okay, I didn't catch that, but now I get what you're saying... And yeah, VERY good point. It will be similar to SO-50 in that the steps and number of times to adjust should be about the same; similar frequency, so similar doppler shift. And one's HT doesn't usually have an AFC, so the receivers should treat them the same. The difference would be in the fact that with SO-50 it's easy to judge when it's time to adjust... the downlink starts sounding funny. With Fox-1Cliff, we'll just have to remember (and/or realize why we're not hitting the bird) and 'adjust according to schedule' like AI6DO suggests...
Which also brings to my mind that it will also be similar to SO-50 in that the adjustments will come more quickly during the middle of the pass. (Where those that do adjust their AO-85/91/92 uplinks, tend to make 1-2 adjustments.)
The way you worded it, I'm going to assume you mean moreso than the AFC birds... which only makes sense given all the facts and discussion.
This has been very helpful for me... my conclusion is: Yes, knowledge gleaned from linear doppler skills, should be of some advantage. We'll likely have to adjust the uplink more often than AO-85/91/92. In addition, one will have to do it more frequently during TCA. BUT, it shouldn't be as frequent as adjusting for 'normal voice' on the linear birds, more akin to adjusting SO-50 downlink. In short... it'll take a combination of previously learned skills adopted and put together. You know... like everything else in ham radio.
You bring up an interesting point. I wonder how far off the uplink carrier can be and still be captured. I'd think it might be possible that an operator with an all-mode rig might have an advantage in getting preferentially captured over an operator using an amateur rig with 5 kHz increments or a Chinese rig with 2.5 kHz increments. My FT-818 can tune in FM mode to 0.2 kHz increments if the FM dial mode is activated in the menu, and the FT-857 has 0.1 kHz increments. That would also likely give an advantage to those using computer control to automatically adjust frequency for Doppler.
73, Ryan AI6DO